SS1 1ST TERM Biology Scheme of Work PDF

SCHEME OF WORK FOR FIRST TERM Week 1 – Biology as a Science Week 2 – Concept of living things Week 3-5 – Taxonomy and Cladistics Week 6 - Cell Structure and Organization of life Week 8 - The cell and its environment Week 9 - Properties a...

SCHEME OF WORK FOR FIRST TERM Week 1 – Biology as a Science Week 2 – Concept of living things Week 3-5 – Taxonomy and Cladistics Week 6 - Cell Structure and Organization of life Week 8 - The cell and its environment Week 9 - Properties and functions of the living cell (Nutrition) Week 10 - Nutrition (Enzymes) Week 11 - Plant Nutrition MEANING OF BIOLOGY The word biology is coined from two Greek words ‘bios’ (life) and ‘logos’ (to study). Hence Biology can be defined as the study of life i.e. living things (plants and animals). BRANCHES OF BIOLOGY Biology has three main branches which include: Botany- study of plants Zoology- study of animals Microbiology-study of microorganisms BIOLOGY-RELATED OCCUPATIONS These include, but not limited to, Medicine, Pharmacy, Biochemistry, Physiotherapy, Microbiology, Medical Laboratory Technology, Nursing & Midwifery etc. THE SCIENTIFIC PROCESS This is systematic approach to investigating inquiries/researches that arise from an observed natural phenomenon It involves the following steps: (1) Making observation (2) Identifying problems (3) Formulating hypothesis (4) Designing experiment  (5) Conducting experiment (6) Analyzing and drawing conclusions from experiment results (7) Sharing findings (Publication) (8) Acceptance of hypothesis (9) Theory (10) Law ✓ It should be noted that if the hypothesis is not accepted, it must be modified/reformulated and taken through all the necessary steps all over again. IMPORTANT TERMS HYPOTHESIS - A reasonable/tentative explanation for a particular observation or natural phenomenon. It is often called a guess statement. A hypothesis should be testable by experimentation. THEORY - This is a hypothesis that has been tested and found to be repeatedly correct within the limits of available evidence. LAW/PRINCIPLE - This is a theory that has been extensively tested and proven to be true. CONTROLLED AND REAL EXPERIMENTS Experiments are designed in two groups in order to allow for comparison and to also eliminate all bias. One group where all factors affecting the result of the experiment are kept constant is called Controlled experiment (or Control). The other group where all factors affecting the result of the experiment, except the factor being tested, are kept constant is called Variable (Real experiment). For example, to investigate the effect of one-sided light on shoots of plants, the control plant receives equal lighting on all its sides while the variable plant receives one-sided lighting. FORMAT FOR RECORDING EXPERIMENTS (1) AIM (2) MATERIALS (3) PROCEDURE (4) METHOD (5) OBSERVATION (6) CONCLUSION CHARACTERISTICS OF LIVING THINGS Life forms have the ability to carry out certain characteristics which can be represented with the acronyms: M-R-N-I-G-E-R-D-A-C or MRS GREN Each letter of the acronym represents a life characteristic as detailed below. (1) MOVEMENT - An action by an organism or part of an organism causing a change of position or place. Animals are able to exhibit locomotion (movement from place to place) while plants cannot exhibit locomotion but can exhibit tropism/tropic movement (bending of body parts in response to external stimuli). (2) RESPIRATION - The chemical reactions in cells that break down nutrient molecules (food) in living cells to release energy for metabolism. Respiration can also be defined as the act or process of breathing in and out in order to breakdown food particles to release energy. All living things respire. (3) NUTRITION - Taking in of materials for energy, growth and development. Plant require light, carbon dioxide and ions: animals need organic compounds and ions and usually need water.. Plants demonstrate autotrophic/holophytic nutrition (produce their food via photosynthesis). Animals demonstrate heterotrophic nutrition (depend on plants for food).the act of feeding. (4) IRRITABILITY/SENSITIVITY - The ability to detect or sense stimuli in the internal or external environment and to make appropriate responses. Animals demonstrate fast/quick response to stimuli while plants show slow response. (5) GROWTH - A permanent/irreversible increase in size and dry mass by an increase in cell number or cell size or both. Animals stop growing when fully matured (definite growth) while plants continue to grow through their lifetime (indefinite growth). Also animals grow all over their body (intercalary growth) while plants grow at the tips of their shoots and roots (apical growth). (6) EXCRETION - Removal from organisms of the waste products of metabolism (Chemical reactions in cells including respiration), toxic materials, and substances in excess of requirements. Animals can remove all their excretory products from their bodies while plants are able to remove gaseous excretory wastes but store their liquid and solid excretory products in body parts for future removal. (7) REPRODUCTION – as the processes that make more of the same kind of organism. (8) DEATH - Ceasation of life. All life forms must taste death and decay. (9) ADAPTATION - Ability of features that enable organisms to survive in their environments. Such adaptations could be structural or behavioural. (10) COMPETITION - Ability of organisms to struggles with other organisms for basic necessities of life such as space, food, shelter and mates.  DIFFERENCES BETWEEN PLANTS AND ANIMALS ANIMALS PLANTS - Move from place to place / Move Are fixed /do not move from place to with the whole body place and move only parts of the body - Heterotrophic mode of nutrition Autotrophic mode of nutrition - No chlorophyll / chloroplast Chlorophyll / Chloroplast present - No cell wall Has cell wall made of cellulose - Sense organs present Sense organs absent - Growth is intercalary Growth is apical - Response is fast/ short term Response very slow / long termed - Store carbohydrates as glycogen Store carbohydrate as starch Taxonomy & Cladistics KEY TERMS  TAXONOMY is the branch of biology that classifies all living things  CLASSIFICATION: means putting things into groups based on common features.  SPECIE: a group of organisms that can reproduce to produce fertile offspring  BINOMIAL SYSTEM: an internationally agreed system in which the scientific name of an organism is made up of two parts showing the genus and species  DNA: the chemical (genetic material) from which our chromosomes are made  -Classification is traditionally based on studies of morphology(form and shape of their bodies) and anatomy(details of dissected body structure).  -Nowadays, the sequences of bases in DNA and of amino acids in proteins are used as a more accurate means of classification.   -Therefore Organisms which share a more recent ancestor (are more closely related) have base sequences in DNA that are more similar than those that share only a distant ancestor  In this way, classification systems aim to reflect evolutionary relationships CLASSIFICATION OF LIVING THINGS The number and diversity of living organisms makes detailed studies of each organism a herculean task for Biologists. However, a method of sorting organisms into smaller groups each comprising of members with common features called classification/taxonomy was developed. A reliable and acceptable classification method comprising of seven hierarchies was introduced by a Swiss Scientist called Carl Von Linne (latinized to Carolus Linnaeus). The hierarchy of classification is as follows: KINGDOM (largest group of organisms) ↓ PHYLUM (Animals) * DIVISION (Plants) ↓ CLASS ↓ ORDER ↓ FAMILY ↓ GENUS ↓ SPECIES (smallest group of organisms) MNEMONIC: KING PHILLIP CAME OVER FOR GOOD SPAGHETTI From the hierarchy of classification, the species is thus the basic/smallest unit of classification. It contains members with the largest number of common features, and members are capable of BINOMIAL NOMENCLATURE Carolus Linnaeus also developed a system of naming organisms (called binomial nomenclature). Binomial nomenclature is a system of naming species in which the scientific name of an organism is made up of two parts: using names obtained from the last two hierarchies of classification i.e. Genus (Generic name) + Species (Specific name). In writing the names, the first name is the generic name and must start with a capital letter. The second name is the specific name which is written in small letters. The combination of the two names is called the scientific name and is usually written in italics or is underlined. Examples: (1) Man – Homo sapiens (2) Lion – Panthera leo (3) Cocoa – Theobroma cacao (4) Rice – Oryza sativa (5) Housefly – Musca domestica CLASSIFICATION OF HUMAN AND LION USING THE 7 HIERARCHIES HUMAN Kingdom – Animalia Phylum – Chordata Class – Mammalia Order – Primate Family – Homnidae Genus – Homo Species – sapiens LION Kingdom – Animalia Phylum – Chordata Class- Mammalia Order – Carnivora Family – Felidae Genus – Panthera Species – leo  THE FIVE KINGDOMS OF LIVING ORGANISMS (1) MONERA (2) PROTISTA (3) FUNGI (4) PLANTAE (5) ANIMALIA KINGDOM MONERA (Characteristics) Unicellular/single-celled Cells are prokaryotic (lack membrane-bound organelles) No definite nucleus Lack complex chromosomes May be motile/non motile Exhibit asexual mode of reproduction There are two phyla in this kingdom; (i) Schizophyta – Bacteria and (ii) Cyanophyta – Blue-green Algae (Nostoc) KINGDOM PROTISTA (PROTOCTISTS) (Characteristics) Unicellular/single-celled Cell are eukaryotic (contain membrane-bound organelles) Some members are autotrophs while others are heterotrophs Exhibit asexual mode of reproduction Members move either by cilia, flagella or by amoeboid motion Some members are motile while others are non-motile Kingdom Protista is divided into four phyla: (i) Protozoa – Paramecium, Plasmodium etc. (ii) Euglenophyta – Euglena (iii) Chrysophyta – Diatoms, golden-brown algae and yellow-green algae (iv) Pyrrophyta – Dinoflagellates. KINGDOM FUNGI-characteristics  Usually multicellular  Have nuclei  Have cell walls, not made of cellulose but chitin  Do not have chlorophyll  Feed by saprophytic or parasitic nutrition  Examples include mushroom, toadstool, rhizopus/mucor etc.  KINGDOM PLANTAE-characteristics  Multicellular  Cells have a nucleus, cell walls made of cellulose and often contain chloroplasts  Feed by photosynthesis  May have roots, stem and leaves  PLANT KINGDOM DIVISION 3 DIVISIONS IN KINGDOM PLANTAE 1. Thallophyta : Microscopic , non-vascular plants 2. Bryophyta : Macroscpic , non-vascular plants 3. Tracheophyta : include all vascular plants THALLOPHYTA-Characteristics Simple microscopic, aquatic plants Can be unicellular or multicellular Are filamentous with undifferentiated bodies. Can exhibit both sexual & asexual reproduction without specialized reproductive organs/cells Are mainly autotrophic. Examples: Chlamydomonas, Spirogyra and Volvox and other algae BRYOPHYTA-Characteristics Are complex, multicellular green plants that inhabit moist places. Their cells form tissues They lack true root, stem and leaves but possess structure similar to these.  They reproduce both sexually and asexually. They exhibit alternation of generation. Examples: Mosses, Liverworts. DIVISION TRACHEOPHYTA This group is subdivided into two: (1) Pteridophyta (2) Spermatophyta DIVISION TRACHEOPHYTA (Characteristics) Are multicellular, vascular green plants Are non-flowering, non-seed producing plants They have true roots, stem and leaves Majority of members are terrestrial while few are aquatic They reproduce sexually by spore formation They exhibit alternation of generation (Sporophyte is dominant) Common examples include ferns (dryopteris, felimas and water ferns). SUBDIVISION SPERMATOPHYTA (Characteristics) Are multicellular, seed-producing plants Are vascular plants with well-developed vascular tissues They have true roots, stem and leaves They reproduce sexually and do not rely on water for reproduction Are mainly terrestrial green plants There are two classes under this subdivision and they are: (a) Gymnosperms/Gymnospermae (b) Angiosperms/Angiospermae CLASS GYMNOSPERMAE (Characteristics) Bear naked seeds They are non-flowering but have flower-like structures called cones  Are vascular green plants They have true roots, stem and leaves They bear needle-like leaves They are often called conifers Common examples include pine, spruce, cypress, cycads and gingkos. CLASS ANGIOSPERMAE (Characteristics) Are the most complex green plant Are vascular green plant They bear complete, well developed flower Their seeds are enclosed in the fruit They exhibit specialized reproductive mechanisms such as pollination and fertilization Angiosperms are subdivided into two classes (a)monocotyledonaceae/monocotyledonous plants (b)dicotyledonaceae/dicotyledonous plants SUB-CLASS MONOCOTYLEDONACEAE (Characteristics) Bear seeds with only one cotyledon Their leaves have parallel venation They do not undergo secondary growth/thickening They have fibrous root system Their floral parts exist in groups of three or multiples of three Their vascular bundles are scattered in the stem Common examples include Cereals, Oil palm and grasses SUB CLASS DICOTYLEDONACEAE (Characteristics) Bear seeds with two cotyledons/leaves Their leaves have reticulate/network venation (net-veined) They do undergo secondary growth/thickening They have tap root system Their floral parts exist in groups of four or five Their vascular bundles are arranged in ring form, in the stem Common examples include Mango, Orange, Cowpea, Balsam plant, Water leaf etc. DIFFERENCES BETWEEN MONOCOTYLEDONOUS PLANT AND DICOTYLEDONOUS PLANT MONOCOTYLEDONOUS PLANT DICOTYLEDONOUS PLANTS - They possess only one seed leaf or They possess two seed leaves or cotyledon cotyledons - They have scattered vascular bundles Vascular bundles are arranged in a regular pattern - Floral parts exist in group of three or Floral parts exists in group of four or multiples of three five  - They possess parallel venation They possess net venation - They exhibits hypogeal germination They exhibits epigeal germination - They do not undergo secondary growth They undergo secondary growth KINGDOM ANIMALIA This consists of nine phyla: (1) Porifera (2) Coelenterata (3) Platyhelminthes (4) Nematoda (5) Annelida (6) Mollusca (7) Arthropoda (8) Echinodermata and (9) Chordata PHYLUM PORIFERA (Characteristics) Are simple aquatic invertebrates Are sessile often attached to rocks or shells Members live in colonies Are primitive multicellular animals They possess asymmetrical bodies (can be divided into several parts) They exist as colonies of cells without forming specialized tissues Common example is found among the sponges. PHYLUM COELENTERATA (Characteristics) Are multicellular aquatic organisms Have two layers in their bodies (Diploblastic/diploblasts) Their bodies have radial symmetry (i.e radially symmetrical) They have soft jelly-like bodies They have tentacles and stinging cells for capturing their preys They reproduce asexually by budding Common members include Hydra, Sea anemones and Coral PHYLUM PLATYHELMINTHES (Characteristics) Are multicellular flatworms They have three-layered bodies (triploblasts/triploblastic animals) Their bodies have bilateral symmetry (i.e bilaterally symmetrical) They are parasites of man and other animals Members are hermaphrodites and exhibit asexual reproduction They lack body cavity or lumen/coelom Their alimentary canals have one openings (incomplete alimentary canal) Common members include Tapeworm, Planarians, Liverfluke and bloodfluke.  PHYLUM NEMATODA (Characteristics) Possess round and cylindrical bodies They have a pseudo-coelom body cavity They have three-layered bodies (triploblasts/triploblastic animals) Their bodies are bilaterally symmetrical Some are hermaphrodites while others reproduce sexually Some members are parasites while others are free-living Common members include roundworms, hookworms, guineaworms, threadworms and filarial worms. PHYLUM ANELLIDA (Characteristics) Are metamerically segmented worms (i.e Body have internal and external body segments) They have long and cylindrical bodies They have true body cavity or coelom Some are aquatic while others are terrestrial (soil dwellers) Their alimentary canals have two openings (complete alimentary canal) Some members reproduce sexually while others are hermaphrodites They have three-layered bodies (triploblasts/triploblastic animals) Common members include earthworms, leeches and tubeworms. PHYLUM MOLLUSCA (Characteristics) Possess soft unsegmented bodies They bear tentacles on their heads They have muscular foot for crawling or burrowing A soft tissue called mantle covers their bodies Some members have calcareous shell Some are aquatic while others are terrestrial They use their eyes and tentacles for sensitivity Common members include mussels, periwinkles, snails, octopus, oysters and slugs PHYLUM ARTHROPODA The largest phylum in the kingdom Animalia. It comprises of four classes which include: (i) Crustacea – lobster, prawns, shrimps, crayfish and crab (ii) Insecta – grasshoppers, cockroach, butterfly, housefly (iii) arachnida – spiders, scorpions, mites and ticks (iv) myriapoda – centipedes and millipedes. PHYLUM ARTHROPODA (Characteristics) They have segmented bodies They have hard chitinous exoskeleton They have jointed appendages/legs They exhibit moulting/ecdysis (shed their skeleton at intervals for growth) Some are aquatic while others are terrestrial Their bodies may bear two or three segments They are bilaterally symmetrical They are triploblastic animals They may respire by means of gills, trachea, lung book or body surfaces FEATURES OF CRUSTACEANS, INSECTA ARACHNIDA FEATURES CRUSTACEA INSECTA ARACHNIDA Body 2 – cephalothorax & 3 – head, thorax & 2 – prosoma & divisions abdomen abdomen opisthosoma Wings Absent Present Absent A pair of stalked A pair of compound Eyes 8 simple eyes eyes eyes Antenna 2 pairs 1 pair None 4 pairs of jointed Walking legs 5 pairs of jointed legs 3 pairs of jointed legs legs Respiratory Gills Trachea Lung book organs  Draw the above diagrams PHYLUM ECHINODERMATA (Characteristics) They are radially symmetrical They have spiny skin They are triploblastic animals Their body is unsegmented, lacking head and brain They are marine animals They have tube feet for movement Common members include starfish, sea cucumbers, sea urchins, brittle star etc. PHYLUM CHORDATA Chordates are animals possessing: (a) Dorsal nerve (Spinal) cord (b) Notochord or backbone/vertebrae (c) Tail (at some stage of the life cycle) (d) Muscle Blocks (e) Gill Slits (at some stage of the life cycles). VERTEBRATES/VERTEBRATA – They are divided into five classes namely: (a) Pisces (b) Amphibia (c) Reptilia (d) Aves and (e) Mammalia SUB-PHYLUM VERTEBRATA (Characteristics) They possess endoskeleton made of cartilage and or bone They are bilaterally symmetrical Their body is divided into head, trunk and tail They have two pairs of limbs They have well developed central nervous system with brain and spinal cord They have well developed sense organs They have closed circulatory system having blood vessels and heart They are triploblastic animals They have efficient excretory organs They have skin which may be naked or covered with feathers, scales or hairs.  CLASS PISCES (Characteristics) They are aquatic animals Most members have scaly skins but few are without scales They possess fins for movement in water They are poikilothermic/cold blooded animals (their body temperature varies with that of their environment) They have gills for gaseous exchange (respiration) They have lateral line for sensitivity in water They have swim bladders for buoyancy ( for floating in water) They exhibit sexual reproduction, with external fertilization They are oviparous (they lay eggs) They have two-chambered heart They show parental care to their young ones Common members are categorized into two: (a) bony fish (with bony skeletons) – tilapia, carp, salmon, mackerel etc. (b) cartilaginous fish (cartilage skeletons) – dog fish, minnow, skates, ray fish, shark. Draw the above diagram CLASS AMPHIBIA (Characteristics) They live both in water and on land They are poikilothermic/cold blooded animals They bear two pairs of limbs (tetrapods) Their skin is naked or moist, glandular and without external scales They respire by means of gills, lungs, skin and mouth They exhibit sexual reproduction with external fertilization  Are herbivores when young but carnivores at adult stage Their skin bears poison gland for defence They have three-chambered heart Their tongue is extensible and retractable They lack parental care for their young ones Common examples include toads, frogs, newts and salamanders. Draw the above diagram CLASS REPTILIA (Characteristics) They are poikilothermic/cold blooded animals They have dry, scaly skin They bear two pairs of limbs except snakes Some are aquatic (crocodiles and turtles) while others are terrestrial (snakes and lizards) They respire by means of lungs They exhibit sexual reproduction with internal fertilization They have a partially formed four-chambered heart The females lay eggs (oviparous animals) They have same set of teeth (homodont dentition) They lack parental care for their young ones Common examples include lizards, wall geckos, tortoise, crocodiles, turtles, and chameleon.  Draw the above diagram CLASS AVES (Characteristics) Are homoiothermic (warm-blooded) animals Feathers cover their body and scales their legs They have two pairs of limbs, a pair of which are modified to form wings for flight Their mouth is modified into beaks (without teeth) They have rigid and hollow bones (light) for flight They have four-chambered heart They exhibit sexual reproduction with internal fertilization They have a fully formed four-chambered heart The females lay eggs (oviparous animals) They respire with their lungs They show parental care for their young ones Common examples include pigeons, domestic fowls, ducks, ostrich, hawks, sparrow, weaverbird, woodpeckers etc. Draw the above diagram CLASS MAMMALIA (Characteristics) Are homoiothermic (warm-blooded) animals They bear hairs on their bodies They have different types of teeth (heterodont dentition  They have diaphragm that separates their thorax from their abdomen They feed their young ones with milk from the mammary glands (on their skin) Are tetrapods They have glandular skins They show parental care for their young ones They exhibit sexual reproduction with internal fertilization They bear their young ones alive (viviparous animals) They have well developed brains They have a fully formed four-chambered heart They respire by means of their lung They are bilaterally symmetrical They have external ears called pinnae Common examples include rabbit, rat, bats, monkeys, goats, lions, elephants, man etc. Draw the above diagram EUGLENA AS A BORDERLINE ORGANISM Euglena viridis shares some animal and plant features, hence it is considered a borderline organism between the two kingdoms.  PLANT FEATURES OF EUGLENA (1) Possession of chloroplast (2) Possession of pyrenoids for starch storage (3) Possession of paramylum granules (stored starch) (4) Exhibits autotrophic (holophytic) nutrition. ANIMAL FEATURES OF EUGLENA (1) Possession of flagellum for movement (2) Possession of gullet for food passage and reservoir (3) Possession of contractile vacuole for osmoregulation (4) Possession of eye spot for photosensitivity (5) Possession of pellicle on the body (6) Possession of myonemes which aid movement (7) Exhibits holozoic nutrition in the absence of light. Draw the above diagram VIRUS Viruses have no nucleus , cytoplasm , cell organelles or cell membrane , though some forms have a membrane outside their protein coats. Virus particles , therefore , are not cells. Features of Virus as living things  Has protoplasm / Protein coat / Membrane  Contain DNA/ RNA/ Nucleic acid/ Genetic material  Features of Virus as Non-living things  Appear as crystal  Lack of organelles Examples include Influenza, Ebola, HIV and Corona Draw the above diagram DICHOTOMOUS KEYS Dichotomous keys are used to identify unfamiliar organisms. They simplify the process of identification. Each key is made up of pairs of contrasting features (dichotomous means two branches), starting with quite general characteristics and progressing to more specific ones. Note : Use past questions CELL Cells are the basic unit of life. The Cell Theory states that: 1) All organisms are made up of one or more cells and the products of those cells. 2) All cells carry out life activities (require energy, grow, have a limited size). 3) New cells arise only from other living cells by the process of cell division. CELL ORGANELLES Cell organelles are minute structures within the cell which carry out specialised functions. Almost all cells , except prokaryotes, have mitochondria and rough endoplasmic reticulum. The main cell organelles include the following : (1) PLASMA MEMBRANE/ CELL MEMBRANE Structure - a bi-lipid membranous layer composed of proteins and carbohydrates. It is fluid-like. Function - the cell membrane separates the cell from its external environment, and is selectively permeable (controls what gets in and out). It protects the cell and provides stability. Proteins are found embedded within the plasma membrane, with some extending all the way through in order to transport materials. Carbohydrates are attached to proteins and lipids on the outer lipid layer. (2) CYTOPLASM Structure - The jelly-like substance composed of mainly water and found between the cell membrane and nucleus. The cytoplasm makes up most of the "body" of a cell and is constantly streaming. Function - Organelles are found here and substances like salts may be dissolved in the cytoplasm. (3) NUCLEUS Structure - The largest organelle in the cell. It is dark and round, and is surrounded by a double membrane called the nuclear envelope/membrane. In spots the nuclear envelope fuses to form pores which are selectively permeable. The nucleus contains genetic information (DNA) on special strands called chromosomes. Function - The nucleus is the "control centre" of the cell, for cell metabolism and reproduction. (4) "ER" OR ENDOPLASMIC RETICULUM The Endoplasmic Reticulum is a network of membranous canals filled with fluid. They carry materials throughout the cell. The ER is the "transport system" of the cell. There are two types of ER: rough ER and smooth ER. Rough Endoplasmic Reticulum is lined with ribosomes and is rough in appearance and smooth endoplasmic reticulum contains no ribosomes and is smooth in appearance. (5) RIBOSOMES Ribosomes are small particles which are found individually in the cytoplasm and also line the membranes of the rough endoplasmic reticulum. Ribosomes produce protein. They could be thought of as "factories" in the cell. (6) GOLGI BODY/APPARATUS Golgi bodies are stacks of flattened membranous stacks (they look like pancakes!). The Golgi body temporarily stores protein which can then leave the cell via vesicles pinching off from the Golgi. (7) LYSOSOMES Lysosomes are small sac-like structures surrounded by a single membrane and containing strong digestive enzymes which when released can break down worn out organelles or food. The lysosome is also known as a suicide sac. (8) MITOCHONDRIA The mitochondria are round "tube-like" organelles that are surrounded by a double membrane, with the inner membrane being highly folded. The mitochondria are often referred to as the "powerhouse" of the cell. The mitochondria releases food energy from food molecules to be used by the cell. This process is called aerobic respiration. Cells with high rates of metabolism require large numbers of mitochondria to provide sufficient energy. (9) VACUOLES Vacuoles are fluid filled organelles enclosed by a membrane. They contain cell sap and usually large in plants. They are small or many where they are present in animal cells. They can store materials such as food, water, sugar, minerals and waste products. (10) CELL WALL The cell wall is a rigid organelle composed of cellulose and lying just outside the cell membrane. They are found in plant cells. The cell wall gives the plant cell its box-like shape. It also protects the cell. The cell wall contains pores which allow materials to pass to and from the cell membrane. (11) PLASTIDS Plastids are double membrane bound organelles. These are not present in animal cells.If they contain the green substance chlorophyll , the organelles are called chloroplasts. Colourless plastid usually contain starch, which is used as a food store. Note ; Draw the diagrams of plant animal cell in your note  SIMILARITIES IN PLANT AND ANIMAL CELL They both have; 1. Cytoplasm 2. Nucleus 3. Vacuole 4. Mitochondrion 5. Golgi body 6. Smooth /rough endoplasmic reticulum 7. Cell membrane/ Plasma membrane 8. Ribosomes DIFFERENCES BETWEEN A PLANT CELL AND AN ANIMAL CELL Plant cell Animal cell -Has cellulose cell wall /rigid Lacks cellulose cell wall -Has on large central vacuole Has numerous /small vacuoles -Has chloroplast Lacks chloroplast -Contains starch granules in its Contains glycogen granules in its cytoplasm cytoplasm -Usually large in size Usually small in size -Has a regular shape Has an irregular shape -Does not have lysosome Has lysosome -Does not have centrioles Has Centrioles -Cytoplasm less dense Cytoplasm more dense LEVELS OF ORGANIZATION OF LIFE Multicellular organisms have the following 5 levels of organization ranging from simplest to most complex: (1) CELL: Basic unit of structure and function in living things. May serve a specific function within the organism. Example – (Plant: phloem cells, xylem vessels); (Animal: blood cells, nerve cells, bone cells, etc). (2) TISSUE: Group of cells with similar structures , working together to perform a shared function. Example – (Plant: mesophyll layer in leaves, epidermal tissues, schlerenchyma tissue, xylem tissue, parenchyma tissue); (Animal: blood, bone, muscle, cartilage). Note – Humans have 4 basic tissues: connective, epithelial, muscle, and nerve. (3) ORGAN: Group of tissues , working together to perform specific functions. Example – (Plants: leaves, flower, root, stem, seed); (Animal: heart, brain, skin, etc). (4) ORGANSYSTEM: Group of organs with related functions , working together to perform body functions. Examples – (Plants: root system and shoot system); (Animals: circulatory system, nervous system, skeletal system, etc). NOTE: The Human body has 11 organ systems - circulatory, digestive, endocrine, excretory (urinary), immune (lymphatic), integumentary, muscular, nervous, reproductive, respiratory, and skeletal. (5) ORGANISM:An organism is formed by the organs and systems working together to produce an independent plant or animal. They are usually made up of organ systems, but an organism may be made up of only one cell such as bacteria or a Protist. Examples - bacteria, amoeba, mushroom, sunflower, human. The levels of organization in the correct order then are: Cells → Tissues → Organs → Organ Systems → Organisms STRUCTURE ANALYSIS: Comparing component parts with the larger system(s) they are a part of. Two human examples are: neurons (nerve cells) → nervous tissue → brain → central nervous system → human Bone cells (osteoblasts) → connective (bone) tissue → bones → skeletal system → vertebrate  SPECIALISED CELLS Specialized cells are those which have developed certain characteristics in order to perform particular functions. These differences are controlled by the gene in the nucleus. These cells are: 1. Ciliated cells: movement of mucus in the trachea and bronchi 2. Root hair cells: absorption of water and mineral ions from the soil 3. Xylem vessels: Conduction of water through the plant and support of the plant 4. Palisade mesophyll cells: for photosynthesis 5. Nerve cells: For conduction of impulses 6. Red blood cells: transport of oxygen 7. Sperm and egg cells: for reproduction  SIZE OF SPECIMEN Organelles in cells are too small to be measured in millimetre (mm). A smaller unit , called the micrometre is used. DIFFUSION Diffusion is defined as the net movement of particles from a region of higher concentration to a region of lower concentration down a concentration gradient, as a result of their random movement. The energy for diffusion comes from the kinetic energy of random movement of molecules and ions. Substances move into and out of cells by diffusion through the cell membrane.  FACTORS AFFECTING THE RATE OF DIFFUSION 1. State/nature of the diffusing substance: Molecules in gaseous state diffuse faster than those in liquid or solid states. Molecules in solid state diffuse slower than those of liquid. 2. Size of the molecules/particles: Smaller molecules will move or diffuse faster than large molecules. 3. Presence of concentration gradient: When the concentration of substance is high, the rate of movement of molecules will increase from the region of higher concentration to the region of lower concentration leading to an increase in the rate of diffusion. 4. Temperature: Increase in temperature increase the movement of molecules while decrease in temperature slows down the rate of diffusion. 5. Surface area: Large surface area will allow more molecules of substance to diffuse. IMPORTANCE OF DIFFUSION TO FLOWERING PLANTS 1. Movement of carbon dioxide through the stomata of the leaves during respiration. 2. Movement of carbon dioxide through the stomata of the leaves during photosynthesis. 3. Water vapor leaving the leaves during transpiration. 4. Movement of oxygen into the leaves through the stomata during respiration.  IMPORTANCE OF DIFFUSION TO ANIMALS 1. Gaseous exchange in organism e.g Amoeba. 2. Exchange of nutrient from maternal blood. 3. Diffusion of food from the placenta to the foetus. 4. Transfer of food and oxygen from the intestine into the villi from tissue fluid into the cell. OSMOSIS Osmosis is the net movement of water molecules from a region of higher water potential (dilute solution) to a region of lower water potential (concentrated solution) through a partially permeable membrane. Water diffuses through partially permeable membranes and moves in and out through the cell membrane by osmosis. Plants are supported by the pressure of water inside the cells pressing outwards on the cell wall.  CONDITIONS NECESSARY FOR OSMOSIS TO TAKE PLACE 1. Presence of a stronger solution e.g. sugar or salt solution. 2. Presence of a weaker solution e.g. distilled water. 3. Presence of a selectively or differentially permeable membrane. LIVING CELL AS OSMOMETER In osmosis, there are three solutions namely: 1. Hypotonic solution: is the weaker solution in which the solute concentration is lower. 2. Isotonic: when the solute concentration of the cell and its surrounding medium are the same, the solution is said to be isotonic. 3. Hypertonic: is the stronger solution in which the solute concentration is higher than the solvent. IMPORTANCE OF OSMOSIS TO LIVING ORGSNISMS IN PLANTS IN PLANTS 1. Movement of water or materials from one cell to another. 2. Absorption of water or mineral salts from the soil by the roots hairs. IN ANIMALS 1. Movement of water into the contractile vacuole in paramecium. PLASMOLYSIS Plasmolysis is defined as the outward movement or flow of water from living cells when they are placed in hypertonic solution. The process of plasmolysis involves the withdrawal of water from living cells up to the extent that it will result in the pulling away of the cytoplasm from the cell membrane or cell wall. As a result of this, the cytoplasm will shrink and the whole cell will collapse. HAEMOLYSIS Haemolysis is defined as the process by which red blood cell or corpuscles become split or burst when place in hypotonic solution. The red blood cell takes in water and become swollen and become swollen and may even burst. ANIMAL CELL AND OSMOSIS SIMILARITIES AND DIFFERENCES BETWEEN PLASMOLYSIS AND HAEMOLYSIS SIMILARITIES 1. They both occur in living cells 2. Both processes can lead to the death of the cells concerned 3. Cells expand initially as more water comes into the cells in both processes DIFFERENCES Plasmolysis Haemolysis It occurs in plant cells It occurs in red blood cells Plant cell shrinks Red blood cell burst It occurs in a hypertonic solution It occurs in hypotonic solution TURGIDITY Turgidity is defined as the condition in which cells absorb plenty of water up to a point where the cell is fully stretched. At this point, the cell is said to be turgid. Turgidity is useful to plants because it makes them firm, give supports to the stem, leaves , flower and guard cells. FLACCIDITY Flaccidity is defined as the condition in which plants lose water to their surroundings faster than they can absorb PLANT CELL AND OSMOSIS  ACTIVE TRANSPORT Active transport is the movement of particles through a cell membrane from a region of lower concentration to a region of higher concentration i.e against a concentration gradient using energy from respiration. Active transport works by using carrier proteins embedded in the cell membrane to pick up specific molecules and take them through the cell membrane against their concentration gradient. IMPORTANCE OF ACTIVE TRANSPORT IN ANIMALS 1. Absorption of glucose by the epithelial cells in the villi of small intestine is against the concentration gradient 2. Reabsorption of glucose into the blood stream in the cells of the kidney tubules IN PLANTS 1. Active transport allows root hairs of plant roots to take up salts from dilute solution against concentration gradient MODES OF NUTRITION Modes of nutrition can be grouped into two major classes referred to as autotrophic and heterotrophic nutrition AUTOTROPHIC NUTRITION It is the type of nutrition in which organisms are able to manufacture their food. Autotrophic nutrition is further divided into two groups. These are : i. Holophytic/Photosynthetic Nutrition : is the type of nutrition in which all green plants are able to manufacture their own food using water from the soil and carbondioxide from the atmosphere in the presence of sunlight ii. Chemosynthetic Nutrition : is the type of nutrition in which certain bacteria are able to synthesis organic compound from simple inorganic matter such as carbon dioxide , ammonia , water or nitrite to manufacture their food e.g Nitrosomonas , Nitrobacter, Nitrococcus , Sulphur bacteria e.t.c HETEROTROPHIC NUTRITION This is the type of nutrition in which organisms cannot manufacture their food but depend directly or indirectly on plants (autotrophs) for their own food. Heterotrophic nutrition is sub-divided into the following groups or types i. Holozoic Nutrition: It involves the feeding on other organisms or solid organic substances. The organisms ingest, digest and assimilate these food into their bodies e.g dog, cat , lion , man , pig e.t.c ii. Parasitic Nutrition: is the nutrition in which certain organisms feed on another organism in order to derive nourishment from it. E.g tapeworm , tick , flea, bug, plasmodium , roundworm , ustilago e.t.c iii. Saprophytic : is the mode of nutrition in which an organism obtain its food from non-living organic matter such as the  remains of plants and animals and their excretory products e.g mushroom , mould , rhizopus , mucor, toadstool e.t.c iv. Carnivorous / Insectivorous Plants : is the type of nutrition in which these plants in addition to photosynthesizing have a special devices for trapping and digesting insects and other small organism to balance a deficiency in nitrogen e.g sundew, venus flytrap , pitcher plants , bladderwort , butterwort e.t.c v. Symbiotic / Mutualistic : in symbiotic , two organisms live together for mutual benefits of each other e.g rhizobium and leguminous plants, fungi and algae in lichen , sea anemone and hermit crab , protozoa in the intestine of termite PHOTOSYNTHESIS Photosynthesis is the process by which green plants manufacture / synthesis their food / organic compounds from carbon dioxide and water in the presence of sunlight giving off oxygen as by product 6Co2 + 6H2O C6 H12 O6 + 6O2 Process / Mechanism of photosynthesis Photosynthesis takes place in two ways : i. Light reaction /stage ii. Dark reaction / stage I. Light reaction/stage: occurs during the day in the presence of sunlight. The light energy is captured by the chlorophyll and electrons are excited. The energy trapped is used to split water into hydrogen ion (H+) and hydroxyl ion (H-) and this is called (photolysis) 4H2O 4H+ + 4 (OH-) Water Hydrogen ion + Hydroxyl ion The hydroxyl ion (OH-) converted to water 4 (OH-) 2H2O + O2 Hydroxyl ion Water + Oxygen Major Products of Light – dependent Stage a. ATP ( Adenosine triphosphate) / Energy b. H+ ( Hydrogen ion ) c. OH- (Hydroxyl ion ) d. NADPH2 ( Reduced Nicotinamide Adenine Dinucleotide Phosphate ) e. O2 ( oxygen ) Importance of Product a. ATP to generate energy for the dark stage b. OH- to give water and oxygen c. 2H+ and NADP will give NADPH2 d. O2 given off into the atmosphere for organisms to use for respiration II. Dark reaction /stage : occurs at night or in the absence of light in which carbon dioxide is reduced by combining with hydrogen atoms provided by the enzyme NADP to form sugar. 4H+ + CO2 CH2O + H 2O Hydrogen ion Carbon dioxide Sugar Water Materials and Conditions Necessary for Photosynthesis The conditions necessary for photosynthesis are grouped into two namely : 1. External factor e.g a. Sunlight b. Carbon dioxide c. Temperature d. Water e. Pollution 2. Internal factors e.g a. Hormones b. Presence of chlorophyll / chloroplast c. Enzymes d. Number / State of Stomata LIMITING FACTORS A limiting factor is something present in the environment in short supply that it restricts life processes. The following are the limiting factors: a. Light intensity determines the energy available to photosynthesis b. Temperature influences the activity of enzymes in the chloroplasts c. Carbon dioxide , if the concentration increases there is more available to make carbohydrates Evidence of Photosynthesis in Plants The main product formed during photosynthesis is a simple sugar. The simple sugar formed is partly used by the plant and excess of it is converted to starch immediately for storage. USE AND STORAGE OF CARBOHYDRATES The carbohydrates produced by plants during photosynthesis can be used in the following ways: a. Converted into starch molecules which acts as an energy store b. Converted into cellulose to build cell walls c. Glucose can be used in respiration to provide energy d. Converted to sucrose for transport in phloem e. As nectar to attracts insects for pollination f. Converted into lipids (for energy source) and amino acids to make proteins Importance of Photosynthesis 1. Production of food 2. Purification of the atmosphere 3. Release of oxygen to the environment 4. It serves as building blocks for other substances MINERAL REQUIREMENT OF PLANTS Plant require mineral elements or elements obtained from the soil inform of solution for good growth and healthy development. These elements or plant nutrients are grouped into two classes. They are as follows : a. Macro –nutrients ( Major elements ) : are mineral elements required in large quantities for healthy growth in plants e.g Nitrogen , Phosphorus, Magnesium , Calcium , Oxygen , hydrogen e.t.c They are also called essential elements  b. Micro-Nutrients (Trace elements) : are mineral elements requied in small quantities for healthy growth of plants e.g Copper, Boron , Molybdenum, Cobalt, Chloride and Maganese. They are also called non-essential elements FUNCTIONS AND DEFICIENCY SYMPTOMS OF ELEMENTS Element Functions Deficiency Symptoms Nitrogen - Aids protein synthesis - Stunted growth - Formation of nucleic acid - Yellow leaves - Formation of chlorophyll - Small or reduced leaves - Constituent of all enzymes Phosphorus - Aids protein formation - Poor growth - Formation of co-enzymes - Leaves and stems turn reddish brown -Controls nuclear division - Poor root development - Its helps in root development resulting in logging - For fruit formation and maturity Potassium -It aids cell formation - Delayed growth - It aids synthesis of - Brown colour at margin carbohydrate of leaves - It activates various enzymes reaction - Cell membrane formation Calcium - Formation of cell walls - Weak slender Plants  - Activates certain enzymes - Poor root development -Neutralizes organic acids - Stunted growth - Normal growth of root tips LEAF STRUCTURE A leaf consists of a broad , flat part called Lamina which is joined to the rest of the plant by a leaf stalk or petiole. Running through the petiole are the vascular bundles,which forms the vein of the leaf. The top and bottom of the leaf are covered with a layer of closely fitting cells called the Epidermis.these cells do not contain chloroplasts and it protect the inner layers of cells in the leaf.The cells of the upper epidermis secrete a waxy substance called the cuticle which helps to stop water evaporation from the leaf. In the lower epidermis , there are small openings called stomata (singular ; stoma).Each stoma is surrounded by a pair of sausage-shaped guard cells which can open or close the hole.Guard cells contains chloroplasts. The middle layer of the cells are called mesophyll (meso means middle , and phyll means leaf ). These cells contain chloroplasts. The cells nearer to the surface are arranged like a fence and they form the palisade layer.The cell beneath them are rounder and arranged quite loosely, with large air spaces between them called spongy layer. Running through the mesophyll are the veins of vascular bundles.Each vein contains xylem vessels for carrying water and phloem tubes for carrying sucrose and other organic products of photosynthesis  LEAF ADAPTATIONS Leaves are adapted to obtain carbon dioxide, water and sunlight Adaptation Function Supported by stem and To expose as much of the leaf as possible to petiole sunlight and air Large surface area To expose as large an area as possible to the sunlight and air Thin To allow sunlight to penetrate to all cells ;to allow carbon dioxide to diffuse in and oxygen to diffuse out Stomata in the lower To allow carbon dioxide to diffuse in and epidermis oxygen to diffuse out Air spaces in spongy To allow carbon dioxide and oxygen to diffuse mesophyll to and from all cells No chloroplast in the To allow sunlight to penetrate to the epidermis mesophyll layer  Xylem vessels within short To supply water to the cells in the leaf , some distance of every mesophyll of which will be used in photosynthesis cell Phloem tubes within short To take away sucrose and other organic distance of every mesophyll products of photosynthesis cell Chloroplast inside palisade To expose as much chlorophyll as possible to cells often arranged sunlight broadside on Chlorophyll arranged on flat To expose as much chlorophyll as possible to membranes inside the sunlight chloroplast HUMAN NUTRITION AND DIET BIOLOGICAL MOLECULES Biological molecules are large molecules necessary for life ,that are built from smaller organic molecules. There are four major classes of biological macromolecules. These are ; 1. Carbohydrate 2. Lipids 3.Protein 4. Nucleic acid (DNA) CARBOHYDRATES  Carbohydrate is made up of carbon, hydrogen and oxygen  Types of Carbohydrates  1.Monosaccharide ; This sugar contains a single ring. They are the simplest sugar e.g glucose ,fructose and galactose. They have a general formula of C6 H12 O6 Sub-unit – Glucose GLUCOSE 2. Disaccharide (Reducing sugar) ; These contain two carbon rings in their molecules and are represented with the formula C12 H22 011 e.g (i) Maltose = glucose and glucose (ii) Sucrose = glucose and fructose (iii) Lactose = glucose and glactose 3. Polysaccharide ; are made of long chains of monomers (simple sugar) held together by chemical bond. The general formula is (C6 H10 O5)n e.g starch, cellulose , glycogen.Polysaccharide are not soluble in water IMPORTANCE OF CARBOHYDRATES  Provides energy FATS AND OILS Fats and oils are known as lipids.They contain high proportion of carbon, hydrogen but very little oxygen. Fats are solid.When fats are liquid they are known as oils. A molecule of fat or oil is made up of three molecules of fatty acid and one molecule of glycerol e.g olive oil, cold liver oil , waxes , melon oil, butter e.t.c Sub-unit- Fatty acid and glycerol IMPORTANCE OF FATS AND OIL 1. Formation of cell membrane and nuclear membrane 2. Provides more energy than carbohydrates 3. Serves as solvent for some vitamins 4. It protects vital organs 5. It smoothens the skin PROTEINS Protein is composed of carbon , hydrogen , oxygen , nitrogen and sometimes phosphorus and sulphur.Their molecules are made up of long chains of simpler chemicals called amino acids. There are about 20 different amino acids in animal protein and each type has its amino acid arranged in a special sequence e.g enzymes , muscle, haemoglobin, cell membranes, meat ,fish , beans ,groundnut ,soyabeans e.t.c Break down of protein during digestion takes place in the following stages Protein – Peptones – Polypeptides – Amino acid Sub unit – Amino acids Importance of protein 1. For body building 2. For growth 3. For repair of damaged tissues 4. For the supply of the necessary amino acids 5. For formation of hormones , enzymes, antibodies and forming of fibrinogen necessary for blood clotting  PROTEIN SHAPE There are thousands of different proteins in the human body and other organisms. Different sequence of amino acids give different shapes to protein molecules. For example: - Enzymes have an area in them known as the active site, This is important as this is the place where another molecule fits into the enzyme in order for a reaction to take place - If the shape of the active site does not match the shape of the molecule that fits into it, the reaction will not take place - Every enzyme has a different shaped active site - Antibodies are proteins produced by certain types of white blood cell to attach to antigens on the surface if the pathogens - The shape of the antibody must match the shape of the antigen so that it can attach to it and signal it for destruction - In this way every protein has a unique 3- D shaped that enables it to carry out its function STRUCTURE OF DNA  A DNA is made up of long chains of nucleotides , formed into two strands(double helix).  Each nucleotide is made up of ; 1) Deoxyribose – a 5-carbon sugar molecule 2) Phosphate group 3) An organic base which is either Adenine (A), Thymine (T) , Guanine (G) or Cytosine (C).Cross-links between the strands are formed by pair of bases  The bases always pair up in the same way : Adenine (A) with Thymine (T) and Guanine (G) with Cytosine (C) STRUCTURE OF DNA The size of the DNA molecules makes sure that A always pair with T and C with G. They are complementary strands. The double strands is twisted to make a helix. Scientist that are involved in the discovery of DNA ; 1. Crick and Watson 2. Rosalind Franklin MINERAL SALT Mineral salts are required for metabolic activities within the body. They are taken in minute quantity through the food we eat. Lack of these mineral salts will result in nutritional deficiency.Mineral salt include Calcium , Phosphorus , Magnesium , Potassium, Suphur , Sodium , Chlorine , Iron , Iodine , Msgaaese e.t.c  THE SOURCE, FUNCTION AND DEFICIENCY SYMPTOMS OF SOME MINERAL SALTS Mineral Sources Functions Deficiency Symptoms Calcium Milk, Cheese, Egg, - Bone and teeth formation -Rickets Fish and development - Tooth decay - For blood clotting - Osteomalacia - Normal functioning of heart , Nervous system and muscles Phosphorus Milk , Cheese , Egg , - For strong development of - Ricket Fish and Wheat teeth and bones - Tooth decay - Forms part of DNA and - Osteomalacia RNA - For respiration Iron Eggs , Liver , - Formation of haemoglobin - Anaemia kidneys , Beans , in red blood cells Vegetables Sodium and Table salt , Fish , - Transmission of nervous - Dehydration Chlorine Friuts impulses - Muscle cramp - Maintenance of osmotic balance of the cells Iodine Seafoods - Required by the thyroid - Goitre gland to make thyroxine VITAMINS Vitamins are inorganic compounds and they are biocatalyst i.e they promote chemical reactions in the body. Groups of vitamins : i. Fat soluble vitamins e.g Vitamins A,D,E and K Ii. Water soluble vitamins e.g Vitamins B- Complex and Vitamin C  Vitamins required by humans Vitamin Source Function Deficiency Symptoms Vitamin A Liver, eggs, fish , - For proper vision of the eye - Night blindness (Retinol ) milk , palm oil , - Required for normal growth - Skin becomes fresh vegetables flaky Vitamin B1 Yeast , unpolished - needed for synthesis of co- - Beriberi ( a (Thamine) rice , milk, beans , enzymes condition due to palmwine - involved in cellular loss of appetite , respiration weight, tiredness and paralysis) Vitamin B2 Yeast, Soyabeans , - Formation of co-enzymes - Cracking of the ( Riboflavin) egg , milk , green involved in cellular respiration skin around the vegetables corners of nose , mouth and eyes Vitamin B3 Yeast , beans , milk - needed for cellular - Pellagra ( Scally (Niacin ) , palmwine , yam , respiration pigmented skin , vegetables sore mouth and tongue , nervous disorder ) Vitamin B5 Yeast, egg , rice - Formation of co-enzymes - Disorder of ( Pantothenic ) bran involved in cellular respiration nervous system and gut Vitamin B6 Yeast , egg , cereal - Formation of enzymes - Anaemia ( Pyridoxine ) involved in synthesis of amino- - Diarrhoea acids Vitamin B12 Kidney, liver , fish , -Formation of red blood cells - Pernicious milk aneamia ( Cyanocobalamin) Vitamin C Fresh fruits e.g - aids wound healing - Scurvy (Ascorbic acid ) orange and green - helps to resist infection vegetables Vitamin D Fish , milk , egg, - needed for strong bone and - Ricket (Calciferol ) liver , formed in teeth formation and - softening of the skin by sunlight development bones in adult Vitamin E Green vegetables , - promotion of fertility in -Sterility and (tecopherol) egge , butter , liver animals premature abortion Vitamin K Fresh green - aids clotting of blood -Haemorrhages vegetables , liver i.e inability of blood to clot in time WATER Water is composed of two elements: Hydrogen and oxygen. IMPORTANCE OF WATER 1. Aids excretion 2. Acts as solvent for soluble substances in digestion 3. It is necessary for the digestion of food 4. It can be used for the maintenance of body temperature 5. Acts as a medium of transportation for nutrients 6. It helps to maintain the osmotic content of the body tissues ROUGHAGES Roughages consists of indigestible fibre materials derived from vegetables, fruit, carbohydrates and proteins IMPORTANCE OF ROUGHAGES 1. Stimulates bowel movement / peristalsis 2. Reduces blodd cholesterol / bowel cancer / Gall stones 3. They do not contribute to weight gain / High blood sugar 4. It releases glucose slowly 5. It prevents constipation / Add digestion FOOD TEST TEST FOR VITAMIN C BALANCED DIET Balanced diet is a diet containing all nutrients/components in correct proportions to maintain health and appropriate energy requirements.Balanced diet requirements varies according to age/sex/ lifestyle/pregnancy. IMPORTANCE OF BAKANCED DIET 1. It encourages growth and normal development of the body 2. It increases resistant to diseases 3. It provides energy required for normal activities 4. Balanced diet prevents malnutrition / deficiency disease Lack of some food substance e.g protein in a diet can cause a nutritional disease called kwashiorkor in children and Marasmus as a result of early weaning is characterized by: a. Retarded growth b. Loss of weight c. Diarrhoea d. Fatigue e. Muscle wasting f. Pale body g. Change in the colour of the hair , the hair becomes reddish brown  ENZYMES Enzymes are catalyst that speed up the rate of a chemical reaction without being changed or used up in the reaction. Enzymes are proteins. They are biological catalyst. Enzymes are necessary to all living organisms as they maintain reaction speeds of all metabolic reactions Characteristics of enzymes 1. All enzymes are proteins 2. Enzymes are influenced by temperature. 3. Enzymes are specific in action 4. Enzymes are influenced by pH 5. Their action is retarded by co-enzymes 6. Their action is reversible 7. They can be used again and again 8. Enzymes are required in small quantities ENZYME SPECIFICITY Enzymes are specific to one particular substrates as the active site(the part of the enzyme where the substrate fit and where the reaction takes place ) of the enzymes of the enzyme, where the substrate attaches, is a complementary shape to the substrate. This is because the enzyme is a protein and has a specific 3-d shape. This is called a lock and key hypothesis. When the substrate moves into the enzyme’s active site they become known as the enzyme – substrate complex. After the reaction has occurred, the products leave the enzyme’s active site as they no longer fit it and its free to take up another substrate.  EFFECTS OF TEMPERATURE ON ENZYMES The activity of an enzymes is influenced by temperature. The temperature at which the maximum rate of reaction of an enzyme occurs is called the optimum temperature. At first, increasing the temperature of an enzyme controlled reaction will increase the rate. This is because enzyme and substrate molecules have greater kinetic energy. They move around quickly and there are more chances of them colliding, the substrate fitting into the active site and a reaction taking place. At higher temperature the bonds holding the enzyme molecule together start to break down. This changes the shape of the active site, so the substrate no longer fits – this is known as denaturation and it can no longer catalyze the reaction. ENZYMES AND PH Enzymes are influenced by the pH of their surroundings. Many enzymes work best in neutral conditions (pH 7), but some work best in acidic conditions, such as the stomach (pH) and some in alkaline conditions , such as the duodenum (pH 8 or 9). If the pH is too high or too low, the bonds that hold the amino acid chain together to make the protein can be destroyed. This will change the shape of the active site, so the substrate can no longer fit into it, reducing the rate of activity. Moving too far away from the optimum pH will cause the enzyme to denature and activity will stop  RESPIRATION Respiration is a chemical process that involves the breakdown of nutrient molecules (glucose) to release energy stored within bonds of these molecules. Respiration is a series of reactions that are controlled by enzymes. Adenosine Triphosphate ( ATP) is the form in which energy is carried , stored and used by all living cells for the various metabolic processes. USE OF ENERGY IN THE BODY OF HUMANS Humans need energy to do the following things 1. Muscle contraction 2. Protein synthesis 3. Cell division (make new cells ) 4. Active transport 5. Growth 6. Passage of nerve impulses 7. Maintenance of a constant body temperature TYPES OF CELLULAR RESPIRATION 1.Aerobic Respiration : aerobic respiration can be defined as the chemical reactions in cells that use oxygen to breakdown nutrient molecules to release energy. C6 H12O6 + 6O2 6CO2 + 6H2O + ATP Glucose + oxygen Carbon dioxide + Water + Energy The breakdown of glucose in the body passes through several pathways before it can produce energy.These pathways are; a) Glycolysis b) Kreb’s cycle a) Glycolysis; is the process by which glucose is broken down into pyruvic acid.During glycolysis, no oxygen is required and it takes place in the cytoplasm of the cells.A net formation of 2ATPs and 2 reduced NAD are produced Stages of glycolysis i. Phosphorylation: glucose (6C) is phosphorylated by 2ATP to form fructose biphosphate (6C) Glucose + 2ATP Fructose biphosphate ii. Lysis : Fructose biphosphate (6C) splits into two molecules of triose phosphate (3C) Fructose biphosphate 2 Triose phosphate iii. Hydrogen is removed from each molecule of triose phosphate and transferred to coenzyme NAD to form 2 reduced NAD 4H + 2NAD 2NADH + 2H+ iv. Dephosphorylation : phosphate are transferred from the intermediate substrate molecules to form ATP through substrate linked phosphorylation 4Pi + 4ADP 4ATP v. Pyruvate is produced 2. Kreb’s cycle; the kreb’s cycle also known as Citric Acid Cycle or Tricarboxylic Acid Cycle (TAC) involves a series of cyclic reactions in which pyruvic acid under the influence of enzymes is oxidized to Acetyl – coenzyme A (AcetylCoA) releasing carbondioxide.AcetylCoA enters krebs cycle where series of changes take place and oxygen combines with hydrogen to form water.Kreb’s cycle takes place in the mitochondria and a total net of 36ATPs are produced. 2. Anaerobic Respiration :is defined as the chemical reactions in cells that break down nutrient molecules to release energy without using oxygen. During anaerobic respiration , glucose is broken down to yield carbondioxide, alcohol (ethanol) and energy. C6H12O6 2C2H5OH + 2CO2 + Energy Glucose Alcohol + Carbon dioxide + Energy In Yeast cells anaerobic respiration is called fermentation. Anaerobic respiration in animals takes place during vigorous exercise which results into the build up of lactic acid in the blood and muscles causing oxygen debt.Cells excrete the lactic acid into the blood which is taken to the liver cells where it is oxidized producing carbon dioxide and water, this is the reason we continue to breath after exercise and our heart rate remains high even after finishing exercise because there is need to transport the lactic acid from the muscles to liver.This is known as repaying oxygen debt  Differences between aerobic and anaerobic respiration Aerobic Respiration Anaerobic Respiration Takes place in the presence of Takes place in the absence of oxygen oxygen Takes place in mitochondria Takes place in cytoplasm Large amount of energy released Much less energy released from each from each molecule of glucose (38 molecule of glucose (2 ATP) ATP) Sugar is completely oxidized Sugar is incompletely oxidized No alcohol or lactic acid made Alcohol (In yeast and plants ) or Lactic acid (in animals ) is made Carbon dioxide and water are given Carbon dioxide and alcohol are given out out