Photosynthesis and Cellular Respiration - PowerPoint Presentation

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Photosynthesis and Cellular RespirationSlide2

Outline

I. Photosynthesis

A. Introduction

B. Reactions

II. Cellular Respiration

A. Introduction

B. ReactionsSlide3

What organisms go through photosynthesis?

Producers/autotrophs

,

such as plants, trees, algae, some bacteriaSlide4

Photosynthesis

Method of converting sun energy into chemical energy usable by cells

Autotrophs

: self feeders, organisms capable of making their own food

Photoautotrophs: use sun energy e.g. plants photosynthesis-makes organic compounds (glucose) from lightChemoautotrophs

: use chemical energy e.g. bacteria that use sulfide or methane chemosynthesis-makes organic compounds from chemical energy contained in sulfide or methaneSlide5

Factors that affect photosynthesis

1.

Water

– needed to start the LD reaction

2.

Temperature – proteins work best between 0-35 degrees Celcius3. Light – need light to excite e- in chlorophyllSlide6

Where does photosynthesis take place?

In the chloroplasts of plant cells found in the leaves!

Plant

Plant Cell

ChloroplastSlide7

Leaf Structure

Most photosynthesis occurs in the

palisade

layer.

Gas exchange of CO

2 and O2 occurs at openings called stomata surrounded by guard cells on the lower leaf surface.

Palisade

SpongySlide8

Chloroplasts have chlorophyll

Chlorophyll is a green pigment that reacts to sunlight by transferring energy to e- (electrons)

Makes chloroplasts and plants look green

Reflect green light waves from the sunSlide9

Pigments

Chlorophyll A is the most important photosynthetic pigment.

Other pigments called antenna or accessory pigments are also present in the leaf.

Chlorophyll B

Carotenoids (orange / red)

Xanthophylls (yellow / brown)These pigments are embedded in the membranes of the chloroplast in groups called photosystems.Slide10

Photosynthesis

Photosynthesis

takes place in specialized structures inside plant cells called

chloroplasts

Light absorbing pigment molecules e.g. chlorophyllSlide11

Parts of a Chloroplast

Granum

Thylakoid

(single sac)

Stroma (fluid)

Inner Membrane

Outer MembraneSlide12

Chloroplast Structure

Inner membrane called the

thylakoid

membrane.

Thickened regions called

thylakoids. A stack of thylakoids is called a granum. (Plural – grana)

Stroma

is a liquid surrounding the thylakoids.Slide13

Photosynthesis Chemical

Eqn

:

Sunlight + 6CO

2

+ 6H

2

O = C

6

H

12

O

6

+ 6O

2

carbon dioxide

water

sugar (glucose)

oxygen

Reactants

“what is used”

Products

“what is made”Slide14

Overall Reaction

6CO

2

+ 12 H

2O + light energy → C

6H12O6 + 6O2+ 6H2O

Carbohydrate made is glucose

Water appears on both sides because 12 H

2

O molecules are required and 6 new H

2

O molecules are madeWater is split as a source of electrons from hydrogen atoms releasing O2

as a byproductElectrons increase potential energy when moved from water to sugar therefore energy is required Slide15

Light-dependent Reactions

Overview

: light energy is absorbed by chlorophyll molecules-this light energy excites electrons and boosts them to higher energy levels. They are trapped by electron acceptor molecules that are poised at the start of a neighboring transport system. The electrons “fall” to a lower energy state, releasing energy that is harnessed to make ATP Slide16
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Energy Shuttling

Recall

ATP

: cellular energy-nucleotide based molecule with 3 phosphate groups bonded to it, when removing the third phosphate group, lots of energy liberated=

superb molecule for shuttling energy around within cells.Other energy shuttles-coenzymes (nucleotide based molecules): move electrons and protons around within the cellNADP+, NADPH NAD+, NADP FAD, FADH

2Slide18

Light-dependent Reactions

Photosystem

: light capturing unit, contains chlorophyll, the light capturing pigment

Electron transport system

: sequence of electron carrier molecules that shuttle electrons, energy released to make ATPElectrons in chlorophyll must be replaced so that cycle may continue-these electrons come from water molecules, Oxygen is liberated from the light reactionsLight reactions yield ATP and NADPH used to fuel the reactions of the Calvin cycle (light independent or dark reactions)Slide19
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Calvin Cycle (light independent or “dark” reactions)

ATP and NADPH generated in light reactions used to fuel the reactions which take CO

2

and break it apart, then reassemble the carbons into glucose.

Called carbon fixation: taking carbon from an inorganic molecule (atmospheric CO2) and making an organic molecule out of it (glucose)Simplified version of how carbon and energy enter the food chainSlide22
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Photosynthesis

Light-Dependent Reaction

Light-Independent Reaction AKA Calvin Cycle

- Occurs in thylakoid membrane

- sunlight is required

O

2

is produced from water

e- fuel many reactions by going through Electron Transport Chain

- Occurs in stroma

sunlight is NOT required

Glucose is produced from CO

2

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Harvesting Chemical Energy

So we see how energy enters food chains (via autotrophs) we can look at how organisms use that energy to fuel their bodies.

Plants and animals both use products of photosynthesis (glucose) for metabolic fuel

Heterotrophs

: must take in energy from outside sources, cannot make their own e.g. animalsWhen we take in glucose (or other carbs), proteins, and fats-

these foods don’t come to us the way our cells can use themSlide25

Cellular Respiration Overview

Transformation of chemical energy in food into chemical energy cells can use: ATP

These reactions proceed the same way in plants and animals. Process is called

cellular respiration

Overall Reaction:C6H12O6

+ 6O2 → 6CO2 + 6H2OSlide26

Anatomy of MitochondriaSlide27

Cellular Respiration Overview

Breakdown of glucose begins in the cytoplasm: the liquid matrix inside the cell

At this point life diverges into two forms and two pathways

Anaerobic cellular respiration (aka fermentation)

Aerobic cellular respirationSlide28

C.R. Reactions

Glycolysis

Series of reactions which break the

6-carbon glucose

molecule down into two 3-carbon molecules called pyruvateProcess is an ancient one-all organisms from simple bacteria to humans perform it the same wayYields 2 ATP molecules for every one glucose molecule broken down

Yields 2 NADH per glucose moleculeSlide29
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Anaerobic Cellular Respiration

Some organisms thrive in environments with little or no oxygen

Marshes, bogs, gut of animals, sewage treatment ponds

No oxygen used= ‘an’aerobic

Results in no more ATP, final steps in these pathways serve ONLY to regenerate NAD+ so it can return to pick up more electrons and hydrogens in glycolysis.End products such as ethanol and CO2

(single cell fungi (yeast) in beer/bread) or lactic acid (muscle cells)Slide31
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Aerobic Cellular Respiration

Oxygen required=aerobic

2 more sets of reactions which occur in a specialized structure within the cell called the

mitochondria

1. Kreb’s Cycle2. Electron Transport ChainSlide33

Kreb’s Cycle

Completes the breakdown of glucose

Takes the pyruvate (3-carbons) and breaks it down, the carbon and oxygen atoms end up in CO

2

and H2OHydrogens and electrons are stripped and loaded onto NAD+ and FAD to produce NADH and FADH2Production of only 2 more ATP

but loads up the coenzymes with H+ and electrons which move to the 3rd stageSlide34
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Electron Transport Chain

Electron carriers loaded with electrons and protons from the Kreb’s cycle move to this chain-like a series of steps (staircase).

As electrons drop down stairs, energy released to

form a total of 32 ATP

Oxygen waits at bottom of staircase, picks up electrons and protons and in doing so becomes water Slide36
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Energy Tally

38

ATP for aerobic vs. 2 ATP for anaerobic

Glycolysis 2 ATP

Kreb’s 2 ATP

Electron Transport 34 ATP 38 ATPAnaerobic organisms can’t be too energetic but are important for global recycling of carbonSlide38
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