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Nutrition > Unit 6: Protein; Amino Acids > Flashcards

Unit 6: Protein; Amino Acids Flashcards

1
Q

Define Amino Acid

A

The nitrogen atoms give the name amino (nitrogen containing) to the amino acids–links in the chains of proteins

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2
Q

Describe the basic structure of an amino acid

A
  1. Central carbon with a Hydrogen atom
  2. Amino group (NH2)
  3. Acid group (COOH)
  4. Unique R-side group
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3
Q

What distinguishes one amino acid from the next? Makes proteins more complex than lipids or carbohydrates.

A

Unique R-side group

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4
Q

Define Protein

A

Cells link amino acids end-to-end in a variety of sequences to form thousands of different proteins.

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5
Q

Approximately how many amino acids make up a protein?

A

20

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6
Q

What links amino acids together to form a protein?

A

Peptide bonds

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7
Q

Describe a Peptide bond

A

-Condensation reaction (produces H2O)

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8
Q

Two amino acids bonded form a?

A

Dipeptide

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9
Q

3 amino acids bonded together form a?

A

Tripeptide

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10
Q

More than 3 amino acids bonded together form a?

A

Polypeptide

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11
Q

Amino Acid Sequence–Primary structure is determined how?

A

By the sequence of amino acids, to form a chain

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12
Q

Polypeptide Shapes-Secondary Structure is determined how?

A

By the weak electrical attractions within the polypeptide chain. Positively charged hydrogens attract negatively charged oxygens and the chain twists to a helix or a pleated sheet

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13
Q

What does secondary structure (helix/pleated sheet) do for protein?

A

Provides strength and rigidity

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14
Q

Polypeptide Tangles-Tertiary Structure are determined how?

A

Occurs has long polypeptide chains twist/fold into complex tangled shapes. Unique side groups give characteristics that attract or replenish from surrounding fluids and other amino acids
Hydrophobic
Hydrophilic
Disulphides bridges
For shapes such as globular/spherical or linear structures

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15
Q

What does the tertiary structure do for protein?

A
  • Enable them to perform various tasks

- Give maximum stability and shape must be retained to remain functional

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16
Q

Define Hydrophillic

A

Attracted to water

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17
Q

Define Hydrophobic

A

Repelled by water

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18
Q

Multiple Polypeptide Interactions-Quaternary Structure is determined by what?

A

Involves interactions between 2 or more polypeptides. Form a functional protein

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19
Q

Define Denaturation

A

Protein subject to heat, acid, (other conditions to disturb stability) uncoil and lose their shape. Therefore, their ability to function. Past a certain point denaturation is irreversible. Proteins are denatured when exposed to stomach acid allowing them to be digestible

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20
Q

Nonessential (Dispensable) Amino Acids: can be synthesized by the body. What are they?

A 
Alanine
Asparagine
Aspartic Acid
Glutamic Acid
Serine
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21
Q

Essential (Indispensable) Amino Acids: (9) must be supplied by the diet, as the body cannot synthesize/adequately synthesize them. What are they?

A 
Histidine
Isoleucine
Leucine
Lysine
Methionine
Phenylalanine
Threonine
Tryptophan
Valine
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22
Q

Conditionally Essential Amino Acids: are sometimes nonessential but become essential under special circumstances. What are they?

A 
Arginine
Cysteine
Glutamine
Glycine
Proline
Tyrosine
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23
Q

Protein digestion in the mouth

A

Chewing and crushing moisten protein-rich foods and mix them with saliva

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24
Q

Protein Digestion in the Stomach

A

Hydrochloric acid (HCl) uncoils protein strands and activates stomach enzymes

Protein –> Pepsin, HCl –> Smaller polypeptides

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25
Q

Protein digestion in the Small Intestine

A

Pancreatic and small intestinal enzymes split polypeptides further

Polypeptides –> Pancreatic/Intestinal Protease –> Tripeptides, dipeptides and amino acids

Enzymes on the surface of the small intestinal cells hydrolyze these peptides and the cells absorb them

Peptides –> Intestinal tripeptidases/Dipeptidases –> Amino Acids (absorbed)

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26
Q

Only free amino acids enter the general blood circulation at the portal vein. What is an exception to this?

A

Newborn infants receive immunity from mother’s when intact protein antibodies present in human colostrum enter the mucosa. A few days after birth the mucosal cells are closed to whole proteins

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27
Q

Digestive enzymes in the stomach are? (2)

A

Hydrochloric Acid (HCl): denatures protein structure, activates Pepsinogen to pepsin

Pepsin: C;eaves proteins to smaller polypeptides and some free amino acids. Inhibits pepsinogen synthesis

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28
Q

A proenzyme (or zymogen) is the inactive form of an enzyme. What is the inactive form of pepsin?

A

Pepsinogen

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29
Q

A string of 4-9 amino acids is known as a?

A

Oligopeptide

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30
Q

Pepsin works best in the low pH of the stomach. When it enters to small intestine (higher pH) what happens?

A

Becomes inactive and is digested

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31
Q

Once inside intestinal cells amino acids are used for? If they are not used for this what happens?

A

-Energy
-Synthesize needed compounds
If not used for this:
-Transported across cell membrane into surrounding fluid where they enter the capillaries on their way to the liver

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32
Q

Enzymes in the small intestine are? (8)

A 
Enteropeptidase
Trypsin
Chymotrypsin
Carboxpeptidases
Elastase and collage are
Intestinal Tripeptidases
Intestinal Dipeptidases
Intestinal Aminopeptidases
33
Q

What 2 factors determine protein quality?

A
  1. Amino Acid Composition (especially essential amino acids)

2. Digestibility of the protein

34
Q

Proteins that occur naturally in food are balanced in terms of amino acids, because they are biologically similar to human proteins and so…

A

Competition for absorption is not significant

35
Q

Define Complete Protein

A

A protein containing all the essential amino acids in amounts and proportions required by humans.

36
Q

Define Incomplete Protein

A

Lacks one or more essential amino acid

Ex. Plant proteins (corn)

37
Q

Define high-quality protein

A

A complete protein that provides all essential amino acids in amounts and proportions

38
Q

Define Limiting Amino Acid

A

An essential amino acid supplied in less than the amount needed to support protein synthesis.
If one amino acid is missing protein synthesis stops

39
Q

Define Complementary Proteins

A 
Amino acids in different food complement each other to form a complete protein 
Ex. Animal + plant protein
Ex. Grains + legumes 
Ex. Legumes + seeds 
Ex. Leafy vegetables + grains
40
Q

Is it necessary to balance amino acids in each meal? (Complementary amino acids must be consumed at the same time)

A

NO

As long as protein intake is varied and energy intake is sufficient

41
Q

Protein Function 1: Structural Growth and Maintenance of Body Tissues

A

Primary function of proteins because they are building blocks of a cell
Ex.
Collagen – formation of scars, tendons, ligaments, bones, teeth
Contractile Proteins – formation of muscle tissues
Cell Membrane Proteins – formation of barrier around cells

42
Q

Protein Function 2: Regulation of Body Functions

A

Enzymes – catalysts for metabolic reactions
Proteins in blood and lymph – fluid and acid-base balance
Antibodies – Immunity
Some hormones:
Insulin – regulation of blood glucose
Thyroid Hormone – regulation of metabolic weight
Transport Proteins:
Hemoglobin – oxygen transport in blood
Lipoproteins – fat transport
Transferrin – iron transport
Prothrombin, Fibrin – clotting of blood
Opsin – vision
Some neurotransmitters – nerve impulse transmission

43
Q

Protein Function 3: Source of Energy

A

Not a primary function but in instances of carb/fat shortage protein is broken down for energy. The nitrogen part of amino acids is secreted as urea via urine and remaining carbon-containing element is metabolized to produce energy, can also be converted to glucose or stored as fat

44
Q

Explain Nitrogen Balance

A

Proteins are the only nitrogen containing nutrient (16%).
Nitrogen balance can be determined by analyzing the intake of nitrogen (food consumed over a period of time) and the nitrogen loss (urine, feces, skin, hair, nails, sweat, tears, menses, mucus etc.)
Generally only urine and feces nitrogen loss is measured.

45
Q

Define Nitrogen Equilibrium

A 
Intake of nitrogen = loss of nitrogen 
Healthy adults (neither gaining/losing weight or pregnant) 
When protein intake is high the body excretes more nitrogen to maintain equilibrium because protein cannot be stored
46
Q

Define Positive Nitrogen Balance

A

Greater input than output

Growing children, pregnant women, patients recovering from illness or tissue injury

47
Q

Define Negative Nitrogen Balance

A

Input less than output
Fasting, illness, tissue injury/breakdown, cancers, burns, surgery, infection, stress, prolonged immobilization, poor quality/quantity proteins in diet

48
Q

Define Protein Turnover

A

Continuous creation and breakdown of proteins in a cell. When proteins break down they free amino acids. These amino acids mix with dietary amino acids to form a small amino acid pool

49
Q

Define Endogenous Amino Acids

A

Derived from within the body

50
Q

Define exogenous amino acids

A

Derived from foods

51
Q

Define acidosis

A

Above-normal acidity in the body

52
Q

Define Alkalosis

A

Above-normal alkalinity (base) in the blood and body fluids

53
Q

Define Edema and the cause

A

In critical illness and protein malnutrition, blood vessels become “leaky” and allow plasma proteins to move into the tissues. Because proteins are attracted to water, the tissues swell

54
Q

Define Buffer

A

Compounds that keep a solution’s pH constant when acids or bases are added

55
Q

Protein-Energy Malnutrition (PEM)

A

When protein intake falls below required level the body becomes more efficient. Once it falls below a critical level PEM occurs. Results in swelling, weakness, increased risk of infection. More common in children than adults because in relation to body weight children have higher protein requirements. Occurs in developing countries, areas of poverty in North America, patients with tuberculosis, cancer, GU tract disease, anorexia nervosa

56
Q

Protein Excess can result in:

A

Severe dehydration (especially in children) because the kidney cannot concentrate urine and water is excreted with urea

57
Q

Protein-Energy Undernutrition (PEU) previously called PEM is divided into 2 groups. What are they?

A

Marasmus and Kwashiorkor

58
Q

A child underweight for their height might be suffering from:

A

Acute PEU

59
Q

A child short for their age might have experienced what:

A

Chronic PEU

60
Q

Explain Marasmus

A 
Infancy (less than 2 years)
Severe deprivation, impaired absorption of protein, energy, minerals, vitamins
Chronic PEU (slow development)
Severe weight loss
Muscle wasting (no body fat)
Growth <60% weight-age 
No detectable edema
No fatty liver
Anxiety, apathy
Good appetite possible
Hair sparse, dry, thin, easy to pull out
Skin dry, thin, wrinkles
61
Q

Explain Kwashiorkor

A 
Older infants/children (1-3)
Inadequate protein intake or infections
Rapid onset (Acute PEU)
Some weight loss
Some muscle wasting with retention of body fat
Growth: 60-89% weight-age
Edema
Enlarged fatty liver
Apathy, misery, irritability, sadness
Loss of appetite
Hair is dry, brittle, easy to pull out, changes coulour, becomes straight
Skin develops lesions
62
Q

Explain Marasmus-Kwashiorkor Mix

A

Combination of symptoms. Characterized by edema of kwashiorkor with wasting of marasmus. Effects of both malnutrition and infections

63
Q

Vegetarian diets are superior from an environmental perspective as they:

A

Require less energy and water

64
Q

Define Lacto-vegetarians

A

People who include milk and milk products but exclude meat, poultry, fish, seafood, and eggs from their diet

65
Q

Define Lacto-ovo-vegetarian

A

People who include milk, milk products, and eggs but exclude meat, poultry, fish, and seafood

66
Q

Define Vegetarian

A

General term used to describe people who exclude meat, poultry, fish, or other animal derived products from their diet

67
Q

Define Vegan

A

People who exclude all animal-derived products (meat, poultry, fish, eggs, dairy products) Also called pure, strict, or total vegetarians

68
Q

Benefits of vegetarian Diets

A

-May increase life expectancy
-reduce obesity (lower body weight)
-reduce risk of diabetes
-decrease hypertensions
-decrease risk of heart disease (fats common in plant-based diets-monounsaturated)
-lower cancer rates (high intake of vegetables)
_Osteoporosis, diverticular disease, gallstones, rheumatoid arthritis

69
Q

Risk of Vegetarian diet and how to solve them

A
  • lack of protein, vitamins, minerals (iron, zinc, B12)

- ensure a well planned diet with meat alternatives and fortified milk/soy beverages

70
Q

What are the factors considered when establishing the RDA for protein?

A
  • Age/physiological state (requirements are highest during first year of life, adolescence, pregnancy, lactation)
  • Lean body mass (protein need increases as muscle mass increases)
  • Protein quality
  • Energy intake (Protein can only be used efficiently when adequate energy from carbs/fats is available)
  • Health status (physiological/psychological stress increases protein requirements)
  • Individual variation (protein requirements are established with margin of 30% above to allow for individual variation)
71
Q

What is the RDA for adults per kilogram of body weight per day?

A

0.8 grams/kilogram of body weight/day

Substantially overweight/underweight base your calculation on appropriate weight for your height

72
Q

What percent of energy intake should protein be?

A

10-35% of energy intake

73
Q

What is the protein recommendation for athletes?

A

1.2-1.7 grams/kilogram of body weight/day

74
Q

In Canada high protein content in food means the average consumption exceeds the recommended levels. TRUE OR FALSE?

A

TRUE

75
Q

Protein from animal sources is a major source in Canadian diets. So the Food Guide has done what?

A

Put an emphasis on vegetables, fruit and grain products to encourage a shift to eating less meat

76
Q

What segment of Canada’s population may have inadequate protein intake?

A

Women over 65 (0.78 grams/kilogram body weight/day)

77
Q

High protein intake can be harmful in connection to…

A

Bone loss (But bone loss is also associated with low protein intakes especially, in the elderly)

78
Q

Protein intake should be moderate in persons with:

A

Kidney Disease

Nutrition (12 decks)

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