Energy in a Cell

All Cells Need Energy Cells need energy to do a variety of work: Making new molecules. Building membranes and organelles. Moving molecules in and out of the cell. Movement.

Where Does A Cell Get Energy? Food is broken down to a form the cell can use. Extra energy is stored in an ATP molecule, a nucleotide.

What Is ATP? ATP – adenosine triphosphate is a molecule made up of an adenine, ribose, and 3 phosphate groups. Adenine Ribose

How Does ATP Work? Energy is stored in the bond between the second and third phosphate group. When the bond is broken, energy is released and ADP is formed. Adenine Ribose

ATP – Energy Currency Within a cell, formation of ATP from ADP and phosphate occurs over and over, storing energy each time. As the cell uses energy, ATP breaks down repeatedly to release energy and form ADP and phosphate.

Making Energy Cells make energy in two ways: Photosynthesis – takes place in the chloroplasts. Respiration – takes place in the mitochondria.

Photosynthesis Autotrophs make their own food by trapping light energy and converting it to chemical energy (carbohydrates).

Photosynthesis Using light from the sun, plants combine water and carbon dioxide to make sugar. General Equation: 6CO 2 + 6H 2 O + energy C 6 H 12 O 6 + 6O 2 Reactants Products

Photosynthesis 2 Reactions Light Reactions Calvin Cycle

Photosynthesis Light Reactions – Light energy is converted to chemical energy to split hydrogen from water. Takes place in the grana of the chloroplasts (the coin- like stacks of sacs). Byproducts are oxygen, NADPH, and ATP.

Photosynthesis Calvin Cycle – ATP and NADPH from the light reactions are used along with CO 2 to form a simple sugar (glucose). Takes place in the stroma of the chloroplasts (the liquid filling). Byproducts are C 6 H 12 O 6 (glucose), ADP, and NADP + (which return to the light reactions).

Sunlight NADP + ADP NADPH CO 2 H2OH2O O2O2 CHLOROPLAST ATP

Chemosynthesis Some autotrophs can convert inorganic substances to energy. Most are adapted to live in conditions where there is no oxygen. Marshes. Lake sediments. Digestive tracts of mammals. Deep in the ocean.

Respiration The process of breaking down food molecules to release energy. Occurs in the mitochondria. Two types: Aerobic – requires oxygen. Anaerobic – requires an absence of oxygen.

Respiration Two types of anaerobic respiration: Fermentation – occurs when bacteria break down plants (vegetables and fruit) and release alcohol or vinegar. Lactic Acid Fermentation – occurs in muscles – a buildup of lactic acid causes soreness.

Respiration Steps Glycolysis Citric Acid Cycle Electron Transport Chain

Respiration Glycolysis – glucose is split to form pyruvate. Takes place in the cytoplasm of the cell. ATP is a byproduct.

Respiration Citric Acid Cycle – pyruvate is used to build citric acid (a carbon compound), which is broken down to release ATP. Takes place in the cristae (the folded membrane in the mitochondrion). CO 2 is released, and NADH carries hydrogen ions to the electron transport chain.

Respiration Electron Transport Chain – hydrogen ions are stripped of their energy, and large amounts of ATP are formed. Takes place in the inner membrane of the mitochondrion. The used ions are combined with oxygen to form H 2 O.

MITOCHONDRION CO 2 H2OH2O O2O2 ATP NADH Heat Electron Transport System ATP NAD + Pyruvate Glucose ATP

Sunlight Photo- System I Photo- system II NADP + ADP NADPH ATP Calvin CO 2 H2OH2O O2O2 ATP NAD + NADH Electron Transport System Cycle Citric Acid Heat CHLOROPLASTMITOCHONDRION ATP Glycolysis Glucose Pyruvate Cycle

Sunlight Photo- System I Photo- system II NADP + ADP NADPH ATP Cycle Calvin CO 2 H2OH2O O2O2 ATP NAD + NADH Electron Transport System Cycle Citric Acid Heat CHLOROPLASTMITOCHONDRION Glucose ATP Pyruvate Glycolysis