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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
Q

Complementary/ supplementary value

A

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
Q

Properties - denaturation

A

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
Q

Properties - denaturation (heat)

A

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
Q

Properties - denaturation (chemical)

A

Rising or lowering PH levels by the addition of acids and alkaline can denature structure
Eg. Vinegar based marinade tenderises meat

29
Q

Properties - denaturation (mechanical action)

A

Whipping/beating causes chains to unfold and partial coagulation occurs
Eg. Beating eggs - meringues

30
Q

Properties - denaturation (enzymes)

A

Cause change to structure
Eg. Rennin in rennet causes caseinogen in milk to coagulate during cheese making (curds and whey)

31
Q

Properties - Maillard reaction

A

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
Q

Properties - solubility

A

Most - insoluble
Exceptions - collagen (hot water) + albumin (cold water)
Eg. Moist heat tenderised meat by converting collagen - gelatine (stewing)

33
Q

Properties - foam formation

A

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
Q

Effects of heat - dry

A

Maillard reaction - roast potatoes

35
Q

Effects of heat - moist

A

Tenderises meat - collagen —> gelatine (pulled pork)

36
Q

Effects of heat - dry and moist

A

Coagulation - whites 60 yolks 68
Colour change - myoglobin - haematin
Overcooking - becomes indigestible

37
Q

Biological functions - structural

A

Production of cell membranes, muscle tissues and skin
Cell repair and replacement
Growth

38
Q

Biological functions - physiological

A

Production of hormonal proteins (coordinate body activity), blood proteins (moves molecules around body - haemoglobin) and antibodies (defend body from harmful substances)

39
Q

Biological function - nutrient

A

Provide body with EAAs
Excess - source of energy when carbs and fat reserves run out

40
Q

RDA + RI

A

1g per kg of body weight
Children - 30-50g
Adults + older people - 50-75g
Adolescence - 60-80g
Pregnant + lactating - 70-85g

41
Q

Digestion

A

Stomach - gastric juice - (rennin - caseinogen - casein) (pepsin - proteins - peptones)
Pancreas - pancreatic juice - trypsin - peptones - peptides
S intestine - intestinal juice - pepidase - peptides - amino acids

42
Q

Absorption + utilisation

A

Small intestine —> walls of villi —> bloodstream —> hepatic portal vein —> liver —> deaminated

43
Q

Deamination

A

Excess protein —> liver —> (NH2) converted to ammonia and urea and excreted as urine through kidneys) (COOH) oxidised for heat and energy)

44
Q

Properties - gel formation

A

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
Q

What are the properties of protein

A
  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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