AQA A Level Biology - 25 Mark Essays

The structure and function of carbohydrates

1) Monosaccharides: glucose, fructose, galactose

2) Disaccharides: condensation / hydrolysis / glycosidic bonds

3) Energy source (e.g. glucose, fructose, galactose released via respiration)

4) Respiration - use of carbs

5) Photosynthesis (formation of carbs/glucose)

6) Polysaccharides

7) Starch

8) Glycogen

9) Structural e.g. cellulose

10) Transport e.g. sucrose in phloem

11) Food store e.g. lactose in milk, starch in plants, glycogen in animals.

12) Glycoproteins, glycolipids

13) Homeostasis

14) DNA/RNA (pentose)

The importance of shapes fitting together in cells and organisms

1) Enzyme properties and digestion

2) Protein structure

3) Plasma membrane structure and cell transport

4) Antigens, antibodies, B cells & T cells

5) Vaccines

6) Structure of DNA

7) DNA Replication (not PCR)

8) Transcription & translation

9) Transcriptional factors, oestrogen, siRNA

10) Restriction enzymes

11) Haemoglobin

12) Action potentials & synaptic transmission

13) Muscle contraction

14) Control of blood glucose

concentration

Describe how the structures of different polymers are related to their functions

1) Biological molecules - carbs/proteins

2) release of energy from carbs

3) control of blood glucose

4) enzymes

5) DNA - structure

6) principles of immunology

7) transport of respiratory gases

The importance of hydrogen bonds in living organisms

1) passage of water through a plant - cohesion-tension mechanism

2) structure of proteins/starch/carbs

3) enzymes

4) DNA

5) gene technology

The importance of water in organisms

1) Properties of water

2) Condensation and hydrolysis

3) Photolysis

4) Digestion and absorption

5) Circulation

6) Tissue fluid and its circulation

7) Temperature control

8) Water potential and osmosis

9) Cell walls and support in plants

The different ways in which organisms use ATP

1) Muscle contraction

2) Active transport

3) Maintaining resting potential

4) Re-synthesis of acetylcholine and rhodopsin

5) Respiration

6) Light independent reactions of photosynthesis

7) Synthesis (anabolism)

8) Kidney function

9) Translocation

10) Nitrogen fixation

Inorganic ions include those of sodium, phosphorous and hydrogen. Describe how these and other inorganic ions are used in living organisms

1) nitrogen cycles

2) action potentials and nerve impulses

3) receptors convert stimuli into electrical impulses

4) respiration and ATP

5) photosynthesis uses energy to synthesis organic molecules from inorganic sources

6) DNA

7) fertilisers and plant growth

8) hydrogen ions affect pH

9) factors which affect enzyme action

10) digestion in stomach and small intestine

11) role of H+ in respiration and photosynthesis

The importance of responses to changes in the internal and external environment of an organism

1) Transport in and out of cells (of specific substances)

2) Immune response

3) Haemoglobin

4) Transpiration - gas exchange in plants

5) Behaviour

6) Adaptation and selection

7) Changes in populations - selection pressures

8) Responses to stimuli

9) Taxes and kineses

10) Receptors

11) Simple reflexes and neurones and synapses

12) Homeostasis - response to changes in internal environment

13) Feedback

14) Gene

The importance to humans of the control of growth, reproduction and development of organisms, including themselves

1) Pathogens (and invasion of human tissues)

2) Antibiotic resistance - control of bacterial growth

3) Immune response and vaccination

4) Human influence on biodiversity

5) Human populations

6) Humans and farming practices - and selective breeding

7) Use of fertilisers and pesticides

8) Succession - control of

9) Genetics - prediction of inherited conditions

10) Control of gene expression - stem cells

11) Regulation of gene expression - Mitosis and cancer

12) Gene cloning and transfer

13) Gene therapy

Movements inside cells

1. Plasma membranes and movement across

2. Protein synthesis

3. Movement through ER and Golgi

4. Cell division and chromosome

movement

5. Water movement in plants/xylem

6. Translocation

7. Neurones and synaptic vesicles

8. Actin and myosin

9. DNA replication and mutation

10. Electron transport chains

11. Molecular/atomic/ionic movement

The importance of proteins in the control of processes and responses in organisms

1) Enzymes as catalysts

2) Enyzmes control metabolic pathways

3) Proteins/enzymes in respiration

4) Proteins/enzymes in photosynthesis

5) Control of movement across Membranes

6) Immunology

7) Haemoglobin

8) DNA

9) Pacinian corpuscles - stretch mediated sodium channels

10) Action potentials

11) Synaptic transmission

12) Protein/peptide hormones

13) Enzymes in gene transcription and Translation

14) Transcription factors and receptors

15) Gene therapy involving proteins

The causes and importance of variation and diversity in organisms

1) Antigenic variation in pathogens - antigenic variation in e.g. viruses

2) Evolution of antibiotic-resistance in Bacteria

3) Genetic diversity because of differences in DNA - comparing base sequences

4) Genes, alleles and proteins produced

5) Comparing protein sequences

6) Selection - selective breeding, artificial selection

7) Founder effect/genetic bottlenecks

8) Species diversity and index of Diversity

9) Causes of variation in populations - Meiosis

10) Advantages of variation - disease, food chains, adaptation

11) Succession

12) Gene pools and evolution, natural Selection

13) Speciation, geographical isolation

14) Gene mutation

15) Differences in gene expression

16) Genetically modified organisms

17) Genetic fingerprinting

Cells and organisms carry out exchanges with their external environment to maintain their internal environment

1) Homeostasis (concept of)

2) Digestion and absorption

3) Cells

4) Lung function

5) Gas exchange

6) Passage of water through plant

7) Nutrient cycles

8) Response to stimuli

9) Neurones

10) Temperature control

11) tissue fluid and its formation

12) Control of blood glucose concentration

13) Negative feedback

14) Gene expression

How energy is transferred within and between organisms

1) Photosynthesis

2) Energy transfer through ecosystems

3) Food production

4) Digestion (as in fuel)

5) Absorption (by cells)

6) Mass transport

7) Respiration

8) ATP

9) Stimuli and responses

10) Muscle contraction

11) Nerve impulses

The membranes of different types of cells are involved in many different functions

1. Membrane function as selectively permeable barrier

1. Transport mechanisms across membranes

1. Absorption and co-transport of sodium ions and glucose

2. Photosynthesis, chloroplast, thylakoids

2. Respiration, mitochondrion and cristae

2. Protein secretion, RER, SER and Golgi

3. Surface receptors/antigen and immune response

3. Cell division

3. Vertical and horizontal transmission - membranes and bacteria

3. Pacinian corpuscle

4. Tropisms - movement of IAA

4. Nerve impulses/action potentials

4. Synaptic transmission

4. Muscle contraction, calcium ion movement/storage

4. Hormones - eg Blood glucose regulation - insulin and glucagon

4. Osmosis, including water movement in plants

There are many different types of relationships and interactions between organisms

1. Pathogens and effects on host 1. Cholera

1. TB

2. Taxonomy

2. Classification and evolution

2. Inheritance and evolution 2. Genetic code, universal

2. Behaviour

2. Populations and evolution, variation between individuals within a species

3. Relationships within ecosystems - eg predator/prey

3. Energy transfer in ecosystems

3. Nutrient cycles, the organisms involved

3. Succession, biodiversity, species and

individuals in a community

4. Human impacts on the environment and its effect on relationships between organisms - including farming

4. Gene technology and GMO and selective breeding

4. Antibiotic resistance

Using DNA in science and technology

1) Structure of DNA

2) Differences in DNA lead to genetic diversity

3) Comparison of DNA base sequences

4) DNA hybridisation

5) Plasmids

6) The use of recombinant DNA to produce transformed organisms that benefit humans

7) Cell cycle and treatment of cancer Gene therapy;

8) Medical diagnosis and the treatment of human disease;

9) The use of DNA probes to screen patients for clinically important genes.

A cycle is a biological pathway or process in which the end product of one cycle becomes the starting point for the next. Write an essay about cycles in biology

1) Nitrogen cycle

2) Enzyme action

3) Synthesis of ATP from ADP

4) Light-independent reaction

5) The Krebs cycle

6) The mechanism of breathing

7) The cardiac cycle

8) The cell cycle/mitosis

9) meiosis

10) Muscle contraction

The movement of substances within living organisms

1. Osmosis

2. Across cell membranes

3. Movement of water/mineral ions in

plants

4. Enzymes, kinetic energy and reactions

5. Gut and absorption

6. DNA Transcription and translation

7. Mitosis and Meiosis

8. Blood vessels and heart

9. Exchange in capillaries

10. Electron transport

11. Nerve impulses/action potential

12. Synapses

13. Muscle contraction

14. Alveolar gas exchange

15. Translocation

16. Photosynthesis

17. Kidneys

DNA and the transfer of information

1. Genes/how information is carried on

2. DNA

3. Replication of DNA

4. Cell division - Mitosis and meiosis

5. Transcription and translation

6. Mutation

7. Genetic engineering

8. Gene therapy

9. Genetically modified organisms

10. Variation (in populations)

11. Evolution

12. Inheritance

Why the offspring produced by the same parents are different in appearance

1) Genes incorporate coded information which influence phenotype

2) Gene mutation

3) Environment variation

4) Dietary requirements of insects

5) Meiosis

6) Principles of Mendelian inheritance

7) Polygenetic inheritance

The importance of nitrogen-containing substances in biological systems

1) proteins and enzymes

2) nucleic acids

3) DNA replication

4) ATP

5) ribosomes

6) cell division

7) transport across membranes

8) immune response

9) digestion and absorption

10) haemoglobin

11) genes and chromosomes

12) protein synthesis

13) mutation

14) investigating diversity

15) photosynthesis

16) respiration

17) nitrogen cycle

18) nervous coordination

19) muscles

20) control of blood glucose (and peptide/protein hormones)

21) inheritance

22) alteration of DNA sequences

23) regulation of transcription and translation

The importance of diffusion in organisms

1) water and inorganic ions

2) transport across membranes

3) gas exchange

4) digestion and absorption

5) mass transport in animals

6) mass transport in plants

7) DNA and protein synthesis

8) photosynthesis

9) respiration

10) nutrient cycles

11) plant responses to stimuli

12) receptors

13) nerve impulses

14) synaptic transmission

15) muscle contraction

16) control of blood glucose concentration

17) control of blood water potential