3c - life structure, function and control (photosynthesis and cellular respiration)

7/18/2019 3C - Life Structure, Function and Control (Photosynthesis and Cellular Respiration)

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ology 1 Topic 3C- Life Structure,

nction and Control (Photosynthesis

d Cellular Respiration)

Topic 3C- Life Structure, Function and

Control (Photosynthesis

and Cellular Respiration)

F. Photosynthesis

G. Cellular Respiration

This handout is for lecture use only and not

for commercial reproduction and

distribution.

hotosynth sis

• producers of the biosphere, producing organic

molecules from CO2 and other inorganic

molecules

• photoautotrophs - use the energy of sunlight to

make organic molecules from H2O and CO2

• feed not only themselves but also most of the

living world

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Autotrophs

• obtain their organic material from other

organisms• consumers of the biosphere

• almost all heterotrophs depend on

photoautotrophs for food and O2


Heterotrophs






Photosynthesis

• process that converts solar energy into chemical

energy

•

directly or indirectly nourishes almost the entireliving world

• occurs in plants, algae, certain other protists,

and some prokaryotes


(a) Plants

(c) Unicellular protist10 µm

1.5 µm

40 µm(d) Cyanobacteria

(e) Purple sulfur bacteria

(b) Multicellular alga

Chloroplasts: The Sites of

Photosynthesis in Plants

• leaves - major locations of photosynthesis

• chlorophyll - green pigment within chloroplasts

• light energy absorbed by chlorophyll drives the

synthesis of organic molecules in the chloroplast

• CO2 enters and O2 exits the leaf through

microscopic pores called stomata


5 µm

Mesophyll cell

StomataCO2 O2

Chloroplast

Mesophyll

Vein

Leaf cross section

1 µm

Thylakoidspace

Chloroplast

GranumIntermembranespace

Inner membrane

Outer membrane

Stroma

Thylakoid

• chlorophyll is in

the membranesof thylakoids

• chloroplasts

also contain

stroma, a

dense fluid

Photosynthesis

•Process by which plants use light energy to make

food molecules (glucose) from carbon dioxide and

water.

•Most important chemical process on earth.

•Provides fuel for energy production in most organisms.

(CARBON

DIOXIDE)

(WATER) (GLUCOSE) (OXYGEN)






Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Photosynthesis

• Stages of Photosynthesis

1. 2.

grana stroma

Calvin cycle (in

the stroma) formssugar from CO2,

using ATP and

NADPH

Calvin cycle begins

with carbon fixation,incorporating CO2

into organic

molecules

Two Stages of Photosynthesis

• Light reactions (the photo part) and Calvin cycle

(the synthesis part)

•

the light reactions (in the thylakoids): – split H2O

– release O2

– reduce NADP+ to NADPH

– generate ATP from ADP by photophosphorylation


• Calvin cycle (in the stroma) forms sugar from

CO2, using ATP and NADPH

• Calvin cycle begins with carbon fixation,

incorporating CO2 into organic molecules


Two Stages of Photosynthesis

Light

H2O

Chloroplast

LightReactions

NADP+

P

ADP

i+

ATP

NADPH

O2

CalvinCycle

CO2

[CH2O]

(sugar)

Calvin cycle (in

the stroma) formssugar from CO2,

using ATP and

NADPH

Calvin cycle begins

with carbon fixation,incorporating CO2

into organic

molecules

Calvin cycle

• builds sugar from smaller molecules by using

ATP and the reducing power of electrons carried

by NADPH


• carbon enters the cycle as CO2 and leaves as

a sugar named glyceraldehyde-3-phospate

(G3P)

• three phases:

– Carbon fixation (catalyzed by rubisco)

– Reduction

– Regeneration of the CO2 acceptor (RuBP)






Ribulose bisphosphate(RuBP)

3-Phosphoglycerate

Short-livedintermediate

Phase 1: Carbon fixation

(Entering oneat a time)

Rubisco

Input

CO2

P

3 6

3

3

P

PPP

ATP6

6 ADP

P P6

1,3-Bisphosphoglycerate

6

P

P6

6

6 NADP+

NADPH

i

Phase 2:Reduction

Glyceraldehyde-3-phosphate(G3P)

1 P

Output G3P(a sugar)

Glucose andother organiccompounds

CalvinCycle

3

3 ADP

ATP

5 P

Phase 3:Regeneration of the CO2 acceptor (RuBP)

G3P

Incorporationof eachCO2

molecule, one at a time, by

attaching it to a five carbonsugar named ribulose

bisphosphate (abbreviatedRuBP).RuBP carboxylase, or

rubisco catalyzes this first step.Product of the reactionis a six-

carbonintermediate that splitsinhalf, forming two molecules

of 3-phosphoglycerate

Eachmolecule of 3-phosphoglycerate receives

anadditional phosphategroup fromATP, becoming

1,3·bisphosphoglycerate.Next, a pair of electrons

donated fromNADPHreduces 1,3-

bisphosphoglycerate, whichalso loses a phosphate

group, becoming G3P. Onemolecule exits the cycle to be

used by the plant cell, but theother five molecules must be

recycled to regenerate thethree molecules of RuB.

Carbon skeletons of five

molecules of G3P are

rearranged by the last steps

of the Calvin cycle into

three molecules of RuBP.

To accomplish this, the

cycle spends three more

molecules of ATP. The

RuBP is now prepared to

receive CO2 again, and the

cycle continues.

The Calvin cycle

LightReactions:

PhotosystemElectron transport chain

PhotosystemElectron transport chain

CO2

NADP+

ADP

P i+

RuBP3-Phosphoglycerate

CalvinCycle

G3PATP

NADPHStarch(storage)

Sucrose (export)

Chloroplast

Light

H2O

O2

Review of photosynthesis

Cellular

Respiration

Energy Flow and Chemical Recycling

• 2 major routes of energy

flow and nutrient recycling

is cellular respiration andphotosynthesis

• ATP is used to power

all forms of cellular

work

Energy Flow and Chemical Recycling


• ATP – source of energy in cells






Cellular Respiration

•The energy-releasing (ATP) chemical breakdown of

glucose molecules

•The storage of energy in a form that the cell can

use to perform work

(GLUCOSE) (OXYGEN) (ATP) (CARBON

DIOXIDE)

(WATER)



•Phosphorylation – transfer of a phosphate group to

ADP

Mitochondrion

Substrate-level

phosphorylation

ATP

Cytosol

Glucose Pyruvate

Glycolysis

Electrons

carried

via NADH

Substrate-level

phosphorylation

ATP

Electrons carried

via NADH and

FADH2

Oxidative

phosphorylation

ATP

Citric

acid

cycle

Oxidative

phosphorylation:

electron transport

and

chemiosmosisGlycolysis, which occurs in the cytosol,

begins the degradation process by

breaking glucose into two molecules of a

compound called pyruvate

Pyruvate enters the

mitochondrion.

where the citric

acid cycle oxidizes

it to carbon

dioxide.

NADH and electron carrier

coenzyme called FADH

transfer electrons derived

from glucose to electron

transport chains which are

built into the inner

mitochondrial membrane.

During oxidative

phosphorylation,electron

transportchains convertthe chemical

energyto a formused for ATP

synthesis in theprocess calledchemiosmosis.

1.

2.

3.

matrix

inner

membrane

An Accounting of ATP Production


• Related Metabolic Process

•Fermentation – enables some cells to generate ATP

without oxygen (ANAEROBIC)

1. Alcohol fermentation

2. Lactic acid fermentation













•Alcohol fermentation by yeast is used in

brewing and winemaking.








•Lactic acid fermentation by some fungi andbacteria is used to make cheese and yogurt.




•Muscle cells switch fromaerobic respiration to lacticacid fermentation to

generate ATP when O2 isscarce.•The waste product,lactate, may causemuscle fatigue, but

ultimately it isconverted back topyruvate in the liver.

Glucose

Glycolysis

Pyruvate

CYTOSOL

No O2 present:Fermentation

O2 present:Aerobic cellular

respiration

MITOCHONDRION

Acetyl CoAEthanolor

lactateCitricacidcycle

Proteins Carbohydrates

Aminoacids

Sugars

Fats

Glycerol Fattyacids

Glycolysis

Glucose

Glyceraldehyde-3-

Pyruvate

P

NH3

Acetyl CoA

Citricacidcycle

Oxidativephosphorylation

The catabolism of

various moleculesfrom food.

- Glycolysis and the citric

acid cycle connect to manyother metabolic pathways.

- Carbohydrates, fats, and

proteins can all be used as

fuel for cellular respiration.

Monomers of these

molecules enter glycolysis or

the citric acid cycle at various

points.

- Glycolysis and the citric

acid cycle are catabolic

funnels through which

electrons from all kinds of

organic

molecules flow on their

exergonic fall to oxygen.

3c - life structure, function and control (photosynthesis and cellular respiration)

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