Cellular Metabolism Flashcards
2 Laws of thermodynamics
Energy can be transferred and transformed, but it cannot be
created or destroyed (energy of the universe is constant)
• Every energy transfer or transformation makes the universe
more disordered (every process increases the entropy of the
universe)
Thermodynamics =
Study of energy transformations
Gibbs free energy or spontaneous potential of reaction. What is favorable?
-ve
Entropy =
Quantitative measure of disorder that is proportional to randomness (designated by the letter S)
• Energy is stored in
molecules which are ‘ordered’ such as
glucose (many carbon bonds)
• Energy transfer from glucose breaks down the molecule into
smaller parts and creates
a more disordered state (↑ entropy)
Closed system =
– Open system =
collection of matter under study
that is isolated from its surroundings.
one in which energy can be transferred between the system and its surroundings.
Highly ordered living organisms are ____systems
open
in an Open System the entropy of a system may ________, but the entropy of the system plus its surroundings must always _________.
decrease
increase
Processes that Supply Energy (ATP)
- Anaerobic
(a) Alactic (i.e. doesn’t produce lactate)
(i) Creatine phosphokinase reaction
(ii) Adenylate kinase reaction
(b) Lactic
Glycolysis (and glycogenolysis) - Aerobic
Oxidative phosphorylation
Anaerobic Processes that Supply Energy (ATP)
- Anaerobic
(a) Alactic (i.e. doesn’t produce lactate)
(i) Creatine phosphokinase reaction
(ii) Adenylate kinase reaction
(b) Lactic
Glycolysis (and glycogenolysis)
The Creatine Phosphokinase Reaction eqn
CrP + ADP Cr + ATP
Catalysed by creatine phosphokinase.
• In a resting cell 99% of total adenine pool exists as ___.
• ________acts as a buffer to maintain [ATP] high during high energy demand.
The Creatine Phosphokinase Reaction
ATP.
ATP
• CrP acts as a buffer to maintain [ATP] high.
The Creatine Phosphokinase Reaction
rate?
What size/extent?
- extremely rapid (a function of enzyme kinetics)
2. of small extent (a function of reactant concentrations)
ATP conc. remains stable until ____ of PCr is converted to Cr
90%
Creatine phosphate “\_\_\_\_\_\_\_” chemical energy from \_\_\_\_\_\_\_\_\_ to the various cellular locations of the ATPases (e.g. Na+K+ATPase, SRCa2+ATPase, actomyosinATPase)
shuttles
mitochondria
- Cr is phosphorylated by newly generated ____in mitochondria.
- CrP then diffuses to the various cellular “_____” where it re-phosphorylates ADP.
- Cr & Pi diffuse down their conc gradients to the _________.
- Benefit is that it is the small (mobile) Cr molecule that “_____” back & forth with Pi.
ATP
sinks
mitochondria
shuttles
The Adenylate Kinase Reaction eqn
2ADP AMP + ATP
- catalysed by the enzyme adenylate kinase
- independent of _____ -________
- “____ _____” process used only when ATP is v. low
Adenylate Kinase Reaction
Creatine Phosphate
Last ditch
Adenylate Kinase Reaction
rate?
size/ extent?
• characterised by small extent & rapid kinetics
The Adenylate Kinase Reaction: degradation products • In the absence of ATP (to regenerate ADP), AMP is deaminated to inosine monophosphate: AMP -> IMP + NH4+
catalysed by the enzyme ______ -________
AMP deaminase
The Adenylate Kinase Reaction:
degradation products
IMP & NH4+ both inhibit what?
muscle contraction
actomyosin ATPase activity
Alactic anaerobic metabolism does not require
O2 or substrate
the weight-lifter’s maximal
anaerobic, alactic rate of
energy expenditure is several
times his?
maximal aerobic rate
of energy expenditure
glucose yields net \_\_\_\_ through glycolysis • glycogen yields net \_\_\_\_ through glycolysis (glycogenolysis)
2ATP
3ATP
Anaerobic Lactic Processes:
Glycolysis/Glycogenolysis
rate?
extent?
moderate kinetics
• moderate extent
Anaerobic glycolysis eqn
1glucose + 2ADP +↔ 1Lactate + 2ATP
Goldfish and Crucian Carp can live in ______ water
for months! By getting drunk with blood alcohol > 50 mg per ml
anoxic
\_\_\_\_\_ consists of long chains of \_\_\_\_\_\_\_\_molecules joined end-to-end with many branches. Completed chains can have up to 6000 \_\_\_\_residues making glycogen one of the largest molecules in living cells.
Glycogen
glucose
Advantage of converting G6P to
glycogen is that it compacts all the
molecules into single large polymers
for ?
storage by the cell as large granules
of sugar.
Mammalian glycogen stores glucose in times of plenty (after a meal) and supplies glucose in times of need (during
fasting or in “fight-or-flight” situations).
– In muscle, glycogen provides fuel for ?
– In contrast, liver glycogen is largely converted to ?
muscle contraction.
glucose that exits liver cells and enters the bloodstream for transport to other tissues that require it
[The Cori Cycle].
The Cori cycle
Gluconeogenesis
The liver uses ATP to convert lactate back to glucose
Consequences of Anaerobic
Energy Production
Extensive glycolytic activity leads to decreased?
cellular pH (i.e. increases [H+]
Anaerobic
Energy Production with decr. pH on cellular level
Protons:
I. inhibit Ca2+ release from the sarcoplasmic reticulum &
II. compete with Ca2+ for binding-sites on
Troponin-C,
III. thereby potentially diminishing contractile force (thus potentially contributing to skeletal muscle fatigue).
• With more intense exercise, _______metabolism alone is not
‘fast’ enough to meet the ATP demand
• Anaerobic metabolism contributes ATP and produces ______
• ______begins to accumulate and rise exponentially at ~55%
VO2max for an untrained subject
aerobic
lactate
Lactate
Oxidative phosphorylation
• Glycogen, fats & proteins can be broken down & enter the ?
• Series of reactions take place in mitochondria in combination
with electron transfer chain.
tricarboxylic acid (citric acid or Kreb’s) cycle.
Oxidative phosphorylation eqn
1 glucose + 6O2 + 32ADP + 32Pi 6CO2 + 6H2O + 32ATP
Oxidative phosphorylation
rate?
extent?
slow kinetics
– enormous extent (provided at sub-maximal rates)
high energy electron carriers
NADH and FADH2
produced by the citric acid cycle is used in the electron
transport chain at complex I & II
A transmembrane charge is set up (via transport of H+ ions at complex I to
IV) which is then utilised to generate ATP at complex V
Link between glycolytic and oxidative metabolism
Lactate Shuttle Hypothesis:
Lactate as Mitochondrial Fuel
Hence, rate of energy expenditure can exceed?
VO2
max – but only briefly.
The Adenylate Kinase Reaction:
degradation products
IMP & NH4+
