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)
glucose      pyruvate
2x 3C
6C
– Occurs in the cytoplasm
– A little ATP energy is harvested,
– but it’s inefficient
• generate only 2 ATP for every 1 glucose
Overview
10 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
Mitochondria — Structure
• Double membrane
–
–
–
–
–
–
smooth outer membrane
highly folded inner membrane
intermembrane space
Matrix
DNA, ribosomes
enzymes
outer
intermembrane
membrane
inner
space
membrane
cristae
matrix
mitochondrial
DNA
Stage 2:
Pyruvate
grooming and the
Kreb’s Cycle
This happens
twice for each
glucose
molecule that
started
glycolysis…wh
y?
Cellular respiration
Electron Transport Chain and
Chemiosmosis: ATP payoff!
• Electron Transport Chain
– series of proteins built into
inner mitochondrial membrane
Remember the Electron Carriers?
Glycolysis
2 NADH
Time to
break open
the piggybank!
Krebs cycle
8 NADH
2 FADH2
Electron Transport
Chain
What powers the proton
(H+) pumps?…
Electronegativity!
Chemiosmosis and oxidative phosphorylation
oxidative phosphorylation
Cellular respiration
2 ATP
+
2 ATP
+
34 ATP
Summary of cellular respiration
C6H12O6 + 6O2
•
•
•
•
•
•
•
•
 6CO2 + 6H2O +~34-38 ATP
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?
Taking it beyond…
• What is the final electron acceptor in
Electron Transport Chain?
O2
 So what happens if O2 unavailable?
 ETC backs up
nothing to pull electrons down chain
 NADH & FADH2 can’t unload H

 ATP production ceases
 cells run out of energy
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 considerations
For 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
Stomate
Guard cells
Vascular tissue
Chloroplast structure
Grana
Thylakoid
Stroma
Double
membran
e
Stage 1:
Lightdependent
reactions
Light energy
is converted
to chemical
energy (as
NADPH and
ATP).
Stage 2:
Calvin cycle
Glucose is made from
CO2 and hydrogens
carried by NADPH
using ATP energy.
Calvin cycle
SUMMARY
What factors might affect the rate of
photosynthetic reactions?