Chapter 5: Photosynthesis Flashcards Preview

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Flashcards in Chapter 5: Photosynthesis Deck (15):

Photosynthesis Overview

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.


Photosynthetic Pigments

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


Chlorophyll A and B

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



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


Action Spectrum

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



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



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



Where the light-independent reactions occur.


Photosystems I and II

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


Light-Dependent Reactions

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.


Noncyclic Photophosphorylation

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.


Cyclic Photophosphorylation

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.


Calvin Cycle

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.



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.


C-4 Photosynthesis

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