SAC - enzymess, photosynthesis, respiration

Question 1

What is a biological catalyst?

Answer 1

Catalysts are substances that speed up the rate of chemical reactions. The basic function of enzymes is to act as a catalyst and increase the rate of almost all chemical reactions.

Question 2

What are products?

Answer 2

the outputs of an enzyme-catalyst reaction.

Question 3

What is a substrate?

Answer 3

is the molecule that the enzyme acts on or the input to an enzyme-catalysed reaction.

Question 4

What is an enzyme substrate complex?

Answer 4

the compound produced by the bonding of an enzyme with its specific substrate, at the active site of the enzyme.

Question 5

What are the types of enzyme specificity?

Answer 5

Absolute or substrate specificity, bond specificity, group specificity.

Question 6

What is absolute or substrate specificity?

Answer 6

means that the enzyme acts only on one substrate. E.g. lactase only can hydrolyse lactose.

Question 7

What is bond specificity?

Answer 7

means enzyme can act only on one kind of chemical bond. E.g. peptidase enzymes act on only peptide bonds b/w two amino acids.

Question 8

What is group specificity?

Answer 8

means an enzyme can act only on molecules with particular functional groups. E.g. trypsin only acts on peptide bonds adjacent to amino acids with basic side chains.

Question 9

What are the types of enzyme specificity models?

Answer 9

Lock and key models, induced fit models.

Question 10

Explain lock and key model

Answer 10

Proposed in 1894 by Emil Fischer. Explains that the enzyme acts as the lock, and the substrate as the key. Therefore only the correctly shaped key (substrate) can fit the lock (active site).

Question 11

Explain induced fit model

Answer 11

Proposed in 1958 by Daniel Koshland. Explains that the active site of an enzyme has a defined shape, but one with a degree of flexibility. The active site changes shape to fit tightly around the substrate, and returns to its original shape in resting state.

Question 12

What is catabolism?

Answer 12

cellular reactions that release useful energy from the breakdown of complex molecules.

Question 13

What is anabolism?

Answer 13

cellular reactions when complex molecules required by cells are synthesised from simpler building blocks, a process that requires an input of energy.

Question 14

What is exergonic?

Answer 14

metabolic reactions that release energy.

Question 15

What is endergonic?

Answer 15

reactions that require energy.

Question 16

When something is synthesised what does this mean?

Answer 16

It means that the molecule is being made from smaller molecules.

Question 17

What is a cofactor?

Answer 17

It is a molecule that sits in the active site of an enzyme so that the substrate can now fit into the active site better. This in turn increases the rate and efficiency of reaction.

Question 18

What are two type of cofactors?

Answer 18

Regular cofactors, coenzymes.

Question 19

What are coenzymes?

Answer 19

They are organic cofactors (they contain carbon and hydrogen bonded together) and unlike regular cofactors, they get affected in the reaction, so they must be thrown away and replaced by a new coenzyme between each new substrate.

Question 20

What are inhibitors?

Answer 20

Is a molecule that binds to an enzyme, reducing its activity by interfering with the enzyme in some way.

Question 21

What are the two types of inhibitors?

Answer 21

competitive inhibitors, non-competitive inhibitors.

Question 22

What are competitive inhibitors?

Answer 22

Are a compound that resembles the substrate molecule, meaning that they fit into the active sit, but do not react. This competitive inhibitor “blocks” the substrate from fitting into the active site, and therefore reduces the amount of product formed.
Can be reversible or non-reversible.

Question 23

What are non-competitive inhibitors?

Answer 23

Are compounds that bind to a site that is seperate from the active site. This binding inhibitor changed the shape of the enzyme (and therefore the shape of the active site). This change of the active site does not allow substrate to bind to the active site, and therefore reduces the product formed.

Question 24

What is the equation for photosynthesis?

Answer 24

6CO2 + 6H2O –light–chlorophyll–> C6H12O6 + 6O2

Question 25

What are the input and outputs of P/S?

Answer 25

INPUTS - light, carbon dioxide, water.

OUTPUTS - oxygen, glucose.

Question 26

What is meant photoautotrophic ?

Answer 26

Organisms that use light to make organic molecules, and can turn simple compounds to organic compounds.

Question 27

Definition of photosynthesis

Answer 27

Is the process in which plants, algae and some bacteria and protests use energy from the sun to make organic molecules. They are described as photoautotrophic.

Question 28

What are the two phases of photosynthesis?

Answer 28

Light dependent phase, light independent stage (Calvin cycle).

Question 29

What is the light dependent phase and where does it occur?

Answer 29

It occurs in the thylakoid membranes of the chloroplast. It requires light energy which drives the movement of electrons across the thylakoid membranes which is known as ‘electron transport chain’ (ETC). The electrons power the pump of H ions into thylakoid space, and produce energy to form new NADPH (NADP+H–>NADPH+H)

Question 30

What are the inputs and outputs of the light dependent phase?

Answer 30

INPUTS - H2O, NADP, light

OUTPUTS - O2, ATP, NADPH

Question 31

What is the light independent phase and where does it occur?

Answer 31

also called the Calvin cycle, this stage occurs in the stroma of the chloroplast. It does not need light as a direct input, but needs the light dependent stage to occur in order to work. This is because it takes ADP and NADPH from the light dependent stage to put into the Calvin cycle.

Question 32

What are the inputs and outputs of the light independent phase?

Answer 32

INPUTS - ATP, NADPH, CO2

OUTPUTS - Glucose and H2O

Question 33

What are factors affecting enzymes?

Answer 33

Temperature, pH, enzyme concentration, substrate concentration.

Question 34

What are factors affecting photosynthesis?

Answer 34

light intensity, type of light (wavelength), CO2 availability, water availability, temperature.

Question 35

What is the equation of aerobic respiration?

Answer 35

C6H12O6+6O2—>6CO2+6H2O+36ATP

Question 36

What is the process of cellular respiration and where does each stage occur?

Answer 36

1. Glycolysis - occurs in the cell cytoplasm
2. Kreb cycle (transition reaction) - occurs in the mitochondrial matrix
3. ETC - occurs in the mitochondrial cristae.

Question 37

Explain the process of glycolysis including inputs and outputs.

Answer 37

Glycolysis means ‘sugar splitting’. This stage converts glucose to pyruvate. Has two main functions, produce ATP and NADH. Produces pyruvate.
INPUTS - glucose, ADP+Pi, NAD+H
OUTPUTS - pyruvate, 2ATP, 2NADH.

Question 38

Explain the process of transition reaction including inputs and outputs.

Answer 38

Links pyruvate with the kerb cycle (is an intermediate step in the process). Pyruvate is taken into the matrix and is converted to CoA.
INPUTS - pyruvate
OUTPUTS - CoA

Question 39

Explain the process of the Kreb Cycle including inputs and outputs.

Answer 39

Is a series of chemical reactions in the matrix of the mitochondria. Requires “two turns” to completely break down (oxidise) a molecule of glucose.
INPUTS - pyruvate
OUTPUTS - CO2, 2ATP, NADH, FADH

Question 40

Explain the process of ETC including inputs and outputs.

Answer 40

Final stage of aerobic respiration, occurs in the cristae of the mitochondria. This is where 02 is used. Energy from NADH and FADH are used to power pumps to move the H atoms.
INPUTS - NADH, 02, FADH
OUTPUTS - 32 ATP, H20