Download Cell Respiration

Cell Respiration
3.7 and 8.1
http://www.youtube.com/watch?v=3aZrkdzrd04
What is cell respiration?
Process by which energy in food molecules
(glucose) is made available for an organism to
do biological work via breakdown/being
metabolized
Each redox reaction causes a small amount of
energy to be released; the end goal is to convert
the energy into making ATP molecules
Typically we discuss in terms of glucose, but other organic
molecules can also be broken down; fats very important
in making ATP and contribute to energy used in
muscles, heart, liver, kidneys
OIL RIG
• An easy way to remember redox reactions is
O – oxidation
I – is
Note: This is true when
L – loss
dealing with electrons
and/or Hydrogen atoms
R – reduction
I – is
G - gain
It is thought that aerobic respiration evolved after anaerobic
respiration; possibly ~ 2.4 bya when O2 accumulated on
Earth
The breakdown of glucose via respiration
must be done in small steps in a controlled
manner so that the heat produced does
not destroy the cell/organism
3 steps in aerobic cellular respiration:
1)Glycolysis
2) Kreb’s cycle
3) electron transport system (ETS)
Step 1: Glycolysis
• Glucose enters the cell through the plasma
membrane (via facilitated diffusion) and goes
into the cytoplasm
• Process activated by 2 ATP molecules breaking
down into ADP and phosphate (phosphate goes
to energize glucose)
• A series of enzymes modifies and splits the 6carbon glucose into two 3-carbon molecules of
pyruvate
From the series of reactions in Glycolysis the
following are produced:
2 Pyruvate
Net 2 ATP
2 molecules NADH
Let’s Review what happened in Glycolysis!
But first, what if NO oxygen is available:
Plants and Fungi  alcohol fermentation
Animals  lactate fermentation
Alcohol Fermentation
• Converts the pyruvate molecules to
ethanol (ethyl alcohol) and CO2; these are
waste products that are given off to
environment
• No further yield of ATP
• Ex: yeast for breads/beer
C6H12O6  2C2H5OH + 2CO2
Glucose
Ethanol
Carbon Dioxide
Lactic Acid Fermentation
• Used by human muscle cells when oxygen
is scarce
• Converts pyruvate molecules to lactate
• After strenuous exercise, you can feel the
build up of lactic acid as muscle
fatigue/pain; it will gradually be carried to
liver via bloodstream
C6H12O6  2C3H6O3
Glucose
Lactate
And now, what if oxygen IS available:
Aerobic Respiration
• Cells with mitochondria and sufficient O2
use aerobic respiration
• Takes place in the mitochondria
• Formula below:
C6H12O6 + 6O2  6CO2 + 6H2O + Energy
(energy is ATP + heat)
• Most efficient pathway to produce ATP
(net 36 ATP per 1 glucose)
The Link Reaction
1. Pyruvate enters matrix of
mitochondria via active
transport
2. Each pyruvate is converted to
acetyl-CoA; this conversion
involves the removal of:
one CO2 molecule and
Hydrogen (oxidation) to make
NADH
Kreb’s Cycle
**Occurs in matrix of mitochondria**
•
•
Acetyl-CoA sends acetyl
group (2 carbon molecule)
into Kreb’s cycle to start
reactions and detaches to be
used again
For each glucose broken
down in glycolysis (2
pyruvate were made) so the
cycle occurs twice
Main purpose of Kreb’s Cycle:
• Feed electrons into the next stage of
aerobic respiration via NADH and FADH2
From the breakdown of one glucose (2 turns
of the cycle):
• 2 ATP molecules produced
• 6 molecules of NADH produced
• 2 molecules of FADH2 produced
• 4 molecules of CO2 released
Let’s Review The Kreb’s Cycle!
Electron Transport System (ETS)
**occurs on inner membrane of mitochondria**
•
Uses molecules that are electron carriers (easily
reduced and oxidized) that are close together and
vary in electronegativity (stronger pull as you go
down the line)
•
ATP produced from molecules NADH and FADH2
as they shuttle their electrons to electron carriers
and their Hydrogen into the intermembrane space
NADH enters system
before FADH2,
therefore NADH
makes 3 ATP and
FADH2 makes 2 ATP
O2 is final
electron
acceptor…
making
H 20
•
The electron carriers use some of the energy from
the redox reactions to pump H+ across mitochondrial
membrane so that ATP synthase can use the H+
energy gradient to convert ADP + Phosphate to ATP
•
Note: The ETS has allowed for Chemiosmosis
and Oxidative Phosphorylation
Chemiosmosis – the
movement of H+ ions to
provide energy
Oxidative
Phosphorylation – using
an electron transport chain
to make ATP
Summary of ATP Production in Cell Respiration
Process
ATP used
ATP produced
Net ATP gain
Glycolysis
2
4
2
Kreb’s Cycle
0
2
2
ETS and
Chemiosmosis
0
32
32
Total
2
38
36
Let’s Review the Electron Transport System!