AP Bio Exam Review: Cell Energy (Respiration & Photosynthesis)
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Transcript of AP Bio Exam Review: Cell Energy (Respiration & Photosynthesis)
AP Bio Exam Review:Cell Energy
(Respiration & Photosynthesis)
• Catabolic pathways release energy by breaking down complex molecules into simpler compounds
• C6H12O6 +6O2 6H2O + 6CO2 +E
• Anabolic pathways consume energy to build complex molecules from simpler ones
• 6H20+6CO2 + E C6H12O6 +6O2
Concept 8.3 ATP powers cellular work by coupling exergonic reactions to endergonic reactions
• A cell does three main kinds of work:– Mechanical– Transport– Chemical
• To do work, cells manage energy resources by energy coupling, the use of an
exergonic (energy releasing) process to drive an endergonic (energy absorbing) one
Concept 8.4: Enzymes speed up metabolic reactions by lowering energy barriers
A catalyst is a chemical agent that speeds up a reaction without being consumed by the reaction
An enzyme is a catalytic protein
Hydrolysis of sucrose by the enzyme sucrase is an example of an enzyme-catalyzed reaction
Substrate Specificity of Enzymes• The reactant that an enzyme acts on is called the
enzyme’s substrate • The enzyme binds to its substrate, forming an enzyme-
substrate complex• The active site is the region on the enzyme where the
substrate binds
CofactorsCofactors are nonprotein enzyme helpers such as
mineralsCoenzymes are organic cofactors such as vitamins
Enzyme Inhibitors
Allosteric Regulation
• a protein’s function at one site is affected by binding of a regulatory molecule at another site
• Allosteric regulation may either inhibit or stimulate an enzyme’s activity
Feedback Inhibition
• In feedback inhibition, the end product of a metabolic pathway shuts down the pathway
Energy Harvest• Energy is released as electrons “fall” from
organic molecules to O2
• Broken down into steps:Food NADH ETC O2
– Coenzyme NAD+ = electron acceptor– NAD+ picks up 2e- and 2H+ NADH (stores E)– NADH carries electrons to the electron transport
chain (ETC)– ETC: transfers e- to O2 to make H2O ; releases
energy
Cellular Respiration
Mitochondrion Structure
Citric Acid Cycle(matrix)
Citric Acid Cycle(matrix)
ETC(inner membrane)
ETC(inner membrane)
Glycolysis
Fermentation• Occurs in plants and
animals• Occurs in cytosol• Keep glycolysis going• No oxygen needed• Creates alcohol [+ CO2] or
lactic acid
Respiration• Release E from breakdown
of food with O2
• Occurs in mitochondria• O2 required (final electron
acceptor)• Produces CO2, H2O and up
to 38 ATP (NADH, FADH2)
O2 presentWithout O2
Types of Fermentation
Alcohol fermentation
• Pyruvate Ethanol + CO2
• Ex. bacteria, yeast• Used in brewing,
winemaking, baking
Lactic acid fermentation
• Pyruvate Lactate• Ex. fungi, bacteria, human
muscle cells• Used to make cheese,
yogurt, acetone, methanol• Note: Lactate build-up does
NOT causes muscle fatigue and pain (old idea)
PURPOSE = NAD+ recycled for glycolysis
Various sources of fuel
• Carbohydrates, fats and proteins can ALL be used as fuel for cellular respiration
• Monomers enter glycolysis or citric acid cycle at different points
Respiration(mitochondria)
Respiration(mitochondria)
Krebs cycle(citric acid cycle)Krebs cycle(citric acid cycle)
ENERGY
glycolysis(cytosol)
glycolysis(cytosol)
fermentationfermentation
ethanol + CO2(yeast, some bacteria)
ethanol + CO2(yeast, some bacteria)
anaerobic (without O2)
aerobic (with O2)
lactic acid(animals)
lactic acid(animals)
electron transport
chain
electron transport
chain
chemiosmosischemiosmosis
Oxidative Phosphorylation
Leaf cross sectionVein
Mesophyll
Stomata CO2 O2
Mesophyll cellChloroplast
5 µm
Outermembrane
Intermembranespace
Innermembrane
Thylakoidspace
Thylakoid
GranumStroma
1 µm
Sites of Photosynthesis
• mesophyll: chloroplasts mainly found in these cells of leaf
• stomata: pores in leaf (CO2 enter/O2 exits)
• chlorophyll: green pigment in thylakoid membranes of chloroplasts
Photosynthesis = Light Reactions + Calvin Cycle“photo” “synthesis”
Light Reactions
Both respiration and photosynthesis use chemiosmosis to generate ATP
Calvin Cycle = produce 3C sugar (G3P)
Photorespiration: low carbon-fixation when stomata closed in hot, dry climate
C3 C4 CAMC fixation & Calvin
togetherC fixation & Calvin in
different cellsC fixation & Calvin at different TIMES
Rubisco(normally fixes CO2)
PEP carboxylase fixes CO2
Organic acid
Mesophyll cellsMesophyll: fix CO2
Bundle Sheath: Calvin Cycle
Night: fix CO2 in 4C acids
Day: Calvin Cycle
Ex. rice, wheat, soybeans Ex. sugarcane, grass Ex. cacti, pineapple,
succulent
Comparison
RESPIRATION PHOTOSYNTHESIS• Plants + Animals• Needs O2 and food
• Produces CO2, H2O and ATP, NADH
• Occurs in mitochondria membrane & matrix
• Oxidative phosphorylation• Proton gradient across
membrane
• Plants• Needs CO2, H2O, sunlight• Produces glucose, O2 and
ATP, NADPH• Occurs in chloroplast
thylakoid membrane & stroma
• Photorespiration• Proton gradient across
membrane