Due to Adobe’s decision to stop supporting and updating Flash® in 2020, browsers such as Chrome, Safari, Edge, Internet Explorer and Firefox will discontinue support for Flash-based content. As a result, this site has been retired. Show If you have additional questions please contact Savvas Learning Company to find either your sales rep or the technical support form. Click Here - Free KCSE Past Papers » KNEC Past Exams » Free Downloads » KCSE Papers & Marking SchemesBiology Questions and Answers Form 1KCSE Revision Questions and Answers K.C.S.E Online Revision Biology Notes Form 1 - Biology Form 1 Notes - Form 1 Biology Notes Introduction to Biology Biology is a branch of science that deals with the study of living things. There are diverse forms of life on earth ranging from the invisible microscopic living things to the gigantic life forms. It aims at explaining the living world in terms of scientific principles. It is important to note, however, that living things interact with the non living things in the environment as Well. Biology, therefore also entails the study of non living things as well. The role of human beings in shaping the environment is also investigated in biology. In summary, biology deals with the study of origins, types, nature, growth, development, interactions and maintenance of all life forms on earth. Branches of Biology Biology is such a broad field of knowledge. It is divided into two broad branches 1. Zoology- This is a branch of biology that deals with the study of animal life. 2. Botany- This is a branch of biology that deals with the study of plant life. Within the two branches, there exist even smaller branches because the branches (botany and Zoology) are very wide and complex. The smaller branches of biology include: a) Ecology- This is the study of the interrelationships between organisms and their environment. Ecology aims at establishing how organisms are related to each other and their environment. Ecology is further subdivided into smaller branches. These can be forest ecology, marine ecology, rangeland ecology etc. b) Genetics- This sub-branch of biology deals with the study of inheritance and variation. It deals with the study of how variations (differences) occur between parents and their offspring. It is also concerned with how various characteristics are passed on from parents to offspring. c) Entomology- This is the study of insects. d) Parasitology- This is the study of parasites. e) Physiology- This deals with the study of the functions of various structures of an organism. It deals with the processes that take place in the body of organisms. f) Anatomy- The study of the internal structure of organisms g) Microbiology- This is the study of microorganisms h) Bacteriology- The study of bacteria i) Ornithology- This is the study of birds j) Itchthology-This is the study of fishes This list is in-exhaustive as there are very many other branches of biology. Importance of biology > Joint development of HIV/AIDS vaccine by Kenyan and British scientists. > The coordinated fight against Severe Acute Respiratory Syndrome involving scientist all over the world. > The fight to save the ozone layer from depletion through various international agreements such as the Kyoto protocol. > Management of resources through international treaties such as the CITES (Convention against International Trade on Endangered Species). Characteristics Of Living Things Living things share a lot of characteristics in common. These characteristics are discussed below. a) Nutrition Nutrition is the process by which living things obtain and assimilate (utilize) nutrients. Living things require nutrients for various purposes; growth, repair of worn out tissues and for provision of energy. Plants manufacture their own food using light energy, carbon (IV) oxide, water and mineral salts through the process of photosynthesis. Conversely, animals feed on already manufactured foods from plants and other animals. b) Respiration Respiration is the process by which food substances are chemically broken down to release energy. During respiration, oxygen is used while energy, carbon (IV) oxide and water are released. Respiration occurs in all living cells. The energy produced in living things is very useful as it enables the living things carry out some of their physiological processes. The energy is also required for growth and development, movement and repair of worn out tissues. c) Gaseous Exchange Gaseous exchange refers to the process by which living things exchange oxygen and carbon (IV) oxide across the respiratory surfaces. Animals always take in air rich in oxygen and give out air rich in carbon (IV) oxide. Carbon (IV) oxide is a waste product of chemical reactions in the body. Animals require oxygen for respiration. Gaseous exchange, therefore, enables animals obtain oxygen for respiration and get rid of carbon (IV) oxide, a waste product. Plants, however, require carbon (IV) oxide for photosynthesis during the day. They give away oxygen as a by-product. The plants equally require oxygen for respiration and give away carbon (IV) oxide. d) Excretion This is the process by which living things separate and eliminate the waste or harmful materials resulting from chemical reactions Within the cells. These harmful waste products of metabolism maybe toxic to the body if they are left to accumulate in the cells of the living things e) Growth and Development Growth refers to an irreversible increase in size and mass while development refers to the irreversible change in complexity of the structure of living things. Growth and development of living things is essential as it enables the living things to attain maximum size that can enable them to perform their functions and roles. f) Reproduction This is the process by which living things give rise to new individuals of the same kind. All living things reproduce. Reproduction is essential as it leads to perpetuation of species and it avoids extinction of certain animals and plants. g) Irritability This is the ability of living things to perceive (detect) changes in their environment and respond to them appropriately. Living things respond to changes in temperature, humidity, light, presence or absence of certain chemicals. Response of organisms to these changes is crucial as it enables them to escape from harmful stimuli. Ability to detect changes in the environment also enables organisms to obtain resources in their environment. h) Movement Movement refers to change is position (displacement) of a part or parts of an organism. Movement in plants includes folding of leaves, closing of flowers and growing of shoots towards light. The change of position of an entire organism from one position to another is locomotion. Study questions a) Motor vehicles move, use energy and produce carbon dioxide and water. Similar characteristics occur in living organisms yet motor vehicles are not classified as living. List the other characteristics of living things that do NOT occur in motor vehicles. b) Give the name to the study of: Collection of Specimen We have defined biology as the study of living things. For effective study, a biologist may have to collect some living things or some parts of living things for observation and analysis. The living things or parts of living things that are used for biological study are called specimens. Biological studies always take place in laboratories. A laboratory is a building or a room that is designed and equipped for scientific studies. Collections of living things especially animals may not be very easy. Some of the animals are not easy to catch while some are quite dangerous. Knowledge on proper specimen collection and handling of is very important. We will discuss some of the apparatus used in specimen collection. a) Sweep net- This is used for catching flying insects. b) Fish net- This is used for trapping small fish and other small Water animals. c) Pooter- This is used for sucking small animals from rock surfaces or barks of trees. d) Bait trap- This is used for attracting and trapping small animals including rats. e) Pit fall trap- This is used for catching crawling animals. f) Pair of forceps- This is an apparatus used for picking up small crawling animals e.g. stinging insects. g) Specimen bottles- These are bottles used for keeping collected specimen. They are of different sizes depending on the size of the specimen being studied. h) Magnifying lens- This is used to enlarge small objects. A hand lens is a common magnifying lens used in the laboratory. The magnifying power of the hand lenses is always indicated on the lens e. g. X10, X5, X8. The magnifying power of a lens shows how many times the image will be enlarged compared to the object. How to use a magnifying lens To use a magnifying lens, place the object to be enlarged on the bench. Hold the magnifying lens on one hand and while closing one eye, move the lens towards the object until the image comes into clear focus. If a magnifying lens is used to make a drawing of a specimen, the magnification of the drawing will have no relation with the size of the drawing. The magnification of the drawing can be calculated using the formula shown below. Drawing magnification: Length of drawing divided by Length of the actual object The sign of “times” must come before the magnification value e. g. X10, X5, X15 etc. Precautions During Collection and Observation of Specimen While collecting specimen for observation, a biologist should play close attention to the following: Comparison Between Plants and Animals Plants Animals Chapter Two: Classification 1 Introduction In particular, animals and plants are all living things yet they differ in many aspects. Amongst animals and plants also there exist a lot of differences. There are millions of different plant and animal types exhibiting a range of differences. This created a need for a classification system of living things to make study of the living organisms easier. External features of plants used in classification External features of animals used in classification Importance of Classification Historical background of Classification a) Edible or non edible b) Flowering or non-flowering Taxonomic Units of Classification 1. Kingdom 2. Phylum (animals)/division (plants) 3. Class 4. Order 5. Family 6. Genus 7. Species All living organisms are classified into five major kingdoms: a) Kingdom Monera- This is composed of microscopic unicellular organisms mainly bacteria e.g amoeba. b) Kingdom Protoctista- This kingdom is comprised of members who are microscopic. Though, some are large enough to be seen with the naked eyes. Members of this kingdom include algae and protozoa. c) Kingdom Fungi- Members of this kingdom comprises the mushrooms, toadstools, moulds and yeast. d) Kingdom Plantae- This kingdom comprises the moss plant, ferns, maize plants, hibiscus, meru oak tree etc. e) Kingdom Animalia — Members of this kingdom include the tapeworms, hydra, fishes, human beings, lizards, earthworms etc. In hierarchy of classification, a kingdom is further divided into several phyla (plural of phylum) or divisions (in plants). Within the phyla or divisions, organisms are further sorted out into groups known as classes based on their similarities and mode of life. Each class is further subdivided into small groups called orders based on structural similarities. Orders subdivide into families which subdivide into genera (plural for genus). Genera are then subdivided into smaller units of classification called the species. Species is the smallest unit of classification whose members share many similarities and can freely interbreed to give rise to fertile or viable offspring. Members of a particular species can, however, exhibit various differences e. g. differences in skin colour or body forms. Within the species, organisms can further be classified based on the differences in colour or forms. In humans, this gives the races, in animals the term used is breed while in plants, variety is preferred. In bacteria, the term strain is used to describe the variant forms. Members of different but very closely related species can breed but the resulting offspring will be sterile (infertile). In particular, a mule is a sterile offspring between a horse and a donkey. Moving from kingdom to species, it is important to note that the number of organisms in each taxon decreases. The similarities, however, increase as one moves from kingdom to species. Scientific Naming of Living Organisms Rules of Binomial Nomenclature Binomial nomenclature requires that: a) The first part of the scientific name is that of the genus name which should begin with a capital letter. The second name is that of species. The species name should be written in small letters e. g. a) Maize- Zea mays b) Lion- Panthera leo c) Leopard- Panthera pardus d) Domestic dog- Canisfamiliaris e) Human being- Homo sapiens b) When printed in books and other printed works, the scientific names should be printed in italics. However, in handwritten manuscripts and typed works, the genus and species names should be lined separately. Printed work- Homo sapiens c) The specific name is frequently written with the name of the scientist who first adequately described and named the organism e. g. Balanus balanoides Linneaus. d) Scientists must give a latinised name for a newly described animal or plant species where a Latin name is missing e,g. Aloe kilzfiensis- A type of aloe found in kilifi Meladogyne kikuyuensis- A nematode found in kikuyu. Origin of scientific names Scientific names assigned to organisms can be: Chapter Three: The Cell Introduction The Light Microscope Magnification=Eyepiece magnification X Objective lens magnification = 10 X 8 =X80. Figure 1. The light microscope Handling and Care of the Microscope Part of the microscope: Limb function: supports the body tube and stage Base: function: provides firm and steady support to the microscope Body tube: function: holds the eyepiece and the revolving nose piece Coarse adjustment knob: function: raises or lowers the body tube through longer distances to bring the image into sharper focus Fine adjustment knob: function: raises or lowers the body tube through smaller distances to bring the image into sharper focus. it is mostly used with the high power objective lens Diaphragm: function: an aperture that regulates the amount of light passing through the condenser to illuminate the specimen Eye-piece: function: contains a lens which contributes to the magnification of the specimen under review Objective lens: function: bring image into focus and magnifies it. Mirror: function: reflects light through the condenser to the object on the stage Revolving nose piece: function: holds the objective lenses in place and enables the change from one objective lens to the other Condenser: function: concentrates light on the object on stage Stage: function: flat platform where specimen on the slide is placed.it has two clips to hold the slide into position The following rules should be observed when handling the microscope: > Always use both hands when carrying the microscope. One hand should hold the base to provide support while the other hand holds the limb. > Never place the microscope too close to the edge of the working bench or table. > Do not touch the mirror or the lenses with your fingers. > Dirty lenses should be cleaned using a special soft lens tissue paper or tissue paper moistened with ethanol. The other parts of the microscope may be cleaned using a microscope. > Do not wet any part of the microscope. > Make sure the low power objective lens clicks into position in line with the eye piece before and after use. > After use, always clean and store the microscope in a safe place, free from moisture and dust. How to use the Microscope Cell Structures as seen under the Light Microscope Figure 2 Plant and animal cells as seen under the light microscope The cell as seen under the Electron Microscope Figure 4. The plant cell Structure and Functions of the Cell Organelles Cell membrane Cytoplasm c) Mitochondrion > Mitochondria are self replicative that is they can divide to form new ones. Figure 5. The Mitochondrion (Animal) Figure 6, (generalize(lmage23 mitochondrion Structure) d) Endoplasmic Reticulum e) Ribosomes f) Lysosomes g)Golgi bodies/Golgi apparatus 1) They package and transport glycoproteins. 2) They are involved in secretion of synthesized proteins and carbohydrates. 3) They manufacture lysosomes. Note: Golgi bodies are abundant in cells that are active in secretion. For instance pancreatic cells which secrete enzymes and the nerve cells which secrete neurotransmitter substances. h)Centrioles i) Chloroplasts j) Vacuoles k) Cell wall 1. It gives plant cells their definite shape 2. It provides mechanical support and protection against mechanical injury. 3. The cell wall allows gases, water and other substances to pass through it. i) Nucleus Comparison between Plant Cells and Animal Cells While there exist many similarities between plant and animal cells, there are a number of differences. Plant cells Animal cells Estimation of Cell Size The light microscope can be used to estimate the size of a cell. Most cells have diameters smaller than a millimeter. Due to this, cell sizes are always measures in smaller units. These are micrometres and nanometers. These units of measurements are related as shown below. 1 millimeter (mm) = 1000 micrometres (pm). 1 micrometer (pm) = 1000 nanometres (nm). Procedure in cell size estimation cell diameter = diameter of the field of view in micrometers divided by number of cells. Cell Specialization. Tissues. Organs and Organ Systems Cell Specialization/Cell Differentiation Tissues a) Tissue types in animals 1. Epithelial tissue- This is a thin continuous layer of cells for lining and protection of internal and external surfaces. 2. Skeletal muscle- This is a bundle or sheets of elongated cells with fibres that can contract. Its contraction and relaxation brings about movement. 4. Blood tissue- This is a fluid containing red blood cells, white blood cells and platelets. The main functions of blood tissue are transportation of nutrients and gases as well as protection of the body against infections. 5. Connective tissue- This tissue consists of strong fibres that connects other tissues and organs thereby holding them in position. b)Tissue types in plants 1. Epidermal tissue- This is a single thin layer of cells covering the outer surfaces. It protects inner tissues of plants from mechanical damage and infection. 2. Palisade tissue- This is a group of cells rich in chloroplasts containing chlorophyll. It has a site for the absorption of light energy and manufacture of food by photosynthesis. 3. Parenchyma tissue- This tissue consists of special thin walled irregularly shaped cells. They form packaging and storage cells. 4.Conducting tissue/Vascular bundle- This tissue consists of xylem and phloem. Xylem conducts water and dissolved mineral salts in a plant while phloem conducts food substances in solution. Organs a) Heart- composed of connective, muscle, epithelial and blood tissues. b) Kidney- Composed of connective, epithelial and muscle tissues c) Brain- Composed of epithelial, connective tissues d) Lungs- Composed of epithelial, connective tissues. a) Roots- composed of epidermal, conducting and parenchyma tissues. b) Flowers- This is composed of epidermal, conducting tissues. c) Stem- Composed of conducting, parenchyma, and epidermal tissues and palisade tissues in some cases d) Leaves- Composed of palisade, conducting and epidermal tissues. Organ system This is a group of organs Whose functions are coordinated and synchronized to perform the same function. Organ systems are more pronounced in animals than in plants Organ systems in animals include a) Digestive system composed of organs such as oesophagus, stomach, intestines and their associated glands. b) Circulatory system composed of the heart, blood vessels (arteries, veins, capillaries). c) Excretory this is composed of kidney, liver, and blood vessels. d) Respiratory system composed of trachea, bronchus, and lungs. e) Reproductive system composed of the reproductive organs and associated glands. f) Nervous systems composed of the brain, spinal cord, eye, ear organs. Chapter Four: Cell Physiology Introduction a) Chloroplasts play a vital role in carbohydrate synthesis. b) Mitochondrion produces energy required to carry out life processes. c) Ribosomes manufacture of proteins. Structure of the membrane Properties of the cell membrane a) The cell membrane is semi permeable- The pores that occur on the cell membrane allows the passage of the small size molecules but does not allow the passage of the large sized molecules. Such a membrane is said to be selectively permeable or semi-permeable. In particular, when a cell is surrounded by a dilute sugar solution, the small sized water molecules will enter the cell but the larger sugar molecules will not pass through the cell membrane. In contrast, the cell wall is permeable as it allows both sugar and water molecules to pass through it; it has larger pores. This property of selectively permeability enables the cell membrane to select what enters and leaves the cell. b)The cell membrane is sensitive to changes in temperature and pH- Cell membranes are made up of protein. Proteins are adversely affected by extreme changes in temperature and pH. Changes in temperature and pH will alter the structure of the cell membrane thereby hindering the normal functioning of the cell membrane. High temperature denatures (destroys) the proteins thereby impairing the functions of the cell membrane. c)The cell membrane possesses electric charges- The cell membrane has both positive and negative charges. These charges affect the manner in which substances move in and out of the ells. The charges also enable the cell to detect changes in the environment. Physiological Processes of the Cell membrane a) Diffusion b) Osmosis c) Active transport Diffusion Demonstration of the process of diffusion using_potassium manganate (VII) Requirements: potassium manganate (VII) crystals, glass tubing, 100 cm3 beaker and water. Procedure a) Hold the glass tubing vertically in a beaker so that one end of the tubing rests on the bottom of the beaker. b) Cautiously and quickly drop a crystal of potassium manganate (VII) through the upper opening of the glass tubing. c) Close the upper hand of the glass tubing with the thumb. d) Half fill the beaker with water. e) Carefully withdraw vertically the glass tubing so that the crystal is left undisturbed at the bottom of the beaker. f) Record your observations for the first 15 minutes. g) Explain your observations. Expected observations Explanation The Role of Diffusion in Living Organisms a) In Plants Diffusion plays an important role in plants in that: b) In Animals In animals diffusion plays the following important roles These include the skin, gills, lungs, tracheal system and the cell membrane (in unicellular organisms). Gaseous exchange at these surfaces occurs through the process of diffusion. Factors affecting the rate of Diffusion a) Diffusion gradient b) Surface area to volume ratio c) Thickness of membranes and tissues d) Size of molecules e)Temperature Osmosis Demonstration of Osmosis Using a Visking Tubing Requirements 5OOcm3 beaker, visking tubing, a piece of thread, glass rod, concentrated sugar solution, 500 cm3 distilled Water. Procedure 1. Into the beaker, put 350 cm3 of the distilled water. 2. Dip the visking tubing in water to moisten it. Open the visking tubing and tie one end with the thread provided. 3. Half fill the visking tubing with the sugar solution provided and then tie the open end of the tubing. Ensure no sugar solution spills out of the tubing. 4. Immerse the visking tubing into the distilled water in the beaker and suspend it using the glass rod provided. 5. Leave the set up for about 30 minutes. 6. Record your observations. 7.Explain the observations made. Observations Explanation Even though there is a higher concentration of sugar molecules in the visking tubing, they were not able to diffuse out of the visking tubing due to their large molecular sizes. The visking tubing is semi permeable. Osmosis explained Osmotic pressure Osmotic potential Water Relations in Animals a) Red blood cell in hypotonic solution e. g. distilled water When a red blood cell is placed in a hypotonic solution, water will move into the cell through osmosis. The cell will swell and burst. Swelling of red blood cell when placed in a hypotonic solution is referred to as haemolysis. The cell is said to be haemolysed. b) Red blood cell in hypertonic solution Water will, therefore, be drawn out of the cell into the hypertonic solution. The cell will shrink and become small. The cell is said to be crenated. The process by which animal cells shrink and become smaller when placed in hypertonic solutions is referred to as crenation. c) Red blood cell in isotonic solution When placed in an isotonic solution, the cell remains unchanged. This is because there will be no net inflow or outflow of water between the cell and the solution. Note: This will prevent bursting or shrinking of the cells that would otherwise impair their physiology. Water Relations in Plants a) Plant cell in hvpotonic solution e. g. distilled water Wilting Role of Osmosis in Organisms As glucose accumulates in the guard cells, the osmotic pressure of the guard cells increase making them to draw water from adjacent cells through osmosis. When the guard cells become turgid, they bulge outwards leading to opening of the stomata. Opening of the stomata is crucial as it allows for gaseous exchange in plants. At night, there is no glucose synthesis. The glucose available in the guard cells is respired on leading to reduction of glucose and consequently reduction in osmotic pressure. The guard cells lose turgidity and close the stomata. The change in turgor pressure enables the special structures to rapidly close thereby trapping the insects. Factors Affecting the Rate of Osmosis Active Transport Some of these mineral salts cannot be absorbed by the plants through diffusion. A mechanism that would move them into the cells against the concentration gradient will be useful. Role of active transport in living organisms Factors affecting the rate of Active Transport a) Oxygen concentration Oxygen is required in respiration process that yields energy for active transport. Under low oxygen concentration, the rate of respiration will be low hence there will be production of little energy leading to low rate of active transport. Increase in oxygen concentration translates into a higher energy production leading to high rate of active transport. b) Change in pH Change in pH affects the respiratory process which is enzyme controlled. Respiratory enzymes require optimum pH for their efficient activity. Extreme pH conditions will increase lower the rate of active transport since the enzymes controlling respiration Will be denatured. c) Glucose concentration Glucose is the chief respiratory substrate. At low glucose concentration, there will b less production of energy leading to decreased rate of active transport. Rate of active transport increases with increase in glucose concentration due to increase in the rate of energy production. d ) Temperature Temperature affects the enzyme controlled respiration process. At low temperatures, the enzymes are inactive hence the rate of respiration will be low resulting into low rate of active transport since there will be less production of energy. An increase in temperature increases the rate of respiration since the enzymes become more activated. At temperatures beyond 40 degrees celcius, the enzymes become denatured, respiration stops and so does active transport. e) Presence of metabolic inhibitors e. g. cyanide. These are substances which act as metabolic poisons. They stop the rate of respiration leading to production of no energy. Active transport is, thus, stopped. Nutrition Plants And Animals Introduction a) The nutrients are required for growth and development of the living organisms. b) The nutrients are required for energy provision as they are broken down to release energy. c) They nutrients are also required for repair of worn out tissues d) Nutrients are required for synthesis of very vital macromolecules in the body such as hormones and enzymes. Modes of nutrition There are two main nutrition modes: a) Autotrophism mode of nutrition through which living organisms manufacture their own food from simple inorganic substances in the environment such as carbon (IV) oxide, water and mineral ions. Organisms that make their own food through this mode are autotrophs. b) Heterotrophism mode of nutrition in which living organisms depend on already manufactured food materials from other living organisms. Heterotrophs are the organisms that feed on already manufactured food materials. Autotrophism In this mode of nutrition, organisms manufacture their own food from readily available materials in the environment. These organisms use energy to combine carbon (IV) oxide, water and mineral salts in complex reactions to manufacture food substances. Depending on the source of energy used to manufacture the food, there are two types of autotrophism: a)Chemosynthesis This is the process whereby some organisms utilize energy derived from chemical reactions in their bodies to manufacture food from simple substances in the environment. This nutrition mode is common in non green plants and some bacteria which lack the sun trapping chlorophyll molecule. b) Photosynthesis Importance of Photosynthesis 1. Photosynthesis helps in regulation of carbon (IV) oxide and oxygen gases in the environment. 2. Photosynthesis enables autotrophs make their own food, thus, meet their nutritional requirements. 3. Photosynthesis converts sunlight energy into a form (chemical energy) that can be utilized by other organisms that are unable to manufacture their own food. External leaf structure This helps reduce the rate of water loss in such plants. However, the plants in areas of water abundance have broad leaves to enable them lose the excess Water. a) Cuticle Functions of the cuticle a) Being waterproof, it minimizes water loss from the leaf cells to the environment through transpiration and evaporation. b) It protects the inner leaf tissues from mechanical damage. c) It prevents entry of pathogenic microorganisms into the leaf. b) Epidermis Functions of the epidermis: a) It protects the leaf from mechanical damage. b) It also protects the leaf from entry of disease-causing microorganisms. c) It secretes the cuticle. Adaptations of the guard cells c) Palisade mesophyll d) Spongy mesophyll layer e) Vascular bundle/tissue Chloroplast Adaptations of the leaf to photosynthesis Raw materials for photosynthesis Conditions for photosynthesis Photosynthesis Process a)Light reaction/Light stage i) Photolysis of water Water-- Hydrogen atoms + Oxygen gas ii) Formation of adenosine triphosphate (ATP) ADP + P = ATP b) Dark reaction/Dark stage Testing for starch in a leaf Requirements Procedure Observations Factors affecting the rate of photosynthesis a) Carbon (IV) oxide concentration At this point, other factors such as light intensity, water and temperature become limiting factors. b)Light intensity c)Temperature Rate of photosynthesis is optimum at (35-40) °C. Beyond 40°C the rate of photosynthesis decreases and eventually stops since the enzymes become denatured. d) Water Experiment to investigate the gas produced during photosynthesis Requirements Procedure a) Set up the apparatus as shown in the figure below b) Place the set up in the sunlight to allow photosynthesis to take place. c) Leave the set up in the sun until sufficient gas has collected in the test tube. d) Test the gas collected with a glowing splint. e) Record your observations. Note: 1) Carbon (IV) oxide concentration: Carry out the experiment using different amounts of dissolved sodium hydrogen carbonate e. g 5 g, 10g, 15g, 20g and examine the rate at which the gas collects. 2) Light intensity: An artificial light source can be used. Illuminate the plant and vary the distance between the set up and the light source While recording the time it takes for the gas jar to fill or counting the number of bubbles peer unit time. 3) Temperature: carry out the experiment at varying temperatures and record the rate at which the gas collects. Experiments on factors necessary for photosynthesis Light Requirements Carbon (IV) oxide Requirements Procedure Chemicals Of Life Carbohydrates Monosaccharides Properties of Monosaccharides Note: Disaccharides Properties of Disaccharides Functions Polysaccharides Properties of polysaccharides Examples of polysaccharides a) Starch- Made by linking numerous glucose molecules. It is a form in which carbohydrates are stored in plants. b) Glycogen- Is a storage carbohydrate in liver and muscles of animals. It is broken down to glucose in animals when blood glucose falls. c) Cellulose- This is a structural polysaccharide in plants. It is a component of the cell wall d) Chitin- A structural carbohydrate found in cell wall of fungi and arthropod exoskeletons Functions of polysaccharides Lipids Properties of lipids Functions Proteins a) Essential- These are those amino acids that cannot be synthesized by the body systems hence have to be supplied in the diet. b) Non essential- These are amino acids that can be synthesized by the body mechanisms hence do not need to be supplied in the diet. a) First class proteins- Contain all essential amino acids b) Second class proteins- Proteins lack one or more essential amino acids Protein synthesis Properties of Proteins Functions of proteins a) They are structural compounds of the body. Cell membrane is protein in nature. Hair, nails and hooves are made up of protein keratin. b) Proteins are broken down to release energy during starvation when all carbohydrate and lipid reserves are depleted. c) Functional proteins play vital roles in metabolic regulation. Hormones are chemical messengers while enzymes regulate the speed of metabolic reactions. d) Proteins such as antibodies provide protection to the body against infections e) Some protein molecules are transport molecules. Haemoglobin molecule plays a crucial role in transportation of respiratory gases. f) Proteins play a vital role in blood clotting e. g. fibrinogen. g) Contractile proteins such as actin and myosin bring about movement. Enzymes What are enzymes? Types of enzymes a) Extracellular: Are produced within the cells but used outside the cells e. g. digestive enzymes. b) Intracellular: Are enzymes produced and used within the cells e. g. respiratory enzymes. Importance of Enzymes Enzyme nomenclature a).Trivial naming Examples b). Use of suffix -ase Substrates Processes/Reactions Hydrolysis .................... ..hydrolase Reduction ..................... ..reductase Oxidation ...................... ..oxidase Mechanism of action of Enzymes Properties of Enzymes Factors affecting enzyme activity a)Temperature b)pH c)Enzyme Specificity d)Substrate Concentration e) Enzyme Concentration f) Enzyme co-factors g) Co-enzymes Examples NAD- Nicotine Adenine Dinucleotide. FAD- Flavine Adenine Dinucleotide. NADP- Nicotine Adenine Dinucleotide Phosphate. h) Enzyme inhibitors 1. Competitive 2. Non- competitive Competitive inhibitors Non competitive inhibitors Examples of non competitive inhibitors Heavy metals (such as lead, mercury, silver), Cyanide, organophosphates such as malathion. Heterotrophism Modes of Heterotrophism a) Parasitism b) Symbiosis > Rhizobium and leguminous plants: rhizobium fixes nitrogen for the legume while the bacteria obtains manufactured food from the legumes. > Lichen: association of fungi (absorbing water and nutrients) and algae (manufacturing food for the association. > Catalase digesting bacteria and ruminants. Dentition Types of Dentition a) Incisors a. Canines b. Premolar and molar Classes of Holozoic Heterotrophs a) Herbivores: heterotrophs that exclusively feed on vegetation. b) Carnivores: heterotrophs exclusively feed on flesh. c) Omnivores: heterotrophs that feed on both flesh and vegetation. Dental Formula a) i-incisors. b) c-canines. c) pm-premolars. d) m-molars. a) Write down its dental formula. b) State its mode of feeding. c) Give a reason. Herbivores Carnivores Dental Diseases a) Dental Carries b) Periodontal Diseases Are of two types: a) Gingivitis- Characterized by reddening of gums, bleeding and pus in the gums. b) Pyorrhea- The teeth become loose due to infection of the fibres holding the teeth in the sockets. Dental Hygiene Digestion Digestion in the mouth a) Sublingual salivary gland; beneath the tongue b) Sub mandibular gland: under the jaw c) Parotid gland: Found in the cheeks in front of the ears. Digestion in the stomach a) Pepsinogen-This is activated to pepsin which breaks down proteins to peptides. b) Rennin- Digests caseinogens protein in milk to casein (curd). e) Hydrochloric acid- This: d) Mucus- Forms a protective barrier to the stomach wall against corrosion by the HC1. Mucus is secreted by goblet cells in the epithelial membrane of the alimentary canal. Duodenum a) Gall bladder in the liver- Secretes bile. b) Pancreas- Secrete hormones and digestive enzymes. i. Secretin hormone from the pancreas: Secretin stimulates secretion of pancreatic juice into the duodenum ii. Cholecystokinin from the duodenal wall: This stimulates secretion of bile from the gall bladder. a) Pancreatic amylase- This facilitates breakdown of the remaining starch into maltose b) Trypsin- Digests proteins into peptides. c) Pancreatic juice-Digests lipids into fatty acids and glycerol d) Sodium hydrogen carbonate- This: Provides alkaline medium for activity of the duodenum enzymes. i. Aid in emulsification (breakdown of fat molecules into tiny fat droplets to increase surface area for digestion). ii. The salts also provide a suitable alkaline medium for action of the duodenal enzymes. iii. In addition they neutralize the acidic chyme. Digestion in the ileum a) Maltase: speeds up breakdown of maltose to glucose b) Sucrase: speeds breakdown of sucrose to glucose and fructose c) Peptidase: speeds breakdown of peptides to amino acids d) Lipase: speeds breakdown of lipids to fatty acids and glycerol. e) Lactase: speeds breakdown of lactose to glucose and galactose. f) Polypeptidase: speeds breakdown of plypeptides into amino acids Note: The mucus secreted by the goblet cells lubricates food along the alimentary canal and also protect the canal from being digested by enzymes. At the end of digestion in the ileum, the resulting watery emulsion is called chyle; it contains soluble end products of digestion ready to be absorbed. Absorption a) It is long to provide a large surface area for absorption b) It has a narrow lumen so as to bring the digested food into close contact with the walls of the ileum for easier absorption c) It is highly coiled to slow down movement of food thus allowing more time for digestion and absorption of food. d) The inner surfaces have numerous villi and microvilli to increase surface area for absorption of end products of digestion. e) The epithelial lining is one cell thick to reduce the distance through which digested food diffuses. f) Has a dense network of blood capillaries into which digested food materials diffuse to increase transport and thus maintain a steep concentration gradient. g) Have lacteal vessels in the villi for absorption of fatty acids and glycerol. Egestion > This is the process through which the undigested and indigestible food substances are eliminated from the body. Caecum and Appendix a) Glucose b) Fatty acids and glycerol c) Amino acids Vitamins a) Fat soluble vitamins- They dissolve in fats and are often stored in the liver. Include Vitamins A, D, E, K. b) Water soluble vitamins- Dissolve in water. Include vitamins B1, B2, B5, B12 and C. Vitamin A (retinol) main food source Vitamin B1 (thiamine) main food source uses in the body deficiency disease symptoms Vitamine B2 (riboflavine and nicotinic acid) main food source uses in the body deficiency disease symptoms Vitamin B5 (pentathonic acid) main food source uses in the body deficiency disease symptoms main food source uses in the body deficiency disease symptoms Vitamin C (absorbic acid) main food source uses in the body deficiency disease symptoms Vitamin D (calciferol) main food source uses in the body deficiency disease symptoms Vitamin E (tosopherol) main food source uses in the body deficiency disease symptoms Vitamin K (quinone) main food source uses in the body deficiency disease symptoms Mineral salts a) Macro-nutrients: Nutrients required in large quantities. These include nitrogen, sulphur, phosphorous, calcium, sodium, iron and magnesium. b) Micro-nutrients: Nutrients required in small quantities. Include copper, manganese, boron, iodine and cobalt. Element: Nitrogen source function in the body deficiency symptoms - Element: Phosphorous source function in the body deficiency symptoms Element: Calcium source function in the body deficiency symptoms Element: Iodine source function in the body deficiency symptoms Element: Potassium source function in the body deficiency symptoms Element: Iron source function in the body deficiency symptoms Element: Sodium source function in the body Element: Chlorine source function in the body Element: Sulphur source function in the body Element: Magnesium source function in the body deficiency symptoms Roughage Importance of roughage a) It rubs against the walls of the alimentary canal stimulating secretion of digestive enzymes and mucus to lubricate the epithelial lining. b) Roughage enhance peristalsis since as they rub against the walls of the alimentary canal, they stimulate contraction and relaxation of the muscles. c) Roughage is an absorbent; it extracts water from the alimentary canal making the fecal matter bulky and moist hence can be easily propelled by peristaltic movements. This prevents constipation. Factors affecting energy requirements in humans Discuss how the following factors affect energy requirements in humans: Biology Notes FAQ FormPlease insert your question in the form below. Check and ensure that your question has not been asked and answered in the enquiries appearing beneath the form. Which cell organelle controls the activities of the entire cell?Nucleus. Known as the cell's “command center,” the nucleus is a large organelle that stores the cell's DNA (deoxyribonucleic acid). The nucleus controls all of the cell's activities, such as growth and metabolism, using the DNA's genetic information.
What is the name of the part of the cell that controls its activity quizlet?Nucleus works as the cell's control center, directing all of the cell's activities.
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