Cellular physiology

Question 1

non-hypoxic causes
of pyruvate accumulation

Answer 1

which include; circulating catecholamines, exercise, sepsis or lack or mitochondria (RBCs)
-2020 first sitting question 8

Question 2

‘lactate sink’

Answer 2

allowing a period of ongoing ATP production from glycolysis when cells become oxygen deplete or the Kreb’s cycle is inhibited;
-2020 first sitting question 8

Question 3

allowing a period of ongoing ATP production from glycolysis when cells become oxygen deplete or the Kreb’s cycle is inhibited;

Answer 3

‘lactate sink’
-2020 first sitting question 8

Question 4

HO- CO - COH -CH3

Answer 4

Lactic Acid
-2020 first sitting question 8

Question 5

Lactate production
2 main categories

Answer 5

Production:
* It is produced by anaerobic metabolism of pyruvate either:
o Physiologically → in RBC (no mitochondria), renal medulla (↓ PO2), cornea/ lens (↓PO2) → hence, normal plasma [lactate] is 0.5-2 mmol/L (and NOT zero!)
o Pathologically → reduced tissue perfusion and/or O2 delivery (Eg. shock, hypoxaemia) →thus, plasma [lactate] ↑↑↑ (> 2 mmol/L)
-2020 first sitting question 8

Question 6

Lactate can be used as a fuel source from

Answer 6

Used as a fuel source by the heart and brain
-2020 first sitting question 8

Question 7

Lactate can be Transported to the liver where it is

Answer 7

▪ Converted back to glucose via gluconeogenesis (requires 6x ATP), which is then
transported back peripherally for use → “Cori cycle”
▪ Converted to pyruvate intermediate → utilized locally in TCA cycle for ATP production via oxidative phosphorylation
-2020 first sitting question 8

Question 8

What is the Cori cycle

Answer 8

Lactate is Converted back to glucose via gluconeogenesis (requires 6x ATP), which is then
transported back peripherally
-2020 first sitting question 8

Question 9

How many ATP involve in converting lactate back to glucose

Answer 9

6
-2020 first sitting question 8

Question 10

What happens to lactate with the Resolution of hypoxia

Answer 10

Resolution of hypoxia (Ie. tissue O2 tension restored) → intracellular lactate can be oxidised
back to pyruvate for use in local tissue aerobic metabolism (Ie. fed into TCA cycle)
-2020 first sitting question 8

Question 11

what is the lactate sink

Answer 11

A
Lactate Sink:
* Lactate acts as a sink in heart, liver, muscle etc, allowing a period of ongoing ATP production
from glycolysis when:
o cells become oxygen deplete
o Kreb’s cycle is inhibited
o Other causes of pyruvate accumulation: circulating catecholamines, exercise, sepsis or
lack of mitochondria (RBCs
-2020 first sitting question 8

Question 12

Lactate can be Intracellular shuttle:

Answer 12

▪ mitochondrial membrane
▪ peroxisomes
-2020 first sitting question 8

Question 13

What are type 1 and type 2 muscle fibers

Answer 13

slow-twitch (red) and fast-twitch (white) respectively
-2020 first sitting question 8