Packet 6
Cellular Energy
ATP: cellular energy
Why do cells need energy?
• Cells carry out three kinds of energy-requiring work:– Chemical– Mechanical– Transport
Making ATP: Aerobic cellular respiration
Glycolysis (Stage 1) • Breaking down glucose
– “glyco – lysis” (splitting sugar)
– Occurs in the cytoplasm– A little ATP energy is harvested, – but it’s inefficient
• generate only 2 ATP for every 1 glucose
glucose pyruvate2x6C 3C
Overview10 reactions– convert
glucose (6C) to 2 pyruvate (3C)
– produces: 4 ATP & 2 NADH
– consumes:2 ATP
– net yield: 2 ATP & 2 NADH
Substrate-level phosphorylation
Substrate-level phosphorylation
Products of glycolysis move on to stage 2 or 3
intermembranespace inner
membrane
outermembrane
matrix
cristae
Mitochondria — Structure• Double membrane
– smooth outer membrane– highly folded inner membrane– intermembrane space– Matrix– DNA, ribosomes– enzymes
mitochondrialDNA
This happens twice for each glucose molecule that started glycolysis…why?
Stage 2: Pyruvate
grooming and the Kreb’s Cycle
Cellular respiration
Electron Transport Chain and Chemiosmosis: ATP payoff!
• Electron Transport Chain – series of proteins built into
inner mitochondrial membrane
Glycolysis Krebs cycle
8 NADH2 FADH2
Remember the Electron Carriers?
2 NADH
Time tobreak open
the piggybank!
Electron Transport Chain
What powers the proton (H+) pumps?…
Electronegativity!
Chemiosmosis and oxidative phosphorylation
oxidative phosphorylation
Cellular respiration
2 ATP 2 ATP 34 ATP+ +
~38 ATP
Summary of cellular respiration
• Where did the glucose come from?• Where did the O2 come from?
• Where did the CO2 come from?
• Where did the CO2 go?
• Where did the H2O come from?
• Where did the ATP come from?• What is recycled for use again?• Why do we breathe?
C6H12O6 6O2 6CO2 6H2O ~34-38 ATP+ + +
ETC backs up nothing to pull electrons down chain NADH & FADH2 can’t unload H
ATP production ceases cells run out of energy
Taking it beyond…• What is the final electron acceptor in
Electron Transport Chain?O2
So what happens if O2 unavailable?
Anaerobic respiration
Making ATP without oxygen
• All cells carry out glycolysis: prokaryotes and eukaryotes.• Eukaryotes and many prokaryotes also carry out oxidative phosphorylation
(remember this requires oxygen).
How can some bacteria carry out aerobic respiration if they don't have mitochondria?
FUN FACT: many bacteria have ETC’s in their cell membranes.
Reminders!A net of 2 ATP is generated in glycolysis.
NAD+ must be present available for this process.
New considerationsFor aerobic organisms this is not a problem, NAD+ is regenerated by the ETC.
Not all organisms can use oxygen, they are anaerobic
Anaerobic organisms use glycolysis only to make ATP
They regenerate , NAD+ through fermentation processes
Alcohol fermentation
Lactic acid fermentation
Review: Answer all of the following questions in your notebook.
• What are the products of pyruvate grooming for 1 molecule of glucose?
• What are the products of the citric acid cycle for 1 molecule of glucose?
• After glycolysis, pyruvate grooming, and the citric acid cycle, what are your net products?
• What is phosphorylation?• What is substrate-level phosphorylation?• What is the main goal for stages 1-3?
Review: Answer all of the following questions in your notebook
• What is the summary equation for cellular respiration?
• If oxidation is a loss of electrons (in the form of hydrogen atoms) and reduction is the gain of electrons (in the form of hydrogen atoms), – what is oxidized during cellular respiration? – what is reduced during cellular respiration?
• How does glucose get to your cells for cellular respiration?
• What is the point of cellular respiration?• What are the net molecular products of glycolysis?
Where does glucose come from for cellular respiration?
Photosynthesis!
Photosynthesis
Leaf structure
Mesophyll cells
Vascular tissueStomateGuard cells
Chloroplast structure Double membran
e
Stroma
ThylakoidGrana
Stage 1:
Light-dependent reactions
Stage 2:
Calvin cycle
Light energy is converted to chemical energy (as NADPH and ATP).
Glucose is made from CO2 and hydrogens carried by NADPH using ATP energy.
Calvin cycle
What factors might affect the rate of photosynthetic reactions?
SUMMARY
