Biological molecules

Question 1

What is the molecular formula of glucose?

Answer 1

C6H12O6

Question 2

How are monosaccarides joined together?

Answer 2

Condensation reaction

Question 3

What bond forms between two monosaccarides?

Answer 3

glycosidic bond

Question 4

What is the name of two monosaccarides joined together?

Answer 4

disaccaride

Question 5

What is sucrose made up of?

Answer 5

a glucose and a fructose molecule

Question 6

What is lactose made up of?

Answer 6

a glucose and galactose molecule

Question 7

What test can be used to test for reducing sugars and what are the results?How do you carry the test out?

Answer 7

Benedicts test
Add Benedictus reagent (blue) and heat in a water bath that’s been brought to boil if the test positive it will form a coloured precipitate.
The colour of the precipitate changes from blue to green to yellow to orange, the further on the colour the higher the concentration of the reducing sugar.

Question 8

What test can be used to test for non-reducing sugars and what are the results?How do you carry the test out?

Answer 8

If Benedictus test is negative then you probably have a non-reducing sugar.
Add hydrochloric acid to break the sugars down into monosaccarides.
Heat in a water bath that’s been brought to boil.
neutralise it with sodium hydrogen carbonate.
Then carry out the Benedictus test.

Question 9

What is a polysaccaride?

Answer 9

Many sugars joined together

Question 10

How do plants store excess glucose?

Answer 10

In starch

Question 11

What two polysaccharides is starch a mixture of?

Answer 11

alpha glucose-amylose and amylopectin

Question 12

What makes starch a good storage molecule?

Answer 12

The amylose has a coiled structure so its compact meaning you can fit lots of it into a small space.
The amylopectin is branched so enzymes that break down the molecule have easy access to the glycosidic bonds meaning glucose can be released quickly.

Question 13

What test is used for starch?

Answer 13

The iodine test.
Add iodine dissolved in potassium iodide solution to the test sample, if starch is present the sample changes from browny-orange to blue-black.

Question 14

What is the main energy storage material in animals?

Answer 14

Glycogen

Question 15

What is the monomer of starch and glycogen?

Answer 15

alpha-glucose

Question 16

What make glycogen a good storage molecule?

Answer 16

It has many branches so glucose can be quickly released.

It is a compact molecule so is good for storage.

Question 17

What monomer is cellulose made from?

Answer 17

beta-glucose

Question 18

Describe the structure of cellulose

Answer 18

The beta-glucose form straight chains, the chains are linked together by hydrogen bonds to form strong fibres called microfibrils.The strong fibres mean that cellulose provides structural support for cells.

Question 19

Name a type of lipid

Answer 19

Triglyceride

Question 20

What are triglycerides made up of?

Answer 20

One glycerol molecule with three fatty acids attached to it.

Question 21

Name a property of fatty acids

Answer 21

Insoluble in water.
Fatty acids have long hydrocarbon ‘tails’ which are hydrophobic.All fatty acids have the same basic structure however the hydrocarbon tail varies.

Question 22

What type of reaction occurs when a glycerol molecule joins with a fatty acid? What bond is formed?

Answer 22

A condensation reaction and an ester bond.

Question 23

What do unsaturated fatty acids have that saturated fatty acids don’t?

Answer 23

a carbon-carbon double bond

Question 24

Describe the structure of a phospholipid.

Answer 24

a glycerol molecule joined to two fatty acids and one phosphate group. The phosphate grouping hydrophilic.

Question 25

What makes triglyceride molecules good energy storage molecules?

Answer 25

- The long hydrocarbon chains of the fatty acids contain lots of chemical energy which is released hone there are broken down. - They're insoluble so don't affect water potential of the cell and don't cause water to enter the cell by osmosis.The triglycerides clump together as insoluble droplets because the hydrophobic tails face inwards shielding themselves from water with their glycerol heads.

Question 26

What test can be used for lipids?

Answer 26

The emulsion test. - Shake the test substance with ethanol for about a minute until it dissolves then pour the solution into water. - Any lipid will show up as milky emulsion. - the more lipid there is the more noticeable the milky colour will be.

Question 27

What are the monomers of proteins?

Answer 27

Amino acids

Question 28

What reaction forms polypeptides?What bonds are between amino acids?

Answer 28

- Condensation reaction | - Peptide bonds

Question 29

Describe the secondary structure of proteins:

Answer 29

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

Question 30

Describe the tertiary structure of proteins:

Answer 30

- The coiled or folded chain of amino acids is often coiled or folded further. - More bonds form between different parts of the polypeptide chain, including hydrogen and iconic bonds. - Disulfide bridges also form whenever two molecules of cysteine come close together.

Question 31

Describe the quaternary structure of proteins:

Answer 31

- some proteins are made of several different polypeptide chains held together by bonds. - the quaternary structure is how these chains are assembled together.

Question 32

What is the test used for proteins? What is a positive result?

Answer 32

The Biuret test - Add a few drops of sodium hydroxide solution - then add some copper sulfate solution - if a protein is present it turns purple

Question 33

Give 5 properties of water:

Answer 33

- good metabolite - high latent heat of vaporisation - buffers changes in temperature - good solvent - strong cohesion between molecules

Question 34

Explain the fact that water is a good metabolite:

Answer 34

- Many metabolic reactions involve a condensation or hydrolysis reaction. - A hydrolysis reaction requires a water molecule to break a bond and a condensation reaction releases water as a bond is formed.

Question 35

Explain the fact that water has a high latent heat of vaporisation:

Answer 35

- It takes a lot of energy to break the hydrogen bonds between water molecules - This means a lot of energy is needed to evaporate water. - This means organisms can use water loss through evaporation to cool down without loosing too much water.

Question 36

Explain the fact that water buffers changes in temperatures:

Answer 36

- The hydrogen bonds between molecules absorb a lot of energy. - So water has a high specific heat capacity. - This means that water doesn't experience rapid temperature changes. - This means water is a good habitat as the temperature is more stable that on land. - Also water inside organisms help maintain a constant body temperature.

Question 37

Explain the fact that water is a good solvent:

Answer 37

- A lot of important substances in metabolic reactions are ionic. - because water is a polar molecule both positive and negative ions are attracted to it. - this means ions will get surrounded by water molecules (they'll dissolve)

Question 38

Explain the fact that there is a strong cohesion between water molecules:

Answer 38

- Strong cohesion helps water flow making it great for transporting substances e.g in. the xylem - The cohesion also means water has a high surface tension causing it to from droplets of sweat helping organisms to cool down and it also allows organisms to walk on the surface of water.

Question 39

Describe the structure of ATP:

Answer 39

made up of adenine a ribose sugar and three phosphate groups