Download Section 5 - anabolism. the process by which molecules are

Section 5
- anabolism. the process by which molecules are synthesized into larger molecules in a living
organism.
- catabolism. the process by which larger molecules are broken down into smaller molecules in a
living organism.
- metabolism. the sum total of all the anabolic and catabolic reactions in a cell.
- entropy ( S ). the measure of disorder within a system.
- free energy (Gibb’s). energy that is free to do useful work.
†- laws of thermodynamics.
1. energy is neither created nor destroyed, but transformed from one form to another.
2. in any isolated system, the degree of entropy can only increase.
- biological order and the increase thereof is possible because of the release of heat energy from
cells. the increase of biological order is compensated for with an increase of heat energy, and
therefore, disorder elsewhere.
- often chemical reactions that generate heat are coupled with opposite reactions that cause
greater order. (ex. photosynthesis and cellular respiration)
- oxidation. the removal of electrons, which increases the net charge, considered to ‘release
energy’.
- reduction. the addition of electrons, which reduces the net charge, considered to ‘trap energy’.
NOTE: in some cases, a proton moves with the moving electron in redox reactions.
NOTE: the oxidation of one substance always results in the reduction of another and vice versa.
- remember: “OIL RIG” stands for Oxidation Is Loss (of electrons) and Reduction Is Gain (of
electrons)
- the plasma membrane. a double layer of lipids, phospholipids, glycolipids and embedded proteins,
which serves to:
1. act as a semipermeable membrane
2. transport materials in and out (ex. ions, K + , Na + )
3. site of reactions (ATP formation, protein synthesis)
†
4. site of recognition for enzymes,†hormones
and antibodies
5. site of communication (nerve transmission)
the movement of substances through the plasma membrane is affected by:
1. whether the molecule is hydrophilic or hydrophobic
2. size
3. shape (polar/non polar)
4. concentration of particles (diffusion)
the plasma membrane is fluid and asymmetrical in charge, which is different between the ECF
and the ICF, therefore some particles are moved more efficiently.
- cellular respiration. cellular respiration must occur in order to control the reactions involved in the
catabolism of glucose. too much energy is released to safely do so without cellular respiration.
Fig 1.
Fig 2.
this requires too much acivation energy to start here, the energy is transferred in each step by
the reaction and releases too much energy as energy-carriers.
heat
- ATP. adenosine triphosphate, the cell’s main useable energy-carrier. its makeup is:
adenine
ribose
1
44
42-4
44
3- 3phosphate
adenosine
†
adenine
(nucleic base)
ribose
(sugar)
P
high energy
bonds
P
P
if the cell needs energy, the terminal phosphate is broken off:
ATP ´ ADP + P + energy
A - PPP
P
†
P
energy†
energy
†
†
A - PP
†
endogonic reaction
(energy in)
(called substrate
†
phosphorylation)
†exergonic
reaction
(energy out)
- other energy carriers.
oxidized reduced name
NAD+
†
NADH
nicotine adenine
dinucleotide
FAD+
†
FADH 2
flavin adenine
dinucleotide
NADP +
NADPH
nicotinamide adenine
dinucleotide phosphate
†
†
†
†
role
where used
- glycolysis
- Kreb’s cycle
- E.T.C.
- electron transfer
during the breakdown - Kreb’s cycle
- E.T.C
of fuels.
-photosynthesis
-fatty acid synthesis
Cellular Respiration.
- glycolysis. a process for harnessing energy when glucose is broken down into two pyruvate
molecules in the cytoplasm.
• occurs in the cytoplasm
• anaerobic
• reactants: 2ATP + 2P , 2NAD+ , 4 ADP
• products:
†
†
† (to pyruvate
• 2 pyruvate
oxidation)
• 4 ATP + 2ADP (net 2ATP produced - now useable energy)
†
• 2NADH + 2H + ( 2NADH is converted to 2FADH 2 then sent to E.T.C.)
†
†
glucose
†
†
†
2ADP + 2P
†
2ATP
†
2NAD+
2NADH
†
†
†
2 pyruvate
†
- pyruvate oxidation. two pyruvate molecules are broken down to two acetyl-CoA molecules
• occurs in the mitochondrial matrix
• anaerobic
• reactants: 2 pyruvate , 2NAD+ , 2CoA
• products:
†
† - CoA†(sent to Kreb’s Cycle)
• 2acetyl
• 2NADH + 2H + ( 2NADH sent to E.T.C. and 2H + dissolved in matrix)
†
†
• 2CO2 (expelled as waste)
†
†
pyruvate
†
2NAD+
†
2NADH
CO2
†
†
acetyl - CoA
†
†
†
CoA
- Kreb’s cycle. a series of cyclic reactions that cleaves carbons from acetyl-CoA (from pyruvate
oxidation), releasing them as CO2 molecules and storing energy in energy carriers. it is cyclic
because the reactants are the same as the products.
• occurs in the mitochondrial matrix and the inner membrane
• anaerobic
†
• reactants: 2acetyl - CoA , 2oxaloacetate , 6NAD+ , 2ADP + 2P , 2FAD
• products:
• 2oxaloacetate (goes back to the beginning of Kreb’s cycle to be used again)
• 2CoA (to†pyruvate oxidation)
†
†
†
† • 4CO (expelled
as waste)
2
• 6NADH + + 6H + ( 6NAD+ sent to E.T.C., 6H + dissolved in matrix)
†
• FADH 2 (sent to E.T.C.)
†
• 2ATP (now useable energy)
†
†
†
†
†
†
- electron transport chain (E.T.C.) and chemiosmosis. a series of interrelated reactions which release
energy from energy carriers produced in glycolysis and the Kreb’s cycle.
• occurs in the inner mitochondrial membrane and intermembrane space
• aerobic - the only aerobic process in cellular respiration
• reactants:
• 6NADH (from Kreb’s), 2NADH (pyruvate oxidation)
• 2FADH 2 (from Kreb’s), 2FADH 2 (from 2 cytosolic NADH from glycolysis)
†
• 32ADP + 32P†
†
• 6O2
†
• 12H +
†
†
†• products:
†
• 8NAD+
• 4FAD+
†
• 24H +
†
• 32ATP
†
• 6H 2O
† with 2H + in the matrix, water is formed:
together
†
NADH + 12 O2
FADH 2 + 12 O2
†
3ADP + 3P
†
2ADP + 2P
†
3ATP
2ATP
†
†
NAD+†+ H 2O
NOTE: NADH makes three ATP molecules
†
†
FAD + H 2O
†
NOTE: FADH 2 makes two ATP molecules
†
†
†
†
- chemiosmosis. the hypothesis that the coupling of biochemical and osmotic events leads to the
formation of ATP .
1. electrons are stripped from high energy carriers, NADH and FADH 2 during E.T.C.
†
2. electrons pass down the E.T.C. as they move, they fall to lower energy levels, releasing
†
energy
†
3. this energy released pumps H + across the gradient from the matrix to the intermembrane
space
† back to the matrix through embedded proteins
4. H + eventually flows
5. energy from H + flow is harvested to make ATP
†
6. oxygen acts as the last electron acceptor to join 2H + to make H 2O
†
- cellular respiration
‘balance sheet’.
†
†
glucose:
†
2ATP
* 2NADH Æ 2FADH 2 Æ ETC Æ 4 ATP
pyruvate oxidation:
†
2NADH Æ ETC Æ 6ATP
†
Kreb’s cycle:
†
2ATP
2FADH 2 Æ ETC Æ 4 ATP
6NADH ƆETC Æ18ATP
†
†
36ATP
(total from 1 molecule of glucose)
†
*NOTE: most NADH produced in glycolysis cannot pass into the E.T.C. without being first
converted to FADH 2 , which only produces two molecules of ATP , so the total ATP produced
varies†
from 36 to 38.
†
†
†
- anaerobic pathways. because a cell’s supply of NAD+ is limited, and because NAD+ is reduced to
NADH during cellular respiration, if NADH is not somehow oxidized back to NAD+ , glycolysis
†
will stop. some organisms transfer hydrogen
atoms from NADH †
to other molecules instead of
† fermentation.
using the E.T.C.. this is called
†
- ethanol fermentation.
†
2ethanol(2C )
glucose
2NAD+
2ADP + 2P
†
†
2NADH
2ATP
†
H
-
†
2acetaldehyde(2C ) C = O
-
2 pyruvate
† (3C )
†
††
†
†
- lactate fermentation.
CH 3
†
CO2
†
†
† (3C )
2lactate
glucose †
-
2 pyruvate
† (3C )
O--C -C - CH 3
† ††
CH 3
†
H - C -OH
†
††
†
†
†
†
2NADH
2ATP
†
C =O
†
-
2NAD+
2ADP + 2P
†
-
O-
=
=
†
O O
- metabolism of fats†and proteins. like carbohydrates, fats and proteins can be converted by aerobic
†† †
†
respiration and their energy converted to ATP.
† †
• fats. can be oxidized to form acetyl-CoA, which then enters the Kreb’s cycle. this oxidation
†
†
†
can produce even more ATP than glucose, which is why some organisms store food as fat
• proteins. the amino group ( NH 3 ) is removed by an enzyme (deaminated), the resulting
carbon group is metabolized in the Kreb’s cycle.
†
- aerobic respiration is much more efficient than anaerobic respiration.
- metabolic rate. the amount of energy consumed by an organism in a given time.
- basal metabolic rate (BMR). the minimum amount of energy needed to keep an organism alive. 6070% of the total energy used by an organism daily is the BMR. the BMR declines significantly
after the years of growth and into the years of old age.
- feedback loops in cellular respiration.
1. ATP inhibits the enzyme that catalyzes the 3rd reaction of glycolysis, phosphofructokinase,
while ADP stimulates it.
2. citrate will also inhibit phosphofructokinase if there is enough for it to pass into the
cytoplasm
3. NADH inhibits pyruvate decarboxylase and reduces the amount of acetyl-CoA fed into the
Kreb’s cycle, reducing the amount of NADH produced.
- review questions:
p. 124 #1-5, 8, 13
Chapter 12 Review #1-11, 13-17, 19, UC #2, 4a, 5, 7, 8, 10, 11, 13, 18