cellular respiration. what we will cover adenosine triphosphate atp is the immediate source of...
TRANSCRIPT
Cellular Respiration
What we will cover
• Adenosine triphosphate ATP is the immediate source of energy for most cellular processes
• ATP breaks down to ADP and releases energy
• ATP is generated in the aerobic breakdown of carbohydrate
• In anaerobic respiration ethanol and lactate are produced and NAD (a coenzyme) is regenerated and can be used to make ATP
CC
C
N
N
N
N
NH2
HCCH
H
O
OH OH
CH2
HH
O O
O O O-
O
O
O- O- O-
PP P
Ribose Phosphates
Adenine
Adenosine Triphosphate
In cells ATP is converted to ADP; energy is released when the bond connecting the phosphates is broken.
ATP to ADP +Pi Releases Energy
Aerobic Respiration
There are three phases to Aerobic Respiration ... they are:
1. Glycolysis (same as the glycolysis of anaerobic respiration)
2. Krebs cycle (AKA - Citric Acid cycle)
3. Oxidative Phosphorylation and The Electron Transport Chain
The Separate Biochemical Steps
• GLYCOLYSIS
• LINK REACTION
• TRICARBOXYLIC ACID OR KREBS CYCLE
• ELECTRON TRANSPORT SYSTEM OR OXIDATIVE PHOSPHORYLATION
Phase One: Glycolysis(takes place in the cytoplasm)
4 ATP Yield = 2 ATP Net Gain
2 NAD+ + 2 e- 2 NADH
Glycolysis
Glucose (6 carbons)
Pyruvic Acid (3C)
Pyruvic Acid (3C)2 ATP’s supply the activation energy
4 ATP’s are produced
The First Stage of Respiration for ALL living organisms, anaerobes or
aerobes, is called Glycolysis
and takes place in the Cytosol.
Glycolysis• glyco means “glucose/sugar”, and • lysis means “to split”. Therefore, • glycolysis means “to split glucose”
• This process was likely used to supply energy for the ancient forms of bacteria.
Glycolysis• Function - to split glucose and produce
NADH, ATP and Pyruvate (pyruvic acid).
• Location - Cytosol
Reactants for Glycolysis • Glucose
• 2 ATP…. As activation energy
• 4 ADP and 4P
• Enzymes• 2 NAD+ (Nicotinamide Adenine Dinucleotide, an
energy carrier)
Glycolysis
Glucose
(6 carbons)
Pyruvic Acid (3 Carbons)
Pyruvic Acid (3 Carbons)2 ATP’s
supply the activation
energy
4 ATP’s are produced
4 ATP Yield = 2 ATP Net Gain
2 NAD+ + 2 e- 2 NADH
Products of Glycolysis
• 2 Pyruvic Acids (a 3C acid)
• 4 ATP
• 2 NADH
Net Result• 2 Pyruvic Acid• 2 ATP per glucose (4 – 2 = 2)• 2 NADH• In summary, glycolysis takes one
glucose and turns it into 2 pyruvates (molecules of pyruvic acid), 2 NADH and a net of 2 ATP.
Cellular Respiration
Recap phase 1 - Glycolysis
Phase 2 – Krebs Cycle
Glycolysis
• Function - Split down the glucose molecules so they are small enough to enter the Mitochondria
• Products:– 2 Pyruvic Acids (a 3 Carbon acid)– 4 ATP– 2 NADH
• ATP – is the immediate source of energy for most cellular processes
• NADH – carries electrons to the Electron Transport Chain
Glycolysis1 molecule of
glucose
6
2 molecules of triose phosphate
3 3
2 molecules of pyruvate
3 3
2ATP
2ADP
4ADP
4ATP
2NAD
Reduced 2NAD
What is the net production of ATP?
phosphorylation
(What you need to know)
The story so far
NADH and FADH
• NAD = Nicotinamide Adenine Dinucleotide
• FAD = Flavin Adenine Dinucleotide
• NADH and FADH are Coenzymes which carry energy in the form of electrons
• NADH = reduced NAD
• FADH = FADH2 = reduced FAD
Oxidation and Reduction
• Oxidation describes the loss of electrons / hydrogen or gain of oxygen (NAD/ FAD)
• Reduction describes the gain of electrons / hydrogen or a loss of oxygen. (NADH/ FADH)
In order for Aerobic Respiration to continue the Pyruvic acid is first converted to Acetic Acid by losing a carbon atom and 2 oxygens as CO2.
The Acetic acid then must
enter the matrix region of the mitochondria. The CO2 produced is the CO2 animals exhale when they breathe.
The Link Reaction
Phase Two: The Krebs Cycle(AKA the Citric Acid Cycle)
Sir Hans Adolf Krebs
Once the Acetic Acid enters the Matrix it combines with Coenzyme A to form a new molecule called Acetyl-CoA.
The Acetyl-CoA then enters the Krebs Cycle.
CoA breaks off to gather more acetic acid. The Acetic acid is
broken down.
Produces most of the cell's energy in the form of NADH and FADH2… not
ATP
Does NOT require O2
Citric Acid Production
The Link reaction
Mitochondrion
Link Reaction pyruvate
3
NAD
Reduced NAD
coenzyme A
Carbondioxide
acetyl coenzyme A
2
NAD
Reduced NAD
The Krebs cycle
Citric Acid Production
The Krebs Cycle
Mitochondrion
Krebs Cycle acetyl coA
citrateoxaloacetate
ATP Reduced co enzymes 3NADH
1 FADH
2 Carbon dioxide
64
2
SummaryAs a result of one turn of the Krebs cycle the cell makes:
1 FADH2 3 NADH1 ATP
However, each glucose produces two pyruvic acid molecules…. So the
total outcome is:
2 FADH2
6 NADH2 ATP
The key function of the Krebs cycle is to provide electrons for the Electron Transport Chain, the
production of ATP is a bonus.
The story so far
Phase Three:Oxidative Phosphorylation
• Function: Extract energy (in the form of electrons) from NADH and FADH2 in order to add a phosphate group to ADP to make ATP.
• Location: Mitochondria cristae.
Oxidative PhosphorylationRequires
NADH or FADH2
ADP and P
O2
Electron Transport Chain Uses NADH
• During the electrontransport chain, H+ is moved against a gradient.
• The energy needed to do this is supplied by electrons carried by NADH
What happens along the inner membrane of the mitochondria?
• The loss of electrons from NADH result in the addition of energy to protein pumps in the membrane resulting in a H+ being moved from the inside to the outside of the inner membrane
• This happens many times creating an imbalance (gradient) of H+.
Oxygen pulls electrons to keep them moving.
What happens along the inner membrane of the mitochondria?
• ATP is made as H+ ions are allowed back into the matrix of the mitochondria by a different protein (ATP synthase).
• The energy released by the “rush” of H+ is used by this enzyme to make ATP (kind of like a rush of water in a stream being used to turn a water wheel).Ultimately, aerobic respiration
produces ~36 ATP molecules from each individualglucose molecule.
The Electron Transport Chain
Cytochrome c
• Cytochrome c: • is one of the proteins of the electron
transport chain;• exists in all living organisms;• is often used by geneticists to
determine relatedness.
Chemiosmotic Hypothesis• Biologists still don’t know exactly how
ATP is made. • The best theory we have is called the
Chemiosmotic Hypothesis.
The Chemiosmotic Hypothesis
• proposes that the Electron Transport Chain energy is used to move H+ (protons) across the cristae membrane, and
• that ATP is generated as the H+ diffuse back into the matrix through ATP Synthase.
Electron Transport Chain
NAD
Reduced NAD
Carrier 2
ReducedCarrier 2
Carrier 3
ReducedCarrier 3 Carrier 4
ReducedCarrier 4
Water
Oxygen
ATPATP ATP
FAD enters here so 2 ATP produced
ATP Sum
• 10 NADH x 3 = 30 ATPs
• 2 FADH2 x 2 = 4 ATPs
• 2 ATPs (Gly) = 2 ATPs
• 2 ATPs (Krebs) = 2 ATPs
• Max = 38 ATPs per glucose
However...
Some energy (2 ATP’s) is used to shuttle the NADH from Glycolysis into the
mitochondria…..So, some biologists teach there is an actual ATP yield of 36
ATP’s per glucose.
The Final story