Biological molecules

Question 1

What is a monosacchiride?

Answer 1

Single sugar molecule

Question 2

What is a hexose sugar?

Answer 2

Sugars with 6 carbons

Question 3

Difference between Alpha and Beta glucose…

Answer 3

In alpha the OH group is below the H and vice versa

Question 4

How do monosacchirides join together? What bond is formed?

Answer 4

Join via condensation reactions forming a glycosidic bond

Question 5

Maltose made of

Answer 5

2 glucoses

Question 6

Sucrose made of

Answer 6

Glucose + Fructose

Question 7

Lactose made of

Answer 7

Glucose + Galactose

Question 8

Hydrolysis

Answer 8

Breaks disacchirides or polysacchirides down by adding a water molecule

Question 9

Testing for a reducing sugar

Answer 9

Put solution in test tube
Add Bendict’s reagent
Heat in boiled water bath
Produces a coloured precipitate

Question 10

Colour scale of Benedict’s reagent precipitate from lowest to highest concentration of sugar

Answer 10

Blue, Green, Yellow, Orange, Brick-red

Question 11

Testing for a non-reducing sugar

Answer 11

To break down to monosacchirides, add dilute HCl to sample
Heat in water bath that’s been brought to a boil
Neutralise with sodium hydrogencarbonate
Carry out test with Benedict’s Reagent

Question 12

What is meant by a reducing sugar?

Answer 12

Donates electrons to other atoms (reduces them) while it oxidises itself

Question 13

What polysacchirides is starch a mixture of?

Answer 13

Amylose and Amylopectin

Question 14

What is Amylose?

Answer 14

Long, unbranched chain of alpha glucose. 1-4 Glycosidic bonds giving it a coiled structure, this makes it compact so therefore good for storage.

Question 15

What is Amylopectin?

Answer 15

Long, branched chain of alpha glucose. Side braches allow enzymes to break down the molecule to get to 1-4 and 1-6 glycosidic bonds easily, this means glucose can be released easily.

Question 16

Starch is good for storage because…

Answer 16

It’s insoluble in water so doesn’t affect the water potential of the cell

Question 17

Iodine test for starch

Answer 17

Add iodine dissolved in potassium iodide solution to sample.
Colour change from orange-brown to blue-black

Question 18

What is the structure of cellulose?

Answer 18

Made up of long, unbranched chains of beta-glucose. Cellulose chains have alternating patterns so that hydrogen can make links between cellulose chains to form strong fibres.

Question 19

Why is cellulose good for plant cells?

Answer 19

Provides structural support for plant cells

Question 20

What is glycogen?

Answer 20

Main energy storage in humans.

Question 21

What is glycogen’s structure similar to?

Answer 21

Amylopectin but with more branches

Question 22

How does the structure of glycogen relate to its function?

Answer 22

Branches so that stored glucose can be released quickly - important for energy release in animals
Also a compact molecule which is good for storage.

Question 23

What is a triglyceride? how is it formed?

Answer 23

One molecule of glycerol with 3 fatty acids bonded to it
condensation reaction - Ester bond formed between 2 OH groups releasing water

Question 24

What makes lipids insoluble in water?

Answer 24

Have long hydrophobic tails

Question 25

What is a phospholipid?

Answer 25

Similar to triglyceride but one of the fatty acid molecules is replaced by a phosphate group(hydrophilic)

Question 26

How does the structure of triglycerides relate to their function?

Answer 26

Lipids contain more energy than carbohydrates
Insoluble so don’t affect water potential of a cell

Question 27

How does the structure of phospholipids relate to their function?

Answer 27

Centre of the bilayer they make up is hydrophobic, so water soluble substances can’t easily pass through it

Question 28

What is the monomer of a protein?

Answer 28

Amino acid

Question 29

Dipeptide

Answer 29

Two amino acids joined together

Question 30

Polypeptide

Answer 30

More than two amino acids joined together - proteins made up of one or more polypeptides

Question 31

How do amino acids link?

Answer 31

• Linked via condensation reactions to form polypeptides
• bond formed between two amino acids is called a peptide bond

Question 32

Primary Structure of proteins

Answer 32

Sequence of amino acids in the polypeptide chain

Question 33

Secondary structure of proteins

Answer 33

• Hydrogen bonds form between amino acids in chain.
• This makes it coil into an alpha-helix or fold into a beta-pleated sheet

Question 34

Tertiary structure of proteins

Answer 34

• Coiled and folded further
• Disulfide bridges form when two molecules of amino acid, cysteine, bonds to sulfur atom in the other.
• For proteins made of a single polypeptide chain, the tertiary structure forms their final 3D structure

Question 35

Quaternary structure of proteins

Answer 35

• Some proteins made of several different polypeptide chains are held together by bonds
• contain non-protein (prosthetic groups)

Question 36

Biuret’s test for proteins

Answer 36

• Test solution needs to be alkaline, so add sodium hydroxide
• Add Biuret’s reagent
• If protein present, solution should go from blue to purple

Question 37

How do amino acids differ?

Answer 37

There are 20 amino acids that are common in all organisms and they differ only from their R group

Question 38

Enzymes - structure and functions

Answer 38

• Usually spherical shape due to tight folding of polypeptide chains
• Soluble and have roles in metabolism and other enzymes synthesise large molecules

Question 39

Antibodies - Structure and functions

Answer 39

• Involved in immune response.
• Made up of two light polypeptide chains and two heavy polypeptide chains bonded together

Question 40

Transport proteins function

Answer 40

Transport molecules and ions across membranes

Question 41

Structural proteins - structure and function

Answer 41

• Physically strong
• Consist of long polypeptide chains lying parallel to each other with crosslinks between them
• Include keratin and collagen