Chapter 5: Cell Metabolism Flashcards
Fuels
Carbon-based molecules whose stored energy can be released for use
What is the most common fuel in organisms?
Glucose
How are metabolic pathways regulated?
allosteric mechanisms
Cellular Respiration Equation
C6H12O6 + 6O2 -> 6CO2 + 6H2O + free energy
How much free energy is involved in cellular respiration
-686 kcal/mol
Where is free energy from cellular respiration involved?
32ADP +32Pi + free energy -> 32 ATP
Synthesis of ATP is ________
endergonic
In synthesis of ATP, ________ provides the energy
glucose oxidation
Energy released by exergonic reactions is stored in the bonds of _____
ATP
Synthesis of ATP from ADP and Pi _______ energy
requires
Hydrolysis of ATP to ADP and Pi _____ energy
releases
what is the energy currency of the cell?
ATP
Glycolysis
glucose is converted to pyruvate
Cellular respiration
aerobic and converts pyruvate into H20 and CO2; leads to synthesis of a lot of ATP
Fermentation
anaerobic and converts pyruvate into lactic acid or ethanol + CO2; produces a little ATP
Cellular respiration occurs ______ oxygen present and is ______; Fermentation occurs ______ oxygen present and is _____
with, aerobic
without, anaerobic
Cellular respiration has ___ oxidation; fermentation has _____ oxidation
complete
incomplete
Waste products of Cellular Respiration
H2O, CO2
Waste products of Fermentation
lactic acid or ethanol, CO2
Cellular Respiration Net Energy Trapped per glucose
32 ATP
Fermentation Net Energy Trapped per glucose
2 ATP
All glucose oxidation reactions involve _________ reactions
electron transfer
Reduction
gain of one or more electrons by an atom, ion, or molecule
Oxidation
Loss of one or more electrons
oxidizing agent
the reactant that becomes reduced
reducing agent
the reactant that becomes oxidized
Redox: glucose is _____ and oxygen is _____. Explain?
oxidized
reduced
All the electrons in glucose are transferred to molecules of oxygen to form water
why does the oxidation of glucose occur in steps?
Energy from bonds of glucose is transferred, and it was all released in one step it would fry the cells
What are the functions of the two forms of NAD+
NAD+ (oxidized) revieves e- from glucose
NADH (reduced) carries e- from glucose to other molecules in the mitochondria, ultimately on to O2
Reaction Equation of the oxidation of NADH
NADH + H+ + (1/2)O2 -> NAD+ + H2O
Reaction Equation of the oxidation of NADH
NADH + H+ + (1/2)O2 -> NAD+ + H2O
Steps in Glycolysis and Cellular Respiration
Glucose to Pyruvate which is oxidized and enters the citric acid cycle, leaves through electron transport/ATP synthesis, expells waste of CO2 and H2O
Steps in Glycolysis and Fermentation
Glucose to pyruvate which goes through fermentation and expells lactate or alcohol
CH bonds have higher/lower free energy than CO bonds. Why?
Higher
CH bonds are weaker than CO bonds
Most oxidized/reduced has the highest free energy
reduced
Inputs and outputs of glycolysis
Inputs: glucose, 2 NAD+, 2 ADP + 2Pi
Outputs: 2 molecules of pyruvate, 2 NADH, 2 ATP
How many reactions are in glycolysis? Which require energy and which create energy?
10; 1-5 are energy investment, 6-10 are energy payout
Steps for glucose to pyruvate
A six-carbon sugar is cleaved into 2 three carbon sugars (glyceraldehyde 3-phosphate) which is then converted to pyruvate through substrate-level phosphorylation
What does pyruvate oxidation (decarboxylation) do? Where does it occur?
links glycolysis (in the cytoplasm) and the citric acid cycle (in mitochondria); occurs in the liquid mitochondrial matrix
Chemical formula for pyruvate breaking down
Pyruvate (3C) -> acetate (2C) + CO2
Characteristics of pyruvate breaking down to acetate
CO2 released as waste, NAD+ is reduced to NADH which captures the energy, some energy is stored by combining acetate and Coenzyme A (CoA) to form acetyl CoA
What is the citric acid cycle?
Eight reactions that begin with acetyl CoA; in a steady state, so the concentrations of the intermediates don’t change
Inputs and Outputs of the Citric Acid cycle
Inputs: acetyl CoA, electron carriers NAD+ & FAD, GDP
Output: CO2, reduced electron carriers (NADH, FADH2), and GTP (which converts ADP to ATP)
Each glucose yields:
6 CO2
10 NADH
2 FADH2
4 ATP
Reduce electron carriers must be ______ to take part in the glycolysis and citric acid cycle again
reoxidized
What does oxidative phosphorylation involve
proteins and electron carrier molecules imbedded in the mitochondrial inner membrane
Electron Transport Chain (ETC)
e- from NADH & FADH2 pass through a respiratory chain of inner membrane carriers
What is the ETC made of
4 protein complexes, Ubiquinone, cytochrome
What is the final electron acceptor in the ETC
oxygen
T/F ETC (complexes I-IV) makes ATP
F
Chemiosmosis
Protons (H+) diffuse back into the mitochondria through ATP synthase, a channel protein
Where do protons accumulate? What does that create?
Protons accumulate in the intermembrane space which creates a charge difference across the membrane – potential energy!
What does proton-motive force do?
drives protons back across the membrane where they move through the AATP synthase channel, providing energy to phosphorylate ADP
T/F ATP leaves the mitochondria once it is made, keeping the concentration high
F; ATP leaves the mitochondria once it is made, keeping the concentration LOW
How does ATP synthase work?
H+ flows from intermembrane space through synthase to matrix; this flow rotates the rotor, driving conformation changes in catalytic knob subunits; shape changes force condensation of ADP + Pi to create ATP
Lactic Acid Fermentation
-occurs in microorganisms, some muscle cells
-pyruvate is the electron acceptor and becomes reduced
-oxidizes NADH back to NAD+ so more glycolysis can occur
-2 lactate is the product, and no additional ATP is made
Reactants and products of lactic acid fermentation
reactants: glucose, 2 ADP, 2 Pi
products: 2 lactate, 2 ATP
Alcoholic Fermentation
-yeasts are some plant cells
-requires two enzymes to metabolize pyruvate to ethanol
-CO2 is a waste product
-The intermediate, acetaldehyde is reduced by NADH and H+ producing NAD+ and glycolysis continues
Reactants and Products of alcoholic fermentation
reactants: glucose, 2 ADP, 2Pi
products: 2 ethanol, 2 CO2, 2 ATP
T/F aerobic respiration captures all of the energy released by glucose oxidation but fermentation does not
F; neither aerobic respiration or fermentation capture all of the energy released by glucose oxidation
In catabolism/anabolism, breakdown products eventually enter the aerobic respiration pathways
catabolism
T/F Glucose is the only molecule that can be catabolized
F
What are catabolic pathways
Carbohydrates, lipids, proteins, nucleic acids
Carbohydrate catabolic pathway
polysaccharides –> monosaccharides
Lipid catabolic pathway
triglycerides –> glycerol and fatty acids –> acetyl CoA
Protein catabolic pathway
protiens –> amino acids –> molecules that enter glycolysis
nucleic acids catabolic pathway
nucelic acids –> nucleotides –> phosphate groups, bases, sugars
Anabolic pathways are often ____ of catabolic pathways
reversals
Gluconeogenesis
citric acid cycle and glycolysis intermediates are reduced to form glucose
Autotroph
an organism that is capable of living exclusively on inorganic materials, water, and some energy source such as sunlight
Heterotroph
organism that requires preformed organic molecules as food
Photosynthesis equation
6CO2 + 6H20 –> C6H12O6 +6O2
Is photosynthesis exergonic/endergonic? anabolic/catabolic?
endergonic, anabolic
What are two redox reactions in photosynthesis
CO2 is reduced to form carbohydrates
Water is oxidized to form oxygen
What is a light reaction?
Convert light energy to chemical energy as ATP and NADPH
Light-independent reactions
Use ATP and NADPH (from light reactions) plus CO2 to produce carbohydrates
The energy of light is ______ proportional to it’s wavelength
inversely
Photons
Particles of light
What are the three things that can happen to a photon when it meets a molecules
scattered (bounces off)
transmitted (passed through)
absorbed (acquires the energy of the photon, the molecule goes from ground state to excited state)
T/F The color that we see is the light than an object does not absorb
T
What colors do plants absorb?
red and blue
What happens after a molecule is excited?
energy can be converted to heat, light, or passed to a nearby molecule by resonance energy transfer
Absorption spectrum
plot of wavelengths absorbed by a pigment
Action spectrum
a plot of biological activity as a function of exposure to varied wavelengths of light
T/F multiple pigments are used during photosynthesis
T; the use of several pigments to absorb light of different wavelengths will broaden the action spectrum
What are the main two pigments absorbing light for photosynthesis
Chlorophylls and carotenoids; are both quite nonpolar
Accessory pigments
absorb in red and blue regions, transfer the energy to chlorophyll – cartenoids and phycobilins
What do Cilia and Flagella do?
move the cell
Antenna systems
light-harvesting systems in which pigments are arranged
What does a photosystem consist of
multiple antenna systems and their pigments; surrounds a reaction center
How does energy end up in the reaction center?
excitation energy passes from pigments that absorb short wavelengths to those that absorb longer wavelengths and end up in the reaction center
Key events of light reactions
- photosystem reaction center (Chl) absorbs a photon and becomes excited
-Chl donates an e- to an acceptor molecule (A)
-A is the first in a chain of electron carriers in the thylakoid membrane - A final electron acceptor is NADP+ and becomes NADPH
Photosystem I
-light energy reduces NADP+ to NADPH
- Reaction center has P700 chlorophyll a molecules (absorb in the 700 nm range)
Photosystem II
-light energy oxidizes water –> O2, H+ and electrons
- reaction center has P680 chlorophyll a molecules (Absorb at 680 nm
Noncyclic electron transport
produces NADPH and ATP; light energy is used to oxidize water –> O2, H+, and electrons
Cyclic electron transport
produces ATP only
What is the process of noncyclic electron transport?
light energy oxidizes water, CHI+ is unstable due to excitation by light and takes electrons from water, splitting the water molecule
Process of cyclic electron transport
An e- from an excited chlorophyll molecule cycles back to the same chlorophyll molecule; begins and ends in PS 1
What do non-cyclic and cyclic electron transport drive?
photophosphorylation
Use of light reaction products to synthesize carbohydrates Steps
- CO2 fixation & Calvin Cycle
- CO2 is reduced to carbohydrates
- Enzymes in the stroma use the energy in ATP and NADPH to reduce CO2
Steps of the Calvin Cycle
- CO2 is first added to an acceptor molecule
- the 6C compound breaks into two molecules of 3PG
What enzyme catalyzes the intermediate formation in the calvin cycle?
rubisco
here does the Calvin cycle take place?
the stroma
What are the two parts of photosynthesis and their roles
Light reactions: collect light energy, oxidize water and store energy as ATP and NADPH
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