Download Chapter 6 Cellular Energy

Unit Bioenergetics
A.
1.
2.
3.
4.
5.
Cellular Energy
Uses of cellular energy (ATP)
build molecules & maintain structure
transport materials
move & grow
reproduce
The products of cellular respiration are
the reactants of photosynthesis.
B. What is ATP?
1. Adenosine tri-phosphate – phosphate sugarribose, nitrogen base -adenine
2. Energy is released for cell usage when a
phosphate group is removed.
This produces ADP (di-phosphate) and AMP
(monophosphate) low energy
If ATP is a fully charged battery, ADP would be half charged and AMP
would be nearly out of energy
Phosphorylation -
the metabolic process of introducing a
phosphate group into an organic molecule.
Enzymes activated or deactivated
II. Respiration
A. Breathing “respiration” vs. cellular respiration
Respiration – breathing, an exchange of
gases between organism and
environment
Cellular respiration – aerobic harvesting
of energy from food molecules
B. Cellular respiration – balanced equation
C6H12O6 + 6 O2
Glucose
energy
 6 CO2 + 6 H2O + 38 ATP
40% of the energy from glucose is used in
the cells
60% of the energy is lost as heat
C. Oxidation/Reduction “Redox” reactions –
always occur together
It’s the major source of energy along with the sun
leo says ger
Oxidation – loss of electrons (H atoms) from one
molecule
oxidized if 1 or more electrons are lost
cellular respiration: glucose oxidized – loses H
Reduction – addition of electrons (H atoms) to a
molecule
reduced if 1 or more electrons are gained
cellular respiration: O2 gas reduced – gains H
Fig. 9-UN3
becomes oxidized
becomes reduced
electron transport chain – series of redox
reactions that pass e- from carrier to
carrier
a) NADH & FADH2 are electron carriers
Fig. 9-13
NADH
50
2 e–
NAD+
FADH2
2 e–
40

FMN
FAD
Multiprotein
complexes
FAD
Fe•S 
Fe•S
Q

Cyt b
30
Fe•S
Cyt c1
I
V
Cyt c
Cyt a
Cyt a3
20
10
2 e–
(from NADH
or FADH2)
0
2 H+ + 1/2 O2
H2O
Overview of the stages of
cellular respiration
Glycolysis – “splitting of sugar”, glucose is
broken into 2 molecules of pyruvate
through 9 different chemical reactions
Occurs in the cytoplasm; anaerobic
Net of 2 ATP produced by substrate-level
phosphorylation (-2 ATP + 4 ATP)
2 NAD+ are reduced to 2 NADH for electron
transport chain
Fig. 9-8
Energy investment phase
Glucose
2 ADP + 2 P
2 ATP
used
4 ATP
formed
Energy payoff phase
4 ADP + 4 P
2 NAD+ + 4 e– + 4 H+
2 NADH + 2 H+
2 Pyruvate + 2 H2O
Net
Glucose
4 ATP formed – 2 ATP used
2 NAD+ + 4 e– + 4 H+
2 Pyruvate + 2 H2O
2 ATP
2 NADH + 2 H+
Citric Acid (Kreb’s) Cycle – creates CO2
from pyruvate
2 molecules of pyruvate become 2 molecules of
acetyl CoA, which enters the citric acid cycle
Energy yield is 2 ATP, 6 NADH & 2 FADH2
Provides electrons for respiration
Fig. 9-11
Pyruvate
CO2
NAD+
CoA
NADH
+ H+
Acetyl CoA
CoA
CoA
Citric
acid
cycle
FADH2
2 CO2
3 NAD+
3 NADH
FAD
+ 3 H+
ADP + P i
ATP
Fig. 9-12-8
Acetyl CoA
CoA—SH
NADH
+H+
H2O
1
NAD+
8
Oxaloacetate
2
Malate
Citrate
Isocitrate
NAD+
Citric
acid
cycle
7
H2O
NADH
+ H+
3
CO2
Fumarate
CoA—SH
6
-Ketoglutarate
4
CoA—SH
5
FADH2
NAD+
FAD
Succinate
GTP GDP
ADP
ATP
Pi
Succinyl
CoA
NADH
+ H+
CO2
Oxidative Phosphorylation – phosphorylates
ADP to produce ATP (34)
Electron transport chain – pumps H+ ions across
membrane as electrons are transported
Takes place within inner membrane of mitochondria
Small amounts of energy released – produces ATP
Chemiosmosis – potential energy of the
electrochemical gradient drives the diffusion of H+
ions through ATP synthase ( enzyme) producing
molecules of ATP
Oxygen acts as the final electron acceptor, it bonds with
2 H+ ions to create water
ETC
Fig. 9-14
INTERMEMBRANE SPACE
H+
Stator
Rotor
Internal
rod
Catalytic
knob
ADP
+
P
i
ATP
MITOCHONDRIAL MATRIX
Fermentation
Anaerobic process – cells are starved of oxygen
strict anaerobes are poisoned by oxygen
facultative anaerobes can survive with or without O2
2 ATP produced by glycolysis, 0 ATP from
fermentation
Animals – lactic acid produced, causes sore
muscles
Bacteria – fermentation used to make cheese,
yogurt, soy sauce & sauerkraut
Yeast – alcohol fermentation
Fig. 9-18b
2 ADP + 2 P i
Glucose
2 ATP
Glycolysis
2 NAD+
2 NADH
+ 2 H+
2 Pyruvate
2 Lactate
(b) Lactic acid fermentation
Fig. 9-18a
2 ADP + 2 P i
Glucose
2 ATP
Glycolysis
2 Pyruvate
2 NAD+
2 Ethanol
(a) Alcohol fermentation
2 NADH
+ 2 H+
2 CO2
2 Acetaldehyde
The End …
IV. Photosynthesis
A. Autotrophs – “self-feeders”, make own food from inorganic matter
1.Photoautotrophs – make energy from sunlight through
photosynthesis
Examples: plants, bacteria, algae, & certain protists
B. Photosynthesis – balanced equation
6 CO2 + 6 H2O + sunlight -------- C6H12O6 + 6 O2
Carbon
water
glucose
oxygen
dioxide
gas
• Photosynthesis Facts
• Takes place in the mesophyll (green tissue) of
plant leaves which contain many chloroplasts
– Stroma – thick fluid in chloroplast where sugars are
made
– Thylakoids – membrane sacs that hold pigments
• Pigments trap energy from sunlight
– carotene – orange / red
– chlorophyll – green
– xanthophyll - yellow
– Grana – concentrated stacks of thylakoid membrane
– Stomata – pores that allow CO2 in & O2 out
•
•
•
•
–
Chemical reactions of Photosynthesis - Redox
1. Light reactions – O2 gas is produced by the splitting of
water
a.
Occurs in the thylakoid membrane
c.
Steps that absorb solar energy and store it as chemical energy in
ATP and NADPH, which power the dark reactions
•
•
•
•
Stages
Photosystem II – absorbs energy from sunlight, excites electrons
–
P680 – absorbs red light (680 nm) best
–
P700 – absorbs red light (700 nm) best
–
–
transport protein contains enzyme ATP synthase
powers the creation of ATP from ADP
Electron transport chain – carrier molecules pass along electrons; H+
atoms pumped across membrane
Photosystem I – absorbs more photons of energy; NADP+ & H+
produced NADPH
H+ ions move across the membrane by facilitated diffusion
• Dark reactions – glucose is created
from CO2 and water
– Occurs in the stroma
– Often called the Calvin Cycle
– Uses the enzyme rubisco