BIOL 1001 Study Guide - Midterm Guide: Mitochondrion, Mitochondrial Matrix, Electrochemical Gradient
9 Jun 2018
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Third Stage- Electron Transport
●Occurs in inner membrane of mitochondria (IMM)
●Coenzymes such as NADH (act like hot potatoes) give up high powered electrons to
electron transport chain
●Electrons are transported through the IM membrane system
●The final electron acceptor is oxygen -> water
●H+ (protons) are moved from inner to outer compartment of mitochondria during ET in
mitochondria
●H+ flow back across inner membrane drives ATP synth.
●Key point: as electrons flow downhill protons are released to one side of inner mito
membrane, acts like a battery
●During ET, protons flow to pink area. When ATP is made, protons flow into light pink
area. AREA BECOMES ACIDIC- pH is 5
Mitochondrial Reactions
●Mitochondrial membranes form two distinct compartments
●Most of ATP-making machinery is embedded in the inner mitochondrial membrane
(IMM)
Stage III- Electron Transport Chain
●Occurs in IMM
●Most (but not all) of ATP is produced in stage III- 3two ATPs total in stage III
●Occurs via electron flow mostly from NADH to oxygen, which is reduced to water at the
last step.
●Produced a pH (proton) gradient between IMM and OMM
●pH gradient goes through membrane and turns a protein turbine making ATP
ATP production during ET
●Electron transport produces the most ATP during aerobic respiration (32 out of 36
ATPs, or 88%).
●When electrons are transported in IMM, protons are released to area between outer and
inner membrane.
●Protons build up between inner and outer mitochondrial membrane.
●Protons backflow into the matrix through a lollipop type structure, and cause the lollipop
to rotate.
●ATP is made from ADP and phosphate by this lollipop enzyme that sits in the IMM.
Importance of Oxygen
●Operation of mitochondrial ET requires oxygen
●Oxygen withdraws spent electrons from the electron transport system, then combines
with H+ to form water molecule
●The conversion of oxygen to water is the final step of electron transport, and is thus the
final step of aerobic respiration
Summary of Energy Harvest (per molecule of glucose)
●Glycolysis
○Two ATP formed by substrate-level (enzymatic) phosphorylation (net of two
ATPs), occurs in cytoplasm
●Krebs Cycle and preparatory reactions
○Two ATP formed by enzymatic phosphorylation, occurs in mitochondrial matrix
●Electron transport phosphorylation of ADP to ATP in the inner mitochondrial
membrane by a proton gradient
○3two ATP formed, and electrons end up in water
NET OF 36 ATPs formed from aerobic respiration
Metabolic Pathways
●Catabolic pathways produce ATP from ADP and Phosphate. Glycolysis
●Simple organic compounds- anabolic pathways
Participants in Metabolic Pathways
●Substrates
●Intermediates
●End products
●Enzymes
Metabolic Pathways
●Metabolic pathways can be:
○Linear such as glycolysis and ET
○Circular such as the Krebs Cycle or the Calvin cycle in plants where sugar is
made
○Branched pathways
Enzyme Structure and Function
●Enzymes speed the rate at which certain reactions occur
●Nearly all enzymes are proteins- catalase increases speed one million times
●RNA molecules work as enzymes- known as ribozymes
●An enzyme recognizes and binds to only certain substrates. Enzymes specific for their
substrate (material to be converted)
●1. Reactions do not
alter or use up enzyme molecules
●. enzymes are reversible so that reaction can go either forward or backward. ATP
synthase can work backwards
●3. enzymes lower the energy barrier, or energy activation barrier, so that the reaction
can proceed
●4. Enzymes work in either direction
Induced-Fit Model
●The starting material (substrate) binds to the enzyme at the active site of the enzyme,.
This is usually a cleft in the enzyme.
●Enzyme-substrate complex is short lived
●Enzyme resumes its rebinding shape as a product molecule is released
Factors Influencing Enzyme Activity
1. Temperature
2. pH
3. Salt concentration (also known as ionic strength)
Allosteric regulators (show cooperativity) in enzymes with quaternary structure for example,
hemoglobin which binds 1 to 4
I. Use of Glucose for Energy
●Glucose is absorbed in blood
●Pancreas releases the peptide hormone insulin
●Insulin stimulates glucose uptake by mobilizing glucose transporter membrane proteins
●Glucose goes into cells
●Cells use the enzyme hexokinase to convert glucose to glucose-6-phosphate
●This traps glucose in cytoplasm where it can be used for glycolysis (is a one-way street
into cells)
●Glucose broken down into pyruvate and ATP
●Hexokinase- first enzyme in glycolysis, ten enzymes are used to convert glucose to
pyruvate
Making Glycogen
●If glucose intake is high, ATP- making machinery goes into high gear.
●When ATP levels rise high enough, glucose-6-phosphate is diverted into glycogen
synthesis (mainly in liver and muscle).
● Glycogen is the main storage polysaccharide in animals
●Glycogen stored in liver and muscle
Document Summary
Occurs in inner membrane of mitochondria (imm) Coenzymes such as nadh (act like hot potatoes) give up high po wered electrons to. Electrons are transported through the im membrane system. The final electron acceptor is oxygen -> water. H+ (protons) are moved from inner to outer compartment of mitochondria during et in mitochondria. H+ flow back across inner membrane drives atp synth. Key point: as electrons flow downhill protons are released to one side of inner mito membrane, acts like a battery. During et, protons flo w to pink area. When atp is made, protons flow into light pink area. Most of atp-making machinery is embedded in the inner mitochondrial membrane (imm) Most (but not all) of atp is produced in stage iii- 3two atps total in stage iii. Occurs via electron flow mostly from nadh to oxygen, which is reduced to water at the. Produced a ph (proton) gradient between imm and omm.
