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Home Ec Xmas 2023 > Protein > Flashcards

Protein Flashcards

1
Q

Elemental composition

A

Carbon
Hydrogen
Oxygen
Nitrogen

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2
Q

Chemical structure

A

Amino group (NH2) alkaline
Carboxyl group (COOH) acidic
Central carbon
Single hydrogen
Variable (R) diff with each aa

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3
Q

Glycine

A

When R is H

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4
Q

Cysteine

A

When R is HS-CH2

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5
Q

Essential amino acids

A

Valine
Lysine
Methionine
Threonine
Histidine
Tryptophan
Leucine
Isoleucine
Arginine
Phenylalanine

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6
Q

Non essential amino acids

A

When 2 amino acids join
Acidic (COOH) from one aa reacts with alkaline (NH2) of another resulting in loss of a water molecule (condensation reaction)

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7
Q

Dipeptide

A

2 amino acids joined (after condensation reaction has occurred)

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8
Q

Polypeptide

A

More than 20 aa join

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9
Q

Protein formed

A

More than 50 aa join
Each protein - 1 or more polypeptide chains

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10
Q

Structure of protein (primary)

A

Sequence of aa in protein chains
Arranged in different combinations
Eg insulin 51 aa arranged in diff order

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11
Q

Structure - secondary

A

Folding of primary structure into definite shapes
Polypeptide chains fold in on themselves OR cross link with another polypeptide chain
Causes spiral shape. Cross links give proteins their unique properties

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12
Q

Cross links - disulfide

A

When 2 sulfurs from 2 aa join to form 1 or 2 polypeptide chains
2 Cysteine can form disulfide
Eg insulin has disulfide bond

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13
Q

Cross links - hydrogen

A

When a (H) from the (N-H) group of an aa + an (O) from the C=O of another aa join to form 1 or 2 polypeptide chains
Serine + Tyrosine
Eg collagen has hydrogen bond

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14
Q

Tertiary structure

A

Folding of secondary structure into (3D) shapes. Further cross linking between aa forms definite shapes (fibrous and globular)

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15
Q

Fibrous

A

Polypeptide chains are arranged in straight, spiral and zigzag (2D shapes)
Properties : insoluble in water + not easily denatured
Eg gluten - wheat

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16
Q

Globular

A

Polypeptide chains arranged in globe shape (3D
Properties : soluble in water + easily denatured
Eg ovalbumin - egg white

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17
Q

Classification

A

Simple
Conjugated

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18
Q

Simple proteins

A

Animal
- fibrous — collagen — meat connective tissues
- globular — ovalbumin — egg white

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19
Q

Simple proteins pt 2

A

Plant
- glutenins — glutenin — wheat
- prolamins — zein — maize

20
Q

Conjugated proteins

A

Lipoproteins (lipid + p)
- lecithin — eggs
Phosphoproteins (phosphate + p)
- caseinogen — milk

21
Q

Sources

A

Animal Plant
- meat - beans
- fish - nuts
- eggs - peas
- milk - cereals

22
Q

Biological value (BV)

A

BV- measure of the protein quality in food
%
Determined by no. Of EAA a good contains in proportion to the needs of the body

23
Q

HBV

A

Contain all EAA
Eggs - 100% — ovalbumin
Milk - 95% — lactalbumin
Meat - 80-90% — collagen
Fish - 80-90% — collagen
Soya beans - 74% — glycinin

24
Q

LBV

A

Lack 1 or more EAA
rice - 67% — oryzenin
Wheat - 53% — gluten
Maize - 40% — Zein
Meat bones - 0% — gelatine

25
Complementary/ supplementary value
LBV deficient in 1 or more EAA consuming 2 LBV foods together ensure all EAA are obtained Eg beans (high methionine + low in lysine) + toast (low methionine + high in lysine)
26
Properties - denaturation
Change in the nature of a protein Unfolding of a protein chain results in irreversible change in shape Results in hardening + coagulation of protein foods Causes: heat, chemical, mechanical action + enzymes
27
Properties - denaturation (heat)
Causes protein chains to unfold + bond together causing food to coagulate and set Eg. Egg white coagulate + set Translucent - opaque 60 whites 68 yolks
28
Properties - denaturation (chemical)
Rising or lowering PH levels by the addition of acids and alkaline can denature structure Eg. Vinegar based marinade tenderises meat
29
Properties - denaturation (mechanical action)
Whipping/beating causes chains to unfold and partial coagulation occurs Eg. Beating eggs - meringues
30
Properties - denaturation (enzymes)
Cause change to structure Eg. Rennin in rennet causes caseinogen in milk to coagulate during cheese making (curds and whey)
31
Properties - Maillard reaction
Non enzymic browning of food due to a reaction of a certain aa + sugars under dry heat Produces brown color Eg. Roast potatoes, short bread
32
Properties - solubility
Most - insoluble Exceptions - collagen (hot water) + albumin (cold water) Eg. Moist heat tenderised meat by converting collagen - gelatine (stewing)
33
Properties - foam formation
When egg white whisked, chains unfold and air bubbles form Chains trap air creating foam Whisking also creates heat that begins to set as a permanent foam Eg. Meringues
34
Effects of heat - dry
Maillard reaction - roast potatoes
35
Effects of heat - moist
Tenderises meat - collagen —> gelatine (pulled pork)
36
Effects of heat - dry and moist
Coagulation - whites 60 yolks 68 Colour change - myoglobin - haematin Overcooking - becomes indigestible
37
Biological functions - structural
Production of cell membranes, muscle tissues and skin Cell repair and replacement Growth
38
Biological functions - physiological
Production of hormonal proteins (coordinate body activity), blood proteins (moves molecules around body - haemoglobin) and antibodies (defend body from harmful substances)
39
Biological function - nutrient
Provide body with EAAs Excess - source of energy when carbs and fat reserves run out
40
RDA + RI
1g per kg of body weight Children - 30-50g Adults + older people - 50-75g Adolescence - 60-80g Pregnant + lactating - 70-85g
41
Digestion
Stomach - gastric juice - (rennin - caseinogen - casein) (pepsin - proteins - peptones) Pancreas - pancreatic juice - trypsin - peptones - peptides S intestine - intestinal juice - pepidase - peptides - amino acids
42
Absorption + utilisation
Small intestine —> walls of villi —> bloodstream —> hepatic portal vein —> liver —> deaminated
43
Deamination
Excess protein —> liver —> (NH2) converted to ammonia and urea and excreted as urine through kidneys) (COOH) oxidised for heat and energy)
44
Properties - gel formation
When collagen is heated —> gelatine Gelatine can absorb large amounts of water when heated protein chains uncoil and water gets trapped Forms a sol (solution that contains particles that do not dissolve but are evenly dispersed throughout liquid) When cooling, sol forms a gel (viscosity) Eg. Jelly sweets
45
What are the properties of protein
1. Denaturation 2. Elasticity 3. Maillard reaction 4. Solubility 5. Gel formation 6. Foam formation

Home Ec Xmas 2023 (2 decks)

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