Chapter 4 – Review
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All cells need energy in a form of ATP
ATP is produced when cells break down
molecules of glucose
Plants can produce their own glucose
by process of photosynthesis
Animals and humans need to get
glucose in their food.
ATP = adenosine triphosphate (3 phosphate groups = energy
rich molecule), fuel for all cell processes.
ADP = adenosine diphosphate (2 phosphate groups = energy
poor molecule)
ATP
ADP + P (one phosphate group) + energy (used by cell)
ADP + P + energy
ATP
Photosynthesis:
Plants convert the sunlight energy, carbon dioxide and water into glucose (energy rich carbohydrate)
6 CO2 + 6 H2O + sunlight energy
C6H12O6 + 6 O2
Light energy – energy from the sunlight,
used by plants for photosynthesis
CHLOROPLAST
Outer membrane
Thylakoid: coin-shaped, membrane
enclosed compartment. Membrane
contains pigment chlorophyll
Granum (pl. grana):
stack of thylakoids
Inner membrane
Chlorophyll: Pigment found on the thylakoid
membrane. Two types – chlorophyll a and
chlorophyll b. They absorb most of the red and
blue wavelengths of sunlight. Green is being
reflected = plants appear to be green.
Stroma (fluid)
Step 1 of photosynthesis:
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Light-dependent reaction (happens during daylight!)
Happens in thylakoids of chloroplasts
Chlorophyll absorbs sunlight
Water molecule is broken down
Oxygen is released
Energy carried along thylakoid membrane is transferred
to ATP (energy-rich molecule)
Final products: ATP molecules (enter step 2 of
photosynthesis) and oxygen (released outside the plants)
Chemical energy – energy in the bonds of
molecules like sugar. This energy is released
when bonds are broken and is used to
produce ATP.
Step 2 of photosynthesis:
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Light- independent reaction (happens day or night)
Happens in stroma of chloroplasts
Needs ATP (from step 1) and CO2 (carbon dioxide)
CO2 molecules are added together in a cycle of
chemical reactions, producing larger carbon
molecule
Energy (ATP) from step 1 is used
Molecule of glucose (simple sugar) is produced
Final product: glucose (stores chemical energy)
Chemosynthesis: uses chemical energy (instead of sunlight energy to produce energy-rich molecules like sugar.
Remember organisms deep down on the ocean floor, near hydrothermal vents?
This review is intended to help you study for upcoming test. To be fully prepared and ready, you should still review the book, your
notes, section and chapter review worksheets and any information you accumulated during this chapter (including yeast lab).
How do cell break down glucose to produce needed ATP?
CELLULAR RESPIRATION
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Glucose
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Releases chemical energy from sugars (and other carbon based molecules) to make ATP
when oxygen is present (aerobic process). Happens in mitochondria.
Think opposite to photosynthesis C6H12O6 + 6 O2
6 CO2 + 6 H2O + energy (ATP)
Oxygen
Outer membrane
Mitochondria
Glycolysis:
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Matrix – fluid inside of mitochondria
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Splits glucose molecule into two
3-carbon molecules (pyruvates),
2 ATP and extra energy is
packaged into energy-carrying
molecules (NAD+)
NAD+ + energy = NADH
Anaerobic process (no O2
needed)
Happens in cytoplasm
Final products:
o pyruvates (enters next
stage),
o 2 ATP (energy ready for
cell to use= $1 bill),
o NADH (energy-carrying
molecule, enters next
stage, $20 bill)
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Stage 1 of cellular respiration (Krebs cycle)
3-carbon molecules are broken down in a
cycle of chemical reactions
Final products:
o Small number of ATP
o CO2 (released out)
o Energy-carrying molecules (like
NADH), they enter 2nd stage of CR
Inner membrane – stage 2 of cellular respiration (electron transport)
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Uses energy-carrying molecules from stage 1 and oxygen to produce
more ATP molecules
Energy from energy-carrying molecules is transferred to chains of
proteins in the membrane
Final products: 34-36 ATP molecules, water and heat
Glycolysis (2 ATP) + Cellular Respiration (34-36 ATP) = total of 36-38 ATP
No Oxygen
FERMENTATION
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Anaerobic process
DOES NOT PRODUCE ATP!
Recycles NAD+ (energycarrying molecules)
Without fermentation all NAD+
would be used up and
glycolysis would stop.
Many different cells (like yeast) use fermentation. Thanks to them we have
bread, cheese, yogurt, alcohol. Different end products of fermentation give
different taste and texture to food.
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Lactic acid fermentation: glucose
pyruvate
lactic acid
Waste product (lactic acid) is what causes our muscles to burn after
strenuous exercise. It also contributes to sour taste of milk and yogurt
Alcoholic fermentation: glucose
pyruvate
alcohol + CO2
Yeast uses alcoholic fermentation during bread production. CO2 causes
dough rise. During baking CO2 evaporates and yeast is killed by heat.
Glycolysis (2ATP) + Fermentation (no ATP) = total of 2 ATP