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Protein Flashcards

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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
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

Fundamentals (17 decks)

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