Week 8 Flashcards
1
Q
Hypotonic solution - Clinical application
A
usually 0.45%, min 0.2%
used to give fluids intravenously to hospitalized patients to treat or avoid dehydration
2
Q
Hypertonic solution - Clinical application
A
used for soaking wounds, burns, oedema
3
Q
Isotonic solution - Clinical application
A
used as intravenously infused fluids in hospitalized patients for drug delivery or maintaining osmotic pressure
4
Q
0.9% NaCl, also called
A
normal saline
5
Q
Metabolism -
A
totality of an organism’s chemical reactions through which:
- E is stored (anabolism)
- E is released (catabolism)
6
Q
Catabolic pathways
A
- Break down complex molecules into simpler compounds
- Release energy
- Example: cellular respiration
7
Q
Anabolic pathways:
A
- Synthesize complicated molecules from simpler ones
- Consume energy
- Example: photosynthesis, protein synthesis from aminoacids
8
Q
Εxergonic reactions:
A
– Spontaneous reactions
– Free energy released → ΔG < 0 (negative)
– ΔG = Gfinal- Ginitial => Gfinal < Ginitial
9
Q
Εndergonic reactions:
A
- Absorb free energy from their surroundings (require energy)
- Non-spontaneous reactions → ΔG > 0
- ΔG = Gfinal- Ginitial => Gfinal > Ginitial
10
Q
ATP: structure, function and explanation of it
A
ATP (adenosine triphosphate) - the cell’s E shuttle (energy storage and transfer)
Structure: Nucleotide that stores energy in phosphate bonds (adenine nucleotide base, ribose, 3 phosphate groups)
Function: Provides E for cellular functions, energy rich => unstable → tends to break down and release E to provide for anabolic reactions in the cell
11
Q
Three main kinds of endergonic cellular work (require energy input):
A
– Mechanical (ATP phosphorylates motor proteins)
– Transport (ATP phosphorylates transport proteins)
– Chemical (ATP phosphorylates key reactants)
12
Q
ATP – mediated energy coupling:
A
an endergonic process can by driven by the ATP hydrolysis (exergonic process) => ATP hydrolysis provides the energy required for the endergonic reaction to occur
13
Q
ATP regeneration key reactants in catabolic pathways:
A
regeneration of ATP from ADP and Pi
ATP =>
=>ATP hydrolysis to ADP + Pi yields E - anabolism - E f/ cellular work (endergonic, E-consuming processes)=>
=> ADP + Pi
=>ATP synthesis from ADP + Pi requires E - catabolism - E from catabolism (exergonic, E yielding processes)
14
Q
Enzymes -
A
catalytic proteins that speed up metabolic reactions by lowering energy barriers
15
Q
Catalyst -
A
chemical agent that speeds up a reaction without being consumed by the reaction
16
Q
How Enzymes Lower the EA Barrier:
A
– By lowering the activation energy (EA) barrier => This speeds up the reaction
– The enzyme does not affect whether the reaction will happen spontaneously or not (without the input of E)
– An enzyme will only speed up a reaction that would occur anyway
17
Q
Substrate: what it is and ex
A
reactant an enzyme acts on
ex: sucrose is the substrate for sucrase
18
Q
Substrate specificity -
A
enzyme will only recognize its specific substrates (and no other related compounds)
19
Q
active site
A
region on the enzyme where the substrate binds => Induced fit of a substrate: enzyme changes shape upon substrate binding => brings chemical groups of the active site into positions that enhance their ability to catalyze the chemical reaction
20
Q
Effects of Local Conditions on Enzyme Activity
Environmental factors that may affect enzyme activity (3)
A
Enzymes are proteins => their activity is affected by several environmental factors. Denaturation: the loss of a protein’s native conformation due to unravelling => loss of function
Environmental factors that may affect enzyme activity:
- pH
- Temperature
- Cofactors: non-protein enzyme helpers required for enzyme activity
➢ Inorganic cofactors: e.g. metal ions (e.g. Zn, Cu)
➢ Coenzymes: organic cofactors (e.g. vitamins)
21
Q
Irreversible inhibitors and 2 exs:
A
bind to an enzyme by covalent bonding (very strong) => inhibition is irreversible
exs:
- Sarin, DDT, parathion: inhibit nervous system enzymes
- Penicillin derivatives: inhibit the enzyme transpeptidase that synthesize the bacterial cell wall peptidoglycan
22
Q
Reversible inhibitors -
and 2 types
A
bind to enzymes by weak bonds (non-covalent interactions: H-bonds, hydrophobic interactions and ionic bonds) => inhibition is reversible
2 types of reversible inhibitors:
1. Competitive inhibitors
2. Non-competitive inhibitors
23
Q
Competitive inhibitors and how inhibition can be overcome:
A
- bind to the active site of an enzyme w/ weak binding
- compete with the substrate => inhibit substrate binding to the active site
Inhibition can be overcome by adding excess substrate
24
Q
Non-competitive inhibitors:
A
- bind to another part of an enzyme not to the active site => change the shape of the enzyme => inhibit the function of the enzyme
- Inhibition cannot be overcome by adding excess substrate. It can be overcome by adding other molecule (antidot) that non-competitive inhibitor has greater affinity to => binds to it, leaving enzyme free => back to its original conformation
25
Two basic methods of enzyme regulation:
1. Regulation of **enzyme production** by regulation of gene expression
2. Regulation of **enzyme activity** by feedback inhibition (by allosteric regulation)
26
feedback inhibition, its role and 2 examples:
– The **end product** of a metabolic pathway inhibits the pathway
– Role: prevents a cell from wasting chemical resources by synthesizing more product than is needed
Examples: *Inhibition of catabolic pathways by ATP (ATP is the end product)*, *Inhibition of anabolic pathways by their end product (e.g tryptophan synthesis pathway inhibition by tryptophan)*
27
Allosteric regulation:
- form of reversible modulation common in enzymes (and proteins) made from **polypeptide subunits**. Regulatory molecules bind to regulatory sites via non-covalent binding interactions (similar to reversible non-competitive inhibitors) => Enzyme changes shape when regulatory molecules bind to specific sites, affecting their function
- positive allosteric regulation = **activation**
- negative allosteric regulation = **inhibition**
- **heterotropic** - regulatory molecules bind to sites other than the active sites
- **homotropic** - regulatory molecule is the substrate and binds to active sites
28
Heterotropic allosteric regulation: Allosteric Activation and Inhibition
Heterotropic allosteric modulator (non-competitive inhibitors & activators): *regulatory molecule that is NOT the enzyme's substrate*.
Examples:
- *AMP is a **heterotropic allosteric activator** of PFK* (**phosphofructokinase= glycolysis enzyme**)
- *CO2 is a **heterotropic allosteric inhibitor** (non-competitive inhibitor) of haemoglobin* => reduces haemoglobin's affinity for oxygen => Oxygen is released in the tissues
Allosteric **activators** stabilize the **active form of the enzyme**
Allosteric **inhibitors** stabilize the **inactive form of the enzyme**
29
Homotropic allosteric activation & inhibition ex:
Regulatory site is the active site. Binding of substrate to active site of one subunit locks all subunits into active conformation. **Allosteric activator** is the substrate; locks all subunits into active conformation.
Homotropic allosteric modulator (competitive inhibitors & activators):
- both a substrate for its target enzyme and a regulatory molecule of the enzyme's typically an activator of the enzyme (exception: CO for Hb) activity. Example: *O2 and CO are homotropic allosteric modulators of haemoglobin*: O2 is a **homotropic allosteric activator** of haemoglobin and CO is a **competitive inhibitor**: binds to haemoglobin at the same site as the oxygen => has higher affinity for Hb than oxygen => does not allow oxygen to be released in tissues.
30
Cooperativity (in terms of homotropic allosteric regulation) -
special form of positive allosteric regulation (activation) that can amplify enzyme activity
*Example: O2 binding to haemoglobin*:
The binding of substrate (oxygen) at one subunit increases the binding affinity of the other subunits (oxygen = allosteric activator)
31
Enzyme activity regulation scheme
1. Irreversible regulation (covalent bonding)
2. Reversible regulation (non-covalent)
- 2.1. Allosteric regulation (a type of reversible regulation f/ enzymes made of several subunits)
- 2.1.1 - Heterotropic regulation
- 2.1.1.1 - Heterotropic activation
- 2.1.1.2 - Heterotropic inhibition (Includes non-competitive inhibitors)
- 2.1.2 - Homotropic regulation:
- 2.1.2.1 - Homotropic activation
- 2.1.2.2 - Homotropic inhibition. Includes competitive inhibitors
32
Specific Localization of Enzymes Within the Cell (3)
• Enzymes participating in the same pathway are located close to each other
• Cellular enzymes may be:
– grouped into complexes
– incorporated into membranes
– contained inside organelles
33
2 major cellular catabolic processes:
1. **Cellular respiration** (aerobic respiration):
– the most prevalent and efficient catabolic pathway
– complete degradation of carbohydrates in the presence of oxygen (aerobic)
– Yields high amount of ATP
2. **Anaerobic respiration** (Fermentation):
- partial degradation of carbohydrates in the absence of oxygen
– Yields low amount of ATP
34
Energy conversion during cellular respiration:
the chemical energy in glucose bonds is transferred to the phosphate bonds in adenosine triphosphate (ATP)
=> energy from ATP hydrolysis (exergonic reaction) can then be used to perform cellular work (endergonic reactions)
35
3 stages of cellular respiration and their location:
1. **Glycolysis** in the *cytosol*
2. **Krebs cycle (citric acid cycle)** in *mitochondrial matrix*
3. **Οxidative phosphorylation** in the *inner mitochondrial membrane*
36
Mitochondria outer (smooth) membrane contains:
porins (proteins), some enzymes (e.g. MAO - MonoAminOxidase)
37
Mitochondria inner (rough) membrane contains:
**cristae** formation (contains **ETC (Electron transport chain) complexes**, **ATP synthase (responsible f/ ATP synthesis during oxidative phosphorylation stage)**)
38
Mitochondrial Matrix contains:
mtDNA and free ribosomes
39
Mitochondria: structure (4)
1. Outer membrane
2. Intermembrane space
3. Inner membrane
4. Matrix
40
Oxidation of Organic Fuel Molecules During Cellular Respiration
During cellular respiration, the fuel (**glucose**) is *oxidized* (donates electrones) to CO2, and **O2** is *reduced* (gains electrones) to H2O.
41
overall reaction of respiration
C6H12O6 + 6 O2 => 6 CO2 + 6 H2O + Energy (ATP)
42
three metabolic stages of cellular respiration:
1. Glycolysis: **anaerobic stage** - in the cytosol
2. The citric acid cycle: **Aerobic stage** - in mitochondria
3. Oxidative phosphorylation: **Aerobic stage** - in mitochondria
43
The Stages of Cellular Respiration: OVERVIEW (what happens w/ substrates)
1. Glycolysis: **glucose** breaks down into 2 molecules of **pyruvate** (3C)
2. The citric acid cycle: **Pyruvate** is converted to **acetyl-CoA** which is broken down into **CO2**
3. Oxidative phosphorylation:
– Driven by the electron transport chain (ETC)
– ETC causes *chemiosmosis* which **generates ATP (by ATP synthase)**
44
Production of ATP during cellular respiration (percentage in each stage):
• Glycolysis and the citric acid cycle: generate **some ATP (10% of total)** by **substrate-level phosphorylation**
• **Most ATP (90%)** is generated by **oxidative phosphorylation (by ATP synthase)**
45
Energy from organic compounds is produced in the form of
electrons
46
Electron (energy) transport by redox coenzymes NAD+ and FAD:
• The electrons released from the oxidation of organic compounds (**during glycolysis and Krebs cycle**):
1. First transferred to the coenzymes **NAD+** and **FAD** => become reduced to **NADH** and **FADH2**
2. Then transferred to the electron transport chain (ETC)
3. Finally transferred to O2 => production of H2O
47
NAD -
Nicotinamide adenine dinucleotide
48
FAD -
flavin adenine dinucleotide
49
Dehydrogenases -
enzymes that remove hydrogens (e-) from organic compounds (become oxidized) and transfer them to NAD+ or FAD => NAD+ becomes reduced to NADH and FAD becomes reduced to FADH2 => electrons transferred to the ETC
50
Glycolysis consists of two major phases:
1. Energy investment phase: 2 ATP spent (substrates are phosphorylated becoming more energy-rich (more unstable) => splitting of glucose)
2. Energy payoff phase: ATP produced (4 ATP, 2 NADH, 2 pyruvates)
51
Net products of glycolysis:
2 ATP, 2 NADH, 2 pyruvates
52
Phosphofructokinase (PFK) -
glycolysis investment stage enzyme
53
electron transport chain (ETC) is located
on the inner mitochondrial membrane
54
Chemiosmosis -
H+ gradient drives **ATP synthesis** by *ATP synthase* (enzyme located on inner mitochondrial membrane) - ATP synthesis takes place *in mitochondrial matrix*
55
Inner mitochondrial membrane contains:
- Krebs cycle enzymes
- Electron transport chain (ETC) enzymes/complexes
- ATP synthase complex (F0F1 ATPase)
56
The citric acid cycle completes the oxidation of organic molecules which leads to:
CO2 and energy production
57
Conversion of **pyruvate** (*glycolysis product*) into **acetyl-CoΑ** takes place when?
before the beginning of the citric acid cycle
58
**Acetyl-coenzyme A (acetyl-CoA)** is produced by one of the following processes:
**glycolysis** or **β-οxidation of fatty acids** and then Acetyl -CoA enters Krebs cycle
59
Pyruvate conversion to Acetyl-CoA scheme:
**Pyruvate** (3C) from glycolysis => 1) active transport w/ a transport protein into mitochondrial matrix => 2) enzyme **pyruvate dehydrogenase** removes H+ from pyruvate and donates them to NAD+, which reduces it to NADH, CO2 is also lost => 3) coenzyme A => 2C molecule **Acetyl-CoA** which will enter Krebs cycle
* Acetyl-CoA can also form directly from β-oxidation (fatty acid breakdown)
60
Citric acid cycle essentials (3):
• Pyruvate is broken down and CO2 is released
• Acetyl-CoA binds to oxaloacetate (ΟΑΑ) => citric acid is produced
• NADH and FADH2 are produced and transferred to the electron transport chain (ETC)
61
Krebs cycle products:
Each acetyl-CoA that enters the cycle is converted to:
- 2 CO2
- 3 NADH
- 1 FADH2
- 1 ATP
62
Krebs cycle energy gain and net E profit:
1 ATP, 3 NADH and 1 FADH2
1 NADH = 3 ATP
1 FADH2 = 2 ATP
=> **Net energy profit**: **12 molecules of ATP** from 1 Krebs cycle
63
Overview of the citric acid cycle:
• **1 glucose** molecule produces **2 pyruvates** upon glycolysis => **2 acetyl-CoA** molecules
• From one glucose molecule the 2 citric acid cycles generate:
➢ 4 CO2
➢ 2 ATP
➢ 6 NADH
➢ 2 FADH2
64
Oxidative phosphorylation -
• *Oxidative*: NADH and FADH2 donate electrons to the electron transport chain (ETC)
• *Phosphorylation*: ETC powers ATP synthesis
- Phosphorylation: production of ATP from ADP + Pi (*ATP synthase*)
65
Chemiosmosis as an energy-coupling mechanism:
- couples electron transport chain (ETC) to ATP synthesis during oxidative phosphorylation
- uses energy from a H+ gradient across a membrane (H+ flow) to drive cellular work (ATP production)
66
Electrons enter the ETC in 2 ways:
- NADH oxidation through complex Ι (NADH dehydrogenase)
- FADH2 oxidation through complex II (succinate dehydrogenase)
67
Cellular respiration oxidizes glucose in a series of steps - why?
If electron transfer is not stepwise a large release of
energy occurs
68
The electron transport chain (what is does and electronegativity):
– Passes electrons in a series of steps instead of in one explosive reaction
– Uses the energy from the electron transfer to form ATP
– Each e- carrier is more electronegative than the previous one, so that’s why the e- are pulled to the next one
69
The electron transport chain scheme:
1.
NADH => Complex I: ΝADH dehydrogenase
**or**
FADH2 => Complex ΙI: Succinate dehydrogenase
2.
Coenzyme Q (CoQ): *ubiquinone*
3.
Complex ΙΙΙ: *cytochrome oxidoreductase*
4.
Cytochrome c
5.
Complex ΙV: *cytochrome oxidase*
6.
O2 => forming H2O
70
Oxidative phosphorylation: chemiosmosis (membrane potential explanation)
• ETC causes H+ pumping to the intermembrane space => H+ concentration gradient created
• Electrochemical gradient between the matrix and the intermembrane space (pH (matrix) = 8, pH (intermembrane space) = 7) => membrane potential developed (H+ concentration is greater at the intermembrane space compared to the matrix) => **chemiosmosis**
71
Chemiosmosis -
- H+ flow to the matrix through ΑΤΡ-synthase (down their concentration gradient)
- ATP-synthase uses the energy from the H+ flow to **produce ATP**
72
Proton-motive force -
- proton (H+) gradient created by the flow of e-
- Drives chemiosmosis
- Stores energy => drives ATP production by ATP synthase
73
Function of ETC in ATP synthesis:
• ETC does not directly synthesize ATP
• ETC proteins pump H+ from the mitochondrial matrix to the intermembrane space
74
ATP synthase: definition, location and where it’s found, structure, how it functions
- the enzyme that actually makes ATP from ΑDP and Pi
LOCATION: in the *inner mitochondrial membrane*. Found in mitochondria, chloroplasts and bacteria
STRUCTURE: 2 parts: **F0**: the transmembrane part, composed of subunits a,b,c; **F1**: the matrix part, made by subunits α,β,γ,δ,ε
FUNCTION: Proton pump (Η+): Uses the proton gradient to power ATP synthesis. ATP synthase functions as a pump running in reverse: **proton flow** through ATP synthase => **changes the binding affinity of ATP/ADP** (Each H+ that flows through ATP synthase causes 120° rotation [rotor within the membrane spins clockwise when H+ flows past it down the H+ gradient => stator anchored in the membrane holds the knob stationary => rod (for “stalk”) extending into the knob also spins, activating catalytic sites in the knob => Three catalytic sites in the stationary knob join Pi to ADP to make ATP] => **Every 3H+ that flow through ATP synthase** => **Synthesis of 1 ATP molecule**)
75
Electron Transport Chain and Chemiosmosis scheme:
Complex I - 4 H+
Complex III - 4 H+
Complex IV - 2 H+
Complex II, Q (ubiquinon) and Cyt c don’t pump H+ into inner membrane
=> oxidation of **1 NADH+** pumps 10 H+, oxidation of **1 FADH2** pumps 6 H+
=> oxidation of **1 NADH+** gives 3,33 molecules of ATP, oxidation of **1 FADH2** gives 2 molecules of ATP
76
Sequence of energy flow during aerobic respiration:
Glucose →NADH/ FADH2 → ETC → PMF → ATP
– ETC: Electron Transport Chain
– PMF: Proton-Motive Force
77
Mitochondria use chemical energy to generate ATP by the chemiosmosis mechanism - elaboration
- Redox reactions of electron transport chains generate a H+ gradient across a membrane
- ATP synthase uses this proton-motive force to make ATP
78
Localisation of ATP synthase
Inner membrane
79
Orientation of ATP synthase
From intermembrane space towards the matrix (F1 is in matrix)
80
Proton accumulation area (proton gradient)
Intermembrane space
81
Area of ATP synthesis
Matrix (F1)
82
Total ATP Production by Cellular Respiration in most tissues?
• Aerobic cellular respiration has three stages:
– Glycolysis Products: 2 pyruvates + **2 ATP** + 2 NADH
– Citric acid cycle Products: 3 CO2, 1 ATP, 4 NADH + 1 FADH2 / pyruvate molecule = 6 CO2, **2 ATP**, 8 NADH + 2 FADH2 / glucose molecule
– Oxidative phosphorylation (electron transport chain): **32 or 34 ATP**
**TOTAL PRODUCTION**: 36 or 38 ATP molecules
83
NET ATP GAIN FROM 1 GLUCOSE MOLECULE DURING AEROBIC RESPIRATION
32 ATP
84
Total ATP Production by Cellular Respiration (ATP+electron carriers on each stage)
Glycolysis (Glucose → 2 pyruvates): **2 ATP** + 2 NADH
Pyruvate conversion to Acetyl-CoA (2 pyruvates→ 2 Acetyl-CoA): 2 NADH
Citric acid cycle (2 citric acid cycles for 2 acetyl-CoA produced from 1 glucose molecule): **2 ATP**, 6 NADH + 2 FADH2
Oxidative phosphorylation: **30 ATP** (from 10 NADH) and **4 ATP** (from 2 FADH2)
TOTAL ATP PRODUCTION FROM 1 GLUCOSE MOLECULE DURING AEROBIC RESPIRATION: **38 ATP**
85
Net ATP gain in cytosol by Cellular Respiration
Glycolysis (Glucose → 2 pyruvates): **2 ATP** + 2 NADH
Pyruvate conversion to Acetyl-CoA (2 pyruvates→ 2 Acetyl-CoA): 2 NADH
Citric acid cycle (2 citric acid cycles for 2 acetyl-CoA produced from 1 glucose molecule): **2 ATP**, 6 NADH + 2 FADH2
Oxidative phosphorylation: **25 ATP** (from 10 NADH) and **3 ATP** (from 2 FADH2)
NET ATP GAIN FROM 1 GLUCOSE MOLECULE DURING AEROBIC RESPIRATION: **32 ATP**
86
ATP molecule numbers are not exact for 3 reasons:
1. Some ATP (25% produced in oxidative phosphorylation) is spent for moving the ATP produced in the mitochondrion into the cytosol, where it will be used for cellular work
2. ATP production depends on the type of electron shuttle used to transport electrons from cytosolic NADH (produced by glycolysis) to the mitochondrion (to oxidative phosphorylation):
- Electrons of cytosolic NADH can be passed either to mitochondrial NAD+ (e.g. *liver cells*) or to mitochondrial FAD (e.g. *brain cells*)
3. Some energy is used for the active transport of pyruvate (produced by glycolysis) from the cytosol into the mitochondrion
87
Anaerobic respiration:
- produces **low amount of ATP** (only 2 molecules) in the **absence of oxygen (anaerobic conditions)**
- uses an electron transport chain with an electron acceptor other than O2 (e.g. sulfate)
88
Fermentation and what instead of ETC
Special type of anaerobic respiration
uses phosphorylation instead of an electron transport chain to generate ATP
89
2 stages of Anaerobic cellular respiration:
1. Glycolysis
2. Fermentation
90
Aerobic and anaerobic respiration: pyruvate as a key juncture
Glucose => Pyruvate =>
=> O2 present => cellular respiration => Acetyl-CoA => Citric acid cycle
=> NO O2 present => fermentation => ethanol OR lactate
91
Glycolysis can produce ATP with or without oxygen (in aerobic or anaerobic conditions). In anaerobic conditions:
it couples with fermentation to produce ATP
92
Fermentation (2 types & what about NAD?)
- Lactic acid (human, animal cells) or alcohol (fungal cells) production
- NAD+ regeneration reactions => NAD+ can be reused by glycolysis so that ATP can continue to be generated
93
Types of Fermentation
• Alcohol fermentation: Ethanol and CO2 production in yeasts (unicellular fungi)
• Lactic acid fermentation: Lactic acid production in animal cells
94
Alcohol fermentation applications:
2 pyruvate => 2 ethanol + CO2
wine, beer, bread making depend on this
95
Alcohol fermentation: Yeasts
Yeasts (e.g. *Saccharomyces cerevisiae*) used to produce ethanol in alcoholic drinks (e.g. beer, wine)
Baker’s yeast: special yeast strain (*Saccharomyces cerevisiae*) used to make bread
- CO2 production (alcohol fermentation by-product) causes bread to rise
96
Lactic acid fermentation
• Lactic acid production in animal cells/ bacteria
• Pyruvate is reduced directly by NADH to form lactate
97
When does lactic acid fermentation occur?
Occurs when there is limited presence of oxygen
*Example: Muscle fatigue under strenuous exercise*
**Physiological application**: Large amounts of oxygen are required in muscles due to strenuous exercising => muscles need E faster than the rate of oxygen supply by blood => **Lactic acid fermentation occurs** => *Lactate accumulation causes muscle fatigue* (*muscle cramps and stiffness*)
**Application**: certain bacteria convert lactose into lactic acid in yogurt (e.g. *Lactobacillus*)
98
Comparison of Aerobic and Anaerobic Cellular Respiration
• Both use glycolysis to oxidize glucose and other organic fuels to pyruvate
• Pyruvate is a fork in the metabolic road that leads to two alternative catabolic routes
• Different final products (organic compound vs water)
• Aerobic respiration produces a lot more ATP (Aerobic respiration produces 38 ATP per glucose
molecule, Anaerobic respiration (fermentation) produces 2 ATP per glucose molecule - only in glycolysis stage)
99
2 types of anaerobic microorganisms:
• **Obligate anaerobes**: microorganisms that carry out fermentation or anaerobic respiration and cannot survive in the presence of O2 => treatment way, for ex - *tuberculosis*
• **Facultative anaerobes**: microorganisms that can survive in both the presence and absence of oxygen using either fermentation or aerobic cellular respiration. (e.g. yeasts and many bacteria)
100
Catabolic pathways funnel electrons from many kinds of organic molecules into cellular respiration
Glycolysis and the citric acid cycle connect to many other metabolic pathways:
➢ Proteins: Excess amino acids can enter cellular respiration after losing their amino groups (as NH3) at either of three stages
➢ Lipids:
- Glycerol (in fats) can enter glycolysis in the end of E investment stage
- Fatty acids can enter the citric acid cycle as acetyl-CoA (β-oxidation product)
101
Regulation of Cellular Respiration via Feedback Mechanisms. Metabolism is tightly regulated by:
– Supply and demand of intermediates
– Energy status
– **Feedback mechanisms**
102
Regulation of Cellular Respiration via Feedback Mechanisms. Cellular respiration:
- controlled by **allosteric enzymes**
ex: Phosphofructokinase (PFK) is the major control point. Inhibited by: **ATP, citrate**, stimulated by: **AMP**
- **Feedback inhibition by ATP**
103
Diseases caused by insufficient synthesis of ATP (e.g. due ATP synthase mutations, 3 mentioned):
Lead to **severe neuromuscular disorders**
example: *Leigh* and *ΜΕLAS syndromes* - cause severe encephalopathy)
- **Cardiomyopathies, encephalomyopathies**, etc
example: *Leber’s optic neuropathy* - due to Complex I mutations
**Symptoms in early childhood** max until 2-3 y.o.
104
Free E: definition & formula
living system’s energy that can do work under cellular conditions. organisms live by spending OR consuming free E
free-energy change (ΔG) of a reaction indicates whether the reaction occurs spontaneously or not
ΔG = Gfinal- Ginitial
105
ATP hydrolysis: reaction and what happens to E?
ATP → ADP + Pi => energy release
106
ATP synthesis: reaction and what happens to E?
ADP + Pi → ATP => energy stored (in phosphate bonds)
107
E coupling -
the use of an exergonic process to drive an endergonic one
endergonic process can by driven by the ATP hydrolysis (exergonic process) => ATP hydrolysis provides the energy required for the endergonic reaction to occur
108
ATP hydrolysis is an exergonic reaction:
Energy is released from ATP when any of the 2 terminal phosphate bonds are broken => -ΔG
ATP + H2O => Pi + ADP, ΔG = -7.3 kcal/mol
109
ATP hydrolysis: energy coupling example
Endergonic reaction: ∆G is positive, reaction is not spontaneous
Glu + NH3 => Gln (Glu+NH2) ΔG = +3.4 kcal/mol
ATP + H2O => ADP + Pi, ΔG = -7.3 kcal/mol
overall ΔG is negative, together reactions are spontaneous
110
Photosynthesis reaction:
CO2 + H20 =>light energy=> C6H1206 + O2
111
Cellular respiration (aerobic) reaction:
C6H1206 + Ο2 => CO2 + H20 + ΑΤP
112
Activation E -
initial amount of energy needed to **start** a chemical reaction, needed to de-stabilize the structure of the reactants => they can react more easily
Often supplied in the form of heat from the surroundings in a system
Heat can increase the speed of molecules and cause them to collide more frequently
113
Glycolysis overview (4 points: substrate & products, O2 -?, E products, ATP how?)
Breaks down glucose (6 C) into 2 molecules of pyruvate (3 C)
Anaerobic stage (does not require oxygen)
Products: 2 ATP, 2 NADH, 2 pyruvate molecules
ATP production: by substrate-level phosphorylation
114
ATP in liver cells:
electrons from cytosolic NADH (2 NADH from glycolysis) are passed to mitochondrial NAD+ (e.g. liver cells) => production of 6 ATP molecules ( 2 NADH x 3 ATP = 6 ATP)
115
ATP in brain cells:
electrons from cytosolic NADH are passed to mitochondrial FAD (e.g. brain cells) => production of 4 ATP molecules ( 2FADH2 x 2 ATP = 4 Electron ATP)
