Energy in a Cell

1

• Energy in a Cell

2
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.

3
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.

4
What Is ATP?

• ATP adenosine triphosphate is a molecule made
  up of an adenine, ribose, and 3 phosphate groups.

Adenine
phosphate groups
Ribose
5
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
6
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.

7
Making Energy

• Cells make energy in two ways
• Photosynthesis takes place in the chloroplasts.
• Respiration takes place in the mitochondria.

8
Photosynthesis

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

9
Photosynthesis

• Using light from the sun, plants combine water
  and carbon dioxide to make sugar .

• General Equation
• 6CO2 6H2O energy C6H12O6 6O2
• Reactants Products

10
Photosynthesis

• 2 Reactions
• Light Reactions
• Calvin Cycle

11
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.

12
Photosynthesis

• Calvin Cycle ATP and NADPH from the light
  reactions are used along with CO2 to form a
  simple sugar (glucose).
• Takes place in the stroma of the chloroplasts
  (the liquid filling).
• Byproducts are C6H12O6 (glucose), ADP, and NADP
  (which return to the light reactions).

13
Sunlight
O2
Photosystem I II
H2O
ATP
NADP ADP
NADPH
CO2
Calvin cycle
Glucose
CHLOROPLAST
14
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.

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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.

17
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.

18
Respiration

• Steps
• Glycolysis
• Citric Acid Cycle
• Electron Transport Chain

19
Respiration

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

20
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).
• CO2 is released, and NADH carries hydrogen ions
  to the electron transport chain.

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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
  H2O.

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Heat
Electron Transport System
O2
ATP
H2O
NADH
NAD
CO2
citric acid cycle
Glucose
ATP
Pyruvate
MITOCHONDRION
ATP
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Sunlight
Heat
O2
Photo- System I
Photo- system II
Electron Transport System
ATP
H2O
ATP
NADP ADP
NADPH
NAD
NADH
CO2
Calvin
Citric Acid
Cycle
Cycle
ATP
Glucose
Pyruvate
CHLOROPLAST
MITOCHONDRION
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Sunlight
Heat
O2
Photo- System I
Photo- system II
Electron Transport System
ATP
H2O
ATP
NADP ADP
NADPH
NAD
NADH
Calvin
CO2
Cycle
Citric Acid
Cycle
ATP
Glucose
CHLOROPLAST
MITOCHONDRION
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