8.1 Radiant Energy

Photosynthesis:

What is the chemical reaction of photosynthesis?

What is the relationship between producers, consumers, and photosynthesis?

BIG IDEA: All organisms use the organic molecules produced by photosynthesizers as a source of building blocks for growth and repair, and as a source of chemical energy for cellular work!

Visible Light

2 features are used to describe radiant energy:

When visible light passes through a prism, it splits into colours. Arrange the colours from shortest to longest wavelength, and describe its energy content.

Why does less than half of the solar radiation that hits the Earth reach the surface?

Chlorophylls and carotenoids are pigments within photosynthesizing cells. Describe how they interact with light and affect what we see when we look at plants.

8.2 Structure and Function of Chloroplasts

Chloroplasts:

Describe the structure of a leaf in terms of mesophyll cells and stoma.

Structure of Chloroplasts

Chloroplasts are bound by a double membrane made up of 2 parts: 1. Stroma:

2. Thylakoids:

Where is chlorophyll located in the chloroplast and what is is its function?

Function of Chloroplasts in Photosynthesis

The overall equation of photosynthesis is simplified as:

Water molecules are oxidized: lose electrons and hydrogen ions Carbon dioxide is reduced: gains electrons, breaking up water

Light Dependent Reactions: involves energy

Describe what happens to electrons when chlorophyll absorbs solar energy (include location, and end products).

Light Independent Reactions: take place in the

Calvin Cycle:

CO₂ is taken in and reduced (requires ATP and NADPH) ADP+P and NADP+ return to light-dependent reactions and repeat the cycle

8.3 Solar Energy Capture

Light dependent reactions use two different photosystems: the cyclic electron pathway (PS I) and the noncyclic electron pathway (PS II)

What is each photosystem composed of?

Electron Pathways

The cyclic electron pathway generates only The non-cyclic pathway results in both

I. Cyclic Electron Pathway (also known as PS I) Begins after PS I pigment complex absorbs solar energy

Electron Transport Chain:

Captured energy is stored as .When the cycle is complete, the electrons will return to their starting position in PS I.

II. Noncyclic Electron Pathway (also known as PS II) The electrons move from

Step 1: PS II pigment complex absorbs solar energy High energy electrons leave reaction-center chlorophyll a molecule PS II splits water molecule (H₂O)

o Electron is picked up and used by PS II o Oxygen gas leaves the chloroplast o H+ ions remain in thylakoid space

Step 2: High energy electrons leave PS II, sent by an electron acceptor to an electron transport system

Electrons passed through carriers Energy is captured and stored as hydrogen ions (will be used for ATP creation)

Step 3: Low energy electrons leace electron transport system and enter PS I Replace high energy electron that left PS I

Step 4: PS I absorbs solar energy, exciting electrons

electrons leave reaction-center chloropgyll a and are taken by an electron acceptor passes electrons to NADP+, which takes on a hydrogen ion and becomes NADPH

Organization of Thylakoids

A reservoir for ions

Describe the process of chemiosmosis.

What are the four protein complexes found in the thylakoid membrane (include their function)?

8.4 Carbohydrate Synthesis

Describe some of the uses of glucose and PGAL.

The Calvin cycle is a light-independent reaction. It can be divided into three groups: fixation of carbon dioxide, reduction of carbon dioxide, and regeneration of RuBP.

Stage 1: Fixation of Carbon Dioxide

Occurs when CO₂ is

RuBP (5 carbon molecule) + CO2 6 carbon molecule

What is the role of RuBP carboxylase and why is it so abundant?

Stage two: Reduction of Carbon Dioxide

6 carbon molecule breaks down into 2 PGA molecules (made of 3 carbons)

Using ATP, each PGA molecule undergoes reduction to form PGAL

o Redox reaction: CO2 reduced to a carbohydrate, NADPH is oxidized to NADP

o End products (ADP and NADH) return to PS I

For every turns of the Calvin Cycle, PGAL is produced. It takes 3-carbon molecules to make one 6-carbon glucose molecule.

Stage 3: Regeneration of RuBP

For every three turns of the Calvin cycle, five molecules of PGAL are used to reform three molecules of our RuBP.

Summary

Light-dependent reactions are associated with ̀

1. Solar energy energizes electrons, which are used in chemiosmosis to form ATP and NADPH

2. Water is oxidized and releases oxygen gas

Light-independent reactions are associated with

1. Carbon dioxide is reduced to a carbohydrate (uses ATP and NADPH)

2. ATP becomes ADP + P, and NADPH becomes NADP

Reenergized by light-dependent reactions

How efficient is photosynthesis?

8.5 Other Types of Photosynthesis

C3 vs. C4 Photosynthesis

The process of photosynthesis that we just learned about is call “C3 photosynthesis” because a C3 molecule can be found immediately after CO₂ fixation.

What are the structural differences between C3 and C4 plants?

C4 photosynthesis process:

Fix CO₂ by forming a C4 molecule before the Calvin Cycle

C4 molecule (oxaloacetate) pumped into bundle sheath cells, releasing CO₂ into Calvin cycle

Which process is beneficial in hot/dry weather? Why?

CAM Photosynthesis

Fix CO₂ by forming a C4 molecule, which occurs at night

C4 molecule stored in large vacuoles in mesophyll cells

Portioning due to time, not space

o Conserve water by opening stomata at night and releasing CO₂ during the day

8.6 Photosynthesis vs Cellular Respiration

Create a venn diagram to compare and contrast photosynthesis to cellular respiration