Unit 2: Section 1 - Biological Molecules

Question 1

How does water help with temperature control?

Answer 1

It carries away heat energy when it evaporates from a surface. This cools the surface and helps to lower the temperature

Question 2

Why does it take a lot of heat energy to heat up water and how is this useful for living organisms?

Answer 2

The hydrogen bonds between water molecules can absorb a lot of energy. It stops rapid temperature changes, allowing organisms to keep their temperature fairly stable

Question 3

What is specific heat capacity?

Answer 3

The energy needed to raise the temperature of 1 gram of a substance by 1 degree

Question 4

What does it mean when water is said to have a ‘high latent heat of evaporation’ and why is this the case?

Answer 4

It takes a lot of energy to break the hydrogen bonds between water molecules, so water has a high latent heat of evaporation (a lot of energy is used up when water evaporates).

Question 5

Why is water cohesive?

Answer 5

Because water molecules are polar so they are very cohesive towards each other, this helps water to flow

Question 6

Why is water a good solvent?

Answer 6

A lot of molecules are ionic (one positive atom and one negative atom), because water is polar, the positive end of a water molecule will be attracted to the negative ion and vice versa. This means that the ions will get completely surrounded by water molecules and dissolve.

Question 7

What are dipeptides, polypeptides and proteins made up of?

Answer 7

Dipeptides - Two amino acids joined together
Polypeptides - more than two amino acids joined together
Proteins - One or more polypeptides

Question 8

What is a proteins primary structure?

Answer 8

The sequence of amino acids in the polypeptide chain

Question 9

What is a proteins secondary structure?

Answer 9

The polypeptide chain doesn’t remain flat and straight. Hydrogen bonds form between the amino acids in the chain. This makes it coil into an alpha helix or fold into a beta pleated sheet.

Question 10

What is a proteins tertiary structure?

Answer 10

The secondary structure is folded further. More bonds form between different parts of the polypeptide chain. For proteins made from a single polypeptide chain, the tertiary structure forms the final 3D shape.

Question 11

What is a proteins quaternary structure?

Answer 11

The way the polypeptide chains are assembled together. For proteins made from a single polypeptide chain, the tertiary structure forms their final 3D structure.

Question 12

What type of bonds hold together the primary structure?

Answer 12

Peptide bonds between amino acids

Question 13

What type of bonds hold together the secondary structure?

Answer 13

Hydrogen bonds that form between nearby amino acids

Question 14

What type of bonds hold together the tertiary structure?

Answer 14

Ionic interactions - Weak attractions between negative and positive charges on different parts of the molecule
Disulfide bonds - Only occur when two molecules of the amino acids ‘cysteine’ come close together, the sulfur atoms bond together.
Hydrophobic and hydrophilic interactions - when hydrophobic groups are close together they tend to clump together. So hydrophilic groups will be pushed to the outside
Quaternary structure - All the bonds above

Question 15

How is collagen adapted to its function?

Answer 15

Collagen is a fibrous protein that forms supportive tissues in animals, so it needs to be strong. Its made of 3 polypeptide chains tightly coiled together in a triple helix. The chains are interlinked by strong covalent bonds. Minerals can bind to the triple helix to increase its rigidity.

Question 16

How is haemoglobin adapted to its function?

Answer 16

Haemoglobin is a globular protein with an iron-containing haem group that binds to oxygen, carrying it around the body. Its structure is curled up so the hydrophilic side chains are on the outside. This makes haemoglobin soluble in water, so it can be transported in the blood.

Question 17

What are the features of starch?

Answer 17

Plants store excess glucose as starch. Starch is a mixture of two polysaccharides of alpha glucose (amylose and amylopectin). Starch is insoluble in water, so it doesnt cause water to enter the cells by osmosis. This makes it good for storage.

Question 18

What is the structure of amylose?

Answer 18

Long, unbranched chain of alpha glucose. The angles of the glycosidic bonds give it a coiled structure. This makes it compact, so its really good for storage.

Question 19

What is the structure of amylopectin?

Answer 19

A long, branched chain of alpha glucose. Its side branches allow the enzymes that break down the molecule to get at the glycosidic bonds easily. This means that the glucose can be released quickly

Question 20

What are the features of glycogen?

Answer 20

The main energy storage material in animals. Animals store excess glucose as glycogen (a polysaccharide of alpha glucose) Structure is similar to amylopectin, except that it has loads more side chains, meaning that stored glucose can be released much more quickly. It is also very compact, so good for storage.

Question 21

What are the features of cellulose?

Answer 21

Made of long, unbranched chains of beta glucose. Bonds between sugars are straight so the cellulose chains are straight. The cellulose chains are linked together by hydrogen bonds to form strong fibres called microfibrils. The strong fibres mean cellulose provides structural support for cells.

Question 22

How are triglycerides adapted to their function?

Answer 22

1) The long hydrocarbon tails of the fatty acid contain lots of chemical energy - lots of energy is released when they’re broken down
2) They are insoluble, so they dont cause water to enter the cell by osmosis which would make them swell.