Photosynthesis, ATP, and Microorganisms – Lecture Review

A comprehensive set of Q&A flashcards covering ATP biology, chloroplast structure, photosystems, photophosphorylation, Calvin cycle, limiting factors, and basic bacteriology/virology.

What do autotrophic organisms use to synthesize organic compounds?

Carbon dioxide (usually via photosynthesis).

How do heterotrophic organisms obtain the products of photosynthesis?

By eating plants or animals that have eaten plants.

Which enzyme catalyzes ATP hydrolysis?

ATPase.

How much energy (in kJ mol⁻¹) is released when ATP is hydrolysed?

Approximately 34 kJ mol⁻¹.

What are the products of ATP hydrolysis?

ADP, inorganic phosphate (Pi), and energy.

Where does the energy for ATP synthesis usually come from?

Catabolic or redox reactions.

During redox reactions, what happens when a compound loses electrons?

It is oxidized.

What is an electron transport chain?

A series of carriers that pass electrons through redox reactions, releasing small amounts of energy for ATP synthesis.

Why is ATP considered an immediate energy source?

It can be hydrolyzed quickly and the energy is readily usable by cellular enzymes.

Describe the chloroplast envelope.

Two membranes (outer and inner) surrounding the chloroplast with an inter-membrane space.

What structures make up a granum?

Stacks of disc-shaped thylakoids.

Function of lamellae in chloroplasts?

Connect grana and maintain spacing for optimal light capture.

Where are photosynthetic enzymes for the Calvin cycle located?

In the stroma of the chloroplast.

Name the five main photosynthetic pigments mentioned.

Chlorophyll a, chlorophyll b, carotene, xanthophyll, phaeophytin.

Why do leaves appear green?

Pigments absorb poorly in the green/yellow wavelengths, so this light is reflected.

Define an absorption spectrum.

Graph of light absorbed versus wavelength for a pigment.

Define an action spectrum.

Graph of photosynthetic rate versus light wavelength.

What is an Rf value in chromatography?

Distance travelled by pigment divided by distance travelled by solvent front.

Which photosystem absorbs light best at 700 nm?

Photosystem I (PSI).

Which photosystem absorbs light best at 680 nm?

Photosystem II (PSII).

Where are PSI particles mainly located?

Intergranal lamellae.

Where are PSII particles mainly located?

Grana thylakoid membranes.

State two main functions of the light-dependent stage.

Photolysis of water (providing H⁺) and synthesis of ATP.

What is photolysis?

Light-driven splitting of water into H⁺, e⁻, and O₂.

What is cyclic photophosphorylation?

ATP production using only PSI; electrons return to PSI.

What additional product is made in non-cyclic photophosphorylation besides ATP?

Reduced NADP (NADPH).

What molecule collects electrons and a proton to form reduced NADP?

NADP⁺.

Write the overall role of reduced NADP and ATP from the light reactions.

Provide reducing power and energy for the Calvin cycle.

What enzyme catalyzes the fixation of CO₂ to RuBP?

RUBISCO.

What is the immediate product when CO₂ combines with RuBP?

An unstable 6-carbon compound that splits into two GP molecules.

Which Calvin-cycle molecule is reduced GP converted into?

Glyceraldehyde-3-phosphate (GALP).

What two molecules are required to reduce GP to GALP?

ATP and reduced NADP.

Why is GALP called the primary product of photosynthesis?

It supplies carbon skeletons for glucose, starch, cellulose, amino acids, fatty acids, etc.

Define a limiting factor in photosynthesis.

The factor closest to its minimum value that restricts the rate of the process.

List the three main limiting factors of photosynthesis.

Light intensity (and wavelength), CO₂ concentration, temperature.

How can greenhouse growers increase crop yield with limiting factors?

By optimizing light, increasing CO₂, and controlling temperature.

Give two structural features present in ALL bacteria.

Peptidoglycan cell wall and 70S ribosomes (also cell membrane, nucleoid).

What is a plasmid?

Extra-chromosomal circular DNA in bacteria coding for specific traits.

Function of bacterial flagella?

Rapid rotation to propel the bacterium.

What are pili?

Surface projections that can aid attachment or DNA transfer.

What is a viral capsid?

Protein coat made of repeating capsomeres.

What are VAPs (virus attachment particles)?

Viral antigens that bind specific host membrane proteins for entry.

Why do viruses use repeating capsomeres?

Minimises genetic coding requirements and simplifies assembly.

Difference between DNA and RNA viruses in genome use?

DNA viruses directly template mRNA; RNA viruses use RNA as genome, often single-stranded.

What is a retrovirus?

RNA virus that uses reverse transcriptase to make DNA, which integrates into host genome.

Name the enzyme unique to retroviruses.

Reverse transcriptase.

Give one example of a retrovirus affecting humans.

Human immunodeficiency virus (HIV).

What advantage and disadvantage does a lipid envelope give a virus?

Advantage: easier cell-to-cell spread; Disadvantage: susceptible to solvents like ether.

Explain why RNA viruses mutate more readily than DNA viruses.

RNA replication lacks proofreading mechanisms, leading to higher error rates.

What is the peptidoglycan cell wall’s role in bacteria?

Provides structural support and protection against osmotic lysis.

Define mesosome (historical observation).

Folded bacterial membrane structure once thought to assist respiration.

Give the full form of GP in the Calvin cycle.

Glycerate-3-phosphate.

State the wavelength peaks for PSI and PSII absorption.

PSI: 700 nm, PSII: 680 nm.

What is photophosphorylation?

ATP formation using light energy in photosynthesis.

Why do light-independent reactions stop long after dark?

Because ATP and NADPH from light reactions are depleted.

What compound supplies phosphates for nucleic acid synthesis in plants?

Phosphates absorbed from the soil (often after GALP integration).

Which Calvin-cycle enzyme is rate-limiting?

RUBISCO.

Identify the universal energy currency of the cell.

Adenosine triphosphate (ATP).

What happens to hydroxide ions left after NADP removes H⁺ during photosynthesis?

They combine to form water and O₂, releasing electrons back to chlorophyll.

In cyclic photophosphorylation, do electrons return to PSI?

Yes; the same electrons cycle back to PSI.

In non-cyclic photophosphorylation, what is the final electron acceptor?

NADP⁺ (forming NADPH).

Why is CO₂ concentration often the limiting factor outdoors?

Atmospheric CO₂ is low (~0.04 %), restricting fixation in the Calvin cycle.