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Flashcards in Organelles Deck (40):
1

Why eukaryotic cells need organelles (2)

Membrane-dependent functions, specialization

2

Development of organelles

Invagination of cell membrane - explains double nuclear membrane

3

Areas of cell that are "topographically" equivalent to outside

Nuclear envelope, Golgi, ER

4

Biggest organelles by volume

Mitochondrion, Golgi, ER (NOT nucleus!)

5

Size of mitochondria

0.5-1 micron

6

Cells with high mitochondria content

High energy needs - muscle, nerve, sperm

7

Where are mitochondria found in cell?

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

8

Endocytosis model of mitochondria

Was separate organism - two membrane are organism and plasma

9

Structure of mitochondria

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

10

Mitochondrial ATP production

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

11

Electron transport chain

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

12

ATP synthase

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

13

Thermogenin

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

14

Adaptations of mitochondria

Number in cell, density of christae, location in cell

15

Mitochondrial replication

Fission, also reversible through fusion

16

Mitochondrial DNA

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

17

Characteristics of mitochondrial disease

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

18

Ribosome function

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

19

Ribosome synthesis

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

20

"Polyribosome"

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

21

Membrane-bound ribosome mechanism

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

22

Prokaryotic vs eukaryotic ribosomes

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*

23

Post-translation protein folding

Aided by chaperones, destroyed by proteasome if misfolded

24

Proteasome

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

25

Proteasome function

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

26

Proteasome vs protease

Protease is a specific enzyme that cleaves a protein once
Proteasome much larger organelle, destroys anything ubiquinated, has processivity (cleaves multiple places)

27

Functions of smooth ER

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

28

Transport of lipids to membrane

Lateral diffusion through ER, vesicles or transport protein

29

Cells with high rough ER content

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

30

Structure of Golgi

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

31

Transport through Golgi network

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

32

Golgi enzymes

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

33

Pathways from Golgi

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

34

Lysosome development

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

35

Lysosomal storage diseases

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

36

Development of secretory vesicles

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

37

Peroxisome functions

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

38

Locations of peroxisomes

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

39

Peroxisomal diseases

Zellweger syndrome - absence of enzymes, fatal
Adrenoleukodystrophy - fatty acids can't enter peroxisome, accumulate in nerves and adrenal glands

40

Approx amount of total membrane in organelles

Mitochondria 40%
ER 50%
Plasma membrane only 2%