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Proteins Flashcards

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1
Q

What is the elemental composition of proteins ?

A

Carbon
Hydrogen
Oxygen
Nitrogen(only one with it provides growth and repair)

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2
Q

Chemical structure of proteins?

A

Proteins are made up of amino acids
Amino acids contain carbon hydrogen a variable group(R) an amino group(NH2) and an acidic carboxyl group(COOH)

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3
Q

What is an essential amino acid?

A

Cannot be made by the body
Must get from food

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4
Q

What is a non essential amino acid?

A

Can be made in the body
Don’t need to get from food

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5
Q

Examples of essential amino acids

A

Leucine
Lycine
Isoleucine
Valine

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6
Q

Examples of nonessential amino acids

A

Glycine
Alanine
Proline
Serine

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7
Q

How many common amino acids are there?

A

20

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8
Q

How many amino acids do children need?

A

10

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9
Q

How many amino acids do adults need ?

A

8

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10
Q

What is a peptide bond?

A

Amino acids are linked by a peptide bond
A carboxyl group (COOH) of one amino acid combines with an amino group (NH2) or another
A molecule of water (H20) is released (condensation) during this process and a dipetide is formed.

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11
Q

What is a dipeptide?

A

Two amino acids linked by a peptide bond

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12
Q

What is a tripeptide?

A

Three amino acids linked

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13
Q

What is a polypeptide?

A

Many amino acids linked

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14
Q

What is hydrolysis?

A

The reverse of the condensation process
Peptide bonds are broken down by the addition of water (H2O)
Producing single amino acids

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15
Q

What is the primary structure of a protein?

A

The sequence of amino acids in a polypeptide chain
The chain is formed by peptide links

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16
Q

What is the secondary structure of a protein?

A

Amino acids in a polypeptide chain are further folded by cross links to create definite shapes

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17
Q

What is a disulphide link?

A

Occurs when two sulphurs are linked together on a polypeptide chain or across two polypeptide chains

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18
Q

What is a hydrogen bond?

A

Hydrogen bonds occur in polypeptide chains when a hydrogen in one chain links with oxygen in a nearby chain eg. Collagen

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19
Q

What is the tertiary Structure of a protein?

A

Pattern of folding polypeptide chains into three dimensional shapes
Shapes are held in place by cross links and may be fibrous or globular

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20
Q

What is a fibrous shape?

A

Fibrous shapes are insoluble in water they are difficult to denature
They may be straight , coiled or zigzag in shape
Examples: gluten(wheat) , elastin (meat)

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21
Q

What are globular shapes?

A

Globular shapes are soluble in water and easily denatured they are ball shaped
Examples : myoglobin (meat) , haemoglobin(blood)

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22
Q

What are simple proteins?

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A

Proteins that contain amino acids

23
Q

What are conjugated proteins?

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A

They contain amino acids and a non-protein component

24
Q

What are derived proteins?

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A

Formed from chemical or enzymatic actions on the protein itself eg. Rennin acts on caseinogen

25
How are simple proteins classified?
There are two types animal -classified by shape Plant - classified by solubility
26
Examples of animal simple proteins
Fibrous - collagen and elastin - connective tissue Globular - albumin- egg white
27
Examples of plant simple proteins
Glutelins- insoluble in water soluble in acids and alkalis eg. Glutelin(wheat) oryzenin(rice) Prolactin’s- insoluble in water soluble in alcohol eg. Gliadin(wheat) Zein ( maize)
28
Types of conjugated proteins
There are four types of conjugated proteins Lipoprotein-lecithin-egg yolk Phosphoproteins- casein- milk Chromoproteins- haemoglobin, myoglobin- blood , meat Nucleoproteins- chromosomes- DNA
29
Sources of protein -animal
Meat , fish , poultry , eggs , milk , cheese
30
Sources of protein-plant
Soya beans , whole cereals , nuts , pulses
31
What is Hbv protein?
High biological value protein Contains all essential amino acids Come mainly from animal sources (exception soya beans)
32
What is LBV proteins?
Low biological value proteins lack one or more essential amino acids They come mainly from p,any sources (except gelatine)
33
What is the supplementary role of proteins?
If a protein is deficient in one amino acid the deficiency can be overcome by eating a food rich in the amino acid at the same meal eg beans on toast Beans are high in lysine and low in methionine Toast is high in methionine and low in lysine
34
What is denaturation?
Protein chains unfold and it’s structure changes and cannot be reversed May be due ton Mechanical action - whisking Chemicals - adding acids /alkalis Heat - causes protein to coagulate and set Enzymes - rennin coagulates caseinogen to casein
35
What is the solubility of proteins?
Most proteins are insoluble in water Except collagen in hot water And albumin ( egg white ) in cold water
36
What is the Maillard reaction?
Non enzymic browning of food result when amino acids react with carbohydrates in dry heat eg. Short bread Results in a brown colour
37
What is elasticity?
Gluten is vert elastic it allows breads and cakes to rise during baking
38
What is gel formation?
Gelatine absorbs water and swells to form a gel a gel is a semi- solid viscous solution with a three dimensional network in which molecules of water can be trapped. When heated the gel becomes a sol, on cooling sets and becomes solid Eg. Jellies
39
What is foam formation?
Whisking egg whites causes protein chains to unfold and air bubbles to form which trap air Whisking produces heat which lightly sets the egg white the foam will then collapse unless heated Eg. Meringues
40
What are the biological functions of structural proteins?
growth and repair production of cells,muscles and skin
41
42
Deficiency of structural proteins ?
stunted growth delayes healing of wounds
43
What are the biological functions of physiologically active proteins?
produvtion of antibodies, enzymes, hormones, blood protiens and nucleoproteins
44
What are the deficiencies of physiologically active proteins?
illness and infections malfunction of body systems and organs
45
What are the biological functions of nutrient proteins?
provide essential amino acids excess converted to energy
46
What are the deficiencies of nutrient proteins?
lack of energy marasmus ans kwashiorkor
47
What is the energy value of protein
1g = 4kcal
48
Reference intake of proteins ?
children- 30-50g adolescents - 60-80g adults- 50-75g pregnant women- 70-85g
49
Explain the digestion of proteins
proetins are hydrolysed with the help of protein splitting enzymes and water
50
Deamination
excess proteins are deamninated by the liver the amino group of the amino acid is converted to amnonia and then urea the urea is excreted from the body in urine yhe carboxyl group is oxidised (used for heat and energy ) excess js stored in the body as glycogen
51
Absorption of amino acids/proteins
amino acids are absorbed by the blood vessels in the villi of the small intestine and transported to the liver via the hepatic portal vein
52
How are amino acids utilised?
they are used to repair and maintain liver cells form new cells repair damaged tissue and make antibodies ,enzymes and hormones
53
This does not contain the organ gland table or the biological value of foods distribution of proteins

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