Chapter 5: Photosynthesis

Question 1

Photosynthesis Overview

Answer 1

Formula: sunlight + 6CO2 + 6H2O -> C6H12O6 + 6O2 + ATP

Photosynthesis consists of both light dependent and light independent reactions. The light dependent reactions use light energy to make ATP for the light independent reactions, however, both only occur when there is light present.

Question 2

Photosynthetic Pigments

Answer 2

Absorb light energy and provide energy for photosynthesis. Plants have two major types: chlorophyll and carotenoids.

Question 3

Chlorophyll A and B

Answer 3

Absorbs all the blue, red, and violet wavelengths. Chlorophyll A aids directly in the light dependent reactions.

Question 4

Carotenoids

Answer 4

Absorbs yellow, orange, and red wave lengths. Xanthophyll is a carotenoid with a slight chemical variation.

Question 5

Action Spectrum

Answer 5

A graph that shows the different absorption of wavelengths for different types of pigments.

Question 6

Chloroplast

Answer 6

A double membranous site where the whole of photosynthesis occurs. Contains all the pigments, grana, and stroma.

Question 7

Grana

Answer 7

Where the light-dependent reactions occur. Also contains the thylakoids, the site of photosystems I and II.

Question 8

Stroma

Answer 8

Where the light-independent reactions occur.

Question 9

Photosystems I and II

Answer 9

light-harvesting complexes in the thylakoid membranes. PS II occurs first, then PS I.

Question 10

Light-Dependent Reactions

Answer 10

Light is absorbed by the photosystems, and the electrons go through the electron transport chain. Then can either go through noncyclic flow, or cyclic photophosphorylation.

Question 11

Noncyclic Photophosphorylation

Answer 11

1. Photosystem II: electrons in double bonds become energized and go through the e- transport system.
2. Photolysis: the splitting of water, and replaces the electrons lost in PSII.
3. Electron transport: move toward PSI, exergonic, and makes ATP through chemiosmosis.
4. Chemiosmosis: ATP is formed just like how it is in the mitochondria. Protons are pumped into the thylakoid space and through the ATP synthase.
5. NADPH: NADPH is made from NADP. Carries the H+ to the Calvin Cycle and makes sugar.
6. PSI: electrons of chlorophyll A are energized and captured by a primary electron receptor. Produces NADPH.

Question 12

Cyclic Photophosphorylation

Answer 12

Sole purpose is to make ATP, as no NADPH and oxygen is produced. The Calvin Cycle uses up a ton of ATP to make sugar, so it uses cyclic photophosphorylation to replenish it.

Question 13

Calvin Cycle

Answer 13

Produces the 3-carbon sugar PGAL. Starts with CO2 entering, and attaches to a 5-carbon sugar RuBP, making a 6-carbon sugar. However, RuBP is unstable, and immediately breaks down into 2 3-PGA.

The Calvin Cycle is light independent, so it uses the products of light dependent (ATP and NADPH) to process. BUT, it only functions when light is present anyways.

Question 14

Photorespiration

Answer 14

When rubisco binds to O2 instead of CO2, we get photorespiration. This is different, because no ATP and sugar are produced. Peroxisomes break down the products of photorespiration.

Question 15

C-4 Photosynthesis

Answer 15

Is a modification for dry environments. Minimizes excess water loss while maximizing sugar production. Examples include corn, sugar cane, and crabgrass.