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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:
6CO2 + 6H2O + energy C6H12O6 + 6O2
Reactants Products
Photosynthesis
2 ReactionsLight ReactionsCalvin 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 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).
Sunlight
NADP+
ADP NADPH
CO2
H2O
O2
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
StepsGlycolysisCitric Acid CycleElectron 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).
CO2 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 H2O.
MITOCHONDRION
CO2
H2O
O2 ATP
NADH
HeatElectron
TransportSystem
ATP
NAD+
Pyruvate
GlucoseATP
Sunlight
Photo-System
I
Photo-system
II
NADP+
ADPNADPHATP
CalvinCO2
H2O
O2
ATP
ATP
NAD+ NADH
ElectronTransportSystem
Cycle
CitricAcid
Heat
CHLOROPLAST MITOCHONDRIONATP
Glycolysis
Glucose Pyruvate
Cycle
Sunlight
Photo-System
I
Photo-system
II
NADP+
ADPNADPHATP
CycleCalvin CO2
H2O
O2
ATP
ATP
NAD+ NADH
ElectronTransportSystem
Cycle
CitricAcid
Heat
CHLOROPLAST MITOCHONDRION
Glucose
ATP
Pyruvate
Glycolysis