Biological molecules

Question 1

How do hydrogen bonds form between water molecules ?

Answer 1

Water is a polar molecule meaning oxygen is more electronegative than hydrogen which therefore makes oxygen slightly negative and hydrogen slightly postive .
There are intermolecular forces of attaction between a lone pair of oxygen of one molecule and hydrogen on an adjancent molecule

Question 2

State biological important properties of water

Answer 2

• High specfic heat capacity
• High latent heat of vaporisation
• High surface tension
• Reaches maximum density at 4 degrees
• Cohesion between molecules
• Incompressible
• Good solvent
• Transport medium
• Medium for chemical reactions
• Habitat for organisms

Question 3

Why is it important that ice is less dense then water?

Answer 3

Ice is less dense then water because the hydrogen bonds are held in fixed postions further away.
The ice floats which insulates the water underneath from freezing protecting habitats underneath

Question 4

Why is it important that water has a high surface tension?

Answer 4

• Slows water loss due to transpiration in plants
• Water rises unusually high in narrow tubes, lowering demand on root pressure

Question 5

Why is it important that water is a good solvent ?

Answer 5

Polar universal solvent dissolves and transports charged particles.
This is because waters charge is unevenly distrubted so it is able to dissolve charged particles

Question 6

1.Why is high specific heat capacity important?
2. Why is latent heat of vapourisation important?

Answer 6

1. Acts as a temperature buffer which helps to resist fluctuations in core temperatures to maintain optimum enzyme activity
2. Colling effect when water evaporates from skin surface as sweat

Question 7

What is a:
1. Monomer
2. Polymer

Answer 7

1. Monomers - smaller units that join together to form molecules (monosaccharides, amino acids, nucleotides)
2. Polymer - molecules formed when many monomers join together (polysaccharides, proteins, DNA / RNA

Question 8

What happens in a:
1. Condensation reaction
2. Hydrolysis reaction

Answer 8

1. Chemical bond forms between 2 molecules and a molecule of water is produced
2. A water molecule is used to break a chemical bond between 2 molecules with the help of a enzymes

Question 9

Carbohydrates + lipds : C,H,O
Proteins : C,H,O,N,S
Nucleic acids : C,H,O,N, P

Question 10

Alpha glucose

Properties of a alpha glucose ( monosaccharides + diasaccharides)
* small + water solube = easily transported in the blood
* sweet
* forms crystals

Answer 10

Structure of an alpha glucose
* triose - 3 carbons
* pentose - 5 carbons
* hexose - 6 carbons

Question 11

What is a diaccharides ?

Answer 11

Two monosaccharides join to form a diaccharides

Question 12

1. alpha glucose + alpha glucose =?
2. alpha glucose + fructose =?
3. alpha glucose + galactose =?
4. beta glucose + beta glucose =?

Answer 12

1. maltose
2. sucrose
3. lactose
4. cellulose

Question 13

What are the properties of polysaccharides?

Answer 13

• Insolube in water
• Not sweet
• Cant be crystalisised

Question 14

What is the function of starch ?

Answer 14

• Insolube in water - doesnt affect the water potential ( glucose lowers the water potential)
• Brached - main energy storage in plants ( branched structure in amylopectin means lots of glucose can be released and used quickly for respiration
• Compact - doesnt take up of space + good energy storage molecule

Question 15

What is the structure of starch:

Answer 15

1. amylose - **1,4 glycosidic bonds **with a helix and intermolecular H bonds = compact ( alpha glucose) coiled
2. amylopectin - 1,4 + 1,6 glycosidc bonds , branched to access glucose to be accessed more easily (roots in plants) colied but has branches

Question 16

What is the structure and function of glycogen?

Answer 16

• Function : **main energy storage **of alpha glucose in animal cells (liver +muscles)
• Structure :** 1,4 + 1,6 glycosidic bonds** , branched,less coiled , compact , more ends at the end of the branches
  insolube in water - doesnt affect water potential

Question 17

What is the function and strucutre of cellulose ?

Answer 17

• Structure: Polymer of beta glucose molecules joined together by hydrogen bonds forming strong fibres called mircofibrils - straight chains
• Function: high tensile strength because of the glycosidic bonds and hydrogen bonds between the chains preventing bursting when turgid , fibres go in all directions so gives it extre strength
• ** fully permeable**
• turgid to help protect the strucure of the whole plant
• Fibre - Helps maintain a healthy digestive system

Question 18

How is a glycosidic bond formed with two beta glucose?

Answer 18

the alternate b glucose is rotated through 180 forming strain chains . Forms hydrogen bonds with adjancent molecules

Question 19

What is the function of :
1. amylose
2. amylopectin
3. glycogen
4. cellulose

Answer 19

1. respiration in plants, store of energy
2. respiration in plants, store of energy
3. used to store glucose in the liver + muscles , aerobic respiration
4. cell wall and fibre

Question 20

How does a triglycerides form?

Answer 20

A condensation reaction between 1 molecule of glycerol and **3 fatty acids **with form a ester bonds

Question 21

What is the function of lipids ?

Answer 21

• Energy source
• structure
• thermal insulation
• electrical insulation
• protection + cushioning
• waterproofing
• hormones

Question 22

what are :
1. saturated acids
2. unsaturated fatty acids

Answer 22

1. Saturated
   * all carbon atoms have formed the maximum number of bonds
   * no double bonds = no kinks
   * high melting point = solid at room temp.
2. unsaturated
   * contain atleast one double bond
   * double bonds = liquid at room temperature
   * monounsaturated - one double bond
   * polyunsaturated- two or more double bond

Question 23

What is the function of triglycerides ?

Answer 23

• energy store
• release high amounts of energy
• non-polar so insolube and doesnt affect water potential waterproofing
• respiration which releases water for desert animals
  * thermal insulation

Question 24

What is the structure of phospholipids ?

Answer 24

• glycerol backbone attached to 2 hydrophobic fatty acid tails and 1 hydrophilic polor phosphate head

Question 25

What is the function of phosolipids?

Answer 25

* Forms **phosolipid bilayers** - tails inwards , heads outwards * Forms **micelles** - tiny balls with the tails pointing in and heads out * water proofing

Question 26

What is the structure and function of cholesterol ?

Answer 26

Structure: Steriod structure of 4 hyrdocarbons with a **hydrocarbon** **tail** and a **hydroxyl group** on the other side Function : adds stability to cell surface phospholipid bilayer by reducing fluidity

Question 27

How do polypeptides form?

Answer 27

A condensation reaction between amino acids to form a peptide bond

Question 28

What are the primary structure of a protein?

Answer 28

* primary structure - a **specific** sequence of amino acids

Question 29

What is the secondary structure of a protein?

Answer 29

* **alpha helix** - spiral shape and hydrogen bonds parallel to helical axis * **b- pleated sheets** - a flat sheet where the polypeptide that folds back on itself stablised by hydrogen bonds

Question 30

# W What is the tertiary structure of proteins ? What are the bonds present as well ?

Answer 30

* A **3d structure** formed by futher folding * **Disulfide bonds** - Strong covalent s-s bonds between molecules of the amino acid cysteine (very strong) * **Ionic bonds** - relatively stron bonds between charded R-groups (quite strong) * **Hydrogen bonds** - numerous and easily broken (very weak) * **Hydrophobic/hydrophilic interactions** - whether the R group faces inwards or outwards away from the water or towards the water ( weak) * **Peptide Bonds** - Stong covalent bonds between amino acids ( very , very strong )

Question 31

What is a conjugated protein?

Answer 31

Proteins that contain a **non protein part** which is known as the **prosthetic group** which may be attached to any of the bonds

Question 32

Describe the structure of a globular proteins

Answer 32

* Spherical and compact * precise primary structure with a non repeating amino acid sequence * complex secondary and tertiary structure * solube in water

Question 33

What is the function of globular proteins ?

Answer 33

* Hydrophilic R groups face outwards and hydrophobic r groups face inwards = usually water soluble * Involved in metabolic processes e.g enzymes , amylase. insulin

Question 34

What is the structure of haemoglobin?

Answer 34

* Globulat conjugated proteins with a prosthetic group ( haem) * 2 alpha chains and 2 beta chains * Water soluble so dissovles in plasma * Fe2+ haem group forms a bond with o2 to transport oxygen around the blood

Question 35

what is the structure of fibrous proteins?

Answer 35

* long narrow fibres * simple primary structure with repeating amino acid sequence * simple secondary and tertiary structure * insolube in water

Question 36

What is the function of : 1. Collagen 2. elastin 3. keratin

Answer 36

1. component of bones, cartilage, connective tissue , tendons 2. elasticity to connective tissue , arteries , skin , lungs, cartilage and ligaments 3. structural component of hair , nails , hooves