IB Biology Paper 2

Outline the four levels of protein structure (4)

1) A unique number and sequence of amino acids in a polypeptide

2) regularly repeating structures and beta-pleated sheets

3) Specific 3-dimensional structure of a polypeptide

4) Links two or more polypeptides to form one protein

Describe the lock and key model of enzyme activity and how the induced fit model extends it (6)

- enzymes are globular proteins that act as catalysts

- specific enzyme only works with a specific substrate

- substrate has a complementary shape to the active site

- active site can be changed by pH/temp changes causing the substrate to stop binding to a.s.

- in the lock and key mechanism substrate induces the a.s. to change

- bonds are weakened in the substrate, making it easier to break

- diagram

Draw a simple labeled diagram to show the structure of a double stranded DNA molecule, comprising four nucleotides (6)

phosphate end labeled 5' and sugar end labeled 3' on both sides

label all bases with full names

Describe the use of DNA profiling in forensic investigations (4)

- cut DNA into fragments using restriction enzymes

- satellite DNA is used

- PCR is used to amplify satellite DNA

- DNA separated by gel electrophoresis

- patterns of bands compared to bands of suspected criminals

Using a named example, discuss the effects of genetically modifying an organism (8)

- genetic modification is the transfer of genes from one organism to another

- the universal genetic code allows genes to be transferred between species

- after being placed in host, host cells are cloned

- insulin

- using E Coli.

PROS

- lower cost

- E. Coli reproduce rapidly than farm animals

- virtually unlimited

- same insulin to the one produced in human pancreas

CONS

- bad reactions / may be allergic

- only available in countries with technology

Outline the effects of base substitution mutation in the case of sickle-cell anemia (5)

- DNA sequence changes from GAG to GTG to CAC

-this affects the process of translation

- instead of glutamic acid valine is produced

- changes the shape of haemoglobin

- changes the shape of the red blood cells

- oxygen is transported less efficiently to tissues

- causes muscular pain or severe anemia

- if heterozygous males can be protected against malaria

State the source, substrate, products and optimum pH conditions for one amylase (4)

pancreatic amylase's source is the pancreas, substrate is starch, product is maltose. optimum pH of 7.0-8.0/slightly basic

Outline the energy flow between trophic levels in a food chain (6)

- primary source of energy in a food chain is from sunlight

- captured by plants

- by means of photosynthesis, converted to chemical energy

- plants use this energy and some is lost through cell respiration

- consumers use energy for own requirements from organisms in previous trophic level

- not all material is assimilated or consumed

- only 10% of energy passed between trophic levels

- the loss of energy from organisms in form of heat

Explain the control of blood glucose concentrations in humans (8)

Draw a labeled diagram of the carbon cycle (6)

Outline the effect of carbon dioxide on the rate of photosynthesis and how this can be measured by oxygen release (4)

- no photosynthesis at very low co2 concentration

- positive correlation between increasing amount of co2 and photosynthetic rate

- at high concs the rate of photosynthesis reaches a plateau

- carbon dioxide used in light independent reactions and Calvin cycle

- oxygen is a product of light dependent reactions so it is a measure of the rate

Carbon dioxide is released during cell respiration. Explain anaerobic and aerobic respiration (8)

ANAEROBIC

- glucose is transformed into two molecules of pyruvate

- smaller amount of energy is released

- NAD is regenerated by reducing pyruvate

- pyruvate to co2 and ethanol in yeast

- pyruvate to lactic acid in humans

AEROBIC

- pyruvic acid is fully oxidised

- by link reaction and Krebs cycle

- reduced NADH passes electrons to electron transport chain

- creates a proton gradient

- this is used by ATP synthase

Distinguish between aerobic and anaerobic respiration (5)

- cell respiration is the controlled release of energy from organic compounds to form ATP

- A requires O2 AN doesn't

- A in cytoplasm and mitochondria AN in cytoplasm

- A high yield of ATP AN low yield of ATP

- A end products CO2 and H2O AN end products ethanol and CO2 for yeast and lactate for humans

- A involves Krebs cycle AN doesn't

Outline the metabolic processes during germination of a starchy seed (5)

- for the seed to become metabolically active it must absorb water

- gibberellin is produced in the embryo

- stimulates the production of amylase

- catalyses digestion of starch to maltose

- maltose converted to glucose for aerobic cell respiration to release energy

- can synthesise cellulose for cell growth

Explain the processes involved in the Krebs cycle (8)

- only occurs in aerobic conditions

- in the mitochondria

- during link reaction acetyl CoA releases an acetyl group

- NADH+H^+ and CO2 are formed at each decarboxylation

- the removal of CO2 involves oxidation

- and the release of energy

- acetyl group is joined to a 4-carbon molecule to form a 6-carbon molecule

- decarboxylation changes 6-carbon to 5-carbon molecule

- decarboxylation changes glutamate to a 4-carbon molecule

- this produces one molecule of ATP

- NADH and FADH2 and co2 are end-products of Krebs cycle

State four functions of proteins, giving a named example of each (4)

- movement myosin

-catalysis protease

- structure collagen

- transport hemoglobin

Explain the process of translation (8)

- ribosomes slides along the mRNA to the start codon

- translation takes place in 5' to 3' direction