Drive - proteins synthesis and degredation

Question 1

Where are the majority of proteins produced by the made?

Answer 1

The liver

Question 2

What are the 4 Starling Forces?

Answer 2

Capillary hydrostatic pressure

Interstitial hydrostatic pressure

Osmotic force due to plasma protein concentration

Osmotic force due to intestinal fluid protein concentration

Question 3

What direction of movement does capillary hydrostatic pressure favour?

Answer 3

Fluid movement out of the capillary

Question 4

What direction of movement does interstitial hydrostatic pressure favour?

Answer 4

Fluid movement into the capillary

Question 5

What direction of movement does the osmotic force due to plasma protein concentration favour?

Answer 5

Fluid movement into the capillary

Question 6

What direction of movement does the osmotic force due to intestinal fluid protein concentration favour?

Answer 6

Fluid movement out of the capillary

Question 7

With reference to Starling Forces what happens to fluid at the arterial end of the capillaries?

Answer 7

Bulk filtration out of the capillary

Due to high capillary hydrostatic pressure and low interstitial hydrostatic fluid pressure

Question 8

Why is their a bulk absorption of fluid into the capillaries at the venous end?

Answer 8

As capillary hydrostatic pressure has decreased due to resistance encountered as blood flows through the capillary wall

Question 9

Why can liver failure cause oedema?

Answer 9

Liver is needed to produce albumin.

Albumin is needed to maintain capillary oncotic pressure

Therefore decrease in albumin means less water reabsorbed.

Accumulation of water in the interstitial fluid

Question 10

What is protein turnover?

Answer 10

The continuous degradation and re-synthesis of all cellular proteins

Question 11

List 3 causes of increased rate of protein turnover

Answer 11

Tissue damage

Uterine tissue in pregnancy

Skeletal muscle during starvation

Question 12

What are the 2 primary methods of protein break down?

Answer 12

Lysosomal and Ubiquitin proteasome pathway

Question 13

What is lysosomal breakdown of proteins carried out by? (both general and specific)

Answer 13

The reticulo-endothelial system in the liver.

Specifically the sinusoidal endothelial cells, Kupffer cells and pit cells

Question 14

What is the role of sinusoidal endothelial cells in protein degradation?

Answer 14

Remove soluble proteins and fragment from the blood (through fenestrations). Where they are the fused into lysosomes and hydrolysed

Question 15

What is the role of Kupffer cells in protein degradation?

Answer 15

Phagocytose particulate matter into phagosomes before hydrolysation occurs

Question 16

What are Kupffer cells?

Answer 16

Livers resident macrophages

Question 17

Where does the ubiquitin-protease pathway occur?

Answer 17

In the cytoplasm of cells

Question 18

What is the role of the ubiquitin-protease pathway?

Answer 18

To degrade protein by unfolding it and breaks it down into small peptides.

It preferentially degrades denatured (unfolded) proteins that are defective

Question 19

Where does amino acid degradation and catabolism occur?

Answer 19

In the hepatocytes of the liver

Question 20

What is catabolism?

Answer 20

The break down of complex substances to simpler ones accompanied by the release of energy

Question 21

What are the 2 main amino acid catabolism processes?

Answer 21

Oxidative deamination and transamination

Question 22

What occurs in oxidative deamination?

Answer 22

Production of free ammonia (from amino group) and alpha-keto acid (which is then used in the Krebs cycle)

Question 23

What enzymes is need for the catalysis of oxidative deamination?

Answer 23

Glutamate dehydrogenase

Question 24

What is the problem with excess NH3 in oxidative deamination?

Answer 24

The process of oxidative deamination is reversible. Excess ammonia crosses blood-brain barrier and reacts with alpha-ketoglutarate (which causes a decrease in ATP levels)

Question 25

What occurs in transamination?

Answer 25

Transfer of an alpha-amino group from amino acid to a keto-acid to form an alpha-keto-acid

Question 26

What enzyme is involved in transamination? and where is this found?

Answer 26

Aminotransferase = found in the cytosol of the mitochondria throughout the body particularly those of the liver and kidneys