Cell Energy (Photosynthesis and Respiration) Notes

Energy:• Energy for living things comes from food. Originally,

the energy in food comes from the sun.

• Autotroph- Organisms that use an energy source (such as light from the sun) to produce sugar

• They can make their own food in their cells.• auto = self feedersEx: plants and some microorganisms (some bacteria and

protists)

• Heterotrophs- Organisms that must obtain food (sugar) from another organism.

• Hetero – “other feeder”Ex: animals and most microorganisms

Solar Energy

Process: PhotosynthesisLocation: ChloroplastEnzyme: Rubisco

Pigment: ChlorophyllOccurs in autotrophs

O₂

C6H12O6(glucose)Chemical energy

Process: RespirationLocation: MitochondriaOccurs in: Autotrophs and HeterotrophsPuts a phosphate on ADP to produce ATP (chemical energy)

Some energy lost as HEAT

These energy transformations provide energy for LIFE

CO2 and H2O

Adenine Ribose 3 Phosphate groups (triphosphate)

Cell Energy:• Cells usable source of energy is called ATP• ATP stands for adenosine triphosphate

• ATP is the only molecule the cell can actually use for cell energy. The energy released from breaking down glucose is used to put a phosphate on

Adenosine diphosphate- ADP (2 Phosphates). When ATP provides the energy for the cell it loses a phosphate.

• ADP stands for adenosine diphosphate

Adenine Ribose 2 Phosphate groups

ATP Cycle

ATPLoses a P- Provides energy for all cell work

ADP

Energy from food used to add a P

ATP is like a rechargeable battery

http://media.pearsoncmg.com/bc/bc_0media_bio/blast/index.htm?atp_adp_cycle

• All energy is stored in the bonds of compounds—breaking the bond releases the energy

• When the cell has energy available it can store this energy by adding a phosphate group to ADP, producing ATP

• General formula for photosynthesis:

carbon dioxide + water + light glucose + oxygen

6CO2 + 6H2O + light C6H12O6 + 6O2

Steps of Photosynthesis

1. Light reaction (depends on light)• Traps sunlight• Produces electrons and ATP required to power

the dark reaction• Oxygen given off here

2. Dark reaction, aka Calvin Cycle (does not directly depend on light)

• Uses ATP and electrons from light reaction and CO2 to make glucose

• Diagram Reactants

Products

LightH2O CO2

O2

C6H12O6

Glucose

Chloroplast

LightDependent

Reaction

Calvin Cycle

NADP+ADP + P

ATPNADPH

Summary:• Light Dependent

Reaction—H2O is broken down and light energy is stored temporarily in inorganic energy carriers, ATP and NADPH

• Calvin Cycle—energy is transferred from ATP and NADPH to the organic compound glucose

Cellular Respiration: (2 kinds—Aerobic and Anaerobic)• Cellular respiration is the process by which the energy

of glucose is released in the cell to be used for life processes (movement, breathing, blood circulation, etc…)

• Cells require a constant source of energy for life processes but keep only a small amount of ATP on hand. Cells can regenerate ATP as needed by using the energy stored in foods like glucose.

• The energy stored in glucose by photosynthesis is released by cellular respiration and repackaged into the energy of ATP.

• Respiration occurs in ALL cells and can take place either with or without oxygen present.

Aerobic Respiration: requires oxygen• Occurs in the mitochondria of the cell• Total of 36 ATP molecules produced• General formula for aerobic respiration:

C6H12O6 + 6O2 6 CO2 + 6H2O + 36 ATPglucose + oxygen carbon dioxide + water + energy

Human cells contain a specialized structure – the

mitochondrion – that generates energy.

Overall Reaction

C6H12O6 + 6O2 → 6CO2 + 6H2O + 38 ATP• Overall this is a three stage process1. Glycolysis:

• Occurs in the cytoplasm• Glucose is broken down

2. Krebs Cycle• Breaks down pyruvate into CO2• Occurs in mitochondrial matrix

3. Electron Transport Chain (ETC)• ATP is synthesized

Glycolysis

• Glyco = glucose Lysis = break down• Occurs in the cytoplasm • This stage occurs in BOTH aerobic and anaerobic

respiration• Glucose breaks down into 2 pyruvate (2 ATP are also

made) – Glucose is a 6-carbon sugar – Pyruvate is a 3-carbon molecule (there are two of

them)

Krebs Cycle (Citric Acid Cycle)

• Occurs in the matrix of mitochondria • Main purpose is to generate electrons for use

in ETC• 2 ATP is given off

Electron Transport Chain

• ETC: A series of reactions occur (this is not just one step), to generate ATP and H2O

• Diagram

Glucose GlycolysisElectron

Transport Chain

2

Krebs Cycle

Mitochondria

In Cytoplasm

2 32

Electrons carried in NADH

Electrons carried in NADH and

FADH2

Summary:3 steps: 1st glycolysis

2nd Krebs cycle3rd Electron Transport Chain (ETC)

Anaerobic Respiration: occurs when no oxygen is available to the cell (2 kinds: Alcoholic and Lactic Acid)• Also called fermentation• Much less ATP produced than in aerobic respiration

• fermentation—occurs in bacteria and yeast Process used in the baking and brewing

industry—yeast produces CO2 gas during fermentation to make dough rise and give bread its holes

glucose ethyl alcohol + carbon dioxide + 2 ATP

• Lactic acid fermentation—occurs in muscle cells

Lactic acid is produced in the muscles during rapid exercise when the body cannot supply enough oxygen to the tissues—causes burning sensation in muscles

glucose lactic acid + carbon dioxide + 2 ATP