Essay Topics

Question 0

The causes of disease in humans

Answer 0

Pathogens:
Pathogens include bacteria, viruses and fungi
Pathogens cause disease by damaging cells and producing toxins Cholera bacteria produce toxins resulting in diarrhoea
Symptoms and transmission of pulmonary tuberculosis
Horizontal gene transmission and MRSA

Lifestyle:
Risk factors associated with cancer and coronary heart disease The effects of fibrosis, asthma and emphysema on lung function The biological basis of heart disease

Genetics:
Differences in bases may lead to non-functional enzymes Relationship between the cell cycle and cancer Proto-oncogenes and tumour suppressor genes
Gene mutations

Question 1

Carbon dioxide may affect organisms directly or indirectly. Describe and explain these effects.

Answer 1

Carbon dioxide affects the physiology of organisms:
Pulmonary ventilation and the mechanism of breathing Light-independent reaction of photosynthesis. Limiting factors Role of chemoreceptors in controlling heart rate

The direct effects of increasing carbon dioxide concentration:
Respiration, photosynthesis and human activity giving rise to short-term fluctuations and long-term change. Yield of crop plants
Carbon cycle

Indirect effects of increasing carbon dioxide concentration:
Role of carbon dioxide in producing global warming; Life cycles and number of insect pests;
Distribution of animals and plants;
Effect of temperature on enzymes;

Question 2

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.

Answer 2

Ecological cycles:
Nutrient cycles Carbon cycle Nitrogen cycle

Biochemical cycles:
Enzyme action
Synthesis of ATP from ADP Light-independent reaction The Krebs cycle

Physiological and genetic cycles:
The mechanism of breathing The cardiac cycle
The cell cycle
Muscle contraction Oestrous cycle

Question 3

The importance of shapes fitting together in cells and organisms

Answer 3

Proteins & Enzymes:
Enzyme properties and digestion
Protein structure
Plasma membrane structure and cell transport
Antigens, antibodies, B cells & T cells
Vaccines
Nucleic Acids

Structure of DNA:
DNA Replication (not PCR)
Transcription & translation
Transcriptional factors, oestrogen, siRNA
Restriction enzymes

Physiology:
Haemoglobin
Action potentials & synaptic transmission
Muscle contraction
Control of blood glucose concentration
Control of mammalian oestrous cycle

Question 4

How bacteria can affect the lives of humans and other organisms

Answer 4

Bacteria & Disease:
Pathogens
Lactose intolerance
Cholera
Tuberculosis
Resistance to antibiotics

Ecological Importance:
Carbon cycle
Nitrogen cycle
Eutrophication

Making Use of Bacteria:
Use of bacterial enzymes
e.g. restriction endonuclease, DNA polymerase for PCR
Use of bacterial plasmids
e.g. in vivo gene cloning, genetically-modified crops, gene therapy
Use of bacteria to produce useful chemicals

Question 5

There are many different types of relationships and interactions between organisms.

Answer 5

Pathogen and host:
Pathogens and effects on host
Cholera
TB

Evolution:
Taxonomy
Classification and evolution
Inheritance and evolution
Genetic code, universal
Behaviour
Populations and evolution, variation between individuals

Ecological:
Relationships within ecosystems – eg predator/prey
Energy transfer in ecosystems
Nutrient cycles, the organisms
involved
Succession, biodiversity, species and individuals in a
community

Human intervention in relationships:
Human impacts on the environment and its effect on
relationships between organisms – including farming
Gene technology and GMO and selective breeding
Antibiotic resistance

Question 6

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

Answer 6

Membranes – basic functions:
Membrane function as selectively permeable barrier
Transport mechanisms across membranes
Absorption and co-transport of sodium ions and glucose

Organelle membranes:
Photosynthesis, chloroplast, thylakoids
Respiration, mitochondrion and cristae
Protein secretion, RER, SER and Golgi

Cell surface membranes:
Surface receptors/antigen and immune response
Cell division
Vertical and horizontal transmission – membranes and bacteria

Processes – eg protein secretion, synaptic transmission, cell division:
Pacinian corpuscle
Tropisms – movement of IAA
Nerve impulses/action potentials
Synaptic transmission
Muscle contraction, calcium ion movement/storage
Hormones - eg Blood glucose regulation – insulin and
glucagon
Osmosis, including water movement in plants