2.2 :Biological Molecules

Question 1

State 3 functions of water

Answer 1

• It’s a habitat. Less dense when it freezes means animals can live in it
• Water is a solvent, meaning some substances can dissolve in it.
• Helps with temperature control, because of the high specific heat capacity, and latent heat of evaporation
• Water is a reactant in important chemical reactions, including hydrolysis

Question 2

What are the bonds between two water molecules?

Answer 2

Hydrogen bonds

Question 3

why is water polar molecule?

Answer 3

Because oxygen has a slightly negative charge and hydrogen has a slightly positive charge

Question 4

State the properties of water (5)

Answer 4

• high specific heat capacity
• High latent heat of evaporation
• Very cohesive
• Lower density when solid
• Good solvent

Question 5

why is water good for cooling things?

Answer 5

Because it takes a lot of energy (heat) to break the hydrogen bonds between the molecules so water has a high latent heat of operation, and a lot of energy is used up when water evaporates

Question 6

What is a macromolecule?

Answer 6

A complex molecule with a relatively large molecular mass includes proteins, carbs, and lipids, as well as polymers

Question 7

what happens in condensation and hydrolysis reactions?

Answer 7

in condensation reactions: a bonds between two molecules is made producing a H2O molecule.
in hydrolysis, a water molecule is used to break a bond between two molecules.

Question 8

what elements are found in carbs, lipids, proteins + nucleic acids

Answer 8

Carbs: C H O
Lipids: C H O N S
Nucleic acid: C H O N P
Proteins: C H N O S

Question 9

What is the monomers for carbohydrates? Also state two examples.

Answer 9

carbohydrates are polymers made of lots of monomers called monosaccharides, which combine to make a disaccharide or polysaccharide

Examples are glucose and ribose.

Question 10

what is the structure of glucose?

Answer 10

glucose is a six carbon ringed structure, monosaccharide (hexose)

Question 11

what is the difference between alpha and beta glucose?

Answer 11

Alpha glucose has the OH on carbon one pointing down towards the ankles
whereas beta glucose has the OH on carbon one pointing towards the brain?.

Question 12

describe the structure of ribose

Answer 12

Ribose is a five carbon ring structure (pentose) It is also a monosaccharide

Question 13

what is the difference between ribose and deoxyribose?

Answer 13

ribose is found in RNA and has an oxygen atom on the second carbon, whereas deoxy ribose is found in DNA and has no oxygen on the second carbon therefore is ddee oxy ribose

Question 14

what bond forms when monosaccharides react to form polysaccharides?

Answer 14

Glycosidic bond

Question 15

Name three disaccharides and describe how they form

Answer 15

form when condensation reactions occur to form glycosidic bonds between two monosaccharides
- Maltose (glucose + glucose)
- Sucrose ( glucose + fructose)
- Lactose (glucose + galactose

Question 16

Describe the structure and functions of starch

Answer 16

Energy storage of alpha glucose in plant cells. It’s also large so can’t diffuse out of cells and insoluble.
Starch is made of amylose and amylopectin.
Amylose: is a long and branched chain of glucose. It’s got a coiled structure which makes it compact and good for storage.
Amylopectin: is a Long branched chain of glucose, its branches allow for glucose to be released quickly

Question 17

Describe the structure and functions of glycogen

Answer 17

glycogen is the main energy storage of alpha glucose in animal cells
Its structure is similar to amylopectin however, it has lots more branches. It’s also insoluble and compact.

Question 18

describe the structure + functions of cellulose

Answer 18

cellulose is a polymer of beta glucose and is found in the cell walls of plants. It helps give rigidity to plant walls.
Its structure is made of long unbranched chains of beta glucose linked by hydrogen bonds to form strong fibres called microfibrils. These help provide structural support.

Question 19

describe the structure of triglycerides

Answer 19

Triglycerides are made of one molecule of glycerol with three fatty acids attached to it by condensation using ester bonds.

Question 20

How many ester bonds does one triglyceride molecule have?

Answer 20

Three

Question 21

what is the process called in which triglycerides are synthesised

Answer 21

Esterification

Question 22

what is the difference between saturated and unsaturated fatty acids?

Answer 22

Saturated
- Contain only single bonds
- Found in animal fats
- Higher melting point (solid at room temp)
- Straight chain molecules
Unsaturated
- Contain at least one double bond between the carbon atoms
- Kinked molecules
- Found in plant oils
- Lower melting point (liquid at room, temp)

Question 23

describe the structure and function of phospholipids

Answer 23

Phospholipids are similar to triglycerides but only have two fatty acids and have a phosphate group added. The phosphate group (head) is hydrophilic, and the fatty acid tails are hydrophobic.
The function of phospholipids is that they form a phospholipid bilayer .

Question 24

Describe the structure and function of cholesterol

Answer 24

cholesterol has a hydrocarbon ring structure with an attached hydrocarbon tail and a hydroxyl (HO) group attached.
It adds stability to cell surface phospholipid bilayers by reducing the fluidity

Question 25

What is the food test for proteins and describe it

Answer 25

Biurets test.
1. Add sodium hydroxide to sample and then add copper sulfate solution
blue=negative lilac=positive

Question 26

What is the food test for starch

Answer 26

Iodine test.
1. add iodine.
brown=negative blue\black=positive

Question 27

What is the food test for lipids?

Answer 27

Ethanol emulsion.
1. Shake sample with ethanol then pour into water.
clear=negative milky=positive

Question 28

What is the test for reducing sugars

Answer 28

Benedict’s test.
1.Add benedict’s reagent (blue) to sample and heat in water bath
blue=negative
green/yellow/orange/brick red = positive (traffic light to show how strong red is strongest)

Question 29

What is the test for non reducing sugars?

Answer 29

Benedict’s test.
1. If not reducing sugar might be non reducing so get new sample
2. Add dilute hydrochloric acid (HCL) and heat in water bath
3. Neutralise it with sodium hydro carbonate then carry out normal benedict’s test
results is same as reducing! higher conc = further change in traffic lights

Question 30

What is the monomers for proteins?

Answer 30

Amino acids

Question 31

What bond is formed between two amino acids to form a dipeptide?

Answer 31

peptide bond.

Question 32

Draw out the amino acid structure and label the carboxyl group and amine group.

Answer 32

check book.

Question 33

What elements do proteins contain?

Answer 33

C, O, H, N, S

Question 34

What is the polymer for protein?

Answer 34

Polypeptide.

Question 35

What are the different stages of protein structure?

Answer 35

Primary
Secondary
Tertiary
Quaternary

Question 36

What is the primary structure of a protein?

Answer 36

The number and sequence of amino acids in a polypeptide chain.

Question 37

What is the secondary structure of an amino acid?

Answer 37

Where hydrogen bonds form and it forms alpha helix or beta pleated sheets.

Question 38

What is the tertiary structure of proteins? Also where do these occur?

Answer 38

More bonds form between different parts of the polypeptide chain.
Ionic bonds between R groups.
Disulphide bridges/ bonds.
Hydrophobic/ hydrophilic interactions.
Hydrogen bonds.

Question 39

What is the quaternary structure?
Give an example of a molecule too!

Answer 39

When several polypeptide chains are held together by bonds. eg haemoglobin has 4 polypeptide chains held together. It determines the 3D structure.

Question 40

What is a globular protein? give an example.

Answer 40

Round and compact protein.
Eg haemoglobin.

Question 41

What are fibrous proteins ? give an example

Answer 41

Tough and rope shaped proteins.
eg Collagen