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Principles of human nutrition > Protein > Flashcards

Protein Flashcards

1
Q

What are proteins?

A

-Long chains of amino acids

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2
Q

describe the structure of protein

A

-Consist of amino acids which are made up of carbon (C), hydrogen (H), oxygen (O) and nitrogen, (N)
-The radical (R) group is the part of the amino acid that makes it different from other amino acids.

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3
Q

Difference between peptide/dipeptide and polypeptide bonds

A

peptide-when the amino group of one amino acid can link with the acid group of another amino acid group to form a chain of amino acids
-water is produced as a byproduct (condesation reaction)
dipeptide- when two amino acids are joined together
polypeptide- When many amino acids are joined together

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4
Q

Draw the general structure of an amino acid?

A

google

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5
Q

What are essential amino acids?

A

Can’t be synthesised by the body so must be provided in the diet.

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6
Q

What are the essential amino acids?

A

for adults: Isoleucine
Lysine
Methionine
Phenylalanine
Threonine,
Tryptophan
Valine
-potentially arginine as its non-essential but can only be synthesised slowly
(Children: histidine)

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7
Q

Describe primary protein structure?

A

sequence of a chain of amino acids

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8
Q

Describe secondary protein structure?

A

hydrogen bonding of peptide backbone causes amino acids to fold into a repeating pattern
-2 forms:pleated sheets or alpha helix shape

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9
Q

describe tertiary protein structure?

A

3dimensional folding pattern of a protein due to side chain interaction

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10
Q

Describe quartenery protein structure?

A

protein consisting of more than one amino acid chain

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11
Q

How abundant is protein within the body?

A

2nd most abundant chemical compound in the body after water

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12
Q

Describe the proportion of protein within the average man?

A

Approx 16% of average man weighing 70kg is protein (11kg)
-43% muscle, 15% skin, 16% in blood
50% of which is comprised of 4 proteins:
collagen, haemoglobin, myosin and actin

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13
Q

What are the functions of protein

A

-enzymes (help reactions occur in the body. They function as a catalysts, increasing the rate of chemical reactions.)
-hormones (chemical messengers produced in one part of the body to function in a different part of the body. )
-antibodies (in the immune system, helping to prevent infection.)
-receptors
-neurotransmitters
-transport carriers (in blood and body fluids, eg.haemoglobin)
-make up the structure of the body e.g. cartilage, muscles, skin and hair are made of protein.
- required for growth and repair of body cells when they are damaged or old.
-Used for energy if other energy sources are running out

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14
Q

How are proteins formed?

A

Condensation reactions (water is byproduct)
(if 2 amino acds- dipeptide bonds, many amino acids- polypeptide)

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15
Q

What are the 2 types of animal proteins?

A

fibrous and globular

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16
Q

Describe fibrous proteins?

A

-insoluble
-elastic proteins that form the structural part of tissues eg.keratin,collagen, elastin, myosin

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17
Q

describe globular proteins?

A

-Relatively soluble
-in many food proteins. Also part of
fluids of all body cells
-Eg.Enzymes, protein
hormones, albumins &
globulins (blood), casein
(milk), albumin (egg
white

18
Q

what are the 2 types of plant proteins?

A

Glutelins
Prolamines

19
Q

Describe glutelins proteins?

A

-Insoluble in neutral
solutions
- soluble in acids
& alkalis.
-Storage proteins
-EG.
Glutenin (wheat), oryzenin
(rice)

20
Q

Describe prolamines protein?

A

Insoluble in water
-soluble in alcohol.
-Storage proteins
-EG,
Gliadin (wheat), zein
(maize)

21
Q

What effect does the structure of amino acids have on the protein?

A

-the specific sequence of amino acids determine function of the protein and gives them specificity.
EG: Active sites in enzymes for specific substrates
Antibody binding sites for specific antigens

22
Q

What is the function of amino acids?

A

they regulate all cellular processes and virtually all chemical reactions in living organisms

23
Q

Describe how proteins are digested?

A

-are hydrolysed by protease enzymes converting them into amino acids
-are broken down in 2 stages: first into a dipeptide (contains 2 amino acids) then the dipeptide is split into individual amino acids

24
Q

Where does protein digestion take place and describe what occurs?

A

-Stomach – a protease enzyme called pepsin converts proteins into amino acids. As pepsin is made and released in the stomach, it has an optimum pH is 2. Hydrochloric acid helps set this low pH as well as killing any harmful microorganisms in the food.
-Small intestine (duodenum) – the pancreatic juice also contains protease enzymes, including trypsin. Trypsin convert proteins into amino acids, just like pepsin.

25
Q

Examples of Plant protein?

A

Beans, nuts, seeds, quinoa, leafy greens, whole grains
(soya beans & quinoa- HBV, Peas, nuts & seeds- LBV)

26
Q

What is HBV?

A

High biological value proteins- contains essential amino acids in the necessary amounts
-Found in meat, poultry, eggs, dairy and fish.

27
Q

What is LBV?

A

Low biological value proteins.
Contains a limiting amino acid- the amino acid in shortest supply relative to the amounts needed.
-normally plant proteins are LBV

28
Q

Name some sources of protein in the diet and what protein it provides?

A

Meat & fish
* Muscle proteins – actin, myosin
* Connective tissue – collagen,
elastin, gelatin
Eggs
* Ovalbumin
Milk
* Casein
Wheat & flour
* Gluten

29
Q

What is a limiting amino acid and give examples

A

-when an essential amino acid is present at a low concentration
-eg.-Lysine in wheat protein
-Tryptophan in maize protein
-Methionine and Cysteine in beef protein.

30
Q

benefit of pregnant mothers consuming protein for the baby?

A

Newborn infants can absorb some proteins from their mothers’ milk, including antibodies which provide protection from infection

31
Q

when can protein have an adverse effect on an individual?

A

-coeliac disease- react to gluten
-some can have adverse effect to cows protein or nut protein

32
Q

in what foods can protein be harmful and how can we prevent this?

A

Certain beans including red kidney beans and soya beans contain harmful proteins
-usually require overnight soaking and thorough cooking in moist heat

33
Q

name some diseases associated with protein-energy malnutrition in children?

A

Marasmus – (wrinkled skin & muscle wasting) severe wasting due to
chronic deprivation of energy intake
to meet requirements. Can also occur
in adults
* Kwashiorkor - (scales skin, swollen ankles)
Also as a result of PEM but possibly
complicated by oxidative stress due
to infection

34
Q

Name conditions where protein have an increased rate of protein catabolism (breakdown)

A

-burns injuries
-cancer
-trauma
-sepsis
-major surgery

35
Q

What happens to protein when someone is experiencing starvation?

A

Muscle protein is catabolised to provide amino acids for synthesis of new cells and proteins for
an immune response as well as energy

36
Q

when do denaturation and coagulation occur?

A

when protein is altered by: heat, mechanical agitation, acids or salts and enzymic action.

37
Q

What happens during denaturation and what is it caused by?

A

-Strands of protein arrange themselves in a helix shape.
-Denaturation occurs when
the bonds that hold the helix structure break down
- causes the strands to separate and unravel.
This separation is caused by 5 factors:
-The application of temperature e.g. frying beef steak
-Mechanical agitation e.g. whisking egg white
-Acidity e.g. making sour cream and yoghurt
-Enzymes e.g. marinating meats
-Salt e.g. poaching eggs with salted water

38
Q

Difference of denaturation for globular and fibrous protiens?

A

-occurs in globular proteins more easily and is more easily visible
-Denaturation in fibrous proteins will occur over time

39
Q

Describe what coagulation is what happens during the process

A

-is when a denatured protein separates from other nutrients and turns from a liquid to a solid.
-occurs after denaturation
- the bonds holding the helix shape break apart and coagulation of protein occurs.
-The denatured proteins start to rejoin, forming a different structure and a solid mass.

40
Q

What is the consequences of coagulation?

A

-It’s irreversible as the proteins cannot be turned back into their liquid form
-if it continues for too long overcoagulation will occur where the proteins shrink and toughen forcing liquid out from inside the proteins

Principles of human nutrition (10 decks)

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