Photosynthesis and Autotrophs Overview

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Questions and Answers

What happens to electrons when they are excited to higher energy levels in chlorophyll?

They move to a higher level and remain there without effect.

They fall back to the ground state, releasing energy as light. (correct)

They transfer energy to other molecules without falling back.

They become more stable and remain there indefinitely.

Which statement accurately describes the role of chlorophyll b?

It absorbs wavelengths that chlorophyll a poorly absorbs. (correct)

It absorbs red light and reflects blue light.

It reflects all wavelengths and does not absorb light.

It is the primary pigment responsible for energy transfer in photosynthesis.

What colors of light do chlorophyll a and b primarily absorb?

Chlorophyll a absorbs green light while chlorophyll b absorbs orange light.

Chlorophyll a absorbs all colors equally while chlorophyll b absorbs only ultraviolet light.

Chlorophyll a absorbs red light and chlorophyll b absorbs violet-blue light. (correct)

Chlorophyll a absorbs yellow light while chlorophyll b absorbs red light.

What role do carotenoids play in photosynthesis?

They act as accessory pigments, absorbing specific wavelengths of light. Signup and view all the answers

Which statement explains the visual effect of green wavelengths in leaves?

Green wavelengths are reflected, making leaves appear green. Signup and view all the answers

What contributes to algal blooms in water bodies?

Presence of nitrogen and phosphate Signup and view all the answers

Which process primarily occurs in the chloroplasts of higher order plants?

Photosynthesis Signup and view all the answers

What happens when light activates specific receptors in guard cell membranes?

Protons are pumped out of the cell Signup and view all the answers

Where does photosynthesis take place in a leaf?

In the spongy and palisade mesophyll Signup and view all the answers

What is the role of chlorophyll in photosynthesis?

Absorbs light and excites electrons Signup and view all the answers

How does water move into guard cells during stomata opening?

By osmosis Signup and view all the answers

What is the relationship between energy and wavelength of light?

Energy is inversely proportional to wavelength Signup and view all the answers

Which molecules are responsible for the absorption of light in plants?

Chlorophyll molecules Signup and view all the answers

Study Notes

Prokaryotic Autotrophs

Cyanobacteria are prokaryotic autotrophs; blue-green algae.
Thrive on nitrogen and phosphate, which can cause algal blooms.
Algal blooms discolor water and may be toxic to other species.
First living thing to produce oxygen.
Existed approximately 3.5 to 4 billion years ago.

Eukaryotic Autotrophs

Include algae, plants, and photosynthetic protists.
Contain organelles called chloroplasts that contain chlorophyll.

Photosynthesis in Higher-Order Plants

Occurs primarily in the spongy and palisade mesophyll of leaves.
Chloroplasts are the site of photosynthesis located within the leaves.
Thylakoids, structures within chloroplasts, are the site of chlorophyll molecules, which are crucial for photosynthesis.

Transpiration

Water loss from leaves.
Water cohesion pulls water up from roots.
Assists with photosynthesis.
Aids in the movement of substances like water and minerals to leaves.
Evaporative cooling effect prevents denaturation of photosynthetic enzymes.

Control of Stomata

Stomata are openings on the surface of leaves that allow for gas exchange (CO2 and water vapour).
Guard cells control the size of the stomata.

Control of Stomata (Mechanism)

Light activates receptors in guard cell membranes.
Activates proton pumps, moving protons out of the cell.
Creates an electrochemical gradient causing K+ ions to move into the cell.
Water moves into the cell by osmosis.

Chloroplast Structure

Stroma: Protein-rich fluid.
Grana: Stacks of thylakoids, attached to the stroma.
Thylakoids: Disk-like structures within chloroplasts containing chlorophyll.

Location of Photosynthesis

Occurs in the stroma and thylakoid membrane.
Thylakoid membrane contains light-gathering pigment molecules (chlorophyll) and electron transport chains.
Structure of the thylakoid system enhances surface area and photosynthetic efficiency.

Plant Pigments

Molecules that absorb specific wavelengths of light while reflecting others.
Chlorophylls are easily excited by light, key to photosynthesis.

Properties of Light

Light is a form of energy traveling in wave packets called photons.
Energy is inversely proportional to wavelength (λ) : E=1/λ.
Visible spectrum: 380 nm to 750 nm.

Effect of Light on Atoms

Light energy excites electrons in atoms, causing them to move to higher energy levels.
Electrons at higher levels are unstable and fall back to their ground state, releasing energy (light) as they fall.

Chlorophyll

Green-coloured pigment in photosynthetic organisms.
Head: Porphyrin ring with a Mg atom and carbon double bonds. Light excites electrons in double bond orbitals.
Tail: Phytol Chain – anchors and orients the molecule in the thylakoid membrane.
Chlorophyll a and b differ in the ‘R’ group attached to the head.

Chlorophyll a & b

Chlorophyll a absorbs red light best.
Chlorophyll b absorbs violet-blue light best.
Green wavelengths are not absorbed, reflected into our eyes.

Carotenoid Pigments

Beta carotene: Absorbs yellow light and reflects yellow to red ranges.
Xanthophylls: Absorbs yellows, reflects oranges.

Chlorophyll and Accessory Pigments

Chlorophyll a is the only pigment that can transfer light energy to carbon fixation reactions of photosynthesis.
Chlorophyll b acts as an accessory pigment, absorbing photons chlorophyll a absorbs poorly.
Carotenoids, xanthophylls, and anthocyanins act as accessory pigments.

Absorbance Spectra

Depicts the wavelengths of light absorbed by a pigment.

Action Spectrum

Reflects the rate of oxygen production based on wavelengths of light absorbed.

What Causes “Autumn Leaves”?

As temperatures decrease, chlorophyll production slows down.
Accessory pigments like carotenoids and anthocyanins become more visible, causing leaves to appear red, orange, and yellow.

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Description

Explore the fascinating world of autotrophs, including prokaryotic and eukaryotic types. This quiz covers essential processes like photosynthesis in higher-order plants and the role of transpiration. Test your knowledge about cyanobacteria, chloroplasts, and more!