C1.1

Question 1

Define catalyst.

Answer 1

a substance that increases the rate of a chemical reaction without itself undergoing any permanent chemical change.

Question 2

State the role of enzymes in the chemical reactions on which life is based. ​

Answer 2

Enzymes are proteins that act as catalysts to make the rate of chemical reactions faster and more efficient.
- lower the activation energy for a reaction to take place

Question 3

Enzymes _______ chemical reactions without being altered. Therefore, enzymes can be ______.

Answer 3

speed up, reused

Question 4

Define metabolism

Answer 4

The sum of all chemical reactions in an organism.

Question 5

Define specificity in relation to enzyme structure and function.

Answer 5

The enzyme’s active site can only bind with specific substrates. The ability of an enzyme to select a specific substrate from a range of chemically similar compounds is known as specificity. Charges have to align (+)(-) and shape has to fit together as a puzzle piece. The enzyme can then break the substrate or mold the substrates together.

Question 6

Outline how control of metabolism is regulated by enzymes.

Answer 6

The cell can control a metabolic pathway by the presence or absence of a particular enzyme. Cells have evolved to use feedback inhibition to regulate enzyme activity in metabolism.

Negative feedback loops doesn’t mean it’s a bad thing - refers to dampening or reversal of a condition.
Positive feedback loops doesn’t mean it’s a good thing - refers to increasing or amplifying change of a condition.

Question 7

Contrast anabolic and catabolic reactions.

Answer 7

Anabolism:
- builds molecules for body to function
- require energy input
- endergonic reaction
- condensation (water is produced)
Catabolism:
- breaks down big complex molecules into smaller, easier to absorb molecules.
- releases energy
- exergonic reaction
- hydrolysis (water is consumed)

Question 8

List three examples of anabolic processes.

Answer 8

• photosynthesis (sunlight to plant food)
• peptide bond formation (links connect amino acids to form polypeptide chains, which fold into functional proteins)
• glycosidic bond (covalent chemical bonds that hold together a glycoside -sugar molecules attached to another molecule)

Question 9

List three examples of catabolic processes.

Answer 9

• cell respiration (a series of chemical reactions that break down glucose to produce ATP)
• digestion
• oxidation (a process that occurs when atoms or groups of atoms lose electrons)

Question 10

Outline properties of globular proteins.

Answer 10

• always soluble in water
• often have a spherical or roundish shape

Question 11

Explain the relationship between enzyme structure and enzyme specificity, including the structure and function of the active site.​

Answer 11

• structure/specificity is primarily defined by the enzyme’s shape and the characteristics of its active site (consequence of its amino acid sequence - R groups)
• active site: The part of the enzyme where the substrate binds

Question 12

Outline the stages of enzyme catalysis of a chemical reaction.

Answer 12

-enzyme-substrate are in same area
-enzyme binds with substrate in active site
-catalysis - join or break substrate
-product release

Question 13

Describe the induced fit model of enzyme binding.​

Answer 13

states that when a substrate binds to an active site, the enzyme changes shape slightly, to accommodate the substrate and create an ideal fit for catalysis.

Question 14

Explain the role of random collisions in the binding of the substrate with the enzyme active site.

Answer 14

faster-moving substrates are more likely to randomly collide with an active site (and a reaction can occur).

Question 15

Compare enzyme and substrate movement involved in reactions that occur in the cytoplasm, with large substrates and with immobilized enzymes.

Answer 15

glycolysis-uses enzymes to break down sugar molecules for cell respiration, takes place in cell cytoplasm (intracellular).

Question 16

Discuss variation in specificity of different enzymes.

Answer 16

Enzymes are highly specific so different enzymes are needed to bind and carry of chemical reactions

Question 17

Define denaturation.

Answer 17

an enzyme that has loss of function or is non-functional in reactions due to its change in shape.

Question 18

Outline the causes and effects of denaturation on enzyme structure and function.

Answer 18

-causes: deviations from optimal temperature and pH
-when an enzyme loses its native conformation, or three-dimensional structure, rendering it non-functional (unable to bind to substrate and catalyze product formation)

Question 19

Graphs of temperature, pH, substrate concentration along with enzyme activity

Answer 19

Google docs

Question 20

Explain the effects of temperature on enzyme structure and function with reference to collision theory, temporary and permanent denaturation.

Answer 20

Temp: Raising temperature speeds up a reaction (allows for more collision between substrate and enzymes to bind), and lowering temperature slows down a reaction. However, extreme high temperatures can cause an enzyme to lose its shape (denature) and stop working.

Question 21

Explain the effects of
pH
on enzyme structure and function with reference to collision theory, temporary and permanent denaturation.

Answer 21

pH: Each enzyme has an optimum pH range.
(1-6) acidic environment
(8-14) basic environmenet
Changing the pH outside of this range will slow enzyme activity.

Question 22

Explain the effects of substrate concentration on enzyme structure and function with reference to collision theory, temporary and permanent denaturation.

Answer 22

Increasing substrate concentration also increases the rate of reaction to a certain point. Once all of the enzymes have bonded substrates, any substrate increase will have no effect on the rate of reaction, as the available enzymes will be saturated and working at their maximum rate.

Question 23

Identify the manipulated (independent), responding (dependent) and controlled variation in experiments of enzyme catalyzed reactions.

Answer 23

independent - concentration of enzyme, the concentration of the substrate, the temperature, and the addition of an inhibitor
dependent - rate of reaction
control - enzyme activity

Question 24

State the unit for enzyme reaction rate.

Answer 24

one micromole of substrate per minute (ex. micromol/min)

Question 25

State two methods for determining the rate of enzyme reaction rates.

Answer 25

-measure the appearance of the product as a function of time
-measure the disappearance of substrate as a function of time.

Question 26

Describe three investigative techniques for measuring the activity of an example enzyme.

Answer 26

spectrophotometry - measures the absorption or emission of light by the enzyme or its products
titration - involves measuring the pH change or the consumption of a reactant
enzymatic assays - which use specific substrates and measure quantity of a specific enzyme in an organism or sample.

Question 27

Define activation energy.

Answer 27

The amount of energy needed for a reaction to take place

Question 28

Activation energy is used to ____ or ______ bonds in the substrate.

Answer 28

break, weaken

Question 29

Explain the role of enzymes in lowering the activation energy of a reaction.

Answer 29

Enzymes lower the energy of the transition state, an unstable state that reactants must pass through in order to become products. The transition state is at the top of the energy “hill” in the diagram above.

Question 30

Interpret graphs showing the effect of lowering the activation energy by enzymes.

Answer 30

Google docs

Question 31

Not all enzyme reactions are 100% efficient. _____ energy is generated by metabolic reactions. This refers to energy that is ____.

Answer 31

Heat, lost

Question 32

Metabolic paths can be _____ or _______.

Answer 32

linear, cyclical

Question 33

An example of a linear metabolic pathway is _______ since it __________.

Answer 33

glycolysis, uses enzymes to split a sugar molecule into 2 pyruvate molecules

Question 34

Cyclical pathways involve the products becoming _______ at the end. An example is the _______ which the products are used as ______ to keep the cycle going.

Answer 34

reactants, Calvin Cycle, substrates

Question 35

Describe non-competitive inhibitor

Answer 35

Attach to a different part of the enzyme which changes the shape of the active site

Question 36

Describe competitive inhibitor

Answer 36

attach to a block an enzyme’s active site

Question 37

Describe feedback inhibition:

Answer 37

-In excessive amount, bumps into the enzyme and prevents the body from creating more molecules than it needs
-Isoleucine can bind to the allosteric site of Threonine deaminase to stop the creation of more Isoleucine (amino acid).

Question 38

Mechanism based inhibition

Answer 38

-enzyme can no longer be reused for substrates
-substrate binds to enzyme and creates a stable covalent bond —(valence electrons (octet) stability for cell)
-ex. extremely toxic lead, mercury, other metals