Learn: Macromolecules and Photosynthesis

What are the four macromolecules and their monomers?

Carbohydrates—monosaccharides; lipids—fatty acids and glycerol; proteins—amino acids; nucleic acids—nucleotides.

What elements make up carbohydrates, and what are their functions?

C, H, O; provide quick energy, energy storage, and structure.

What elements make up lipids, and what are their functions?

Mainly C, H, O; store long-term energy, insulate, and form membranes.

What elements make up proteins, and what are their monomers?

C, H, O, N; amino acids.

What elements make up nucleic acids, and what are their monomers?

C, H, O, N, P; nucleotides.

How are monosaccharides, disaccharides, and polysaccharides different?

One sugar, two joined sugars, and many joined sugars.

What are examples and functions of disaccharides?

Sucrose (table sugar) and lactose (milk sugar); both provide energy.

What are examples and functions of polysaccharides?

Starch stores plant energy; cellulose supports plant cell walls.

What are five protein functions and examples?

Enzymes—amylase; structure—collagen; transport—hemoglobin; movement—actin and myosin; defense—antibodies.

A person cannot digest starch. Which protein might be affected?

Amylase, which breaks down starch.

What happens if hemoglobin cannot function?

Oxygen transport decreases.

What happens if collagen production decreases?

Tissues become weaker due to reduced structural support.

How are DNA and RNA different?

DNA stores genetic instructions; RNA helps make proteins.

What are ATP's structural components?

Adenine, ribose, and three phosphate groups.

How is ADP different from ATP?

ADP has two phosphate groups; ATP has three.

How does ATP release energy?

Hydrolysis removes its third phosphate, releasing usable energy.

How is ATP regenerated?

Energy attaches a phosphate to ADP, forming ATP.

Why is ATP called the cell's energy currency?

It transfers energy for cellular activities.

What happens if ATP is used faster than it is regenerated?

ATP decreases and ADP increases.

Why can't glucose directly replace ATP for cellular work?

ATP transfers energy into a form cells can use directly.

Which macromolecule provides the most energy per gram?

Lipids: 9 cal/g; carbohydrates and proteins: 4 cal/g.

Why are carbohydrates used before lipids for energy?

They provide more readily available energy.

Why are proteins broken down last for energy?

They are needed for essential cellular functions.

Where do the light-dependent reactions and Calvin cycle occur?

Thylakoid membranes and stroma, respectively.

What is chlorophyll's function?

Absorbs light and excites electrons.

What is the purpose of the light-dependent reactions?

Produce ATP and NADPH and release oxygen.

What is the purpose of the Calvin cycle?

Use CO₂, ATP, and NADPH to produce G3P.

What is the electron pathway during photosynthesis?

Water → PSII → ETC → PSI → NADP⁺ → NADPH.

What happens when light strikes Photosystem II?

Electrons become excited and enter the electron transport chain.

How are lost electrons in Photosystem II replaced?

Water splits, releasing electrons, H⁺, and oxygen.

What are the products of water splitting?

Electrons, H⁺, and O₂.

What happens to electrons at Photosystem I?

Light re-energizes them to help produce NADPH.

What is NADP⁺'s role?

Accepts electrons and H⁺ to form NADPH.

How is the H⁺ gradient created?

Electron transport pumps H⁺ into the thylakoid; water splitting adds more.

Where is H⁺ concentration highest?

Inside the thylakoid space.

How does ATP synthase produce ATP?

H⁺ flows through it, powering ADP + phosphate → ATP.

What happens if the thylakoid membrane becomes permeable to H⁺?

The gradient disappears, decreasing ATP production.

What happens if ATP synthase stops working?

ATP production decreases because H⁺ cannot flow through it.

What is carbon fixation?

Attaching CO₂ to an organic molecule to build sugars.

What is RuBP's role?

Accepts CO₂ during carbon fixation.

What is Rubisco's role?

Catalyzes the attachment of CO₂ to RuBP.

What is ATP's role in the Calvin cycle?

Provides energy to produce G3P and regenerate RuBP.

What is NADPH's role in the Calvin cycle?

Provides electrons to reduce carbon compounds into G3P.

Why must RuBP be regenerated?

To accept more CO₂ and continue the cycle.

Why does the Calvin cycle depend on light-dependent reactions?

It needs their ATP and NADPH.

What happens to the Calvin cycle in darkness?

It stops when ATP and NADPH are depleted.

What happens when stomata close on a hot, dry day?

CO₂ decreases, slowing the Calvin cycle and sugar production.

A plant has ATP but no NADPH. Can it produce G3P?

No. NADPH provides the electrons needed to produce G3P.

A plant has NADPH but no ATP. What happens?

The Calvin cycle slows or stops because it needs ATP.

What happens if Rubisco becomes inactive?

Carbon fixation and sugar production decrease or stop.

What happens if CO₂ levels decrease?

The Calvin cycle slows because less CO₂ is available.

Will more light always increase sugar production?

No. CO₂, temperature, or enzymes may limit production.

What happens if RuBP cannot regenerate?

Carbon fixation eventually stops.

Why does oxygen production decrease when light-dependent reactions slow?

Less water is split in Photosystem II.

What happens if electron transport between PSII and PSI is blocked?

NADPH and ATP production decrease.

How does photosynthesis store sunlight energy in glucose?

ATP and NADPH power the Calvin cycle to build energy-storing sugars.

How are photosynthesis and cellular respiration connected?

Photosynthesis produces glucose and O₂; respiration uses them to make ATP and releases CO₂ and water.