Biology Notes

1. Explain the terms;

(a) Producer - Producer are plants which acts a the main part of a food chain, where it uses light energy(solar energy) to make food and and leads a food chain by providing food source for the Primary consumers.

(b) Consumers - Consume other organisms for food (eg: lobster eaten by stingray)

- The consumers in a food chain in an ecosystem are classified into primary consumers, secondary consumers and tertiary consumers.

- Primary consumers are herbivores and eat energy-rich plants and release energy during respiration.

- Secondary consumers are carnivores that eat herbivores. Like herbivores, carnivores cannot obtain energy directly from sunlight. Carnivores obtain their energy from energy-rich organic molecules in the herbivores.

- Tertiary consumers are carnivores that eat other carnivores and obtain their energy from energy-rich organic molecules in the carnivores.

2. Explain the reason for the reduction in energy in the proceeds between Gross primary production and Net primary production.

Gross primary production(GPP) is the rate at which green plants and other producers such as algae, some bacteria and cynobacteria convert light energy into chemical energy and store it in the organic food materials.

Net primary production(NPP) is the net gain in energy which remains as chemical energy in the organic materials (biomass).

Reason : GPP is used in respiration, providing energy for plant’s life processes.

Thus, NPP = GPP - Energy loss (through respiration)

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3. Protein structure of an enzyme.

- Enzymes are globular proteins

- Coiled and folded into globular shape

- Globular structure maintained by hydrogen, ionic, disulphide bonds, hydrophobic interactions and Wan der waals interactions.

- Tertiary structure determines its metabolic functions. Relatively unstable structure.

- Irregular amino acid sequence.

- Sequence is highly specific.

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4. Competitive Inhibitor and Non-competitive Inhibitor

Competitive Inhibitor

- Have a shape similar to the natural substrate.

- Can fit temporarily into the active site of the enzyme, prevents substrate binding to it.

- Compete for the same active site of the enzyme

- Entry (or Substrates) would depend on their relative concentration.

- Inhibition reversed by increasing the substrate concentration.

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Non-competitive Inhibitor

- Have no structural similarities to the natural substrate

- They do not attach to the active site but bind with the enzyme at another site (allotteric site)

- Its binding causes a change in the conformation of the enzyme molecule and its active site

- It does not compete with substrate for active site. Thus, substrate concentration does not affect the rate of reaction.

- The rate of reaction decreases as inhibitor concentration increases

- Example : Cyanide attach itself to copper prosthetic group of enzyme cytochrome oxidase and Inhibiting respiratory reactions.

5. Draw and label structure of cell membrane ( Singer’s model - Fluid-mosaic model)

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6. Roles of Structures of the cell membrane in the transportation of substances into the cell.

Membranes

- Selectively permeable and regulate the movement of substances in and out of the cell

- Small molecules such as oxygen, carbon dioxide and hydrophobic molecules diffuse through the phospholipid bilayers down a concentration gradient

- Protein channels and carriers move polar ions and molecules; for example glucose and amino acids across membranes by facilitated diffusion

- Protein pumps actively transport substances against a concentration gradient

7. Explain the following terms:

Biotic Potential : The maximum rate at which a population can increase under ideal conditions, that is when population is low and resources are plentiful.

Natality : The birth rate or natality refers to the number of young produced per female per unit of times.

Carrying Capacity : This is defined as the largest population that a particular habitat can support and sustain for an indefinite period, assuming there are no changes in the environment.

Mortality : Refers to the death of individuals in a population. The mortality rate is equivalent to the death rate in a human population.

8. State the problem faced by organisms that live together in the same habitat in the same habitat and compete for limited resources. Describe the species strategies that enables this organisms to survive.

There are two strategies known as r strategy and the K strategy where the symbols r and K represent two parameters for the sigmoid population growth curve. R is the increase rate(r) and K is the saturated population size or carrying capacity.

Species that use r strategy are opportunists, that is they have the ability to reproduce quickly under brief suitable conditions and can continue to live in intermittent periods of extreme or unsuitable conditions. Such species normally have the following characteristics :

(a) They live at the edge of the habitat so that they can disperse easily and colonise other habitats to survive.

(b) They are seldom involved in interspecies competition and do not have a strong ability to compete

(c) They experience a high death rate, and as such a large amount of energy is used to produce large numbers of progeny that can be widely dispersed.

Examples : weeds and insects

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Organisms that use the K strategy include terrestrial vertebrates and also species that have achieved saturation level and equilibrium in population size. These species normally have the following characteristics:

(a) They exhibit strong interspecies and intraspecies competition.

(b) They also exhibit high efficiency in the use of resources.

(c) They possess adaptation characteristics to continue survival in a crowded habitat.

(d) They have small numbers of progeny, but the progeny are large in size and nurtured well to ensure survival.

9. Explain using named example.

Mutualism – two species mutually benefits

An example of mutualism is the relationship between termites and the flagellate protozoans which live in their intestines.The termite cannot reproduce the enzyme needed to digest the cellulose consumed by them.However, the flagellate protozoans in their intestines can produce the enzyme needed to break down cellulose into simple sugars. Even though a part of these sugars is consumed by the protozoans for their metabolism the rest is sufficient for termite.For the protozoan, its lifestyle is so specialised that it is unable to live in any other environment except the intestines of termites.

Parasitism – Refers to a unidirectional relationship between two species. 1- benefit 2-harmed

Parasites lives inside or outside the body of another species, that is, the host, either temporarily or permanently.Example : The malaria parasite, Plasmodium and Phytophthora which attack and obtain food directly from the living cells of their respective hosts.

Flagellate Protozoans - Mutualistic Phythophthora - Parasitic

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10. Explain the action mechanisms of enzymes in the terms of specificity and activation energy.

– Enzymes are organic catalysts– There are active sites at the enzyme molecules where they help to reduce the activation energy needed

by the substrate molecules before the reaction occur.– Activation energy is the minimum energy required to initiate a chemical reaction. Activation energy is

used to break the bonds of the reagents so that the reaction can take place.– Enzymes has its own specific site which only can catalyse certain reactions

11. State three different types of cofactors and their functions.

Inorganic ions

– Need as enzyme activators.– Examples; Activity of salivary amylase is accelerated by presence of (Cl-) ions, Mg2+.

Prosthetic group

– Is a non-protein compound which is strongly bound to an enzyme and becomes a part of the enzyme structure that is not easily separated.

– Contains heavy metals like iron (Fe), molybdenum (Mo), copper (Cu), or manganese (Mn).– Enzymes that have prosthetic groups belong to class of proteins called conjugate proteins.

Coenzyme

– Is a non-protein compound that is loosely bound to an enzyme.– It can detach itself from one enzyme to participate in other enzyme reactions.– This means same coenzyme can take part in two different enzymic reactions– It can receive and release hydrogen atoms, it can also act as a hydrogen carrier from one reaction to

another.– Examples: Nicotinamide adenine dinucleotide (NAD), Biotin, Coenzyme A (CoA).

12. Describe the structures of a named biosensor and state the advantages of using a biosensor.

A common biosensor is a probe that integrates a biological material for example, an enzyme, an antibody or a cell and, often, also with an electronic component. It is used to detect specific chemicals accurately and rapidly.

This type of biosensor has five components,(a) A biological sensing material(b) A transducer(c) An amplifier(d) A microelectronics and data processor(e) A signal generator

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Advantages

(a) Accurate and quick diagnosis

(b) Safe to use and cost can be reduced in mass production

(c) Biosensors are very sensitive and can detect very low concentrations of specific chemicals.

(d) Helps in early detection of medical cases, so that treatment can begin early. Important in preventive medicine, leading to faster and better treatment for diabetic patients.

13. Describe the replication of DNA

– Enzyme helicase catalyses the unwinding of DNA double helix

– The hydrogen bonds between the bases in DNA are broken

– The two DNA strands open and act as template

– Synthesis of new DNA strand occurs in the direction 5' to 3'

– The free nucleotides in the nucleoplasm pair up with the exposed complementary bases in the parental DNA strand. Base adenine (A) pairs with thymine (T), and cytosine (C) with guanine (G).

– The nucleotides are then linked together by DNA polymerase to form the DNA leading strand

– In the synthesis of the lagging strand, short Okazaki fragments are first synthesised in the 5' ---> 3' direction.

– The enzyme DNA ligase catalyses the formation of linkages between the Okazaki fragments to form a DNA lagging strand

– Replication of DNA is semi-conservative. Two DNA molecules are produced from a single parental DNA molecule. Each DNA double helix contains one new DNA strand and one parental strand.

14. Describe how deforestation may affect the environment.

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Forests, trees and plants are like carbon "sinks" that absorb carbon dioxide from the atmosphere and turn it into oxygen. We need large expanses of forest to remove carbon dioxide which is a greenhouse gas contributing to global warming.

Deforestation means cutting down trees which directly affects the environment so that there will be less pure air or oxygen to breath as trees serve to clean air by taking in CO2 and releasing O2.

The natural habitat for wild animals and birds will be destroyed which will lead to their extinction and the consequently disturbance to the food chain.

Deforestation will also increase floods, drought and climate change and will also cause soil erosion because trees help in binding soil with their roots.

The effect of deforestation on environment can cause floods, fertility of the soil can be gone , there will be soil erosion, water cycle can be disturbed which results in drought and there will be disturbance in nature and there cannot be any shelter for any organisms.

Deforestation has much economic importance but the bad effect is that 1.It causes erosion.2.It leads to loss or extinction of wild life.3.It exposes the bush to burning.4.It destroys the soil structure.5.It contributes to global warming by removing the carbon sinks (trees) that absorb CO2 from the atmosphere.

Deforestation can lead to soil erosion, desertification, and in extreme cases the extinction of plants and animals.Every tree is home to at least 100 animals.

15. Describe the features which are characteristics of a fish (Class Pisces) and five features which are characteristics of all chordates.

Bony Fish– Has a skeleton consisting of bone tissue– It has a vertebral column consisting of a series of similar vertebrae. Abit of notochord still exists in the adult .– The body is protected and covered by by overlapping bony dermal scales.– Most species have mid-fins and paired fins. The rays in the fins consists of bone tissue and cartilaginous tissue. – In the anterior region, part of the body is modified to form operculum.

Features of Chordates

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(a) Notochord

It is a dorsal rod consisting of cartilaginous substance. It is replaced by the vertebral column in vertebrates during development of the embryo

(b) Pharyngeal gill slits

Primitive chordates have gill slits for food filtration. In vertebrates, the gill slits are modified for other functions. In fishes, the gill slits are modified for respiration. In reptiles, birds and mammals, the gill slits are only represented by the Eustachian Tube.

(c) Closed blood circulatory system

Blood flows in the blood vessels. The main ventral blood vessel carries blood to the hart and the main dorsal blood vessel carries blood from the heart to all parts of the body.

(d) Position of the tail

The tail is found just after the anus. In aquatic chordates, the tail is at the posterior end of the digestive canal. It acts as an accessory structure to assist in locomotion. In fishes, the structure is modifies to form caudal fin.

(e) Myotomes or segmental muscle blocks

The muscular tissue is arranged in blocks. This pattern is generally observed in the chordates at the embryo stage. However, it is maintained even in the adults for the same chordates. Examples are amphioxus and fish.

16. Lipid molecule = Refer to text book page 15.

17. Cellulose

– Cellulose is the structural polysaccharide in plant cell walls.– Cellulose is composed of long unbranched chains of up to 10 000 B-glucose units linked B-1,4 glycosidic bonds.– Each B-glucose unit is related to the next by a rotation of 180° with hydroxyl groups projecting outwards on either side of the chain.– Cellulose chains run parallel to one another. This allows the linear chains to lie close together.– Many hydrogen bonds are formed between the hydroxyl groups on adjacent chains.– The chains group together to form microfibrils which are arranged in larger bundles to form macrofibrils– The fibrils give plant cells their high tensile strength and rigidity– The layers of fibrils are permeable to water and solute.

18. DNA and RNA

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RNA (ribonucleic acid) DNA (deoxyribonucleic acid)

Consists of a single polynucleotide strand Consists of two polynucleotide strands which coil which coil around each other two form a double helix.The two polynucleotide strands are arranged in an anti-parallel direction

RNA molecule is shorter DNA molecule is much longer

Contains pentose sugar, ribose Contains pentose sugar, deoxyribose

The nitrogenous bases are adenine, uracil, cytosine and guanine, (The base thymine is replaced by uracil)

The bases are adenine, thymine, cytosine and guanine

Present in the nucleus and the cytoplasm Mainly present in the chromosomes in the nucleus. Small amount is present in the mitochondria and chloroplasts

There are three main types of RNAmessenger RNA – mRNAtransfer RNA – tRNA ribosomal RNA – rRNA

Only one type of DNA

19. Fibrous and globular proteins - refer to page 27 in text book

20. Technique of cell fractionation – Refer page 110&111

21. Comparasion between electron microscopy and light microscopy – Refer page 114 in text book

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