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Human Nutrition > Proteins > Flashcards

Proteins Flashcards

1
Q

What are proteins composed of?

A

Carbon, hydrogen, oxygen and nitrogen

(Body’s main source of nitrogen - 16% weight of protein)

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2
Q

What are amino acids?

A

Building blocks of protein

Proteins make about 20 amino acids

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3
Q

What is the basic stricture of an amino acid?

A

central carbon atom, hydrogen atom, amino group, acid group

Fourth bond is distinct side group chain

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4
Q

What are non-essential amino acids?

A

Body can synthesise them itself
Production is reliant on adequate precursors

11 amino acids

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5
Q

What are essential amino acids?

A

body cannot make in sufficient amount, must be consumed in diet

9 amino acids

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6
Q

What are conditional essential amino acids?

A

if body fails to supply/cannot make conversions - a non-essential can become conditionally essential

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7
Q

What is a peptide bond?

A

A peptide bond link amino acids end to end in a variety of forms

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8
Q

How are amino acid chains formed?

A

Condensation reactions connect amino acids

Dipeptide - 2 amino acids

Tripeptide - 3

Polypeptide - 50-100

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9
Q

What is the primary structure of amino acid sequence?

A

Can be linked in a variety of sequences
Determines identity of protein

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10
Q

What is the secondary structure of amino acid sequence?

A

Determined by weak electrical attractions within polypeptide chain

Positively charged hydrogen atoms attract negatively charged oxygen atoms

Sections twist and fold - strength and identity

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11
Q

What is the tertiary structure - polypeptide tangles?

A

occurs as long chains that fold/twist into complex tangled shapes

Forms shape to perform function, max stability

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12
Q

What is protein denaturation?

A

First step in protein breakdown, uncoiling/losing shape of protein - frees amino acids

Occurs when proteins are subject to heat, acid, etc

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13
Q

What are the major gastric enzymes for protein?

A

hydrochloric acid
Pepsin
Rennin

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14
Q

How are proteins absorbed and transported?

A

Once inside intestinal cells, amino acids are transported to liver via portal vein

Liver responsible to either
- oxidise for energy
- build new proteins in body
- use as spare spart for other nitrogen containing compounds

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15
Q

What happens in stomach during digestion?

A

hydrolysis, hydrochloric acid denatures tangles

Converts pepsinogen (inactive) into pepsin (active)

Pepsin cleaves proteins into smaller amino acids

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16
Q

What happens in the small intestine during digestion?

A

Proteases (from intestine and pancreas) hydrolyse short peptide chains

Peptide enzymes on membrane surface of intestinal cells split into single amino acids

17
Q

What happens in the transcription of proteins?

A

Messenger RNA (ribonucleic acid) carries gene code across nuclear membrane into body of cell

Attaches itself to ribosome (protein making machines)

18
Q

What happens in the translation of protein?

A

Messenger RNA directs sequences of amino acids to line up for synthesis of protein

Thousands of RNA carry amino acid, cluster and await to unload

Messenger cells can call for specific amino acid, RNA moves into position

19
Q

How does gene expression come into play with proteins?

A

Nutrient can play roles in activating or silencing of genes

20
Q

What are the roles of proteins?

A

Hormones
Regulate fluid balance
Building material/structure
Enzymes
Acid-base regulator
Transporter (channels/pumps)
Anti-bodies
Source of energy/glucose

21
Q

What order does the body prefer foods?

A

Glucose
Fatty acids
Proteins

22
Q

What is protein turnover?

A

Proteins being made and broken down to free amino acids

23
Q

What is the amino acid pool?

A

When freed amino acid mix with amino acid from diet - forms amino acid pool

24
Q
A
25
Q

When is the nitrogen balance equal, positive and negative?

A

Equilibrium - nitrogen intake equals nitrogen output

Positive - growing infants, pregnant women, recovering from illness

Negative - people starving, suffering severe stressors (burns, infections, fever)

26
Q

What other proteins can amino acids make?

A

Neurotransmitters, serotonin, tyrosine

27
Q

How are amino acids used for energy and glucose?

A

when glucose/fatty acids are limited, cells forced to use amino acids for energy

This is why starvation causes wasting of lean body tissue, fat loss

28
Q

How are amino acids used for glycogen and fat?

A

when energy intake exceeds demand, excess protein is converted to glucose or ketone bodies, which is stored as glycogen and fat

29
Q

What are deaminated amino acids?

A

Stripped of nitrogen containing amino groups

Makes:

Ammonia
Keto acid (used for energy, production of glucose, ketones, cholesterol, fat)

30
Q

How do you prevent ammonia?

A

toxic compound - disturbs body’s acid-base balance

Liver combines ammonia with carbon dioxide to make urea

31
Q

How does the body excrete urea?

A

Out through urine

Urea is body’s principal vehicle to excrete unused nitrogen

High protein diet - drink lots of water to dilute extreme urea from diet

32
Q

What is a good way to ensure protein quality?

A

Contains all essential amino acids in correct proportions to needs of body
Mostly animal foods
Grass fed, butcher
Cooked wel - medium rare, no frying or charring

33
Q

What is reference protein?

A

Quality of food protein determined by comparing amino acid composition with requirements of small children

Generates amino acid score

Better the score, more growth will occur

34
Q

What are complementary proteins?

A

combining plant protein foods that have different but complementary proteins

All together contain essential amino acids sufficiently

35
Q

What is PEM and how does it show up?

A

Protein energy malnutrition
Kwashiorkor - swollen belly, fatty liver
Marasmus - body’s adaptation to starvation
Infection - antibodies decrease to provide amino acids, leaves body vulnerable

36
Q

What is the protein RDI?

A

10-35% of diet - protein

37
Q

What are the drawbacks of protein powders?

A

Provides no other nutrients needed
If excess protein, body dismantles and stores as fat
Deaminaiton of excess amino acids places extra burden on kidneys to excrete unused nitrogen

38
Q

What is the downside of amino acid supplements?

A

body not designed to handle high concentrations

Excess of one amino acid - over demand for carrier that it limits absorption of other amino acids

Can result in deficiencies or toxicity

39
Q

Where can you find the essential amino acids in the diet?

A

Fish, meat, eggs, soy, quinoa, buckwheat, hempseed, spirulina

Human Nutrition (6 decks)

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