Paper 3 Cram

Question 1

How does gas exchange occur in fish?

Answer 1

Ventilation begins with the fish opening its mouth followed by lowering the floor of buccal cavity, thus enabling water to flow into it. Afterwards, fish closes its mouth, causing the buccal cavity floor to raise, thus increasing the pressure. The water is forced over the gill filaments by the difference in pressure between the mouth cavity and opercular cavity. The operculum acts as a valve and pump and lets water out and pumps it in.

Question 2

Hormones released from the adrenal medulla

Answer 2

The adrenal medulla releases the adrenaline and noradrenaline hormones

Question 3

Hormones released from the adrenal cortex

Answer 3

The adrenal cortex releases steroid hormones. This includes glucocorticoids, mineralcorticoids and androgens.

Question 4

Role of glucocorticoids

Answer 4

Glucocorticoids regulates glucose and protein metabolism, as well as supression of the inflammatory response

Question 5

Role of mineralcorticoids

Answer 5

Mineralcorticoids maintain salt concentrations to control blood pressure.

Question 6

What’s the difference between coenzymes and cofactors?

Answer 6

Cofactors = inorganic ions that aid enzyme function
Coenzymes = organic ions that are derived from vitamins

Question 7

Examples of human cells specialised for their functions

Answer 7

→ Erythrocytes → Biconcave shape (increased surface area to volume ratio to transport more oxygen), No nuclei (more space for haemoglobin), flexibility (move through capillaries)
→ Neutrophils → multi-lobed nucleus → fit through gaps to reach sites of infection
→ Sperm → flagella for movement, lots of mitochondria for ATP supply
→ Squamous epithelium → flat for increased diffusion
→ Cilliated epithelium → contains goblet cells which release mucus that traps pathogens
→ Cartilage (connective tissue) → prevents ends of bones rubbing and causing damage

Question 8

Plant cell examples that are adapted to their functions

Answer 8

→ Palisade cells in plants → thin walls for diffusion and large vacuoles to maintain turgor pressure
→ Root hair cells → root hairs increases surface area to increase water uptake through the roots of the plant
→ Guard cells in stomata → can change shape to prevent excessive water loss, has a thicker cell wall one side to prevent symmetrical shape change
→ Epidermis → found on plant surface and contains the stomata, contains waxy cuticle which helps prevent excessive water loss in plants
→ Xylem → contatains lignin for strength
→ Phloem → transports sucrose via mass flow

Question 9

What is tidal volume?

Answer 9

Tidal volume = maximum volume of air in a normal resting rbeath

Question 10

How to calculate pulmonary ventilation rate?

Answer 10

Pulmonary ventilation rate = tidal volume x breathing rate

Question 11

What are the different structures found within the liver and their functions?

Answer 11

→ Hepatocytes = main liver cell which divide and replicate
→ Sinusoids = spaces between hepatocytes where blood from hepatic artery and portal vein mixes
→ Kupfer cells = macrophages
→ Canaliculi = spaces where bile is secreted and then drained into ductules
→ Hepatic artery = Supplies the liver with oxygenated blood
→ Hepatic portal vein = supplies blood rich in products for metabolism
→ Hepatic vein = supplies the liver with deoxygenated blood
→ Bile duct = transports bile to gall bladder
→ Gall bladder = bile is stored then released into small intestine
→ Ligaments seperates liver lobes

Question 12

What are the primary non-specific animal defences against pathogens?

Answer 12

→ Skin (secretes sebum that inhibits pathogen growth)
→ Mucous from globet cells
→ Lysosomes in tears and urine
→ Stomach acid
→ Blood clotting (platelets clump at broken vessel and adhere, thrombrin + fibrin released that helps clot)
→ Fever
→ Inflammatory response
→ Phagocytosis

Question 13

What is the action of the inflammatory response?

Answer 13

Inflammatory response:
→ Inflammation localised and results in pain, swelling and redness
→ Histamines released which causes vasolidation → temperature increase, plasma forced out (swelling)
→ Cytokines attract phagocytes

Question 14

What are baroreceptors?

Answer 14

Baroreceptors are pressure receptors. They are sensitive to blood pressure. Too high = impulses sent to medulla oblongata centre which decreases HR (impulses sent along parasympathetic neurones to SAN) and vice versa.

Question 15

What are chemoreceptors?

Answer 15

Chemoreceptors detect changes in chemical levels. They are sensitive to pH level of blood (CO2 increase = pH decrease due to carbonic acid) → heart rate increased to increase blood flow

Question 16

How does pregnancy tests work?

Answer 16

1 → Wick soaked in urine (highest hCG levels)
2 → Monoclonal antibodies beads attach only to hCG
3 → 2nd set of monoclonal antibodies are immobolised so binds to hCG complex regardless.

Question 17

Outline the action of giberellin/germination

Answer 17

1 = Seed absorbs water
2 = Embryo activated
3 = Giberellins stimulate enzymes to break down food stores
4 = ATP produced → ABA works againsts giberellins to determine when the seed germinates.

Question 18

How auxins stimulate apical growth?

Answer 18

1 = Auxins synthesised in meristems
2 = Auxins diffuse away from tip or shoot
3 = Auxins ind to cell receptors
4 = Vacuoles form and pH lowers > optimum conditions for expansin enzyme
5 = Expansins break down cell wall to increase flexibility and vacuoles can absorb more water
6 = Auxin destroyed and cell wall of vacuole becomes rigid

Question 19

What are the commercial uses of plant hormones?

Answer 19

→ Ethene used to control fruit ripening, exposed to to ethene gas so all plants ripen at same rate
→ Hormone rooting powders → ease of propogation
→ Auxin → seedless fruit
→ Giberellins → delays ripening and ageing of fruit

Question 20

Outline the process of transcription and translation of DNA

Answer 20

1). DNA helicase breaks H bonds between complementary bases
2). Free nucleotides bind to the exposed bases on the antisense strand
3). RNA polymerase forms phosphodiester bonds between nucleotides and mRNA detaches
4). mRNA binds to subunits of ribosome
5). Anticodons on tRNA binds to mRNA codons, forming the amino acid sequence

Question 21

DNA replication

Answer 21

1). Helicase seperates DNA strands
2). Free nucleotides bind to exposed bases and are lined up via DNA polymerase

Question 22

Active transport across membranes

Answer 22

1). Moleculebinds to receptors of carrier proteins
2). ATP binds to the carrier protein (and is hydrolysed)
3). Protein changes shape and molecule gets released inside

Question 23

Gillventilation

Answer 23

1). Buccal cavity lowered -> volume increasesand pressure decreases -> causing water to move in
2). Operculum cavity expands, lowering pressure and causing water to move in and then across the gills

Question 24

Translocation in the phloem

Answer 24

Translocation in the phloem:
1). Sucrose enters via active loading
2). Facillitated diffusion of hydrogens bring sucrose into the companion cells, creating a gradient
3). Sucrose enters sieve tube elements, water follows by osmosis and hydrostatic pressure increases
4). Assimilated move from source to sink via mass flow

Question 25

Sliding filament model

Answer 25

Sliding filament model:
1). Action potential arrives at neuromuscular junction and sodium ion channels open
2). Calcium released from sarcoplasmic reticulum and binds to troponin, changing its shape
3). Troponin is displaced from myosin binding sites
4). Myosin and actin form cross-bridges
5). Myosin sweeps actinalong, sarcommere shortening in length
6). ATP binds to myosin head which causes it to detach frmoactin

Question 26

Stomatal control by ABA

Answer 26

Stomatal control by ABA:
1). Roots detect water abiotic stress
2). ABA released and binds to stomata receptors
3). Ionic concentration change in guard cells
4). Water potential reduced and cells close stomata