bio energetics (b1- SMS) Flashcards

Question

what is the difference between substrate level phosphorylation and oxidative phosphorylation

Answer 1

**substrate level phosphorylation** is in glycolysis and the Krebs cycle → phosphate group is attached to ADP to make ATP, ATP made directly **oxidative phosphorylation** is with ETC, ATP made indirectly using energy from electron transport

Answer 2

because free electrons are very high in energy, and therefore **very dangerous** - lots of free radical damage possible therefore, passing them around decreases their energy so that it can be captured and used also, transferring energy to O2 all of a sudden would cause **combustion**

Answer 3

complex II

Answer 4

**outer**: contains specialized channels formed by protein *porin*, freely permeable to most ions and small molecules **inner**: specialized structure that is IMPERMEABLE to most small ions, including H+!! - rich in proteins, half of which are involved w/ oxidative phosphorylation - also has **cristae** that increase surface area, where ETC occurs

Answer 5

oxidation of pyruvate, fatty acids, amino acids, and where the TCA cycle occurs (Krebs cycle)

Answer 6

only 2 (complex I & II) are **flavoprotein complexes** the rest are all **cytochromes** - cytochrome c, complex III, IV (excluding ATP synthase)

Answer 7

1. agricultural poisoning (farmers & agricultural workers) 2. occupational exposure (workers in pesticide manufacturing plants) 3. accidental poisoning in rural areas (contaminated food/water) 4. intentional poisoning (suicide/homicide)

Answer 8

carboxin = complex II inhibitor patient presents with **mitochondrial defect symptoms**: - confusion, dizziness, headache, seizures (extreme cases) - lactic acidosis (accumulation of lactic acid)

Answer 9

**structure**: quinone head w/ long hydrophobic isoprenoid tail (makes it hydrophobic- *why it floats in the middle of the phospholipid bilayer*) **function**: transfers electrons to complex III, links the flavoproteins dehydrogenases to the cytochromes

Answer 10

proteins that **contain heme group** with has an **iron** atom at the center the iron atom inside switches b/w 2 oxidation states (Fe3+ & Fe2+) - this fast, reversible switching allows cytochromes to **accept & donate electrons** helping move e's down the ETC

Answer 11

- patient is presenting with all the other mitochondrial deficiency symptoms (seizures, muscle weakness, accumulation of lactate) - muscle mitochondria are isolated & studied = **individual** complex activity is fine but combined activities of **I + III** and **II + III** were decreased - treatment with CoQ improves muscle weakness

Answer 12

**complex I**: 4 H+ **complex II**: 0 **complex III**: 4 H+ **complex IV**: 2 H+ total= 10 H+, 1 is lost to heat, the others are used for ATP generation (3 H+ = 1 ATP molecule)

Answer 13

other name: **cytochrome bc1 complex** **contents**: - cytochrome b - iron sulfur protein - cytochrome c1

Answer 14

**antimycin A**: a pesticide - blocks e' transfer from cytochrome b to c1 **myxothiazol**: used as anti fungal agent - blocks e' transfer b/w Q & Fe-S centers *dont rlly need to know blocking where to where, but maybe better if you do*

Answer 15

in the **intermembrane space** (it's not embedded in the inner mitochondrial membrane) *cytochrome c also has only 1 single heme so it can only accept e's 1 at a time*

Answer 16

they include **copper ions** - together they stabilize O2 effectively to make sure reduction is complete (*imp bc not reduced properly = harmful*)

Answer 17

transported e's, molecular O2, and free protons are brought together to produce **2 H2O** O2 is the final acceptor of the electrons here **4 e's needed for 1 O2 molecule** its also the only e' carrier in which **heme iron has a free site** that can react directly w/ O2

Answer 18

2 hemes (**cyto a, cyto a3**) 2 copper centers (**CuA & CuB**)

Answer 19

imp inhibitors are **cyanide & carbon monoxide** - lethal b/c block the transfer of electrons to O2 so e's just stopped moving *apricot seeds & bitter almonds* have a lot of cyanide in them **azide** **H2S**

Answer 20

**unresponsive** = whereas other complexes patient is weakened, here patient is completely unresponsive **skin cherry red** = O2 is present but not being taken up (person turns blue when there is no O2) little amount of cyanide = patient unconscious, a lot = patient dead

Answer 21

**explains how the free energy generated from the proton gradient is used to produce ATP from ADP + Pi** basically states that there is an **electrical & chemical (pH) gradient** that drives the production of ATP (**proton gradient part**) *electrical = more + outside than inside chemical = lower pH on outside than inside* **2 components of this theory**: proton pump & ATP synthase (*the whole structure of ATPase*)

Answer 22

H+ reenter the matrix by passing through a H+ channel in the ATP synthase the energy (proton-motive force) generated by these gradients (electrical & chemical gradient) drives the ATP synthesis

Answer 23

**3 ATP** it takes 3 H+ pumped to form 1 ATP so 3 ATP = 9 H+ the ETC pumps **10 H+ total** so that 1 extra goes towards **generating heat**

Answer 24

cause **conformational change** in the 3 **beta** subunits of F1 that allows them to: 1. bind **ADP + Pi** 2. phosphorylate the ADP to ATP 3. release the ATP

Answer 25

**Fo**: embedded in the inner mitochondrial membrane, contains the c rings (that rotate) and the H+ channel **F1**: outside the membrane, protrudes into the matrix, made of **3 alpha & 3 beta** that actually attach the ADP and convert to ATP

Answer 26

**oligomycin**: binds to Fo (*hence the o*) - **closes the H+ channel** preventing reentry of H+ into matrix → **inhibits phosphorylation** of ADP to ATP → **ETC stops** b/c of the difficulty of pumping any more H+ against the **steep gradient** → CAUSES SEVERE ENERGY DEPLETION *brain, heart, muscles are most affected - most energy needing tissues*

Answer 27

they form channels that allow H+ to reenter the mitochondrial matrix without energy being captured as ATP

Answer 28

**UCP1/Thermogenin**: natural uncoupler **Synthetic**: - Aspirin (1-2 doses is fine but ridiculous amounts can cause death) - 2,4 DNP (dinitrophenol) - some antibiotics: Gramicidin

Answer 29

natural uncouplers proteins (like **UCP1/thermogenin**) form channel that allow H+ to reenter mitochondrial matrix w/o energy being captured as ATP - **energy is released as heat** happens in babies b/c they dont have enough muscle for shivering, in brown fat mammals, and in extreme cold (*catecholamine activates in body*)

Answer 30

**high temp**: energy being released as heat instead of going down gradient but uncontrolled levels **metabolic acidosis**: body is trying to make ATP but still not getting it so shifting to anaerobic respiration → build up of lactic acid

Answer 31

study of how energy flows through living things OR **transfer/utilization of energy in biologic systems**

Answer 32

**∆G**: energy available in a system to do work **∆G = ∆H - T∆S** depends on: - **enthalpy**: measure of change in heat - **entropy**: measure of change in randomness or disorder of reactants/products

Answer 33

**∆G = 0**: reaction at equilibrium (rate of reactants & products is equal) **∆G = -**: net loss of energy, spontaneous reactions, exergonic (*favorable*) **∆G = +**: net gain of energy, reaction is not spontaneous, endergonic

Answer 34

molecule of **adenosine** (adenine + ribose) that has **3 phosphate groups** attached

Answer 35

**∆H neg.** (b/c heat being released- *think easier to melt*) **∆S pos.** (b/c everything going towards randomness)

Answer 36

acts as primary energy carrier for cellular processes

Answer 37

**why needed**: inner mitochondrial membrane is highly impermeable- *does not allow most molecules to pass through easily* - but still needs certain molecules to make ATP so *special transport proteins allow selective entry* **3 different systems**: 1. ATP & ADP transport 2. Pi & H+ transport 3. Reducing Equivalent Transport (*glycerol-3-phosphate & malate-aspartate shuttle*)

Answer 38

- ATP used in cytosol (outside mitochondria) for energy but is made INSIDE so needs to get out and ADP + Pi need to get in to make it 1. **adenine nucleotide antiporter (ADP/ATP Translocase)**: brings 1 ADP from cytosol into matrix & sends 1 ATP from matrix into cytosol - *exchange molecules in opposite directions* 2. **Pi-H+ Symporter**: symporter (*transports molecules in the same direction*) - co transports: **Pi** (inorganic phosphate) + **H+ ion** from cytosol to matrix

Answer 39

**problem**: NADH and FADH₂ are reducing equivalents (*molecules that carry electrons for the ETC*) - are produced during glycolysis and other metabolic pathways in **the cytosol* - but inner mitochondrial membrane has NO direct transporter for NADH so NADH made in the cytosol **can’t directly enter the matrix** **solution**: special shuttle systems used to transfer electrons (not the NADH itself) from the cytosol to the matrix **2 shuttle systems**: glycerol-3-phosphate shuttle & malate-aspartate shuttle

Answer 40

cytosolic NADH donates e- to **DHAP (dihydroxyacetone phosphate)** → DHAP gets converted into **glycerol-3-phosphate** **G3P** enters the mitochondria → gives e- to **FAD** forming **FADH2** by *mitochondrial isozyme* → FADH2 enters ETC at Complex II **2 ATP are synthesized** for each cytosolic NADH oxidized *easy kaam = not as much return as mushkil kaam → faster & simpler but not as efficient* - mainly used in *muscles & brain*

Answer 41

*more efficient than the glycerol-3-phopshate shuttle* has **2 antiporters involved** 2 e- transferred from NADH to **oxaloacetate** by *cystolic malate dehydrogenase enzyme* → forms **malate** malate crosses the inner mitochondrial membrane through **anti-porter** (*malate goes in, α-ketoglutarate comes out*) malate goes in & is oxidized to **oxaloacetate**, regenerating the **NADH** inside the mitochondria oxaloacetate cant cross membrane so is converted to **aspartate** which exits in exchange for **glutamate** (*2nd antiporter- aspartate leaves, glutamate comes in*) synthesis of **3 ATP**

Answer 42

when cancer cells prefer glycolysis even when oxygen is available - reduced use of oxidative phosphorylation = less need to bring NADH into mitochondria but cells still need to regenerate NAD⁺ in the cytosol to keep glycolysis going = cancer cells may alter the **malate-aspartate shuttle** to regenerate NAD⁺ *good to know- not must to know*

Answer 43

genetic disorder caused by **mutations in mitochondria DNA (mtDNA)** - proteins in Complex I disrupted = **impaired oxidative phosphorylation** energy is really needed in eye so eventually someone just **loses their central vision** just randomly one day

Answer 44

**Bax * Bak** (channel proteins) move to outer mitochondrial membrane in response to stress signals → form **pores/channels** there → **cytochrome c** moves through these pores into the cytosol → cytochrome c binds to proteins forming the **apoptosome** structure → apoptosome recruits family of **proteolytic enzymes** that cause cleavage of key proteins