Biochemistry

Question 1

What was the theory of vitalism?

Answer 1

Organic molecules found in organisms were thought to only be produced in living organisms due to vital force

Question 2

What falsifies vitalism?

Answer 2

The artificial synthesis of urea. Urea is a nitrogen containing component found in urine and it is synthesised in the liver. According to vitalism, urea could only be made in living organisms using vital force. Wohler artificially synthesised urea in the lab without enzymes.

Question 3

What do living organisms consist of?

Answer 3

Water

Question 4

What are the four main classes of organic molecules?

Answer 4

Carbohydrates
Lipids
proteins
Nucleic acids

Question 5

What are macromolecules?

Answer 5

Very large molecules with a high molecular mass.

Question 6

What are polymers?

Answer 6

Macromolecules composed of many repeated subunits(monomer)

Question 7

What is a dimer?

Answer 7

2 monomers bonded together

Question 8

Why is carbon atoms very important?

Answer 8

They can form four covalent bonds allowing a greater diversity of compounds to exist. It can join to other carbon atoms to form chains and is stable.

Question 9

What do organic molecules contain?

Answer 9

Carbon

Question 10

What are exceptions of compounds that contain carbon but are inorganic?

Answer 10

Hydrogencarbonate
Carbon monoxide
Carbon Dioxide
Carbonate

Question 11

What are the most common elements found in living organisms and where are they found?

Answer 11

Hydrogen, Oxygen, Carbon –> in all four main classes
Nitrogen–> Proteins and nucleic acids
Phosphorus–> Nucleic acids, phospholipids, ATP
Sulfur–> in some proteins

Question 12

What are the following elements needed for:
Fe
Na
I
K 
Ca

Answer 12

Fe- haemoglobin and myoglobin
Na and K- nerve impulse transmission
I- thyroxin production
Ca- synaptic transmission, muscle contraction, bone formation and blood clotting

Question 13

What is metabolism?

Answer 13

The web of all enzyme catalysed reactions in a cell or organism

Question 14

What occurs in metabolic pathways?

Answer 14

• one molecule is transformed into another in a series of steps
• each reaction is catalysed by a specific enzyme and the product becomes the reactant
• metabolic pathways are mostly chains but there are sometimes cycles

Question 15

What is anabolism?

Answer 15

The synthesis of complex molecules from simpler molecules - require energy.

Question 16

What are examples of anabolism?

Answer 16

Protein synthesis
DNA replication
Photosynthesis

Question 17

What is catabolism?

Answer 17

The breakdown of complex molecules into simpler molecules including the breakdown of macromolecules in hydrolysis reactions- release energy.

Question 18

What are examples of catabolic reactions?

Answer 18

Digestion, cell respiration , decomposition of dead matter

Question 19

What happens in a condensation reaction?

Answer 19

Two molecules are joined together to form a larger molecule with the removal of water . Each condensation reaction is catalysed by a specific enzyme

Question 20

Give examples of condensation reactions

Answer 20

amino acid + amino acid–> dipeptide + water

Glucose + glucose–> maltose + water

Question 21

What happens in hydrolysis reactions?

Answer 21

A large moleucles is broken down into smaller molecules with the addition of water. Each hydrolysis reaction is catalysed by a specific enzyme.

Question 22

Give examples of hydrolysis reactions

Answer 22

lactose+ water–> glucose + galactose

Glycerides + water–> fatty acids + glycerol

Question 23

How many molecules of water are required to completely hydrolyse a polypeptide made up of 23 amino acids?

Answer 23

22

Question 24

Why does water have unique properties?

Answer 24

1. Because of its polarity

2. Because of its hydrogen bonds

Question 25

Water molecules are polar. Explain this feature.

Answer 25

Two H atoms are linked by covalent bonds to an oxygen atom. These bonds are polar covalent bonds bc there is the unequal sharing of electrons. Therefore, hydrogen atoms have a partial positive charge and the oxygen atom have a partial negative charge. Water has two poles- dipoles

Question 26

There is hydrogen bonds between water molecules. Explain this feature.

Answer 26

Hydrogen bonds form between water molecules because water molecules are polar. The hydrogen bonds form between the hydrogen atom of one molecule with the oxygen of another molecule.

Question 27

What are properties of water?

Answer 27

Cohesion 
Adhesion 
Thermal properties- High latent heat of vaporization 
High specific heat capacity
High melting and boiling point 
Solvent

Question 28

Describe the cohesive property of water and state why it is important.

Answer 28

Water molecules cohere due to hydrogen bonding. This is important in water transport in plants. Due to cohesion, water can be pulled up in xylem vessels in continuous columns without the water molecules separating by the suction forces. Plus, water has a high surface tension allowing small insects to walk on it.

Question 29

Describe the adhesive property of water and state why it is important.

Answer 29

Water molecules adhere to polar surfaces. This is because water molecules are polar and can form hydrogen bonds with other polar molecules. It is important because when water evaporates from the cell walls of spongy mesophyll cells, adhesive forces between the cellulose in cell walls and water cause water to be drawn out of the nearest xylem vessel.

Question 30

Describe the high latent heat of vaporisation of water and state why it is important.

Answer 30

For water to evaporate, hydrogen bonds must break. Energy is needed for this and since there are a lot of hydrogen bond a lot of energy is required. This is important as it is an excellent coolant in sweating

Question 31

Describe the high specific heat capacity of water and state why it is important.

Answer 31

Due to hydrogen bonding, the amount of energy needed to raise the temperature of water is high. This is important because that means that water remains relatively stable compared to air or land so it is a thermally stable habitat for aquatic organisms

Question 32

Describe the high melting/boiling point of water and state why it is important.

Answer 32

For melting and boiling the forces between the molecules need to be overcome so that the molecules can move and break apart. Due to hydrogen bonding, a lot of heat is needed. This is important as water is a liquid between the temperature range found in most habitats on Earth making it suitable for living organisms.

Question 33

Describe the solvent property of water and state why it is important.

Answer 33

Water is an excellent solvent because, dur to its polarity, many substances - ions and polar molecules- can dissolve. This is important as water acts as a medium for metabolic reactions and a medium for the transport of dissolved substances.

Question 34

Which substances dissolve in water?

Answer 34

Hydrophilic substances such as polar molecules and ionic compounds dissolve in water. They dissolve because their ions are attractive to water molecules and form intermolecular bonds with them.

Question 35

What are hydrophobic interactions?

Answer 35

The forces that cause non-polar molecules to join together when placed in water

Question 36

Give two examples of how water is used in living organisms

Answer 36

1. Transport in blood

2. Coolant in sweat

Question 37

What is dissolved in the plasma and describe why/how?

Answer 37

Sodium Chloride- dissolves to form ions
Glucose- polar molecule so dissolves
Amino acids- solubility depends on their R group- they are all soluble enough to be dissolved in blood plasma
Oxygen- non-polar but bc it is small it dissolves in water but only sparingly. Not enough oxygen is found in teh plasma for cell respiration so haemoglobin has binding sites instead for oxygen.

Question 38

What is not dissolved in blood plasma?

Answer 38

Fats and Cholesterol
- non-polar and insoluble in water
They are carried in the blood inside lipoprotein droplets. These droplets are formed by a monolayer of phospholipids and proteins. The fats are carried inside the droplet where the environment is hydrophobic . The cholesterol is positioned in the phospholipid monolayer with their small hydrophilic region facing outwards in the region with of phospholipid phosphate heads.

Question 39

Describe how water is used as a coolant in sweat.

Answer 39

1. Sweating is an effective way of cooling the body because water has a high latent heat of vaporisation
2. When the body is overheated, sweat glands in the skin produce sweat
3. For water to evaporate the hydrogen bonds between water molecules need to break
4. Energy is needed to break the hydrogen bonds - a lot is needed as there are many bonds
5. This heat is removed from the blood/body thus cooling it down.