Chapter 8Photosynthesis

Autotrophs vs. HeterotrophsAutotrophs are organisms that can

make their own food◦Use light energy from the sun to

produce◦Plants are an example

Heterotrophs cannot use the sun’s energy directly◦Obtain energy from the foods they

eat◦Animals and mushrooms are

examples

Autotrophs vs. Heterotrophs

EnergyATP – Adenosine triphosphate – is the

molecule cells use to store and release energy. Be able to draw it. Energy is released when the bond is broken between the last two phosphates.

ADP – Adenosine diphosphateAMP – Adenosine monophosphate

Adenosine

Energy

EnergyAdding a phosphate group to ADP

allows the organism to store energy◦ATP is like a fully charged battery◦ADP is like a partially charged

battery

EnergyEnergy is used for:1. Active transport: Na+ is pumped

out and K+ into the cell2. Motor proteins that move organelles3. Synthesis of proteins, nucleic acids,

lipids…4. Produce light (firefly)5. Cell reproduction and more

EnergyGlucose is better for long term

storage than ATPA single molecule of glucose stores 90

times the chemical energy of a molecule of ATP

Most cells only have a small amount of ATP, only enough to last for a few seconds of activity

What is Photosynthesis?Photosynthesis is the process in

which light, water, and carbon dioxide (CO2) is made into sugar and oxygen (O2)

Carbon dioxide + water sugar + oxygen

6CO2 + 6H2O C6H12O6 + 6O2

PhotosynthesisChlorophyll a

and Chlorophyll b are pigments in the chloroplast that absorb light of the visible spectrum, except for green light. They reflect green, thus the leaf looks green.

PhotosynthesisPhotosynthesis takes place in the

chloroplasts◦Chloroplasts have stacks of

thylakoids (saclike photosynthetic membranes)

◦Proteins in thylakoids organize chlorophyll and other pigments into photosystems, which are the light-collecting units

Light-dependent reactionsTake place in the thylakoid membranesConvert light energy to ATP and

NADPHSplit H2O and release O2

Electron transport chain connects the two photosystems to make an H+ gradient across the thylakoid membrane (ATP synthase uses this force to make ATP). Uses a proton (H+) pump.

Light-dependent reactions

Calvin cycle reactionsTake place in the stromaUse ATP and NADPH to convert CO2 to

sugarReturn ADP, inorganic phosphate, and

NADP+ to the light reactions

Calvin cycle reactions

Photosynthesis

Factors affecting photosynthesis

Water (required raw material)◦Plants in dry climates have a waxy

coating to prevent water lossCO2 concentration (required raw

material)Temperature: enzymes function best

between 0o C and 35o CLight intensity

◦Plants can reach a maximum rate of photosynthesis with light intensity (varies between plant type)

Chapter 9 Cellular Respiration

Chemical EnergyHow much energy is in food?

◦One molecule of glucose contains 3811 calories of heat energy

◦A calorie is the amount of energy needed to raise the temperature of one gram of water one degree Celsius

◦The Calorie (food labels) is actually 1000 calories

Chemical EnergyThe beginning of turning food into

energy is glycolysis (produces small amount of energy)

If oxygen is present 2 other pathways occur to produce more energy

If oxygen is not present, 1 different pathway occurs

Energy PathwaysAerobic – requires oxygen

◦Also called cellular respirationAnaerobic – does not need oxygen

◦Fermentation – name for anaerobic pathway following glycolysis (if oxygen is not present). (The term fermentation includes glycolysis).

What is Cellular Respiration?Cellular Respiration (video)Cellular respiration - the process

that releases energy by breaking down glucose and other food molecules in the presence of oxygen.

Glucose + oxygen carbon dioxide + water + energy

C6H12O6 + 6O2 6CO2 + 6H2O + ATP

What is Cellular Respiration?

Carbondioxide

Water

Oxygen

Carbondioxide

Cellular RespirationSteps of cellular respiration:1. Glycolysis – one glucose is broken in

half to make 2 pyruvic acids. Anaerobic. Occurs in cytoplasm.

2. Krebs cycle – pyruvic acid is broken down into CO2 and energy. Aerobic. Occurs in mitochondrion. Also called citric acid cycle.

3. Electron transport chain – using a series of proteins, the electrons from the Krebs Cycle and glycolysis to convert ADP to ATP.

GlycolysisNADH passes energy from glucose to

the electron transport chain

Energy PathwaysAerobic – requires oxygen

◦Also called cellular respirationAnaerobic – does not need oxygen

◦Fermentation – name for anaerobic pathway following glycolysis (if oxygen is not present). (The term fermentation includes glycolysis).

FermentationTwo types of fermentation:Alcoholic fermentation: yeasts and

some bacteriaPyruvic acid + NADH alcohol + CO2 + NAD+

Lactic acid fermentation: most organisms including us and many bacteria

Pyruvic acid + NADH lactic acid + NAD+

Both processes regenerate NAD+

Lactic Acid Fermentation

Kreb’s Cycle and ETCDuring the Kreb’s cycle pyruvic acid is

broken down into carbon dioxide◦Occurs in the mitochondrion◦NADH and ATP is produced

In the electron transport chain (ETC) high energy electrons (NADH, FADH2) is converted into ATP◦Hydrogen ions are pumped across

membrane◦ATP synthase – enzyme (protein)

that makes ATP using H+ gradient

Cellular Respiration1 glucose results in the production of

36 ATP net◦34 more ATP than anaerobic

processes◦38% of the total energy in glucose,

the other 62% is “lost” through heat◦More efficient than an automobile

(25%-30%) 70-75% is lost to heat

Energy Pathway

Glycolysis

No Oxygen Oxygen

Anaerobic respiration Aerobic respiration

36 ATP2 ATP, lactate oralcohol, and CO2

Fermentation Cellular respiration

Cellular Respiration

Cellular Respiration

Energy Pathway

  Photosynthesis

Cellular Respiration

Fermentation

Function

Energy storage Energy release Energy release

Location

Chloroplasts Mitochondria Cytoplasm

Reactants

CO2 and H2O Glucose and O2 Glucose & NAD

Products

Glucose and O2 CO2 and H2O & ATP

Alcohol & CO2

& ATP orLactic acid & ATP

Comparing photosynthesis, cellular respiration, & fermentation: