Chapter 4 Flashcards
Cell respiration
oxidative reactions where cells gradually release energy from glucose,make it ATP
Energy stored in ATP is
Immediately available for cellular activities such as contracting muscles, passing an impulse , etc.
Equation for complete aerobic respiration of 1 molecule of glucose
C6H12O6 + 6O2 → 6CO2 + 6H2O + energy
Glucose combines with oxygen to produce
Energy (ATP) plus the waste products CO2 and water
ATP is a
A special high-energy molecule that stores energy for immediate use in the cell
ATP consists of
Adenosine (nucleotide adenine + ribose) + 3 phosphates
The removal of 1 phosphate group from
ATP results in the formation of more stable and lower energy molecule, ADP
Energy is absorbed to add a
Phosphate to ADP to produce ATP
Mitochondrion is enclosed by 2 membranes
An outer membrane and an inner folded cristae membrane
Inner membrane divides the mitochondria into
2 internal compartments, the outer compartment and matrix
Krebs cycle takes place in the
matrix
The electron transport chain takes place in the
Cristae membrane
Cell respiration has 2 phases
Anaerobic and aerobic
If oxygen is not present (anaerobic)
Glycolysis is followed by alcohol fermentation or lactic acid fermentation
If oxygen is present (aerobic)
Glycolysis is followed by the Krebs cycle, the ETC, and chemiosmosis
Anaerobic respiration (fermentation) originated
Billions of years ago when there was no free oxygen in Earth’s atmosphere
The 2 types of fermentation
Alcohol fermentation and lactic acid fermentation
Glycolysis produces
Pyruvic acid and a small amount of ATP
Glycolysis
The anaerobic phase of aerobic respiration
1 molecule of glucose breaks apart into
2 molecules of pyruvate
What is pyruvate (or pyruvic acid)?
1/2 a glucose molecule
-is the raw material for the next step in respiration, the Krebs cycle
Where does glycolysis occur?
cytoplasm
Each step of glycolysis is controlled by
a different enzyme
2 molecules of ATP supply the
energy of activation in glycolysis
The energy of activation is the
energy needed to begin the reaction
Glycolysis releases
4 ATP molecules, resulting in a net gain of 2 ATP
glycolysis -1 glucose + 2 ATP —>
2 pyruvate + 4 ATP + 2 NADH (net gain 2 ATP)
alcohol fermentation
certain cells convert pyruvic acid/pyruvate from glycolysis into ethyl alcohol and CO2 in the absence of oxygen
The bread baking industry depends on the
ability of yeast to carry out fermentation and produce the CO2 that causes bread to rise
The beer, wine, and liquor industries depend on
yeast to ferment sugar into ethyl alcohol
Lactic acid fermentation
occurs during strenuous exercise when the body cannot keep up with the increased demand for oxygen by skeletal muscles
What causes fatigue and burning in one’s muscles?
pyruvic acid produced by glycolysis that converts to lactic acid that builds up in muscles
What does the phrase “no pain, no gain” refer to?
pain caused by lactic acid buildup in skeletal muscles
When an increase in blood flow restores proper oxygen levels
the muscle tissue reverts to the more efficient aerobic respiration and lactic acid is removed from the muscles
Where is lactic acid carried?
the liver where it is converted back to pyruvic acid
Aerobic respiration consists of 3 processes:
glycolysis, the Krebs cycle, and the electron transport chain
The krebs cycle is also known as
the citric acid cycle
The krebs cycle is the
first stage of the aerobic phase of cellular respiration
Pyruvic acid (from glycolysis) combines with coenzyme A (a vitamin derivative)
to form Acetyl-CoA , which enters the Krebs cycle
Each turn of the Krebs cycle produces 1 molecule of
both ATP and FADH2 plus 3 molecules of NADH
What is the by-product of the Krebs cycle?
CO2 (which is exhaled)
In summary, the Krebs cycle produces
- a small amount of ATP
- carbon dioxide
- NADH and FADH2
What are NADH and FADH2 molecules?
coenzymes that shuttle protons and electrons from glycolysis and the Krebs cycle to the ETC
NAD+ is
NADH is
oxidized form
reduce form
FAD+ is
FADH2 is
oxidized form
reduced form
NAD and FAD carry
H+ (protons) from the Krebs cycle to the ETC
Each ETC consists of a
series of carrier proteins that transport high energy electrons from the Krebs cycle
The energy from these high energy electrons is coupled with/powers the
pumping of protons across the cristae membrane in the outer compartment in order to create a proton gradient
The potential energy in this proton gradient is then used to
produce ATP through a process called chemiosmosis
Chemiosmosis is also called
oxidative phosphorylation
Almost all the ATP produced during aerobic cell respiration is
produced by chemiosmosis
The ETC produces
a proton gradient
The gradient represents
stored or potential energy that can be used to do work
chemiosmosis uses the stored energy in the proton gradient to
convert ADP into ATP
Chemiosmosis uses the energy stored in the proton gradient to
power the synthesis of ATP
What does chemiosmosis depend on?
a very special molecule located within the cristae membrane called ATP synthetase
What is ATP synthetase?
a proton channel structure that can spin like a turbine
What happens as protons pour through the ATP synthetase channel?
part of the molecule turns and attaches phosphates to ADP molecules, forming molecules of ATP
oxygen has a strong attraction for
electrons and protons
What is oxygen’s role in the chemiosmosis?
- it pulls the electrons through the ETC
- serves as the final electron/proton acceptor in the ETC
When oxygen combines with protons and electrons at the end of the ETC
water is formed as a waste product, this is the water vapor we constantly exhale
Every mitochondrian contains
1000s of ETCs
The ETC carries electrons through a series of
redox reactions as special molecules bind to and let go of electrons
Protons cannot diffuse directly through the cristae membrane but can only cross through
ATP synthetase channels
During respiration, most energy flows in this sequence
glucose –> NAD and FAD –> ETC (chemiosmosis) –> ATP
