Protein Metabolism and Nitrogen Balance

Question 1

What do proteins act as

Answer 1

Receptors 
transport 
regulatory 
contractile 
enzymes 
structural 
hormones and growth factors 
storage

Question 2

What is a protein

Answer 2

A long chain of amino acids linked by covalent peptide bonds

Question 3

How are proteins absorbed

Answer 3

as amino acids via secondary active transport

Question 4

What is the role of albumin

Answer 4

generates colloid osmotic pressure and prevents capillary plasma loss

Question 5

What is the role of globulins

Answer 5

Innate and acquired immunity and enzymatic functions

Question 6

What is the role of transferrin

Answer 6

Carriage of ferrous ions in circulation

Question 7

What is the role of fibrinogen

Answer 7

Mediates clot formation and repairs leaks in circulatory system

Question 8

When will plasma proteins increase

Answer 8

Certain stress conditions

Question 9

When will plasma proteins decrease

Answer 9

In liver disease

Question 10

What happens when AA are absorbed

Answer 10

They are synthesised into a wide range of proteins

Question 11

What is produced in deamination

Answer 11

Glucose
fatty acids
ketones

Question 12

How are AA excreted

Answer 12

As a biproduct of ammonia

Question 13

What breaks down proteins to amino acids

Answer 13

Lysosomal enzymes

Question 14

Where are amino acids mainly stored

Answer 14

Liver

Question 15

What are XS amino acids used for

Answer 15

Used immediately for energy through gluconeogenesis

Question 16

What is transamination

Answer 16

essential AA- to non essential

Question 17

What are the 4 metabolic classes of AA

Answer 17

Essental AA
ketogenic AA
Glucogenic AA
non-essential AA

Question 18

What two classes of AA are metabolised to pyruvate/ TCA intermediate

Answer 18

Glucogenic AA

Ketogenic AA

Question 19

What does growth hormone do

Answer 19

Promotes the synthesis of cellular proteins
Increases AA membrane transport
Increase RNA transcription/translocation

Question 20

How is insulin linked to AA

Answer 20

Promotes the cellular AA
increases translation/ RNA transcription
decrease in gluconeogenesis

Question 21

What can a lack of insulin lead to

Answer 21

Increase in plasma AA

energy/ gluconeogenesis can produce muscle wasting

Question 22

What is the name given to GH and insulin working together for effective protein synthesis

Answer 22

Synergistic interaction

Question 23

What is testosterone

Answer 23

GH which causes transient muscle growth

Question 24

What does oestrogen cause

Answer 24

transient muscle growth

Question 25

What does thyroxine do

Answer 25

Increase in cell metabolism - activate protein pathways

Decrease in fat leading to an increase in protein degradation

therefore adequate fat will lead to an increase in protein synthesis

Question 26

What do glucocorticoids do

Answer 26

Increase protein breakdown
increase circulating AA
increase hepatic and PP

promote gluconeogenesis in the liver

Question 27

what state is +ve nitrogen balance and what are the causes

Answer 27

Anabolic state

Situations increased demand for protein
Childhood growth, pregnancy

Question 28

what state is -ve nitrogen balance and what are the causes

Answer 28

catabolic state

starvation/malnutrition
cachexia
hypermetabolic state

Question 29

How do you quantify a dynamic protein turnover

Answer 29

Labelling of total body protein with isotopic AA tracer

Flux of proteins calculated from measurement of 15 N specific activity

Question 30

What is the dynamic protein turnover estimate each day

Answer 30

3-4kg