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HUNT245 > Lecture 7: Proteins > Flashcards

Lecture 7: Proteins Flashcards

1
Q

What type of proteins are involved in structural roles?

A

Collagen/Keratin

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2
Q

What is the structural roles of collagen and keratin?

A

Bone, skin, hair, nails, tendons, ligaments

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3
Q

What type of proteins are involved in contraction?

A

Actin and myosin

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4
Q

What is the structural roles on actin and myosin?

A

Contractile proteins

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5
Q

What type of proteins are involved in transport?

A

Hemoglobin, cytochromes and lipoproteins

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6
Q

What are the transport roles of hemoglobin, cytochromes and lipoproteins?

A

O2 and CO2 transport, ETC and lipids

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7
Q

What type of proteins are involved in metabolic regulation?

A

Enzymes and hormones

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8
Q

What are the metabolic regulation roles of enzymes and hormones?

A

Nutrient anabolism and catabolism

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9
Q

What type of proteins are involved in immune function?

A

Antibodies

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10
Q

What are the immune function roles of antibodies?

A

Eliminates foreign pathogens

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11
Q

What is low muscle mass associated with?

A

Has been associated with increased morbidity, poorer quality of life and higher mortality

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12
Q

What is low muscle strength shown to be a significant and independent predictor of?

A

Mortality risk

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13
Q

What is the composition of amino acids?

A

Amino acids contain carbon, hydrogen and oxygen and contain nitrogen

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14
Q

What is the composition of CHO and Fat?

A

Carbon, hydrogen and oxygen - not nitrogen

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15
Q

What is the structure of Amino Acids?

A

A carboxyl group, amine group and variable side chain

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16
Q

How do amino acids differ from each other?

A

Each AA has a different side chain

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17
Q

How many amino acids are there?

A

20

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18
Q

What are the 2 categories of amino acids?

A

Essential and non-essential

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19
Q

What are essential amino acids?

A

cannot be synthesised by the body and therefore must be consumed in the diets

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20
Q

What are non-essential amino acids?

A

can be synthesised from other amino acids via transamination

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21
Q

What is transamination?

A

a biochemical process in which an amino group from one amino acid is transferred to a keto acid (α-keto acid), forming a new amino acid and a new keto acid

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22
Q

What essential amino acids are involved in muscle synthesis?

A

Isoleucine and Leucine (BCAA)

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23
Q

What essential amino acid is involved in the blood brain barrier?

A

Valine (BCAA)

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24
Q

What is a BCAA?

A

Branched chain amino acid

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25
Q

What is a dipeptide?

A

Composed of a 2 AA that are joined by a chemical bond, known as a peptide bond

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26
Q

What is a polypeptide?

A

Longer chains of AA are known as polypeptides (>20 AA)

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27
Q

What do proteins consist of?

A

Many polypeptide chains

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28
Q

What is a primary structure?

A

the linear sequence of amino acids in a polypeptide chain

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29
Q

What are primary structures determined by?

A

the AA sequence

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30
Q

What is a secondary structure?

A

refers to the local folding of the polypeptide chain into specific shapes stabilised by hydrogen bonds.

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31
Q

What are secondary structures determined by?

A

the interactions between groups (short)

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32
Q

What is a tertiary structure?

A

overall three-dimensional shape formed by the folding and interactions of its secondary structural elements

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33
Q

What is a tertiary structure determined by?

A

interactions between side chains (3D)

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34
Q

Where does protein digestion begin?

A

In the stomach

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35
Q

After the stomach where is the next stage of digestion?

A

The pancreas

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36
Q

After the pancreas where is the next stage of digestion?

A

The small intestine

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37
Q

How are proteins are digested in the stomach?

A

Hydrochloric acid denatures the proteins and pepsin degrades proteins to large polypeptides and AA

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38
Q

How are proteins digested in the pancreas (arriving as polypeptides and AA)?

A

Pancreatic enzymes include trypsin and chylotrypsin degrade polypeptides to oligopeptides and AA

39
Q

How are proteins digested in the small intestine (arriving as oligopeptides and AA)?

A

Aminopeptidase degrades oligopeptides to peptides and AA

40
Q

How do peptides and AA’s enter the circulation from the small intestine?

A

AA and small peptides are transported across the intestinal membrane. Peptides are hydrolysed in the cytosol and thus AA enter the circulation

41
Q

Can we store excess AA in the body?

A

No we cannot

42
Q

What represents the AA pool?

A

The AA in the blood and ECF

43
Q

How much does protein turnover contribute to BMR?

A

Contributes approx. 20% to BMR

44
Q

Which organ plays a critical role in regulating the composition of the AA pool?

A

The liver

45
Q

Where are amino acids found in the body?

A

ECF, blood, liver and muscle

46
Q

Where can AA be released from?

A

liver and muscle

47
Q

What happens in both the liver and muscle?

A

Proteins are degraded and synthesised

48
Q

What does muscle maintenance mean?

A

Muscle protein synthesis = muscle protein breakdown

49
Q

What does muscle gain look like?

A

Muscle protein synthesis > muscle protein breakdown

50
Q

What is MPS?

A

Muscle protein synthesis

51
Q

How does MPS vary?

A

Varies between different dietary protein sources

52
Q

What does MPS depend on?

A

depends on post-prandial rise in plasma essential amino acid concentrations (especially leucine)

53
Q

What is leucine?

A

an essential amino acid

54
Q

What provides the necessary precursors for protein synthesis rates to increase?

A

Plasma amino acid concentrations

55
Q

What are examples of high protein meats?

A

Lean mince, sirloin steak, chicken and salmon

56
Q

What are high protein foods that are not meat?

A

Peanut butter, almonds, tofu, eggs

57
Q

What does protein quality refer to?

A

How many of the essential AA’s they contain and what concentration of essential AA they contain

58
Q

What are complete proteins?

A

All EAA present (generally animal proteins)

59
Q

What are incomplete proteins?

A

plant proteins are deficient in one EAA (lysine, tryptophan, methionine) - generally plant proteins

60
Q

What are limiting AA’s?

A

the amino acid that is missing from an incomplete protein

61
Q

What is the problem with protein quality in vegetarians?

A

Poor digestibility - cell walls of plant proteins inhibit digestion, anti-nutritional factors inhibit digestion

62
Q

How is problems with protein quality in vegetarians/vegans overcome?

A

By consuming a combination of plant proteins

63
Q

What is PDCAAS?

A

Protein digestibility-corrected amino acid score

64
Q

What is DIAAS?

A

Digestible indispensable amino acid score (DIAAS)

65
Q

What is protein quality often based on?

A

PDCAAS or DIAAS

66
Q

What is food protein quality traditionally dependent on?

A

its amino acid content and the availability of these amino acids in circulation, factors that would influence their metabolism within different body protein pools

67
Q

Which absorbs faster, plant-based or animal-based proteins?

A

Plant-based whole foods have a lower absorbability

68
Q

What percent of the protein in eggs and chicken is absorbed?

A

85-95%

69
Q

What percent of the protein in chickpeas, mung beans and peas are absorbed?

A

50-75%

70
Q

Why do plant-based proteins have a lower absorbability?

A

There are anti-nutritional factors in plant-based protein sources e.g. fibre and polyphenolic tannins attenuate absorption

71
Q

Which has been shown to be more effective, whey or soy?

A

Whey protein

72
Q

Which has been found to increase muscle protein synthesis more, wheat or whey?

A

Wheat

73
Q

How much whey protein strongly increases muscle protein synthesis rates?

A

20-25g (providing 2.2-2.7g leucine)

74
Q

What quantities of food provide 2.7g leucine?

A

33g potato, 37g brown rice, 38g pea, 40g soy, 45g wheat protein

75
Q

Which has more leucine content, animal or plant proteins?

A

As a general rule, the leucine content of animal proteins (8-13%) exceeds plant proteins (6-8%)

76
Q

Animal protein vs Plant protein

A

Animal protein has a higher protein quality, is usually considered to be superior to plant protein for building muscle mass

77
Q

What is the protein intake recommendations for recreational athletes?

A

0.8-1.0g/kg/d

78
Q

What is the protein intake recommendations for elite male endurance athletes?

A

1.6g/kg/d

79
Q

What does current evidence suggest for protein intake to maximise protein synthesis?

A

0.3-0.4g per kg of body mass when consumed with food

80
Q

How is protein synthesis optimised across the day?

A

Protein synthesis is highest when consuming 20-30g of protein over 3-4 feedings per day

81
Q

How is protein involved in recovery?

A

Eating a source of high quality protein soon after exercise will promote muscle protein synthesis

82
Q

How much protein is recommended to repair during recovery?

A

0.25-0.30g/kg BM

83
Q

What is the rate of absorption of PRO, CHO, and Fat?

A

PRO = approx. 2-10g/h
CHO = 60-100g/h
Fat = 14g/h

84
Q

What is the absorption rate of soy protein isolate?

A

3.9g/h

85
Q

What is the absorption rate of casein isolate?

A

6.1g/h

86
Q

What is the absorption rate of whey isolate?

A

8-10g/h

87
Q

What is the LAA in soy?

A

Methionine

88
Q

What is the LAA in corn?

A

Tryptophan, Methionine and Cysteine

89
Q

What is the LAA in rice and wheat?

A

Lysine

90
Q

What is leucine sensed by?

A

senstrin2

91
Q

What does senstrin2 promote?

A

translocation of mammalian target of rapamycin complex 1 (mTORC1) to the lysosome membrane where it becomes activated

92
Q

What happens when mTORC1 is activated?

A

Results in the activation of the downstream anabolic signalling pathways that control muscle tissue protein synthesis

93
Q

What are AA’s in the liver deaminated into?

A

Urea and carbon skeletons

94
Q

What are the essential amino acids?

A

Isoleucine (BCAA)
Leucine (BCAA)
Valine (BCAA)
Lysine
Methionine
Phenylalanine
Threonine
Trytophan

HUNT245 (14 decks)

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