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Nutrition - Proteins Flashcards

1
Q

Proteins are made up of 4 elements. What are they?

A

Carbon, Hydrogen, Oxygen & Nitrogen

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2
Q

What is the function of proteins?

A

Needed for growth and repair of body cells

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3
Q

Some proteins can contain small quantities of?

A

Sulfur, iron (Fe) and phosphorus

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4
Q

What is the basic structure of an amino acid? Each amino acid contains:

A 
An amino acid group (NH2)(basic)
A carboxyl group (COOH)(acidic)
A central carbon (C)
A single hydrogen (H)
A variable group (R)
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5
Q

What are essential amino acids?

A

Cannot be manufactured in the body, so they must be obtained by food.

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6
Q

Name 4 essential amino acids

A

Valine, Lysine, Histidine (children), Arginine (children)

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7
Q

What are non-essential amino acids?

A

Can be manufactured in the body

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8
Q

Name 4 non-essential amino acids

A

Alanine, Cysteine, Proline, Glycine

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9
Q

How are peptide links formed?

A

When two amino acids join together, called a condensation reaction.

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10
Q

Explain the primary structure of proteins

A

The order of sequence of amino acids in protein chains. Can be arranged in many different combinations.
Insulin is the simplest [protein, contains 51 amino acids

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11
Q

Explain Disulfide bonds

A

Occur when two sulfurs from two amino acids join together from either aa single polypeptide chain or two different polypeptide chains
Insulin contains disulfide bonds

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12
Q

Explain Hydrogen Bonds

A

Occur when a hydrogen from the N-H group of one amino acid and and Oxygen from the C=O group of another amino acid join together to form either a single polypeptide chain or two different polypeptide chains.
Collagen contains hydrogen bonds

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13
Q

Explain the Secondary Structure of Proteins

A

Involves the folding of the primary structure of proteins into definite shapes
Polypeptide chains either fold in on themselves or cross-link with another polypeptide chain, causing the chains to form a spiral shape.

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14
Q

Explain the Tertiary Structure of Proteins

A

Involves the folding of the secondary structure of proteins into three-dimensional shapes.
Further cross-linking between amino acids forms definite shapes, which may be fibrous (elongated) or globular (folded over itself to form a compressed unit).

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15
Q

Explain the Fibrous protein structure

A

Polypeptide chains are arranged in straight, spiral or zigzag shapes

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16
Q

What are the properties of Fibrous protein structure

A

Insoluble in water

Not easily denatured

17
Q

Examples of Fibrous proteins

A

Gluten (Wheat)

Elastin and collagen (meat connective tissue)

18
Q

Explain the Globular protein structure

A

Polypeptide chains are arranged in a globular shape

19
Q

List the properties of the globular protein structure

A

Soluble in water

Easily denatured

20
Q

List examples of the Globular protein structure

A

Ovalbumin (Egg white)

Lactalbumin (Milk)

21
Q

Name 2 animal sources of protein and 2 plant sources

A

Beans, nuts, lentils

Meat, fish, eggs

22
Q

What are HBV proteins?

A

Proteins that contain all essential amino acids

23
Q

What are LBV proteins?

A

Lack one or more essential amino acids

24
Q

What are the properties of proteins? (6)

A
  1. Denaturation
  2. Elasticity
  3. Maillard Reaction
  4. Solubility
  5. Gel Formation
  6. Foam Formation
25
Q

What is denaturation?

A

Is the change in the nature of a protein chain

26
Q

What are the causes of denaturation? + Culinary application

A

Heat, causes protein chains to unfold and bond together. CA: egg white coagulate and change from a translucent to opaque colour

Chemicals, lowering or raising pH levels by the addition acids and alkalis. CA: Vinegar based marinade tenderises meat

Mechanical Action, cause protein chains to unfold and partial coagulation. e.g. whipping. CA: Beating of eggs to make sponges.

Enzymes, Cause a change to the structure of protein. CA: Rennin in rennet causes caseinogen in milk to coagulate during cheese-making

Mechanical action

27
Q

What is elasticity? + Culinary application

A

Some fibrous proteins e.g. gluten in wheat are quite elastic. CA: Gluten makes yeast dough elastic

28
Q

What is Maillard Reaction? + Culinary Application

A

The non-enzymic browning of food due to a reaction between certain amino acids and sugars under dry heat. CA: Roast potatoes

29
Q

What is Solubility?

A

Most proteins are insoluble in water apart from collagen and egg albumin. CA: moist heat tenderises mean by converting collagen to gelatine. e.g. beef during stewing

30
Q

What is Gel Formation?

A

Gelatine can absorb large amounts of water when heated, as protein chains uncoil and water becomes trapped. This forms a sol. e.g. jelly sweets

31
Q

What is a sol?

A

A sol is a solution that contains particles that do not dissolve but are evenly dispersed throughout the liquid.

32
Q

What is foam formation?

A

When an egg white is whisked, protein chains unfold and air bubbles form. The protein chains entrap air and foam is created. It will collapse after a while unless it is heated to coagulate and set as a permanent foam.
CA: Meringues

33
Q

Effects of heat on proteins

A

coagulation, Colour change, Maillard reaction on dry heat, overcooked proteins causes them to become indigestable, moist heat tenderises meat.

34
Q

What are the physiologically active protein functions? (Assists with normal functioning of the body)

A

Production of:
+Hormonal proteins - production of insulin.
+Enzymes - speed up chemical reactions
+Antibodies (immunoglobulins) - defend the body from harmful substances e.g. viruses.
+Blood Proteins
+Nucleoproteins (DNA)

35
Q

What is the RDA/RI of protein for adults & older people?

A

50-75g

36
Q

How much energy does protein provide?

A

1g of protein = 4kcal of energy

37
Q

Explain the digestion of proteins

A

Water and enzymes break protein chains into separate amino acids. This process is call hydrolysis. see pg 15

38
Q

Explain the absorption and utilisation of proteins

A

Amino acids are absorbed by the small intestine. They [ass through the wall of the villi and into the bloodstream.

Used to repair liver cells & form new cells, hormones, enzymes & antibodies

39
Q

What is Deamination?

A

Process through which excess amino acids are broken down by the body in the liver

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