Lecture 22 - Cell Energetics & Mitochondria (22) Flashcards by M B

what do organisms use E for?

build complex molecules

maintain their structure

move

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what are the 2 sources of E available to organisms?

electromagnetic - light E

chemical - E of molecules & eletrons

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glycolysis chemical formula

glucose –> 2 pyruvate + 2 ATP + 2 NADH

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why does glycolysis not require?

oxygen

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where does glycolysis occur?

cytoplasm

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where does the citric acid cycle occur?

mitochondria

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chemical formula of the citric acid cycle & TCA

Pyruvate –> acetyl CoA (+NADH) –> 3 NADH + FADH2 + CO2 + GTP `

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what does the ETC use to generate ATP?

NADH & FADH2

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what is the net gain of ATP from TCA + ETC?

36 ATP

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what is the main function of mitochondria?

production of ATP

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structure of mitochondria

Outer membrane: impermeable, contains porins forming non-selective membrane channels, porins don’t require a mitochondria localization signal

Intermembrane space

Inner membrane:
ETC
ATP synthase
Contain cristae which are highly folded to increase the SA for ATP machinery

Matrix:
TCA
DNA
Ribosomes

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what does the mitochondria vary in?

shape: filamentous to spherical
number: oocytes have more than spermatozoa

number & shape of cristae

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how many mitochondria do oocytes have?

300,000

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why do oocytes have more mitochondria than spermatozoa?

undergoes division without gaining size, require the production of many daughter cells prior to growing

undergo many cell divisions

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what cell type has the greatest amount of mitochondria?

egg

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where do mitochondria cluster in sperm cells?

around the base of the flagellum

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where do mitochondria cluster in renal tubular cells?

b/w basolateral membrane invaginations at the periphery which contain ATPase pumps for establishing gradients

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how are mitochondria similar to bacteria?

Double membrane

Membrane composition (ex: cardiolipin –> a gene sequence only found in the mitochondria membrane)

Divide by fission, independent of the host

Circular DNA encoding unique rRNAs & tRNAs

13 PROs in the ETC are similar to bacteria PROs

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Endosymbiotic theory

mitochondria in eukaryotes evolved from aerobic bacteria living within their cells

symbiotic relationship

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where does ETC occur?

inner membrane of the mitochondrial

steps of ATP production

TCA cycle: NAD+ & FADH –> NADH & FADH2

Electrons are fed into enzyme complexes & end up on an oxygen molecule
H+ move to the intermembrane space creating the H+ electrical/concentration gradient
Electrons are transferred to an oxygen which also picks up 2H+ –> H2O
No consumption of ATP, conformational changes are caused
Electron will be received by H –> H-

H+ ions are returned to the mitochondrial matrix by ATP synthase for ATP production

movement of H+ in ETC

from the matrix to the intermembrane space

what is the terminal electron acceptor in the ETC?

oxygen

how much E in the ETC is stored due to the concentration diff of H+?

20%

How much of E stored is electrogenic in the ETC? & why is this?

80% the membrane isn't permeable to the counter-ions --> protects cytoplasm from being too acidic

if too many H+s are pumped out, what can happen?

they can leak through the proins & cause the cytoplasm to become acidic that is why it is important for ATP synthase to bring them back

structure of ATP synthase?

F1 headpiece projects into matrix, responsible for ADP phosphorylation F0 base piece is embedded in the lipid bilayer, contains the H+ ion channel

what does the movement through the H+ channel induce?

conformational changes & drives ATP formation

each NADH produces how many ATP molecules?

each FADH2 produces how many ATP molecules?

how does the movement of H+ produce ATP?

H+ flow through the channel causes a rotation of the F0 rotator this spin causes a conformational change in the F1 headpiece Change of shape enables the phosphorylation of ADP kinetic E (of the F0 rotator) is used to create chemical E

how is ATP synthase being utilized in nanotechnology?

Production of a microscopic motorized propeller: F0 + actin filament Feed an ATP solution through the propeller & rotation occurred This could lead to the production of nano-bots, which would be sent throughout the body carrying out various functions Ex: delivery of medication

how do PROs enter mitochondria?

through a signal system which includes carrier PROs & a mitochondrial receptor PROs require a presequence (target sequence), directs PRO to mitochondria cytosolic chaperone PROs on the outer membrane recruit & unfold the PRO enabling it to enter through the pore once the PRO enters the mitochondria matrix, the sequence is cut off & the PROs refold (pass through the outer membrane & inner membrane)

where are most mitochondrial PROs encoded?

nuclear genome (except 13)

proton leak or mitochondrial uncoupling & what is the result?

protons re-enter the mitochondrial matrix without contributing to ATP synthesis, this is accomplished by facilitated diffusion through a proton channel called thermogenin potential E of the H+ gradient is released as heat

where is thermogenin located?

brown adipose tissue (in newborns)

non-shivering thermogenesis

primary means of heat generation in newborns & hibernating mammals production of heat, but no ATP ATP synthase is blocked

what causes mitochondrial DNA damage

oxygen molecules become superoxide ions if they aren't coupled with H quickly in the ETC

Why do mitochondria have multiple c'some copies?

Divide by fission, require DNA copies to share with daughter cells Highly metabolic organelle requires a high amount of PRO production Enables removal of damaged DNA copies, damage occurs frequently since it is an oxidative organelle

how do mitochondria contribute to aging? & what is the evidence?

Gradual accumulation of mutations in mitochondrial DNA may be the cause of aging Old people have more mutated mtDNA than young Mutator strain of mice have 3-8x more mtDNA mutations than normal mice age prematurely & die at half the normal age

peroxisomes

membrane-bound vesicles with a core of oxidative enzymes

what are 3 similarities b/w mitochondria & peroxisomes?

oxidative metabolism import PROs Formed from pre-existing organelles

what are peroxisomes involved in metabolizing?

FAs

what are the enzymes in peroxisomes?

urate oxidase & AA oxidase

what is the by-product of peroxisomes?

hydrogen peroxide (toxic) causes damage to membranes & PROs

how many oxidative enzymes do peroxisomes have?

over 50

catalase location

peroxisomes & mitochondria

catalase

removes highly reactive peroxide & other oxygen free-radicals

what evidence is there that suggests that catalase prevents aging?

Fruit flies with extra copies of catalase genes live longer than normal flies Nematodes that are induced by drugs to increase catalase activity lived longer than control nematodes