UNIT 5: Photosynthesis and Respiration

BIG IDEA: Energy is produced and released by making and breaking

chemical bonds

Think About It:

• With your partner, come up with a list of activities that you do that requires energy

• What gives us energy?

Energy

• Directly or indirectly , all energy in living things comes from the sun

Obtaining Energy

• Autotrophs• Organisms that are capable of

making food (energy) from simple inorganic substances

• EX: green plants, algae

Two Types of Autotrophs

• 1. Photoautotrophs: use carbon dioxide and light energy to drive reactions needed to make food

Next type…

• 2. Chemoautotrophs: utilize inorganic chemicals for the energy to drive food making reactions

Obtaining Energy

• Heterotrophs• Organisms that cannot make their

own food (energy) and must depend on other plants or animals as food source (energy)

• Examples: Humans, dogs, cats

Photosynthesis

• Process of capturing energy of sunlight and transforming it into chemical energy

• CO2 + H2O----glucose + O2

Photosynthesis• Two stages

– Light reactions- light energy is converted into chemical energy of two intermediate molecules

– Calvin cycle-Organic molecules are formed from CO2

Photosynthesis

• Sunlight, sometimes called white light, is a form of energy that travels in waves

• Wavelength: the distance between the crest of one wave and the crest of the next wave

Visible Light Spectrum

• Depends on wavelength• Blue: 380 (nm)• Green: 500 (nm)• Yellow 560 (nm)• Light red: 600 (nm)• Darker red: 750 (nm)

Photosynthesis• Pigments: absorb light• EX: a red object absorbs all the visible

colors of the spectrum except red which is reflected and gives the object the red color

Types of Photosynthetic Pigments

a. Chlorophylls: absorb red and blue light, appear green

b. Carotenes: absorb blue, appear orange

c. Xanthophylls: appear yellow, may not be used to absorb light

• The color of an egg yolk is from the xanthophyll carotenoids lutein and zeaxanthin

                 

The color of an egg yolk is from the xanthophyll carotenoids lutein and zeaxanthin

CHLOROPLAST

• Site of Photosynthesis

PARTS OF THE CHLOROPLAST

Inner and outer membrane

Thylakoids

Grana

Stroma

Parts of the Chloroplast

• Thylakoid- Membrane of the thylakoid contains photosynthetic pigments; flattened sacs

• Site of the light reactions

Parts of the Chloroplast

• Grana- Stacks of thylakoids• Stroma-Region b/t grana

– Site of the light independent reactions

Photosynthesis Reactions

• Light Dependent Reactions-energy from light makes the reaction happen

• Light Independent Reactions- Doesn’t need the energy from light to make the reaction happen but they do need products of the light reaction to proceed.

Steps in Light Dependent

Light Dependent Reactions- In the Chloroplast

• Pigments in the photosynthetic membranes absorb light (pigments are located in Photosystem I & II

• When the light hits the chlorophyll in Photosystem II the electrons become excited and jump up.

• The electrons are captured by the electron transport chain.

• We need to replace the electrons that are lost so we steal some from water . This breaks the water molecule apart forming H+ and O

• As we transport electrons down the chain we use their energy to produce ATP

• The electrons now go to Photosystem I and it loses electrons to NADP+ to make it NADPH.

The final products of the light reaction

• At the end of the light reaction we have made

1. NADPH

2. ATP

3. O2

Reactants used during the light reaction

• Water

• Also used sunlight

Light independent reaction ( Calvin Cycle)

• A. Use CO2 , ATP, NADPH

• B. Uses products from light reaction (Light is not necessary for this reaction)

• C. Location stroma

Steps in Light Independent Reaction:

• 6 CO2 reacts with the sugar, ribulose phophate (RuBP)sugar called phosphoglycerate (PGA)

• PGA12 phosphoglyceraldehyde (PGAL)

• NADPH and ATP from light reaction provide energy for this step

Steps in Light Independent Reaction (con’t)

• PGAL does 2 things:

a. Makes more RuBP to continue cycle (requires 10 PGAL to do this)

b. Form 1 glucose (requires 2 PGAL)

Photosynthesis

includes

of

take place intakes place in uses

to produce to produce

use

Light-dependentreactions

Calvin cycle

Thylakoidmembranes Stroma NADPHATPEnergy from

sunlight

ATP NADPH O2 ChloroplastsHigh-energysugars

Section 8-3

Concept Map

Chloroplast

Light

O2Sugars

CO2

Light-Dependent Reactions

CalvinCycle

NADPH

ATP

ADP + P

NADP+Chloroplast

Section 8-3

Figure 8-7 Photosynthesis: An Overview

Factors Affecting Photosynthesis

• Four main types:

a. Light intensity

b. Temperature

c. Water

d. Mineral availability

Cellular Respiration

• Release of the energy stored in food

• Occurs in the inside of the cells of both autotrophs and heterotrophs

Adenosine Triphosphate (ATP)

• Energy released during cellular respiration is stored as ATP

• Consists of adenine, ribose and three phosphates

How is energy stored in ATP?

• Energy is stored in the bonds. Once a bond breaks (causing ATP to lose a phosphate group), there is a release of energy.

Release of Energy

Adenosine diphosphate or (ADP)

• Two phosphate groups, adenine, and ribose

• Where would the energy be in ADP

Two Types of Cellular Respiration

Aerobic Respiration:• Occurs in presence of oxygen• Occurs in the mitochondria• Produces about 36 ATP

Second Type of Cellular Respiration

Anaerobic Respiration:• Occurs without oxygen• Occurs in the cytoplasm• Produces 2 ATP

Which type of cellular respiration is more efficient?

• Aerobic because it produces more ATP (more energy)

Two types of Anaerobic Respiration:

• 1. Alcoholic Fermentation: yeast produces alcohol

• 2. Lactic Acid Fermentation: muscles produces lactic acid when they don’t have enough oxygen

What is the equation for cellular respiration?

GLUCOSE+ 6O26 CO2 + 6 H2O + Energy (36 ATP)

What is the relationship between photosynthesis and cellular

respiration?

• Opposite reactions• Let’s write the two reactions to see