Metabolism

What term describes the totality of chemical processes that occur within a cell to maintain life?

Metabolism.

In metabolic reactions, what is the role of an enzyme?

To act as a biological catalyst, speeding up the rate of reaction.

What type of metabolic reaction involves combining smaller compounds to form larger ones, often releasing water?

Anabolism.

The process of combining organic compounds, which is a key part of anabolism, is known as _.

condensation

What type of metabolic reaction involves breaking down large compounds into smaller ones, requiring water as an input?

Catabolism.

The breakdown of organic compounds, a key part of catabolism, involves what type of reaction with water?

Hydrolysis.

Photosynthesis is an example of what kind of metabolic reaction?

An anabolic reaction.

Cell respiration is an example of what kind of metabolic reaction?

A catabolic reaction.

An enzyme is a globular protein that acts as a biological catalyst by lowering the _ energy threshold.

activation

What is the specific indentation or cavity on an enzyme to which a substrate can bind?

The active site.

The model describing how an enzyme's active site undergoes a conformational change to improve bonding with the substrate is known as the _ model.

induced-fit

What is the primary cause of molecular motion that leads to collisions between substrates and enzymes in aqueous solutions?

Brownian motion.

What term describes the loss of an enzyme's tertiary structure and biological activity due to external factors like temperature or pH?

Denaturation.

How does increasing temperature initially affect the rate of an enzyme-catalysed reaction?

It increases the kinetic energy of particles, leading to more frequent enzyme-substrate collisions and a higher reaction rate.

What happens to enzyme activity at temperatures significantly above the optimum?

The enzyme denatures, causing a loss of its tertiary structure and a rapid decrease in activity.

Why does enzyme activity diminish significantly outside of the optimal pH range?

Changes in pH alter the charge of the enzyme's amino acids, disrupting its shape and leading to denaturation.

What happens to the rate of an enzyme-catalysed reaction when the substrate concentration is increased to a point of saturation?

The reaction rate plateaus because all enzyme active sites are occupied.

What is the general relationship between enzyme concentration and the rate of reaction, assuming substrate is not a limiting factor?

There is a linear increase in reaction rate proportional to the enzyme concentration.

What is the process by which cells synthesise organic compounds from inorganic molecules in the presence of sunlight?

Photosynthesis.

What is the overall chemical equation for photosynthesis?

$6 CO2 + 12 H2O \xrightarrow{Light, Chlorophyll} C6H{12}O6 + 6 O2 + 6 H_2O$.

What is the main photosynthetic pigment in plants that absorbs red and blue light most effectively?

Chlorophyll.

Which experimental technique is used to separate different photosynthetic pigments based on their movement through a static material?

Chromatography.

In chromatography, what is the formula for calculating the retardation factor ($R_f$)?

$R_f$ value = distance the pigment travels ÷ distance the solvent travels.

A graph showing the rate of photosynthesis at each wavelength of light is known as an _ spectrum.

action

A graph showing the amount of light absorbed by pigments at any given wavelength is known as an _ spectrum.

absorption

What are the two main stages of photosynthesis?

The light-dependent reactions and the light-independent reactions (Calvin cycle).

Where in the chloroplast do the light-dependent reactions occur?

Within the thylakoids (or grana).

What is the process called where light energy breaks down water molecules into oxygen and hydrogen during the light-dependent reactions?

Photolysis.

What are the main products of the light-dependent reactions that are used in the light-independent reactions?

ATP and hydrogen (carried by NADPH in HL).

Where in the chloroplast do the light-independent reactions (Calvin cycle) occur?

In the stroma.

What enzyme catalyses the combination of carbon dioxide with hydrogen to form organic molecules in the Calvin cycle?

Rubisco.

According to the law of limiting factors, the rate of a chemical process is determined by the factor that is _ its minimum value.

nearest to

Name three conditions that can be limiting factors for the rate of photosynthesis.

Temperature, light intensity, and carbon dioxide concentration.

Metabolic pathways can be organised into linear chains or _ of enzyme-catalysed reactions.

cycles

Glycolysis is an example of which type of metabolic pathway organisation?

A linear chain.

The Calvin cycle is an example of which type of metabolic pathway organisation?

A cyclical pathway.

What is an enzyme inhibitor?

A molecule that binds to an enzyme and disrupts substrate interaction, preventing catalysis.

What type of inhibition involves an inhibitor that is structurally similar to the substrate and binds reversibly to the enzyme's active site?

Competitive inhibition.

How can the effects of a competitive inhibitor be reduced?

By increasing the concentration of the substrate.

What type of inhibition involves a molecule binding to a site other than the active site, causing a conformational change?

Non-competitive inhibition.

The site on an enzyme where a non-competitive inhibitor binds is called the _ site.

allosteric

Why is increasing substrate concentration ineffective against a non-competitive inhibitor?

Because the inhibitor is not competing for the active site.

What is feedback inhibition?

A regulatory mechanism where the final product of a metabolic pathway inhibits an enzyme from an earlier step.

In the synthesis of isoleucine from threonine, isoleucine acts as a non-competitive inhibitor of the first enzyme. This is an example of _.

feedback inhibition

What type of inhibition involves a molecule binding to the active site, being chemically altered, and forming an irreversible covalent bond with the enzyme?

Mechanism-based inhibition.

Penicillin is an antibiotic that functions as what type of inhibitor against bacterial transpeptidases?

A mechanism-based inhibitor.

In plants, where are the molecular arrays of pigments called photosystems located?

Within a thylakoid membrane.

What is the advantage of grouping different pigment molecules into a photosystem?

It maximises the absorption of light over a broader range of wavelengths.

In the light-dependent reactions, the movement of protons from the stroma into the thylakoid lumen creates an _.

electrochemical gradient

What is the process by which protons move back to the stroma through ATP synthase, driving ATP synthesis?

Chemiosmosis.

The synthesis of ATP in the thylakoids, driven by light energy, is specifically called _.

photophosphorylation

Which photosystem replaces its lost electrons through the photolysis of water?

Photosystem II.

Which photosystem transfers energised electrons to reduce NADP+ to NADPH?

Photosystem I.

How are the light-dependent and light-independent reactions of photosynthesis interdependent?

The light-dependent stage provides ATP and NADPH for the light-independent stage, which in turn regenerates ADP and NADP+.

What is the first step of the Calvin cycle, catalysed by Rubisco?

Carbon fixation, where $CO_2$ is attached to a 5C compound called RuBP.

In the Calvin cycle, what is the 6-carbon compound formed after carbon fixation immediately broken down into?

Two 3-carbon compounds called glycerate-3-phosphate (GP).

What energy and reducing power sources are used to convert glycerate-3-phosphate (GP) into triose phosphate (TP)?

ATP and NADPH from the light-dependent reactions.

What is the final step of the Calvin cycle, which requires ATP hydrolysis?

The regeneration of RuBP from triose phosphate.

How many turns of the Calvin cycle are required to synthesise one molecule of glucose?

Two cycles are required (as one cycle produces one net molecule of TP).

What evidence supports the theory that chloroplasts evolved via endosymbiosis?

The presence of circular DNA (naked) and 70S ribosomes.

In chloroplasts, membrane discs called thylakoids are arranged into stacks known as _.

grana