Cell energyCh.9

• All living organisms must be able to produce energy, store the energy for future use and use energy.

Cell processes that require energy

• Active transport• Movement• Cell division• Production and storage of proteins• Cells use energy to maintain

homeostasis

ATP• Molecule in your cells that is a

quick source of energy for any organelle in the cell that needs it.

• This energy is stored in the chemical bonds of

the molecule ATP

• Adenosine Triphosphate is composed of an adenosine molecule with 3 phosphate groups attached.

• AMP - adenosine monophosphate - small amount of energy

• ADP - adenosine diphosphate - more substantial amount of energy

• ATP - When bond is broken, a great amount of energy is released & the cell can use the energy for activities. ADP can then reform ATP by bonding with another phosphate group

Photosynthesis• The process plants use to trap the

sun’s energy and build carbohydrates, called glucose, that store energy.

• Occurs in 2 phases

1. Light-dependent reactions

2. Light-independent reactions

• 6CO2 + 6H2O C6H12O6 + 6O2

Light-dependent reactions

• Convert light energy into chemical energy

• ATP produced in LDR are used to fuel LIR that produce glucose

Chloroplasts

• Cell organelle where photosynthesis occurs

• Within chloroplasts, thylakoid discs contain pigments

• Most common pigment is chlorophyll• Light-dependent reactions take place

in the thylakoid discs

http://en.wikipedia.org/wiki/File:Chloroplast_mini.svg

Chlorophyll

• Absorbs most wavelengths of light except green which it reflects, giving leaves a green appearance

http://en.wikipedia.org/wiki/File:Mikrofoto.de-alge2.jpg

Light-dependent reactions

• Requires sunlight• Sunlight strikes molecules in

thylakoid membrane & light energy is transferred to electrons

• These electrons are passed to an electron transport chain

Electron transport chain

• A series of proteins embedded in the thylakoid membrane

• Each protein passes energized electrons along from protein to protein

• At each step the electron loses energy

• ETC allows small amounts of energy to be released at time

• This energy can be used to form ATP• This energy is not wasted, the

electron is transferred to the stroma of the chloroplast

• NADP+ is used & becomes NADPH

Photolysis

• Electrons must be restored to chlorophyll because many leave with NADPH

• To replace the lost electrons, molecules of water are split through a process called photolysis

Light-independent reactions

• Does not require light• Calvin cycle• Series of reactions that use carbon

dioxide & ATP from Light-dependent Reactions to form carbohydrates

• Takes place in the stroma of the chloroplast

• We know that plants use sunlight energy to split water (H2O) into hydrogen and oxygen.

• The hydrogen is added to the carbon dioxide to make CARBOHYDRATES such as glucose.

• The oxygen produced from this splitting of water is released into our atmosphere.

• We summarise this using a chemical equation:6 CO2 + 6 H20 ------------ C6H12O6 + 6 O2

carbon water glucose oxygendioxide

Cellular Respiration

• The process by which mitochondria break down food molecules to produce ATP

3 Stages

1. Glycolysis (anaerobic)

2. Citric acid cycle (aerobic)

3. Electron Transport Chain (aerobic)

• Anaerobic – no oxygen required

• Aerobic – oxygen required

Glycolysis

• A series of chemical reactions in the cytoplasm of a cell that break down glucose into 2 molecules of pyruvic acid

• Uses 2 molecules of ATP to start & only produces 2 molecules of ATP per glucose broken down

• Not very efficient but can occur in the absence of oxygen

• Uses an electron carrier called NAD+

• NAD forms NADH when it is carrying an electron

• Following glycolysis, the pyruvic acid molecules move to the mitochondria

Citric Acid Cycle• Occurs in mitochondria

• One molecule of ATP is produced for every turn of the cycle

• 2 electron carriers are used– NAD+

– FAD

• Electron carriers pass energized electrons along to the electron transport chain in the inner membrane of the mitochondrion.

Electron Transport Chain

• NADH & FADH2 pass energized electrons from protein to protein within the membrane slowly releasing small amounts of the energy contained within the electron

• Some energy is used to form ATP & some is used to pump H+ ions into the center of the mitochondrion.

• Mitochondrion inner membrane becomes positively charged because of the high concentration of positively charged hydrogen ions.

• Exterior of membrane is negatively charged which further attracts hydrogen ions

• Inner membrane of the mitochondrion forms ATP from this electrochemical gradient of H+ ions across the membrane.

• Overall ETC produce 32 ATP molecules

Fermentation

• When your cells are without oxygen for a short period of time, an anaerobic process called fermentation follows glycolysis.

• Two major types– Lactic acid fermentation– Alcoholic fermentation