JK-TK/Newdata huggingface dataset:
The energy needed comes from respiration. Certain proteins in the cell surface membrane responsible for this movement are referred to as carrier proteins or channel proteins. The shape of each type of carrier protein is specific to the type of substances conveyed through it. It has been shown that the substance fits into a particular slot on the protein molecule,
As the protein changes from one form of shape to another the substance is moved across and energy is expended. Factors Affecting Active Transport
Availability of oxygen
Energy needed for active transport is provided through respiration. An increase in the amount of oxygen results in a higher rate of respiration. If a cell is deprived of oxygen active transport stops . Temperature
Optimum temperature is required for respiration, hence for active transport. Very high temperatures denature respiratory enzymes. Very low temperatures inactivate enzymes too and active transport stops. Availability of carbohydrates
Carbohydrates are the main substrates for respiration. Increase in amount of carbohydrate results in more energy production during respiration and hence more active transport. Lack of carbohydrates causes active transport to stop. Metabolic poisons
Metabolic poisons e.g. cyanide inhibit respiration and stops active transport due to lack of energy. Role of Active Transport in Living Organisms
Processes requiring active transport:
Absorption of mineral salts from the soil into plant roots. Absorption of end products of digestion e.g. glucose and amino acids from the digestive tract into blood stream. Excretion of metabolic products e.g.urea from the cells. Re-absorption of useful substances and mineral salts back into blood capillaries from the kidney tubules. Sodium-pump mechanism in nerve cells. Re-absorption of useful materials from tissue fluid into the blood stream. Practical Activities
1.Experiment to Demonstrate Diffusion
Various coloured substances such as: dyes, plant extracts and chemicals like potassium pennanganate are used. Potassium manganate (VII) crystals are introduced to the bottom of a beaker filled with water using a glass tubing or drinking straw which is then removed. Observations are made and the disappearance of the crystals and subsequent uniform colouring of water noted. 2.Experiment to Demonstrate Osmosis Using a Visking Thbing
A strip of visking tubing 8-10 cm is cut and tied at one end using strong thread. About 2 ml of 25% sucrose solution is put inside and the other end tied with thread. The tubing is washed under running water and then blotted to dry.
2.Experiment to Demonstrate Osmosis Using a Visking Thbing
A strip of visking tubing 8-10 cm is cut and tied at one end using strong thread. About 2 ml of 25% sucrose solution is put inside and the other end tied with thread. The tubing is washed under running water and then blotted to dry. It is immersed in a beaker containing distilled water and left for at least one hour or overnight. It will then be observed that the visking tubing has greatly increased in size and has become firm. A control experiment can be set up using distilled water inside the visking tubing in place of sucrose solution. 3.Experiment to Show Osmosis using Living Tissue
Irish potato tubers are peeled and scooped out to make hollow space at the centre. Sucrose solution is placed inside the hollow, and the potato tuber placed in a beaker or petri-dish with distilled water. A conttrol is set using a boiled potato. Another one using distilled water inside hollow in place of sugar solution. The experiment is left for 3 hours to 24 hours. 4.Experiment to Demonstrate Turgor and Plasmolysis in Onion Epidermal Cells
Two strips of onion epidermis are obtained. One is placed on a slide with distilled water while the other is placed on a slide with 25% sucrose solution and a coverslip placed on top of each. The mounted epidermis is observed under low power microscope and then left for 30 minutes. After 30 minutes, observations are made again. The cells in distilled water have greatly enlarged. Cells in 25% sucrose have shrunk. Nutrition in Plants and Animals
Structure of the Leaf
External Structure
The external structure of the leaf consists of a leaf stalk or petiole and a broad leaf blade or lamina. The lamina has a main vein midrib from which smaller veins originate. The outline of the leaf is the margin and the tip forms the apex. Internal Structure of the Leaf
Epidermis
This is the outer layer of cells, normally one cell thick. It is found in both the upper and lower leaf surfaces. The cells are arranged end to end. The epidermis offers protection and maintains the shape of the leaf. It is covered by a layer of cuticle which reduces evaporation.
The cells are arranged end to end. The epidermis offers protection and maintains the shape of the leaf. It is covered by a layer of cuticle which reduces evaporation. Leaf Mesophyll
Consists of the palisade layer, next to upper epidermis, and the spongy layer next to the lower epidermis. Palisade Mesophyll Layer
The cells are elongated and arranged close to each other leaving narrow air spaces. These contain numerous chloroplasts and are the main photosynthetic cells. In most plants, the chloroplast are distributed fairly uniformly throughout the cytoplasm. In certain plants growing in shaded habitats in dim light, most chloroplasts migrate to the upper region of the palisade cells in order to maximise absorption of the limited light available. Spongy Mesophyll Layer
The cells are spherical in shape. They are loosely arranged, with large intercellular spaces between them. The spaces are airfilled and are linked to the stomatal pores. The spongy mesophyll cells have fewer chloroplasts than the palisade mesophyll cells. Vascular Bundles
These are made up of the xylem and the phloem tissues. The xylem transports water and mineral salts to the leaves. The phloem transports food manufactured in the leaf to the other parts of the plant and from storage organs to other parts. Adaptations of Leaf for Photosynthesis
Presence of veins with vascular bundles. Xylem vessels transport water for photosynthesis. Phloem transports manufactured food from leaves to other parts of the plant. Leaf lamina is thin to allow for penetration of light over short distance to reach photosynthetic cells. Broad lamina provides a large surface area for absorption of light and carbon (IV) oxide. Transparent cuticle and epidermal layer allow light to penetrate to mesophyll cells. Palisade cells are close to the upper epidermis for maximum light absorption. Presence of numerous chloroplasts in palisade mesophyll traps maximum light. Chloroplast contain chlorophyll that traps light energy. Spongy mesophyll layer has large intercellular air spaces allowing for gaseous exchange. Presence of stomata for efficient gaseous exchange (entry of carbon (IV) oxide into leaf and exit of oxygen). Mosaic arrangement of leaves to ensure no overlapping of leaves hence every leaf is exposed to light.
Spongy mesophyll layer has large intercellular air spaces allowing for gaseous exchange. Presence of stomata for efficient gaseous exchange (entry of carbon (IV) oxide into leaf and exit of oxygen). Mosaic arrangement of leaves to ensure no overlapping of leaves hence every leaf is exposed to light. Structure and Function of Chloroplasts
Chloroplasts are large organelles (5 um in diameter) found in the cytoplasm of green plant cells. They are visible under the light microscope. They contain chlorophyll, a green pigment and other carotenoids which are yellow, orange and red in colour. Certain plants have red or purple leaves due to abundance of these other pigments. Chlorophyll absorbs light energy and transforms it into chemical energy. The other pigments absorb light but only to pass it onto chlorophyll. The wall of chloroplast consists of an outer and an inner membrane. The two make up the chloroplast envelop. Inner membrane encloses a system of membranes called lamellae. At intervals, the membranes form stacks of fluid filed sacs known as grana (singular granum). Chloroplast and other pigments are attached to the grana. In between the lamellae is a gel-like stroma, that contains starch grains and lipid droplets. Enzymes for the dark stage reaction (light independent stage) are embedded in the stroma. Enzymes for the light dependent stage occur in the grana. Functions
• .Absorption of light by chlorophyll and other pigments. Light stage of photosynthesis occurs on the grana. (transformation of light energy to chemical energy.)
Carbon fixation to form carbohydrate takes place in the stroma which has enzymes for dark stage of photosynthesis. Process of Photosynthesis
Photosynthesis involves a series of chemical reactions, all of which take place inside chloroplasts. A general equation for photosynthesis is:
Carbon (IV)Oxide+Water light energy---Glucose+Oxygen
chlorophyll
6CO2+6H2O light C6H12O+6O2
chlorophyll
The reaction occurs in two main phases or stages. The initial state requires light and it is called the light dependent stage or simply light stage. It takes place on the lamellae surfaces. Its products are used in the dark stage. The dark stage does not require light although it occurs in the light and is called light independent stage.
It takes place on the lamellae surfaces. Its products are used in the dark stage. The dark stage does not require light although it occurs in the light and is called light independent stage. Light-Stage
Two reactions take place that produce raw materials for the dark stage:
Light energy splits the water molecules into hydrogen and oxygen. This process is called photolysis. The hydrogen is taken up by a hydrogen acceptor called Nicotinamide adenine dinucleotide phosphate (NADP) while oxygen is released as a by-product. 2H2O(l) light energy4H+O2
photolysis
Light energy strikes the chlorophyll molecules and sets in motion a series of reactions resulting in the production of a high energy molecule called adenosine triphophate (ATP). Dark Stage
This stage involves the fixation of carbon i.e. the reduction of carbon (IV) oxide by addition of hydrogen to form carbohydrate. It uses the products formed during the light stage. ATP
Carbon + Hydrogen --- Carbohydrates
(IV) oxide
The synthesis of carbohydrates does not take place in a simple straight line reaction as shown in the equation above. It involves a series of steps that constitute what is known as the Calvin cycle. Carbon (IV) oxide is taken up by a compound described as a carbon (IV) oxide acceptor. This is a 5-carbon compound known as ribulose biphosphate and a six carbon compound is formed which is unstable and splits into two three-carbon compounds. Hydrogen from the light reaction is added to the three carbon compound using energy (ATP) from the light reaction. The result is a three carbon (triose) sugar, (phosphoglycerate or PGA). This is the first product of photosynthesis. Glucose, other sugars as well as starch are made from condensation of the triose sugar molecules. The first product is a 3-carbon sugar which condenses to form glucose (6-C sugar). From glucose, sucrose and eventually starch is made. Sucrose is the form in which carbohydrate is transported from the leaves to other parts of the plant. Starch is the storage product. Other substances like oils and proteins are made from sugars. This involves incorporation of other elements e.g. nitrogen, phosphorus and sulphur. Factors Influencing Photosynthesis
Certain factors must be provided for before photosynthesis can take place.
This involves incorporation of other elements e.g. nitrogen, phosphorus and sulphur. Factors Influencing Photosynthesis
Certain factors must be provided for before photosynthesis can take place. The rate or amount of photosynthesis is also influenced by the quantity or quality of these same factors. Carbon(IV) Oxide Concentration
Carbon (IV) oxide is one of the raw materials for photosynthesis. No starch is formed when leaves are enclosed in an atmosphere without carbon (IV) oxide. The concentration of carbon (IV) oxide in the atmosphere remains fairly constant at about 0.03% by volume. However, it is possible to vary the carbon (IV) oxide concentration under experimental conditions. Increasing the carbon (IV) oxide concentration up to 0.1 % increases the rate of photosynthesis. Further increase reduces the rate. Light Intensity
Light supplies the energy for photosynthesis. Plants kept in the dark do not form starch. Generally, increase in light intensity up to a certain optimum, increases the rate of photosynthesis. The optimum depends on the habitat of the plant. Plants that grow in shady places have a lower optimum than those that grow in sunny places. Water
Water is necessary as a raw material for photosynthesis. The amount of water available greatly affects the rate of photosynthesis. The more water available, the more the photosynthetic rate, hence amount of food made. Effect of water on photosynthesis can only be inferred from the yield of crops. It is the main determinant of yield (limiting factor in the tropics). Temperature
The reactions involved in photosynthesis are catalysed by a series of enzymes. A suitable temperature is therefore necessary. The optimum temperature for photosynthesis in most plants is around 30"C. This depends on the natural habitat of the plant. Some plants in temperate regions have 20°C as their optimum while others in the tropics have 45°C as their optimum temperature. The rate of photosynthesis decreases with a decrease in temperature below the optimum. In most plants, photosynthesis stops when temperatures approach O°C although some arctic plant species can photosynthesise at -2°C or even -3°C. Likewise, increase in temperature above the optimum decreases the rate and finally the reactions stop at temperatures above 40°c due to enzyme denaturation. However, certain algae that live in hot springs e.g.
In most plants, photosynthesis stops when temperatures approach O°C although some arctic plant species can photosynthesise at -2°C or even -3°C. Likewise, increase in temperature above the optimum decreases the rate and finally the reactions stop at temperatures above 40°c due to enzyme denaturation. However, certain algae that live in hot springs e.g. Oscilatoria can photosynthesise at 75°C
Chlorophyll
Chlorophyll traps or harnesses the energy from light. Leaves without chlorophyll do not form starch. Chemical Compounds Which Constitute Living Organisms
All matter is made up of chemical elements, each of which exists in the form of smaller units called atoms. Some of the elements occur in large amounts in living things. These include carbon, oxygen, hydrogen, nitrogen, sulphur and phosphorus. Elements combine together to form compounds. Some of these compounds are organic. Organic compounds contain atoms of carbon combined with hydrogen and they are usually complex. Other compounds are inorganic. Most inorganic compounds do not contain carbon and hydrogen and they are usually less complex. Cells contain hundreds of different classes of organic compounds. However, there are four classes of organic compounds found in all cells. These are: carbohydrates, lipids, proteins and nucleic acids. Carbohydrates
Carbohydrates are compounds of carbon, hydrogen and oxygen. Hydrogen and oxygen occur in the ratio of 2: 1 as in water. Carbohydrates are classified into three main groups: monosaccharides, disaccharides and polysaccharides. Monosaccharides
These are simple sugars. The carbon atoms in these sugars form a chain to which hydrogen and oxygen atoms are attached. Monosaccharides are classified according to the number of carbon atoms they possess. The most common monosaccharides are:
Glucose - found free in fruits and vegetables. Fructose - found free in fruits and in bee honey. Galactose - found combined in milk sugar. The general formula for these monosaccharides is (CH2O)n where n is 6. They have the same number of carbon, hydrogen and oxygen molecules i.e. C6H12O6. Properties of Monosaccharides
They are soluble in water. They are crystallisable. They are sweet. The are all reducing sugars.
They are crystallisable. They are sweet. The are all reducing sugars. This is because they reduce blue copper (II) sulphate solution when heated to copper oxide which is red in colour and insoluble. Functions of Monosaccharides
They are oxidised in the cells to produce energy during respiration. Formation of important biological molecules e.g. deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). Some monosaccharides are important metabolic intermediates e.g. in photosynthesis and in respiration. Monosaccharides are the units from which other more complex sugars are formed through condensation. Disaccharides
These contain two monosaccharide units. The chemical process through which a large molecule (e.g. a disaccharide) is formed from smaller molecules is called condensation and it involves loss of water. Common examples of disaccharides include sucrose, maltose and lactose. Disaccharides are broken into their monosaccharide units by heating with dilute hydrochloric acid. This is known as hydrolysis and involves addition of water molecules. The same process takes place inside cells through enzymes. Sucrose+water_--hydrolysis-----------------glucose+fructose
Properties of Disaccharides
Sweet tasting. Soluble in water. Crystallisable. Maltose and lactose are reducing sugars while sucrose is non-reducing sugar. Sucrose is the form in which carbohydrate is transported in plants:
This is because it is soluble andjchernically stable. Sucrose is a storage carbohydrate in some plants e.g. sugar-cane and sugar-beet. Disaccharides are hydrolysed to produce monosaccharide units which are readily metabolised by cell to provide energy. Polysaccharides
If many monosaccharides are joined together through condensation, a polysaccharide is formed. Polysaccharides may consist of hundreds or even thousands of monosaccharide units. Examples of polysaccharides:
Starch - storage material in plants. Glycogen is a storage carbohydrate in animals like starch, but has longer chains. Inulin - a storage carbohydrate in some plants e.g. Dahlia. Cellulose - structural carbohydrate in plants. Chitin - forms exoskeleton in arthropods.
Dahlia. Cellulose - structural carbohydrate in plants. Chitin - forms exoskeleton in arthropods. Importance and Functions of Polysaccharides
They are storage carbohydrates - starch in plants glycogen in animals. They are hydrolysed to their contituent monosaccharide units and used for respiration. . They form structural material e.g. cellulose makes cell walls. Cellulose has wide commercial uses e.g. Fibre in cloth industry. Cellulose is used to make paper. Carbohydrates combine with other molecules to form important structural compounds in living organisms. Examples are:
Pectins: Combine with calcium ions to form calcium pectate. Chitin: Combine with (NH) group. Makes the exoskeleton of arthropods, and walls of fungi. Lipids
These are fats and oils. Fats are solid at room temperature while oils are liquid. They are made up of carbon, oxygen and hydrogen atoms. The structural units of lipids are fatty acids and glycerol. Fatty acids are made up of hydrocarbon chain molecules with a carboxyl group (-COOH) at one end. In the synthesis of a lipid, three fatty acid molecules combine with one glycerol molecule to form a triglyceride. Three molecules of water are lost in the process. This is a condensation reaction and water is given off. Lipids are hydrolysed e.g. during digestion to fatty acids and glycerol, water is added. condensation
-
Glycerol + 3 Fatty hydrolysis Lipid + Water acids
Properties
Fats are insoluble in water but dissolve in organic solvents e.g. in alcohols. They are chemically inactive, hence used as food storage compounds. Functions of Lipids
Structural materials - as structural material they make up the cell membrane. Source of energy - they are energy rich molecules. One molecule of lipid provides more energy than a carbohydrate molecule. Storage compound - They are stored as food reserves in plants. In animals e.g. mammals, all excess food taken is converted to fats which are stored in adipose tissue, and around internal organs such as the heart and kidneys. Insulation - They provide insulation in animals living in cold climates. A lot of fat is stored under the skin e.g. blubber in seals. Protection - Complex lipids e.g.
A lot of fat is stored under the skin e.g. blubber in seals. Protection - Complex lipids e.g. wax on leaf surfaces protects the plant against water-loss and overheating. Fats stored around some internal organs acts as shock absorbers, thus protecting the organs. Source of Metabolic Water -:-lipids when oxidised produce metabolic water which supplements water requirements in the body. Desert animals e.g. the camel accumulate large quantities of fat in the hump which when oxidised releases metabolic water. Proteins
Proteins are the most abundant organic compounds in cells and constitute 50% of total dry weight. Proteins are compounds which are made up of carbon, hydrogen, nitrogen, oxygen and sometimes sulphur and phosphorus. The structural units of proteins are amino acids. The nature of a protein is determined by the types of amino acids it is made of. There are about 20 common amino acids that make up proteins. Essential and Non-Essential Amino Acids
Essential amino acids are those which cannot be synthesised in the body of an organism and must therefore be provided in the diet. There are ten amino acids which are essential for humans. These are valine, leucine, phenylalanine, lysine, tryptophan, isoleucine, methionine, threonine, histidine and arginine. Non-essential amino acids are those which the body can synthesise and therefore need not be available in the diet. There are ten of them. These are glycine, alanine, glutamic acid, aspartic acid, serine, tyrosine, proline, glutamine, arginine and cysteine. Proteins are essential in the diet because they are not stored in the body. Excess amino acids are deaminated. Formation of Proteins
Proteins are made up of many amino acid units joined together through peptide bonds. When two amino acids are joined together a dipeptide is formed. The chemical process involved is called condensation and a molecule of water is eliminated . When many amino acids are joined together a polypeptide chain is formed. The nature of a particular protein depends on the types, number and sequence of amino acids from which it is made. Functions of Proteins
As structural materials proteins-
Are the basic building structures of protoplasms. Proteins in conjunction with lipid form the cell membrane.