Biological Molecules

Question 1

What are proteins?

Answer 1

Made of aa chains to form a polypeptide. Aa can be broken down and reassembled to make different proteins.

Question 2

What are examples of food groups containing protein?

Answer 2

Animal products, fungi, nuts, seeds, legumes.

Question 3

What are the functions of protein?

Answer 3

Energy, cellular components, hormones.

Question 4

How are polypeptides formed?

Answer 4

Condensation polymerisation in an addition reaction.
Hydrolysis occurs in digestion.

Question 5

How do amino acids act as a buffer?

Answer 5

H+ is highly reactive. In a basic solution, H+ lost from COOH so becomes more acidic.
In an acidic solution, H+ accepted by NH2 so becomes more basic.
Aa act as pH buffer to stabilise blood pH.

Question 6

What are the different levels of protein structure?

Answer 6

Primary - aa sequence. Peptide bonds.
Secondary - how it folds locally. H bonds.
Tertiary - 3D shape of polypeptide. H bonds, hydrophobic interactions, disulfide bridges,
Quaternary - multiple polypeptides, prosthetic groups.

Question 7

What is the difference between fibrous and globular proteins?

Answer 7

Fibrous: rod shaped, structural purposes, simple tertiary, cross links. Eg. Cytoskeleton, extra cellular matrix.
Globular: spherical, tertiary structures. Eg. Enzymes, receptors, hormones.

Question 8

Define lipids.

Answer 8

Heterogeneous group of substances associated with living systems.

Question 9

How to determine if it is omega 3, 6 or 9?

Answer 9

Count from the methyl end, where the first C=C is.

Question 10

How is a triglyceride formed?

Answer 10

By a condensation reaction between glycerol and 3 fatty acid chains.

Question 11

What are the 3 main types of lipid?

Answer 11

Fat - triglycerides. Fats and oils in diet.
Sterols - cholesterol. Membranes, myelin, bile.
Phospholipids - emulsifiers, lipid bilayer.

Question 12

What are the functions of lipids?

Answer 12

1. Structure - phospholipid, glycolipids, cholesterol, fatty acids.
2. Storage - adipocytes in adipose tissue.
3. Metabolism - essential fatty acids in cell membranes and organelles. Can alter membrane properties. Steroid and glucose metabolism impacted.

Question 13

How are lipids transported?

Answer 13

Lipids associate with apolipoproteins which make it miscible in water. Each lipoprotein has a different physiological role.

Question 14

What are the features of low density lipoproteins?

Answer 14

• from VLDL
• low amounts of TG
• highest amounts of cholesterol
• delivers cholesterol to peripheral tissues and back to liver

Question 15

What are the features of high density lipoproteins?

Answer 15

• generated in liver and intestines
• very low levels of TG
• high amounts of cholesterol
• delivers cholesterol from peripheral tissues to liver for elimination

Question 16

What is glucose needed for?

Answer 16

The normal function of the brain, kidneys, bone marrow, RBCs and reproductive tissues.

Question 17

What are the main properties of glucose?

Answer 17

Can appear as components of other molecules, main source of energy in human diets, general formula CH2O, types differ by number and arrangement and availability of nutrients during digestion.

Question 18

What are the roles of carbohydrates in the diet?

Answer 18

Energy for brain, muscles etc.
mono and disaccharides are soluble, provide volume in baked goods, brown at high temps, sweet taste.
Polysaccharides are used as thickening, texture modifiers etc.

Question 19

Describe fructose.

Answer 19

Found in fruits, honey, some veg. Industrially derived in high fructose corn syrup. Cheap to make and more stable than sucrose.

Question 20

Define glycosidic bond.

Answer 20

Type of covalent bond, water given off at carbons 1 and 4 in a condensation reaction.

Question 21

What are oligosaccharides?

Answer 21

3-8 glucose units in plants, 9-10 in animal milk.
Component of fibre from plant tissues.
Fructo-oligosaccharides found in veg, galacto-oligosaccharides found in dairy products.
Prebiotic properties.

Question 22

What are characteristics of polysaccharides.

Answer 22

Form very large molecules, synthesised by plants, animals, humans, stored for food, structural support or energy metabolism.

Question 23

What are the 2 classes of polysaccharides?

Answer 23

1. Starch - amylose, amylopectin.
2. Non starch polysaccharides - indigestible.

Question 24

What is starch?

Answer 24

Plant store of glucose and a major food reserve. Mixture of amylose and amylopectin.

Question 25

What are the types of fibres?

Answer 25

Cellulose - abundant, insoluble, indigestible. Structural support in plant cell walls, beta glucose.
Hemi-cellulose - contains other sugars, lignin and beta glucans.

Question 26

How are carbs digested?

Answer 26

• chewed food mixed with saliva and alpha amylase, hydrolyses 1-4 glycosidic bonds
  Alpha amylase denatured in stomach.
  Stomach contents move to duodenum and broken down by alpha amylase in pancreatic juice.

Question 27

How are monosaccharides absorbed?

Answer 27

Glucose and galactose are absorbed by active transport. Fructose absorbed by facilitated diffusion.

Question 28

How are carbs stored in the body?

Answer 28

As glycogen, synthesised from glucose by glycogenesis. Glycogen stores saturated at 1kg and traps lots of water.