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Mcb1 > Organelles > Flashcards

Organelles Flashcards

1
Q

How is the cell wall of a gram negative bacteria arrange?

A

Outer membrane

Cell wall

Plasma membrane

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2
Q

How is the arrangement of a gram positive bacteria?

A

Cell wall

Plasma membrane

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3
Q

What are the functions of the cell membrane?

A
  1. Enclose and protect cell
  2. Maintain structural and functional integrity
  3. Selectively permeable membrane
  4. Define inside/outside of organelles
  5. Compartmentalizations of biochemical activity
  6. Intercellular interaction and respond to external signal
  7. Scaffol for biochemical activity
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4
Q

What is the function of the golgi?

A

Maturation of glycoproteins and other components of membranes and secretory vessels

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5
Q

What is the function of chloroplasts (plants)?

A

Photosynthesis

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6
Q

What is the function of the mitochondria?

A

CTA, ET and oxidative phosphorylation

Fatty acid oxidation, amino acid catabolism and pyruvate oxidation

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7
Q

What is the function of lysosomes?

A

Segregation of hydrolytic enzymes such as ribonuclease and acid phosphatase

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8
Q

What is the function of the glycogen granules?

A

Glycogen synthesis and degradation

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9
Q

What is the function of the cytoskeleton?

A

Glycolysis; many reactions in gluconeogenesis, pentode phosphate pathway, activation of amino acids, fatty acid synthesis and nucleotide synthesis

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10
Q

What is the function of a vacuole?

A

Water storage

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11
Q

What is the function of the nucleus?

A

Replication of DNA, synthesis of tRNA, mRNA and some nuclear proteins

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12
Q

What is the function of the nucleolus

A

Synthesis of rRNA

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13
Q

What is the function of the ER?

A

Lipid synthesis, direction of biosynthetic products to their ultimate location

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14
Q

What is the function of ribosomes?

A

Protein synthesis

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15
Q

What is the function of microbodies?

A

Amino cid oxidation, catalase and peroxide reactions, sterol degradations; in plants, glyoxylate cycle reactions

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16
Q

What are the lipids in the cell membrane?

A

Phospholipids
Glycolipids
Cholesterol

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17
Q

What are the proteins in the cell membrane?

A

(Two classes: transmembrane and peripheral)

Membrane channels/pumps
Transporters
Membrane receptors
Adhesion molecules
Gap junctions
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18
Q

What are the 3 class of lipids?

A

Phospholipid (ex: phosphatidylcholine)

Triglyceride (ex: triacylglycerol)

Steroid (ex: cholesterol)

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19
Q

Where are glycolipids located?

A

Only on extracellular leaflet

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20
Q

What forms the glycocalyx?

A

The carbohydrate residues on the glycolipids

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21
Q

What is the purpose of cholesterol on the membrane?

A

For structural stability

Note: it’s on both leaflets

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22
Q

What determines the properties of a phospholipid?

A

The tail length and degree of saturation

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23
Q

What are some important phospholipids?

A

Phosphatidic acid (phosphate + glycerol)

Phosphatidyl-choline (choline + phosphate + glycerol)

Phosphatidyl-ethanolamine (ethanolamine + phosphate+ glycerol)

Phosphatidyl serine

Phosphatidyl-inositol

Sphingomyelin (choline and serine)

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24
Q

What do fatty acids form?

A

Micelles

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25
Q

What do phospholipids form?

A

Bilayers

Note: circular bilayers are liposomes

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26
Q

What holds the leaflet of a membrane together?

A

Van der Walls interactions (weak bonds between hydrophobic tails)

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27
Q

In a TEM, membranes appear trilaminar. Why is that?

A

The polar head groups attract osmium tetroxide and become dark

The center lipid section remains clear

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28
Q

How thick is the membrane?

A

7.5 mm thick

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29
Q

What is the membrane fluidity essential for?

A

Exocytosis, endocytosis, membrane trafficking and biogenesis

30
Q

Why aren’t the inner and outer leaflets symmetric?

A

They are composed of different phospholipids

31
Q

Where are glycoproteins and glycolipids on the membrane?

A

On the outer leaflet

32
Q

What increases the fluidity of the membrane?

A

Unsaturated fatty acid tails (increase cis-double bond kinks)

Short chain

Increase temperature

33
Q

What does cholesterol do to the membrane?

A

Increases stability by “filling in the gaps” when lipids are too fluid

I.e. If high unsaturation or high temp

34
Q

What do steroid rigs do to PL hydrocarbon movement?

A

Reduces phospholipid movement

35
Q

What happens when too much cholesterol is within a erythrocyte?

A

Distorted cell shape called acanthocytes

36
Q

What does an acanthocyte look like?

A

Has 5-10 irregular, blunt, fingerlike projections

37
Q

What is acanthocytosis (spur cells) anemia associated with??

A

Chronic liver disease

38
Q

Why is spur cell anemia associated with chronic liver disease?

A

Abnormal lipoproteins with high cholesterol content and high plasma cholesterol levels in these patients

39
Q

What does the decreased deformability of acanthocytes lead to?

A

Sequestration and destruction by spleen (haemolytic anemia)

40
Q

What are lipid rafts rich in? (Butter islands in oil)

A

They are rich in cholesterol and glycosphingolipids (long saturated tails) and are less guild and thicker

41
Q

What is a glyosylphosphatidylinositol anchor?

A

GPI: glycolipid that attaches proteins to PM

42
Q

What kind of proteins are found in lipid rafts?

A

Integral and peripheral membrane proteins

Note: clustering enables proteins to function together and for transport into endocytic vesicles

E.i. GPI

43
Q

What maintains the asymmetry of the phospholipid bilayer?

A

Flippases

Note: these enzymes selectively “flip” particular phospholipids across the membrane

44
Q

What does flip-flop require? ( a type of movement within the bilayer)

A

Flippases

Scrambalases

45
Q

What do scrambalases do?

A

Non-specific scrambling

In ER membrane: mix up newly synthesized PLs

At plasma membrane: activated during apoptosis

46
Q

What is the functional importance of lipid movement?

A

Phosphatidyl serine will be flipped to outer leaflet during apoptosis

47
Q

What are glycolipids used for?

A

Cell to cell recognition

Protection (exposed apical surface of epithelial cells)

Nerve conduction

48
Q

What is the receptor for Cholera toxin found on the intestinal epithelial cells?

A

Gm1 ganglioside

49
Q

What are integral proteins bound to?

A

Actin cytoskeleton

50
Q

What is the difference in protein concentration in myelin and mitochondrial membrane?

A

Myelin : 25% protein

Mitochondrial: 75% protein

51
Q

What are the functions of membrane proteins?

A

Transport (nutrients, metabolites, ions across bilayer)

Anchor membrane to macromolecules on either side

Receptors: signal transduction

Enzymes (lactase in apical membrane of GI epithelial cells)

Cell identity markers: MHC

52
Q

What are the 3 classes of membrane proteins?

A

Integral transmembrane proteins

Peripheral proteins

Lipid-anchored (peripheral) proteins

53
Q

What are the characterisitcs of integral transmembrane proteins?

A

Single/multipass proteins

Often alpha-helical in secondary protein structure

Receptors (signaling and adhesion), channels, transporters/pumps

54
Q

What are the characteristics of peripheral proteins?

A

Located entirely outside but associated with inner/outer leaflet by noncovalent interactions

Part of cytoskeleton, cytochrome C

55
Q

What are the characteristics of lipid-anchored (peripheral) proteins?

A

Located either side of bilayer, have lipid group that inserts into bilayer

Signaling and adhesion proteins

56
Q

What does protein 4.1 link?

A

Actin to glycophorin (single pass transmembrane glycoprotein)

Note: also binds spectrin and band 3

57
Q

What is band 3?

A

Multipass transmembrane protein

58
Q

What does ankyrin bind?

A

Binds band 3; attaching spectrin cytoskeleton to membrane

59
Q

What is hereditary spherocytosis?

A

An autosomal dominant disorder in RBC cytoskeleton membrane

This is due to non-functional skeletal membrane protein; spectrin, ankyrin or protein 4.1

60
Q

What is dysfunctional in hereditary spherocytosis?

A

Spectrin, ankyrin or protein 4.1 (spectrin deficiency)

61
Q

What is the treatment for hereditary spherocytosis?

A

Folate supplement, splenectomy

62
Q

What are the effects of hereditary spherocytosis?

A

Unstable membrane, loses fragments
= RBCs sphenoidal, decreased deformability
-vulnerable to splenic sequestration and destruction
-hemolytic anaemia (splenomegaly, jaundice, gall stones)

63
Q

What is the function of the apical plasma membrane?

A

Regulation of nutrient and water intake

Regulated secretion

Protection

64
Q

What is the function of the lateral plasma membrane?

A

Cell contact and adhesion

Cell communication

65
Q

What is the function of the basal membrane?

A

Cell-substratum contact

Generation of ion gradients

66
Q

What does the glycocalyx repel?

A

Negative charges from sialic acid sugars

67
Q

What are the substances found in the glycocalyx?

A

Glycoproteins, glycolipids, proteoglycans

68
Q

What is different in the glycocalyx of a cancer cell?

A

Different sugar coat than noncancerous cells

69
Q

What are the primary marker for cell recognition ?

A

Carbohydrates

70
Q

What do carbohydrates provide for cell recognition?

A

Attachment for bacteria, viruses, toxins, other cells

Activated endothelial cells express selectins which bind to
oligosaccharides on WBC & platelets

L-selectins recognise addressins on lymphoid organ endothelial
cells

Mcb1 (13 decks)

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