Biochemistry Part 4 Flashcards Preview

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Flashcards in Biochemistry Part 4 Deck (22)
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1
Q

What are the parameters used to describe the relationship between concentration of substrate and rate of catalysed reaction?

A

Vmax and Km

2
Q

What makes the enzyme-substrate complex unstable?

A

The activation energy barrier

3
Q

What is the michaelis constant equivalent to?

A

Substrate concentration where the initial reaction is half maximal

4
Q

Where is Vmax on a line weaver burke plot?

A

Intersection of the straight line with the Y axis

5
Q

Where is Km on the lineweaver burke plot?

A

Intersection with the X axis

6
Q

Define Vmax

A

Maximum velocity of a reaction

7
Q

Define Km

A

Concentration in moles of S which gives 1/2 of Vmax

8
Q

What does a low Km indicate?

A

An enzyme only needs a little substrate to work at half-maximal velocity

9
Q

What does a high Km indicate?

A

Enzyme needs a lot of substrate to work at half-maximal velocity

10
Q

Describe the Km of the hexokinase in red blood cells

A

0.05mM glucose

Low Km maintains energy production in RBC by glycolysis even if glucose level falls dramatically

11
Q

Describe the Km of glucokinase in the liver

A

High Km enables glucose sensing and homeostasis.
Its abundance in liver is regulated by insulin.
Excess blood glucose is metabolised

12
Q

What are prolyl hydrolyses?

A

Prolyl hydrolyses are oxygen sensors which require O2 as a substrate to regulate the HIF transcription factor

High Km for O2- even high than atmospheric oxygen levels

13
Q

How do genes help us survive hypoxia?

A

Prolyl hydrolyses activate the transcription factor hypoxia inducible factor

Transcribes genes for;

  • RBC synthesis
  • Blood vessel growth
  • Anaerobic survival pathways
14
Q

What happens in Von Hippel Lindau syndrome?

A

Excessive blood vessel growth

Haemangiomas in brain

Subcutaneous haemangious track spinal cord

15
Q

What does competitive inhibition do to Vmax and Km?

A

Vmax does not change

Km varies

16
Q

How can methanol poisoning be treated?

A

Substrate for alcohol dehydrogenase: causes conversion to formaldehyde

ADH has a Km for ethanol 20x greater than methanol

Treat with 40% ethanol in combination with dialysis and ventilation

17
Q

What does non-competitive inhibition do to Vmax and Km?

A

Vmax varies

Km does not change

18
Q

What is a rate limiting enzyme?

A

When the end product acts as an inhibitor of the slowest enzyme in the pathway (usually near the beginning)

19
Q

When is feedback inhibition prevalent?

A

Common mechanism of allosteric control

20
Q

What is feedback inhibition useful for?

A

Control mechanism, it avoids build ups of intermediates

21
Q

Do allosteric enzymes follow the michaelis-menten kinetics?

A

No

Increasing substrate results in a sigmoidal curve instead of hyperbola

22
Q

Give an example of allosteric regulation?

A

Binding of oxygen to haemoglobin

Controlled by

  • H+
  • CO2
  • 2,3 bisphosphoglycerate a side product of glycolysis