Biological molecules (water) 2.1.2

Question 1

Organic molecules

Answer 1

• Contain hydrogen and carbon
• Either macromolecules (Molecules containing a large number of atoms) or small molecules

Question 2

Polymers and monomers

Answer 2

Polymers are a chain of repeating units (monomers) joined togther by covalent bonds and formed through a condensation reaction. Monomers are molecules that are covalently bonded to eachpther to form a polymer.

Question 3

What are the biomolecules?

Answer 3

Lipids, nucleic acids, carbohydrates and proteins.

Question 4

How many bonds can the elements carbon, nitrogen, oxygen and hydrogen form?

Answer 4

• carbon atoms can form 4 bonds
• nitrogen atoms can form 3 bonds
  -Oxygen can form 2 bonds
  -Hydrogen forms 1 bond

Question 5

Important cations

Answer 5

• Sodium ion (Na +) necessary for nerve impulse transmission and kidney function.
• Potassium ion (K+) nerve impulse transmission and stomatal opening.
• Calcium ion (Ca 2+) nerve impulse transmission and muscle contraction
• Hydrogen ion (H+ aka a proton) catalysis of reactions and pH determinations
• Ammonium ion (NH4) production of nitrate ions by bacteria

Question 6

Important anions

Answer 6

• Chloride (Cl-) balances charge of sodium and potassium ions in cells
• Hydroxide (OH-) catalysis of reactions and pH determinations
• Nitrate (NO3-) nitrogen supply to plants for amino acids and protein production.
• Phosphate (H2PO4-) cell membrane formation, nucleic acid and ATP formation, bone formation.
• Hydrogen carbonate (HCO3-) maintainence of blood pH

Question 7

The living composition of a cell

Answer 7

70% water, (about)1% inorganic substances, 29% organic polymers and macromolecules, 0-1% organic monomers and other organic molecules.

Question 8

what is an ion?

Answer 8

An atom or molecule in which the total number of electrons are not equal to the number of protons.

Question 9

Carbohydrates

Answer 9

Polymer = Polysaccarides
Name of bond between polymers = Glycosidic bond
Monomer = Monosaccarides
Elements = C, H, O

Question 10

Fats/Lipids

Answer 10

Polymer = Triglycerides
Name of bond between polymers = Ester bond
Monomer = 3 fatty acids + glycerol
Elements = C, H, O

Question 11

Proteins

Answer 11

Polymer = Polypeptide
Name of bond between polymers = Peptide bond
Monomer = Amino acids
Elements = C, H, N, O, S

Question 12

Nucleic acids

Answer 12

Polymer = Polynucleotides
Name of bond between polymers = Phosphodiester bond
Monomer = Nucleotides
Elements = C, H, O, N, P

Question 13

Elements in carbohydrates, fats, proteins and nucleic acids

Answer 13

CHO
CHO
CHNOS
CHONP

Question 14

Hydrolysis

Answer 14

• All polymers are broken down/hydrolysed into their respective monomers by the addition of water to break the covalent bond.
• A catabolic/exothermic reaction so releases energy.
  -(look at diagram on powerpoint)

Question 15

Condensation reaction

Answer 15

• All monomers are joined condensed into their respective polymers by the removal of water to form a covalent bond.
• An anobolic reaction (endothermic) requires an input of energy.

Question 16

The water molecule

Answer 16

• An oxygen atom bonded to 2 hydrogen
• Oxygen is delta negative (s-) whereas oxygen is delta positive (s+)
• It’s a polar molecule as theres an uneven distribution of charge
• Hydrogen bonds are weak
• Hydrogen bonding gives water it’s unique characteristics.

Question 17

Characteristics of water

Answer 17

• Has an unusually high BP
  -A small molecule much lighter than carbon dioxide and water.
• A liquid at room temp due to the hydrogen bonds
• When water turns into ice it becomes less dense.
• ## As water is cooled below 4 degrees the hydrogen bonds fix in the positions of the polar molecules slightly further apart then the average distance in the liquid state.

Question 18

Important functional groups in biological molecules

Answer 18

These are all polar (hydrophyllic)
- Hydroxyl (many in carbohydrates)
- carbonyl
- carboxylic acids (present in amino and fatty acids)
- amino
- Sulfhydryl (involved in protein structure)
- Ester
- Phosphate
Except for:
- methyl/hydrocarbon(non polar/hydrophobic)

Question 19

Solvent properties of water

Answer 19

• Ionic substances can dissolve in water because a shell of orientated water molecules is formed around each ion.
• Polar substances e.g. simple sugars can dissolve in water due to hydrogen bonding between polar group in their molecules.

Question 20

Water is polar

Answer 20

• Known as the universal solvent as it dissolves more substances than any other liquid
• Forms a shell around ions and makes H bonds with polar solutes

Biological importance:
1. Water is the medium for chemical reactions to take place.

2. Cells are 70% water
3. Water acts as a transport medium e.g. in blood, phloem and xylem.
4. Water is a reactant in some reactions e.g. hydrolysis.

Question 21

High specific heat capacity of water

Answer 21

• This is high in water due to the presence of hydrogen bonds

Biological importance
1. Stable temperature for enzyme controlled reactions

2. Both eukaryotic and prokaryotic cells less prone to damage from change in temp
3. Aquatic organisms have a stable environemnt.
4. Thermoregulation for organisms

Question 22

High latent heat of vaporisation for water

Answer 22

• High due to hydrogen bonds

Biological importance
1. water as a coolant (sweating, panting, transpiration)

2. water is a liquid over large range of temperatures.

Question 23

High specific heat capacity of water

Answer 23

• High due to hydrogen bonds
• Stable temp for enzyme reactions
• Eukaryotic and Prokaryotic cells less prone to changes in environment.
• Thermoregulation is facilitated for organisms to keep their temp constant.

Question 24

Which type of bond holds the delta negative oxygen and delta positive hydrogen together between water molecules?

Answer 24

Hydrogen bond

Question 25

Specific latent of vapourisation (Liquid to gas)

Answer 25

- sweat evapourates off skin - panting in animals - transpiration stream keeps plants cool in hot weather.

Question 26

Cohesive forces in water

Answer 26

- The forces of attraction between molecules, high for water due to hydrogen bonds Biological importance: 1. Allows for transpiration stream so water can move up great heights in a tree.

Question 27

Surface tension

Answer 27

- When the surface of a liquid resists external forces, it is formed on water due to strong cohesive forces due to hydrogen bonds. Biological importance: 1. Habitat for insects e.g. pond skaters

Question 28

What is surface tension?

Answer 28

the cohesion of the molecules on the surface of a fluid to occupy the least possible volume.

Question 29

Which type of bond holds the oxygen and hydrogen together within a water molecule?

Answer 29

Covalent bonds

Question 30

What is the name for the substances that are dissolved in a liquid and the name of the liquid that other molecules are dissolved in?

Answer 30

Solvent and solute

Question 31

What are polar molecules?

Answer 31

Any molecule with an uneven distribution of charge across it.

Question 32

Molecules that are attracted to water and molecules that are repelled by water

Answer 32

Hydrophillic and hydrophobic

Question 33

What term describes the structure than forms when water freezes into ice?

Answer 33

Lattice

Question 34

What is the name for water molecules hydrogen bonding to other water molecules?

Answer 34

Cohesion

Question 35

Density of ice and water

Answer 35

- In ice each water molecule is hydrogen bonded to a maximum of 4 other water molecules. - The crystal structure formed requires water molecules to move further away from eachother therefore there are fewer molecules in a given space than in liquid water so this makes ice less dense than water. - The highest density of water is at 4 degrees as ice melts this cold dense water sinks below the water underneath and creates currents which move nutrents around. Biological importance 1. Ice insulates ponds by providing a cover so water remains liquid underneath so aquatic organisims can survive. 2. Forms a habitat for terrestial organisms on the surface of ice

Question 36

Adhesion in water

Answer 36

- The attraction between different molecules this allows for capillary effect e.g. between water and glass Biological importance 1. Water movement in transpiration stream is enabled by attraction to xylem walls

Question 37

It is transparent

Answer 37

Light will penetrate to reach aquatic plants and algae for photosynthesis

Question 38

Sex cells (gametes) can be suspended in it

Answer 38

Sperm can reach eggs for internal and external fertilisation

Question 39

Equal density

Answer 39

Creates buoyancy for aquatic organisms

Question 40

High latent heat of fusion

Answer 40

Contents of cells and aquatic environments are slow to freeze in the winter

Question 41

Polar covalent bonds are characterised by

Answer 41

An unequal sharing of electrons between two atoms in a molecule

Question 42

How does water arrange around dissolved glucose?

Answer 42

Slightly charged parts of water molecules are attracted to the opposite slightly charged regions of a glucose molecule.

Question 43

What is the name for water molecules hydrogen bonding to other water molecules? It is this property that makes small water droplets join into fewer larger droplets. It is also the property of water that maintains a continuous column of water through a plant to enable water transport through the xylem

Answer 43

Cohesion

Question 44

What are the 4 roles of water in the specification?

Answer 44

Coolant, solvent, transport medium and habitat.

Question 45

What is the name for water molecules hydrogen bonding to different types of molecule? It is this property that makes the meniscus when water is hydrogen bonding to the molecules that make the walls of the tube (or container) it is in

Answer 45

Adhesion

Question 46

Which property of water allows it to act as a skeleton (called a hydrostatic skeleton), allows organisms to push against it to move (e.g. fish swimming), and allows hearts to push water around rather than squashing it?

Answer 46

It is incompressible