Protein Flashcards Preview

Fundamentals > Protein > Flashcards

Flashcards in Protein Deck (62):
1

What determines AA chemical and physical structure

AA side chain (r group)

2

What determines the structure and function of a protein

AA composition

3

What determines the 3D nature of a protein?

AA sequence

4

Where does protein digestion begin

Stomach

5

Stomach digestion (5)

HCL rich fluid is secreted from parietal cells
Protein is denatured by low pH
Inactive form of pepsin (pepsinogen) is secreted
HCL activates pepsin
Pepsin cleaves proteins into smaller peptides

6

What is protein denaturation (2)

When protein straighten and uncoils
Thus allowing greater access to proteolytic enzymes

7

Small intestine digestion (5)

Partially broken down protein enter small intestine
Protein exposed to proteolytic enzymes
Pancreas produces proteolytic enzymes in zymogen form
Produces AAs and oligopeptides
Membrane bound enzymes further break down peptides

8

Absorption (2)

Digested products (dipeptides, tripeptides and AAs) are absorbed into epithelial cells
They then pass in capillaries and circulate blood

9

Which AAs are oxidised to provide energy for intestinal walls (3)

Glutamine
Aspartate
Glutamate

10

What do AAs consist of?(4)

Central carbon bound to hydrogen
Amino group (NH3)
Carboxylic group (COOH)
R group - amino acid side chain

11

What type of reaction forms a peptide bond?

Dehydration synthesis (release H20 + requires energy)

One hydrogen and oxygen from carboxyl group
One hydrogen from amino group

12

Describe the primary protein structure (3)

AA sequence
R groups of adjacent AA located on opposite side of the AA chain
No interactions between r groups

13

Describe secondary structure (2)

Determined by the number and sequence of AA
Chemical interactions among the AAs begin forming the primary structure

14

Tertiary structure (2)

3D shape occurs
Interactions among side chains a considerable distance from each other a long chain

15

Quaternary structure (2)

2 or more polypeptide chains interact
To form functional entities

16

What supplies the AA pool?(3)

Diet
De Nono synthesis
Protein degradation

17

What causes AA pool demand?(3)

Oxidation
Other pathways (e.g. gluconeogenesis)
Protein synthesis

18

What processes make proteins in the body?

Transcription and translation

19

_____ AAs must be available for optimal protein synthesis to occur?

All

20

How much does AA oxidation contribute to oxidative metabolism of the body?

10-20%

21

What is ammonia?(2)

Potent neurotoxin
Disposal is crucial for survival

22

Ammonia excretion (3)

Transported to the liver
Enters urea cycle
Urea is excreted by kidneys

23

What is an oxoacid?

Carbon skeleton of the AA

24

What is transamination?(2)

Amino group is transferred via an enzyme to an oxoacid to form a new AA

Used to synthesis non-essential AAs

25

What is the transaminate enzyme?(2)

Pyridoxal phosphate (PLP)
Which is a derivative from vitamin B6

26

Protein is the ____ most abundant chemical in the body

Second

27

Approx how many proteins are encoded by the genome?

35000

28

Which 4 protein makes up half of the total protein in human body?

Collagen (25%)
Haemoglobin
Myosin
Actin

29

What is protein?

Polymers of AAs joined together by peptide bonds

30

Essentials AAs (3)

Can not be produced endogenously
Must be provided in diet
9 of them

31

Non essential AAs (3)

Can be produced endogenously
By transamination of carbon skeleton
Relies on the availability of precursors

32

Conditionally essential AAs (2)

Rate of endogenous production is not sufficient under certain circumstances
Therefore it becomes essential

33

What is pepsin?(3)

Proteolytic enzyme
Cleaves proteins into smaller peptides
Inactive form is pepsinogen

34

Pancreatic enzymes in zymogen form secreted by pancreas (3)

Tripsinogen
Chymotryosinogen
Procarboxypeptidase A+B

35

Activated pancreatic proteolytic enzymes (3)

Trypsin
Chymotrypsin
Carboxypeptidase A+B

36

What is zymogen form (2)

Inactive enzyme precursors
Requires a biochemical change to activates e.g hydrolysis

37

Define proteolysis

Breakdown of proteins by the proteolytic enzymes (hydrolysis)

38

How are AAs oxidised?

By deamination

39

Explain the deamination process (2)

Amino group is removed from the amino acid
The products are an oxo-acid and ammonia

40

What determines the use carbon skeletons

The AA it was derived from

41

How are oxoacid used in energy production?(3)

Converted into either:
Pyruvate
Alpha-ketoglutarate (TCA intermediate)
Oxoloacetate (TCA intermediate)

42

What are the two key types of oxoacid?

Glucogenic
Ketogenic

43

What are ketoacids?(4)

AA derivatives that yield acetyl CoA or acetoacetate
Used as precursors for FA synthesis
Or oxidised as metabolic fuel
Cannot be used in gluconeogenesis

44

What are glucogenic oxoacids?

Used as intermediates for gluconeogenesis

45

How are AAs supplied by de novo synthesis?

Transamination

46

Nitrogen constitutes _____ of most proteins

16%

47

What are the major determinants of nutritional quality of food proteins?(2)

Content of essential AAs
Digestibility of the food source

48

What are complete proteins foods?

Protein sources that contain all essential AAs in quantities sufficient for human requirements

49

Examples of complete protein foods (4)

Poultry
Fish
Eggs
Dairy

50

What are incomplete protein foods?

Protein sources that lack one or more essential AA

51

Examples of incomplete protein foods?(3)

Plant sources
Corn
Legumes

52

Why is plant protein less digestible than animal protein sources?(2)

Restriction of digestion by plant cell walls
Presence of anti-nutritional factors

53

Examples of anti-nutritional factors (3)

Amylase
Trypsin inhibitors
Tannins

54

Digestibility of animal proteins

90-95%

55

Digestibility of plant proteins

60-80%

56

Digestibility of soy

90%

57

Protein loss in malnutrition (3)

Some tissue can only metabolise glucose
Protein must be degraded to provide AAs for gluconeogenesis
Lead to muscle wasting

58

Nitrogen balance (3)

Method used to calculate dietary protein requirement
Measures dietary intake of nitrogenous compounds
And excretion of nitrogen

59

Essential AAs examples

...

60

What is the optimal pH for pepsin activity?

2

61

pH that reduces pepsin activity

5

62

What is required for protein synthesis to occur

All AAs