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Fundamentals > Protein > Flashcards

Protein Flashcards

1
Q

What determines AA chemical and physical structure

A

AA side chain (r group)

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2
Q

What determines the structure and function of a protein

A

AA composition

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3
Q

What determines the 3D nature of a protein?

A

AA sequence

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4
Q

Where does protein digestion begin

A

Stomach

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5
Q

Stomach digestion (5)

A

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

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6
Q

What is protein denaturation (2)

A

When protein straighten and uncoils

Thus allowing greater access to proteolytic enzymes

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7
Q

Small intestine digestion (5)

A

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

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8
Q

Absorption (2)

A 
Digested products (dipeptides, tripeptides and AAs) are absorbed into epithelial cells
They then pass in capillaries and circulate blood
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9
Q

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

A

Glutamine
Aspartate
Glutamate

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10
Q

What do AAs consist of?(4)

A

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

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11
Q

What type of reaction forms a peptide bond?

A

Dehydration synthesis (release H20 + requires energy)

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

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12
Q

Describe the primary protein structure (3)

A

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

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13
Q

Describe secondary structure (2)

A

Determined by the number and sequence of AA

Chemical interactions among the AAs begin forming the primary structure

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14
Q

Tertiary structure (2)

A

3D shape occurs

Interactions among side chains a considerable distance from each other a long chain

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15
Q

Quaternary structure (2)

A

2 or more polypeptide chains interact

To form functional entities

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16
Q

What supplies the AA pool?(3)

A

Diet
De Nono synthesis
Protein degradation

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17
Q

What causes AA pool demand?(3)

A

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

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18
Q

What processes make proteins in the body?

A

Transcription and translation

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19
Q

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

A

All

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20
Q

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

A

10-20%

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21
Q

What is ammonia?(2)

A

Potent neurotoxin

Disposal is crucial for survival

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22
Q

Ammonia excretion (3)

A

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

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23
Q

What is an oxoacid?

A

Carbon skeleton of the AA

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24
Q

What is transamination?(2)

A

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

Used to synthesis non-essential AAs

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25
Q

What is the transaminate enzyme?(2)

A 
Pyridoxal phosphate (PLP) 
Which is a derivative from vitamin B6
26
Q

Protein is the ____ most abundant chemical in the body

A

Second

27
Q

Approx how many proteins are encoded by the genome?

A

35000

28
Q

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

A

Collagen (25%)
Haemoglobin
Myosin
Actin

29
Q

What is protein?

A

Polymers of AAs joined together by peptide bonds

30
Q

Essentials AAs (3)

A

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

31
Q

Non essential AAs (3)

A

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

32
Q

Conditionally essential AAs (2)

A

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

33
Q

What is pepsin?(3)

A

Proteolytic enzyme
Cleaves proteins into smaller peptides
Inactive form is pepsinogen

34
Q

Pancreatic enzymes in zymogen form secreted by pancreas (3)

A

Tripsinogen
Chymotryosinogen
Procarboxypeptidase A+B

35
Q

Activated pancreatic proteolytic enzymes (3)

A

Trypsin
Chymotrypsin
Carboxypeptidase A+B

36
Q

What is zymogen form (2)

A

Inactive enzyme precursors

Requires a biochemical change to activates e.g hydrolysis

37
Q

Define proteolysis

A

Breakdown of proteins by the proteolytic enzymes (hydrolysis)

38
Q

How are AAs oxidised?

A

By deamination

39
Q

Explain the deamination process (2)

A

Amino group is removed from the amino acid

The products are an oxo-acid and ammonia

40
Q

What determines the use carbon skeletons

A

The AA it was derived from

41
Q

How are oxoacid used in energy production?(3)

A

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

42
Q

What are the two key types of oxoacid?

A

Glucogenic

Ketogenic

43
Q

What are ketoacids?(4)

A

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
Q

What are glucogenic oxoacids?

A

Used as intermediates for gluconeogenesis

45
Q

How are AAs supplied by de novo synthesis?

A

Transamination

46
Q

Nitrogen constitutes _____ of most proteins

A

16%

47
Q

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

A

Content of essential AAs

Digestibility of the food source

48
Q

What are complete proteins foods?

A

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

49
Q

Examples of complete protein foods (4)

A

Poultry
Fish
Eggs
Dairy

50
Q

What are incomplete protein foods?

A

Protein sources that lack one or more essential AA

51
Q

Examples of incomplete protein foods?(3)

A

Plant sources
Corn
Legumes

52
Q

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

A

Restriction of digestion by plant cell walls

Presence of anti-nutritional factors

53
Q

Examples of anti-nutritional factors (3)

A

Amylase
Trypsin inhibitors
Tannins

54
Q

Digestibility of animal proteins

A

90-95%

55
Q

Digestibility of plant proteins

A

60-80%

56
Q

Digestibility of soy

A

90%

57
Q

Protein loss in malnutrition (3)

A

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

58
Q

Nitrogen balance (3)

A

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

59
Q

Essential AAs examples

A

…

60
Q

What is the optimal pH for pepsin activity?

A

2

61
Q

pH that reduces pepsin activity

A

5

62
Q

What is required for protein synthesis to occur

A

All AAs

Fundamentals (17 decks)

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