Transcript Aerobic respiration - Northwest ISD Moodle

Cellular Respiration
Lesson Objectives
• Summarize the stages of cellular
respiration
• Identify the role of electron carriers in each
stage of cellular respiration
• Compare alcoholic fermentation and lactic
acid fermentation
Main Idea
• Living organisms obtain energy by
breaking down organic molecules during
cellular respiration.
• Cellular respiration occurs in the
mitochondria!
Overview
• Organisms obtain energy through cellular
respiration.
• The function of cellular respiration is to
harvest electrons from carbon compounds,
like glucose, and use that energy to make
ATP.
• Equation:
C6H12O6 + 6O2  6CO2 + 6H2O + Energy
(opposite of photosynthesis)
Overview
• Cellular respiration occurs in two main parts:
– Glycolysis
– Aerobic respiration
• Anaerobic respiration and processes do not
require oxygen.
• Aerobic respiration includes the Krebs cycle
and electron transport and is an aerobic
process.
• Aerobic processes require oxygen.
Aerobic Respiration
• Must have oxygen to occur
• Takes place in the mitochondria
• Produces a net of 36 ATP molecules from
one glucose molecule
Glycolysis
• Series of reactions in the cytoplasm that breaks
down glucose to pyruvic acid
• Two molecules of ATP and two molecules of
NADH are formed for each molecule of glucose.
• Not very efficient
• Anaerobic respiration
• Uses NAD+ as its electron carrier
• At end, pyruvate moves into the mitochondria
Glycolysis
1. Two phosphate groups (derived from two ATP)
are joined to glucose. Energy is needed to
start, hence the ATP!
2. The 6-carbon molecule is broken down into
two 3-carbon molecules.
3. Two phosphates are added and electrons and
hydrogen ions (H+) combine with two NAD+
molecules to form NADH (similar to the
NADPH reaction).
Glycolysis
4. The two 3-carbon compounds are
converted into two molecules of pyruvate.
• 4 ATP molecules are produced.
• Only 2 ATP molecules are netted though
– Why? 2 ATP molecules were used at the
beginning so 4-2 = 2
The Citric Acid Cycle
• Aka the Krebs cycle
• Most of the energy from the glucose is still
contained in the pyruvate.
• Series of reactions that occurs in the
mitochondrial matrix that breaks down pyruvate
into carbon dioxide.
• One molecule of ATP is produced for every turn
of the cycle
• 2 electron carriers used – NADH and FADH2
• Passes electrons to the electron transport chain
The Citric Acid Cycle
• Prior to the Krebs cycle, pyruvate first
reacts with coenzyme A (CoA) to form a 2carbon intermediate called acetyl CoA.
• Carbon dioxide is released and NAD+ is
converted to NADH.
The Citric Acid Cycle
1. The cycle begins with acetyl CoA combining
with a 4-carbon compound to form a 6-carbon
compound known as citric acid.
2. Citric acid is then broken down in the next
series of steps, releasing two molecules of
carbon dioxide and generating one ATP, three
NADH, and one FADH2 (FAD is another
electron carrier to NAD+ and NADP+).
3. Finally, acetyl CoA and citric acid are
generated and the cycle continues.
The Citric Acid Cycle
• Two pyruvate molecules are formed during
glycolysis so there has to be two “turns” of
the Krebs cycle.
• Net yield:
– 6 carbon dioxide molecules
– 2 ATP
– 8 NADH
– 2 FADH2
Overview of ETC
• 1. Electrons are harvested and carried to
the transport system.
• 2. Electrons provide energy to pump
protons across the membrane.
• 3. Oxygen joins with protons to form water.
• 4. Protons diffuse back in, driving the
synthesis of ATP.
Electron Transport Chain
• Occurs in the inner membrane of the
mitochondria
• Produces the most ATP
• NADH and FADH2 pass electrons from protein
to protein, slowly releasing small amounts of
energy by converting ADP into ATP.
• As NADH and FADH2 release electrons, the
energy carriers are converted to NAD+ and
FAD, and H+ ions are dumped into the
mitochondrial matrix.
Electron Transport Chain
• The H+ ions are pumped into the
mitochondrial matrix across the inner
mitochondrial membrane.
• H+ ions then diffuse down their
concentration gradient back into the matrix
through ATP synthase in chemiosmosis.
• Oxygen is the final electron acceptor in the
ETC in cellular respiration.
Electron Transport Chain
• Protons and electrons are transferred to
oxygen to form water.
• Net yield from electron transport chain: 32
ATP
• Net yield of aerobic respiration: 36 ATP
Anaerobic Respiration
• No oxygen needed
• Takes place in cytoplasm
• Happens after glycolysis if all the NAD+ is
used up and not replenished
• Produces 2 ATP molecules from one
glucose molecule
Fermentation
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Anaerobic process
Occurs in the cytoplasm
Regenerates NAD+
2 main types:
– Lactic acid
– Alcoholic
Lactic Acid Fermentation
• 2 molecules of pyruvic acid use NADH to
form two molecules of lactic acid
• 2 ATP molecules are formed for each
glucose molecule
• Transferred from muscle cells to the liver
so that it can be converted back to pyruvic
acid
• Used to make cheese, yogurt, and sour
cream
Alcoholic Fermentation
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Used by yeast cells and some bacteria
Produces carbon dioxide and ethyl alcohol
Also gives off 2 ATP molecules
NADH donates electrons during this
reaction and NAD+ is regenerated.
Photosynthesis vs. Cellular
Respiration
• Photosynthesis
– Food accumulated
– Energy from the sun is
stored in glucose
– Carbon dioxide taken in
– Oxygen given off
– Produces glucose from
PGAL
– Goes on only in light
– Occurs in presence of
chlorophyll
• Cellular Respiration
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Food broken down
Energy of glucose released
Carbon dioxide given off
Oxygen taken in
Produces carbon dioxide
and water
– Goes on day and night
– Occurs in all living cells