Chapter 10: Photosynthesis I

DOESN'T include Photosynthesis steps

Photosynthesis

The process of turning solar energy into chemical energy through chloroplasts

Autotrophs

Organisms that can sustain themselves without eating anything derived from other organisms

Photoautotrophs

Organisms that use energy from sunlight (and CO2) to make organic molecules to sustain themselves

Heterotrophs

Organisms that are not self-sufficient and have to consume organic material to sustain life

What do Heterotrophs rely on Photoautotrophs for?

Food and Oxygen

Chloroplasts

Organelles that are structurally organized to facilitate the series of chemical reactions of photosynthesis

Where does Photosynthesis happen (overview)?

Plant → Leaves → Mesophyll Tissue → Cells → Chloroplasts → Thylakoid

What is the role of veins in plants?

Transports water and sugar from roots to non-photosynthetic parts

How does Carbon Dioxide and Oxygen exit a leaf?

Stomata Pores

Where are Chloroplasts mainly found in leaves?

Mesophyll Tissue

T or F: Chloroplasts have a single membrane envelope

F, double membrane

Stroma

Internal fluid of Chloroplasts

Thylakoid

Interconnected sacs within the Chloroplast

What is a stack of Thylakoids called?

Granum

Chlorophyll

Pigment protein that absorbs light

Where is Chlorophyll found?

Thylakoid Membranes

Photosynthesis Equation

6 CO₂ + 12 H₂O + solar energy → C₆H₁₂O₆ + 6 H₂O + 6 CO₂

What is the overall process of Photosynthesis?

• Chloroplasts split water molecules into hydrogen and oxygen atoms

• The atoms of hydrogen are incorporated into sugar molecules

What is the byproduct of Photosynthesis?

O₂

T or F: Not all Photoautotrophs use water as hydrogen source

T, some use hydrogen sulfide as an example

What is oxidized and reduced during Photosynthesis?

Water Molecules → Oxidized

Carbon Dioxide → Reduced

T or F: Photosynthesis is an exergonic process

F, endergonic

What are the 2 processes of Photosynthesis?

Light Reactions and Calvin Cycle

Where do the Light Reactions occur?

Thylakoids

What happens in the Light Reactions (simplified)?

• Water molecules are split, providing electrons and protons

• Oxygen is released as a byproduct

• The electron carrier NADP+ is reduced to NADPH

• ATP is made from ADP and phosphate group

Where does the Calvin Cycle occur?

Stroma

What happens in the Calvin Cycle (simplified)?

• Carbon dioxide is incorporated into organic molecules through carbon fixation

• Fixed carbons are then reduced to carbohydrates through NADPH oxidization

• ATP is used to facilitate this synthesis process

What are the 2 forms of Light?

Wavelength and Photons (particle)

Wavelength

A measure of distance between peaks of electromagnetic waves

Electromagnetic Spectrum

The entire range of all known types of electromagnetic energy

What kind of wavelengths are used in Photosynthesis?

Visible Light (380 nm - 740 nm)

What is range of Visible Light?

380 nm - 740 nm

What is the relationship between Light as a wavelength and as photons?

Photons have a fixed energy that is inverse to Wavelength

• Short wavelength → More Energy

What differentiates is unique to Photons and not Wavelengths?

Photons can be absorbed by pigment proteins

T or F: All light hitting a pigment protein is absorbed

F, some is reflected back or transmitted through

Spectrophotometer

Tool used to measure a pigment’s ability to absorb wavelengths of light

Generally how do Spectrophotometers work?

Light is passed through pigments and the transmitted light is matched to a specific wavelength

Absorption Spectrum

A visual graph of the light absorption of a pigment at difference wavelengths

What are the 3 types of Pigments in Chloroplasts?

1. Chlorophyll a

2. Chlorophyll b

3. Carotenoids

Chlorophyll a

Captures light for direct use in light reactions

Chlorophyll b

An accessory pigment for light capture

Carotenoids

An accessory pigment group that acts similarly to Chlorophyll b

Action Spectrum

A profile of which wavelengths of visible light are effective for photosynthesis

What are the best and worst wavelengths (colors) for Photosynthesis?

Best → Violet-blue and Red light

Worst → Green

How does a pigment protein absorbing light effect an Electron?

Causes an electron to go from a stable ground state to an unstable excited state

How do Electrons fall back to ground state after being excited?

By releasing excess energy as heat or light

What is the afterglow after an electron releases energy to return to ground state called?

Fluorescence

Photosystem

Multi-protein structure that has two discrete complexes

What are the 2 complexes of a Photosystem

Reaction Center Complex and Light-Harvesting Complex

What do Reaction Center Complexes contain?

Proteins that hold both chlorophyll a pigment and electron acceptors

What do Light-Harvesting Complex contain?

Multiple different pigment with specialized proteins bound to them

How does the Reaction Center Complex and Light-Harvesting Complex relate when comparing them to a barrel?

Barrel → Light-Harvesting Complex

Tube within Barrel → Reaction Center Complex

What is another name for Photosystem II (PSII)? Why?

P680, it’s chlorophyll a absorbs light best at 680 nm

What is another name for Photosystem I (PSI)? Why?

P680, it’s chlorophyll absorbs light best at 700 nm