Wider Reading for Essays

Question 1

What reactions form tRNA with its amino acid?

Answer 1

aminoacylation

Question 2

What enzyme catalyses the reaction forming aminoacyl-tRNA?

Answer 2

aminoacyl tRNA synthetase

Question 3

What is required for aminoacyl-tRNA to be formed?

Answer 3

tRNA, amino acid, ATP

Question 4

How are complementary shapes linked to the formation of aminoacyl-tRNA?

Answer 4

as tRNA, ATP and amino acid all have complementary binding site in aminoacyl tRNA synthetase

Question 5

What bacterium causes Cholera?

Answer 5

Vibrio cholerae

Question 6

How does cholera cause Cl- ions to leave the cell?

Answer 6

• toxin secreted
• taken up by cells in receptor mediated endocytosis
• works via second messenger model to cause the ATP-mediated release of Cl- ions through CFTR channel proteins

Question 7

How does Cl- ions moving out of cells lead to diarrhoea?

Answer 7

• lowers WP of ileum
• water moves out of cells by osmosis

Question 8

How does IAA cause cell elongation?

Answer 8

• allows cell walls to stretch and expand
• by making them more acidic
• by binding to a complementary protein which activates a H+ pump
  OR
• enters the nucleus and leads to transcription for the gene which codes for the proton pump

Question 9

How does acidifying cell walls allow them to elongate?

Answer 9

• increases the action of enzymes called expansins
• these disrupt interactions between cell wall polymers
• a high turgor pressure pushes walls outwards

Question 10

What is a heterotrophic plant?

Answer 10

a plant that does not produce its own food (through photosynthesis) but gains nutrients from other plants/sources
eg Bird’s nest orchid

Question 11

What is myco-heterotrophy?

Answer 11

a symbiotic relationship between a plant and fungi

Question 12

What is a pelagic food chain?

Answer 12

oceanic/marine food chains that begin with small microorganisms such as phytoplankton

Question 13

Why is there lower primary production in pelagic food chains?

Answer 13

as sunlight is having to penetrate water to reach producers

Question 14

Why are food chains often longer in pelagic food chains?

Answer 14

• single celled organisms absorbed for rapidly and wholly
• less energy lost as heat, as organisms tend to be ectotherms

Question 15

What is kinesin?

Answer 15

A motor protein responsible for the transport of cellular cargo, such as vesicles, along microtubules

Question 16

Outline the mechanism by which kinesin moves along a microtubule…

Answer 16

• Leading head binds to β-tubulin
• ATP binds to binding site on the leading head, this increases the affinity of the kinesin head to the β-tubulin
• causes a slight change in the neck, which causes the trailing head to swing forward (force generating step)
• new leading head (previously the trailing head) binds to a β-tubulin subunit and releases ADP
• ATP binds to the trailing head and is hydrolysed to release ADP + Pi.
• Pi diffuses away, energy released is used as the head detaches
• ATP binds to the leading head and the cycle repeats

Question 17

Give an example where kinesin is important…

Answer 17

• Used in neurons, to move cargo from the soma along the axon
  Without the movement of cargo such as vesicles containing neurotransmitters and mitochondria would not be transported to the end of the axon, so no synaptic transmission ends neural pathways which prevents action potential from reaching effector, preventing things like control of HR

Question 18

How is ATP involved in the action of kinesin?

Answer 18

• when binds to leading head, it causes it to have a higher affinity for B-subunit
• hydrolysed to release energy that allows trailing head to detatch

Question 19

What is Cystic Fibrosis and what causes it?

Answer 19

a genetic disorder impacting the lungs and digestive system caused by a mutation in the CFTR gene

Question 20

What are CFTR proteins?

Answer 20

transmembrane proteins that transport chloride ions

Question 21

What mutation is the most common cause of CF?

Answer 21

delta F508 deletion

Question 22

Why does the mutated CFTR protein cause sticky mucus?

Answer 22

les water moves out by osmosis

Question 23

How does CF impact non-specific defence?

Answer 23

• sticky mucus prevents movement of cilia
• pathogens cannot be moved out of the lungs

Question 24

What gene therapy is being done to treat CF?

Answer 24

introducing correct copies of CFTR which allows correct CFTR proteins to be coded for

Question 25

Why might non-intergrating gene therapy be better?

Answer 25

does not interfere with rest of genome so fewer side effects

Question 26

Describe Hb in deoxy form…

Answer 26

• Fe2+ slightly below ring in heme group
• Histidine F8 further from the ring

Question 27

Describe Hb in oxy form…

Answer 27

• O2 binding allows histidine E7 to form H bonds and pull Fe2+ into the ring
• This pulls the His F8 up, closer to the ring
• changes the tertiary structure, which changes the quaternary structure

Question 28

What is PTH and where is it secreted from?

Answer 28

• Parathyroid hormone
• from the parathyroid glands

Question 29

What 4 things does PTH stimulate/act on?

Answer 29

• increased absorption of Ca2+ from the ileum
• increased reabsorption of Ca2+ in the kidneys
• increased osteoclast activity (breaking down bones releasing Ca2+)
• acts on vit D, to convert it into active forms

Question 30

What does primary hyperparathyroidism lead to?

Answer 30

hypercalcaemia