Organelles

Question 1

Why eukaryotic cells need organelles (2)

Answer 1

Membrane-dependent functions, specialization

Question 2

Development of organelles

Answer 2

Invagination of cell membrane - explains double nuclear membrane

Question 3

Areas of cell that are “topographically” equivalent to outside

Answer 3

Nuclear envelope, Golgi, ER

Question 4

Biggest organelles by volume

Answer 4

Mitochondrion, Golgi, ER (NOT nucleus!)

Question 5

Size of mitochondria

Answer 5

0.5-1 micron

Question 6

Cells with high mitochondria content

Answer 6

High energy needs - muscle, nerve, sperm

Question 7

Where are mitochondria found in cell?

Answer 7

Migrate along microtubules to highest energy need (ie base of cilia)

Question 8

Endocytosis model of mitochondria

Answer 8

Was separate organism - two membrane are organism and plasma

Question 9

Structure of mitochondria

Answer 9

Double membrane with christae on inner membrane, lumens in intermembrane space

Question 10

Mitochondrial ATP production

Answer 10

Pyruvate, fatty acids enter citric acid cycle -> NADH -> electron transport chain pumps H+ into intermembrane space -> ATP synthase driven by gradient

Question 11

Electron transport chain

Answer 11

Small steps in energy so cell is able to harness, passed to three different complexes

Question 12

ATP synthase

Answer 12

Lollipop structure, drives oxidative phosphorylation by electro and chemical H+ gradient

Question 13

Thermogenin

Answer 13

In mitochondria of brown fat, produces heat (no ATP) from electrochemical gradient of inner membrane

Question 14

Adaptations of mitochondria

Answer 14

Number in cell, density of christae, location in cell

Question 15

Mitochondrial replication

Answer 15

Fission, also reversible through fusion

Question 16

Mitochondrial DNA

Answer 16

Replicated before fission, few genes (35?), high mutations/diversity, complement of DNA is inherited from mother

Question 17

Characteristics of mitochondrial disease

Answer 17

Due to mutations in DNA, maternal inheritence, affects high energy cells (muscle, nerves), often progressive and hard to recognize, can have varying presentation dt different DNA complements or different distribution, example MERRF

Question 18

Ribosome function

Answer 18

RNA catalyzes peptide bonds, specific binding of tRNAs into three binding sites (A->P->E), reads RNA 5-3, makes peptide N-C

Question 19

Ribosome synthesis

Answer 19

RNA in nucleolus, proteins imported into nucleus, subunits exported and float free in cytoplasm until bind onto rough ER or polyribosome

Question 20

“Polyribosome”

Answer 20

Multiple ribosomes bound to single mRNA, often appear as spirals in cytoplasm

Question 21

Membrane-bound ribosome mechanism

Answer 21

Begin translation, signal recognition protein recognizes signal sequence and directs to ER

Question 22

Prokaryotic vs eukaryotic ribosomes

Answer 22

Prokaryotic are smaller 3 RNA, 55 proteins, 50S and 30 S subunits vs 4 RNA, 82 proteins, 60S and 40S
Differences are exploited by many antibiotics

Question 23

Post-translation protein folding

Answer 23

Aided by chaperones, destroyed by proteasome if misfolded

Question 24

Proteasome

Answer 24

Free in nucleus, destroys misfolded, injured or foreign proteins labeled with ubiquitin

Question 25

Proteasome function

Answer 25

Four heptameric rings, active site buried inside hollow core, cap recognizes ubiquitin and uses ATP to thread protein into core

Question 26

Proteasome vs protease

Answer 26

Protease is a specific enzyme that cleaves a protein once

Proteasome much larger organelle, destroys anything ubiquinated, has processivity (cleaves multiple places)

Question 27

Functions of smooth ER

Answer 27

Lipid synthesis (phospholipids, cholesterol, steroid hormones), drug detox (cytochrome p450), sequestration of Ca++ (“sarcoplasmic reticulum”)

Question 28

Transport of lipids to membrane

Answer 28

Lateral diffusion through ER, vesicles or transport protein

Question 29

Cells with high rough ER content

Answer 29

High protein secretion - antibodies, hormones, pancreas, active growth site

Question 30

Structure of Golgi

Answer 30

Cis face near rough ER, vesicles transport proteins to medial then trans face, each compartment has specific enzymes and functions

Question 31

Transport through Golgi network

Answer 31

Coat proteins (COP) - COP II moves vesicle “forward” to trans face, COP I moves retrograde towards cis

Question 32

Golgi enzymes

Answer 32

Add oligosaccharides, disulfide bonds, mannose 6 P, glycosylation, sialic acid on oligosaccarides, sulate to tyrosines

Question 33

Pathways from Golgi

Answer 33

Lysosome (if mannose 6 phosphate labelled), secretion, regulated secretory vesicle

Question 34

Lysosome development

Answer 34

Enzymes labelled with mannose 6 phosphate, forms primary lysosome, fuses with endosome or phagosome to become secondary lysosome, can become residual body if indigestible wastes

Question 35

Lysosomal storage diseases

Answer 35

Missing enzyme, non-metabolized products build up in cell
Ex Tay-Sachs (hexosaminidase -> glycolipids in neurons)
Hurler (GAGs in brain, heart, etc)
Glycogen storage

Question 36

Development of secretory vesicles

Answer 36

Labelled by clathrin, bud off from trans golgi, excess membrane returns to Golgi to concentrate secretions

Question 37

Peroxisome functions

Answer 37

Metabolism through oxidation - long fatty acids, EtOH, meds - oxidases create H2O2, catalases process into H20 and O2

Question 38

Locations of peroxisomes

Answer 38

In every cell, abundant in kidney and liver, often near mitochondria

Question 39

Peroxisomal diseases

Answer 39

Zellweger syndrome - absence of enzymes, fatal

Adrenoleukodystrophy - fatty acids can’t enter peroxisome, accumulate in nerves and adrenal glands

Question 40

Approx amount of total membrane in organelles

Answer 40

Mitochondria 40%
ER 50%
Plasma membrane only 2%