photosynthesis

PhotosynthesisChapter 8

photosynthesis rap

Energy and Life8-1

Types of Nutrition

Autotrophs – make their own food

Heterotrophs – consume their food

Forms of energy:◦ Light, heat, sound, electrical, chemical…

The form of energy used by living things is chemical.

The principal chemical compound that stores and releases energy in cells is ATP◦ Adenosine triphosphate

Energy

Adenine Ribose 3 Phosphate groups

Section 8-1

ATP ATP

ATP stores energy in the bonds between the phosphates.

To store energy, ADP adds on a third phosphate to become ATP.

To release energy, ATP gives up the third phosphate to become ADP

ATP

ADP ATP

Energy

EnergyAdenosine diphosphate (ADP) + Phosphate Adenosine triphosphate (ATP)

Partiallychargedbattery

Fullychargedbattery

Section 8-1

Figure 8-3 Comparison of ADP and ATP to a BatteryATP charging

Active transport Charging nerve cells Movement Protein synthesis Cell division ALL chemical reactions!Everything!

Using ATP in Cells

Photosynthesis: An Overview8-2

Jan van Helmont

After careful measurements of a plant’s water intake and mass increase, van Helmont concluded that trees gain most of their mass from water.

1643

1771 Joseph Priestley

Using a bell jar, a candle and a plant, Priestley finds that a plant releases oxygen.

1779 Jan Ingenhousz

Ingenhousz finds that aquatic plants produce oxygen bubbles in the light but not in the dark. He concludes that plants need sunlight to produce oxygen.

1845

Julius Robert Mayer

Mayer proposes that plants convert light energy into chemical energy.

1948

Melvin Calvin

Calvin traces the chemical path that carbon follows to form glucose. These reactions are known as the Calvin Cycle.

1992

Rudolph Marcus

Marcus wins the Nobel prize in chemistry for describing the process by which electrons are transferred from one molecule to another in the electron transport chain.

Great Theories…. Are they made by a single scientist? Or are they the work of many scientists over

many years?

The Photosynthesis Equation Photosynthesis uses the energy of sunlight

to convert water and carbon dioxide into high-energy sugars and oxygen.

Carbon dioxide + water + light glucose + oxygen

6CO2 + 6H2O + light C6H12O6 + 6O2

Light and Pigments Photosynthesis requires the presence of

light- absorbing molecules called pigments.◦ Chlorophyll is the principal pigment.◦ This pigment is located in the chloroplasts.

Light Energy

Chloroplast

CO2 + H2O Sugars + O2

Photosynthesis: Reactants and Products

Photosynthetic Pigments Chlorophyll a absorbs violet and red light the

best.◦ It does NOT absorb green or yellow well.

Chlorophyll b absorbs mainly blue and red wavelengths of light.◦ It does NOT absorb green or yellow either.

There are two other photosynthetic pigments, carotene (orange) and xanthophyll (yellow).◦ They absorb other wavelengths of light and

transfer the energy to chlorophyll.

Absorption of Light byChlorophyll a and Chlorophyll b

V B G YO R

Chlorophyll b

Chlorophyll a

Photosynthetic Pigments

The Reactions of Photosynthesis

8-3

Photosynthesis overview

Chloroplast Anatomy Stacks of internal membranes called

thylakoids contain photosystems. Photosystems carry out the reactions of

photosynthesis involving light (“light reactions”).

In between the thylakoids the stroma carries out more reactions that do not require light (“dark reactions”).

ChloroplastLight

O2Sugars

CO2

Light-Dependent Reactions

CalvinCycle

NADPHATP

ADP + PNADP+Chloroplast

Section 8-3

Figure 8-7 Photosynthesis: An Overview

H20

The Light Reactions Takes place in the thylakoids. Chlorophyll absorbs light. Light energy is used to do two things:

1. Split water into hydrogen and oxygen gas. Oxygen is released to the environment. Hydrogen is carried to the stroma for the next set of

reactions.2. Produce high energy carriers ATP and NADPH

Both are used in the dark reactions.

http://vcell.ndsu.nodak.edu/animations/ http://www.youtube.com/watch?feature=player

_embedded&v=BK_cjd6Evcw

HydrogenIon MovementPhotosystem II

InnerThylakoidSpace

ThylakoidMembrane

Stroma

ATP synthase

Electron Transport Chain Photosystem I ATP Formation

Chloroplast

Section 8-3

Figure 8-10 Light-Dependent Reactions

The “Dark” reactions Take place in the stroma Don’t require light Carbon dioxide is combined with hydrogen

to make glucose. Energy (ATP) from the light reactions runs

the dark reactions. Also known as the “Calvin Cycle” and

“carbon fixation”.

ChloropIast

CO2 Enters the Cycle

Energy Input

5-CarbonMoleculesRegenerated

Sugars and other compounds

6-Carbon SugarProduced

Section 8-3

Figure 8-11 Calvin Cycle

Factors Affecting Photosynthesis Availability of water Temperature Light intensity Availability of minerals Concentration of carbon dioxide

How does water get to the leaves for photosynthesis?

“Transpiration pull” brings water up to the leaves.◦ Transpiration is the loss of water vapor out the

leaves through openings called stomates.

Transpiration

Section 23-5

Evaporation of water molecules out of leaves.

Pull of water molecules upward from the roots.

A B

Transpiration

Section 23-5

Evaporation of water molecules out of leaves.

Pull of water molecules upward from the roots.

A B

Transpiration

What regulates water loss from the leaves?◦ Guard cells open and close the stomates to

regulate water loss. In dry conditions guard cells close the stomates. In wet conditions guard cells open the stomates.

Transpiration

Section 23-4

Veins

XylemPhloem

Vein

Cuticle

Epidermis

Palisademesophyll

Epidermis

Stoma

Guardcells

Spongymesophyll

The Internal Structure of a Leaf

Syringa leaf cross section

Section 23-4

Stoma Open Stoma Closed

Guard cellsInner cell wall

Stoma

Guard cellsInner cell wall

Function of Guard Cells

Guard Cells and Stomates

What else does a plant need from the soil besides water?

Essential Plant Nutrients

Role in PlantProper leaf growth and color; synthesis of amino acids, proteins, nucleic acids, and chlorophyllSynthesis of DNA; development of roots, stems, flowers, and seedsSynthesis of proteins and carbohydrates; development of roots, stems, and flowers; resistance to cold and diseaseSynthesis of chlorophyll

Cell growth and division; cell wall structure; cellular transport; enzyme action

Result of DeficiencyStunted plant growth; pale yellow leaves

Poor flowering; stunted growth

Weak stems and stunted roots; edges of leaves turn brown

Thin stems; mottled, pale leaves

Stunted growth; curled leaves

NutrientNitrogen

Phosphorus

Potassium

Magnesium

Calcium

Section 23-2Essential Plant Nutrients