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Cell Biology Midterm 1 > Cell Biology Midterm 2 > Flashcards

Cell Biology Midterm 2 Flashcards

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1
Q

What are the functions of the Plasma Membrane? (4)

A

Maintain ion and chemical gradients

Control material exchange between cells and its environment

sense and control communication

Malleable: able to change shape

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2
Q

What are membranes composed of?

A

Lipids and proteins!

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3
Q

What are the membrane lipids? (2)

A
  1. Phospholipids
    A.Glycerophospholipids: uses glycerol for backbone
    B. Sphingophospholipids: uses sphingosine for backbone
  2. Sterols
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4
Q

What is the structure of a glycerophosphoipid?

A

Glycerol backbone

ESTERFIED two fatty acid chains attach to glycerol (Hydrophobic)

The 2 fatty acid chain is cis-unsaturated (kinky) reduce packing and rigidity

Phospho-head group linked to glycerol (hydrophilic)

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5
Q

What are the major types of phospholipids? (5)

A

PhosphatidyETHANOLAMINE

PhosphotidylSERINE

PhosphatidylCHOLINE

SphingoMYELIN

SphingoSINE

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6
Q

Why is cholesterol a major component of membranes?

A

STERIOD RING IS HYDROPHOBIC

It is between fatty acid chains of phospholipids

It increase packing of phospholipids and decrease permeability of water

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7
Q

What movement occurs in phospholipid bilayers?

A

Lateral Diffusion

Flexion

Rotation

Flip-flop (rare)

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8
Q

Is transbilayer diffusion of lipids favourable?

A

No its slow.
Lateral diffusion is FAST and favourable

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9
Q

What are membrane rafts?

A

Parts of the membrane that are ENRICHED in specific lipids: Saturated lipids, cholesterol

PACK WELL

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10
Q

What intermolecular force does saturated lipids have?

A

Van der Waals Attraction

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11
Q

What phospholipid is faceing outwards from the cell membrane?

A

PhosphatidyCHOLINE

SphingoMYELIN

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12
Q

What phospholipid is facing inside the cytoplasm?

A

PhosphatidylETHANOLAMINE

PhosphotidylSERINE

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13
Q

Why is it important for the membrane to maitain their ASSYMETRY?

A

Bc loss of PS asymmetry leads to programmed cell death APOPTOSIS

Glycolipids asymmetry is responisble for BLOOD TYPES

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14
Q

What happens why PhosphotidylSERINE is on the cell surface (not suppose to be there)?

A

Cell will undergo apoptosis

Cause a disease: Antipholipid syndrome
genetic mutation alters proteins
Auto-immune

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15
Q

What are signaling molecules?

A

varity of molecules that are attach to membranes to regulate cell function

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16
Q

What are the four types of intergral membrane proteins?

A

Transmembrane alpha helix; multiple pass

Transmembrane alpha helix; single pass

Transmembrane; beta sheet; multipass

Partial Insertion; amphiphilic alpha helix

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17
Q

What proteins covalently modifies proteins with glycolipids (sugar+lipid=glycolipoprotein)

A
  1. Lipid-anchored proteins: Covently modified proteins with lipids
  2. Peripheral membrane proteins: bind non-covalent to transmembrane and/or membrane lipids.
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18
Q

What are the 3 types of covalently attached lipid anchors?

A

Myristoyl achor

palmitoyl anchor

Farnesyl anchor

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19
Q

What can causes a certain alpha-helices to become a transmembrane domain?

A

-most transmembrane proteins cross membrane as a hydrophobic alpha-helix

-Usually 20-30 amino acids long to span the lipid bilayer

-Hydrophobicity can be measure in a hydropathy plot

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20
Q

What is a hydropathy plot?

A

How much a single/multi pass transmembrane protein FREE ENERGY is associated with moving an amino acid from OIL to water

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21
Q

What is a Bacteriohodopsin?

A

is a seven transmembrane alpha helix protein in BACTERIA

capture light to pump H+ out

Make H+gradient to drive ATP production

Was covalently Modified by RETINAL

Photons change retinal shape

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22
Q

What is a disulphide bond? (only bond in extracellular space)

A

Cysteine amino acid residues react to each other to form sulphur to sulphur bridges.
HELPS STABLIZE PROTEIN SHAPE

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23
Q

What is glycosylation?

A

Covalent addition of oligosaccharides to proteins

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24
Q

Where are most plasma membrane proteins mostly glycosylated on?

A

SERINE OR ASPARAGINE RESIDUES

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25
Q

What is a glycocalyx?

A

Its glycosylated proteins coated on the cell surface. (sugar polymers)

Allows cell to adhere to the matrix and to other cells.

GIVES IDENTITY TO CELL

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26
Q

What can FRAP do?

A

Determine lateral diffusion of membrane proteins

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27
Q

What is free or unrestrained diffusion?

A

a proteins can FREELY move across the PS.
FRAP: rapid recovery of fluorescence

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28
Q

What is No or negligible diffusion?

A

A protein is completely immobile or its diffusion is slow

FRAP:slow to no recovery of fluorescence

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29
Q

What is restricted or partial diffusion?

A

protein is FREE to DIFFUSE BUT only within a subsection of a membrane

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30
Q

What are the three subdomains of a sperm?

A

Anterior head

posterior head

TAIL

use restricted diffusion

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31
Q

What are mechanisms to restrict membrane protein movement?

A

self-assemble into large complexes

Tethered to the cytoskeleton inside cells

Tethereed to the extracellular matrix

interact with proteins on another cell.

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32
Q

What is the red blood cell biconcave?

A

Due to membrane protein interactions with a spectrin cortial cytoskeleton

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33
Q

What is spectrin? (peripheral membrane protein)

A

A protein similar to actin that forms a mesh like struction UNDER the cytosolic face of PS.

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34
Q

what is a glycophorin and BAND 3?

A

two diff integral membrane proteins that binds spectrin, link “skeleton” to membrane

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35
Q

What does the junction complex include?

A

It includes a filamentous actin and it is attached to the membrane by the transmembrane GLYCOPHORIN PROTEIN

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36
Q

What are corrals?

A

spectrin cortical cytoskeleton fenced off the plasma membrane into compartments

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37
Q

What is the cortical cytoskeleton?

A

membrane domains that restrict protein diffusion (small corrals)

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38
Q

How can protein diffusion be restricted?

A

Restricted within small corrals

restricted from moving between apical and basolateral membranes in epithelial or endothelial cell layers

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39
Q

What happens in the G1 phase?

A

Preparation of cell for DNA replication

40
Q

What happens in S phase?

A

DNA replication

41
Q

What happens in G2 phase?

A

cell growth (size, biomass, materials)

42
Q

What happens in M phase?

A

Sorting of materials (chromosomes, organelles) TO PREPARE TO SEPERATE

Separation of cell into two daughters cells

43
Q

M-phase: prophase

A

Chromosomes condense,

mitotic spindle assemble

44
Q

M-phase; prometaphasr

A

BREAKDOWN of nuclear envelope

ATTACHMENT of chromosomes to spindles

45
Q

M-phase: metaphase

A

ALIGNMENT of chromosomes

46
Q

M-phase: anaphase

A

Sister chromatids separate

Pulled towards spindles

47
Q

M-phase: telophase

A

full set of DAUGHTER CHROMOSOMES arrive at spindle

Contractile ring pinch the cytosol

Nuclear membrane begins to re-form

48
Q

M-phase: cytokinesis

A

SEPERATING INTO TWO CELLS

CONTRACTILE RING SQUEEZE to form TWO DAUGHTERs

Generates a cleavage furrow, represent final stages of separation

49
Q

What can a Cdk do?

A

Cycling dependent kinase can phosphorykate several different substrate proteins

50
Q

What is the switch mechanism to turn the Cdk on them?

A

Binding to one of several specific cyclin proteins

51
Q

What does M-Cdk trigger??

A

CONDENSIN (protein complex)
Cause condensation of chromosomes

Forms mitotic spindle

52
Q

What does M-Cdk activate?

A

Starts at Mitosis and is removed to finish mitosis

53
Q

What is the APC/C ?

A

A protein complex that is required to allow metaphor to anaphase transition

Leads to degradation of M-Cdk

54
Q

Why is control good?

A

Cyclin-Cdk acts as a timer, cause removal of cycling

Some cases cause upregukation of cyclin

55
Q

What triggers G1-Cdk?

A

favorable extraceller environment

56
Q

What triggers G1/S-Cdk and S-Cdk

A

DNA damage

57
Q

What triggers M-Cdk?

A

Unreplicated DNA And DNA damage

58
Q

What triggers APC/C-Cdc20

A

Chromosome unattached to spindle

59
Q

How can some Cdks be good? (before mitosis)

A

They are effective has cancer drug targets!
Such as
-matastatic breast cancer
-pancreatic cancer
-other cancer

60
Q

When does the mitotic spindle begin?

A

Assemble in EARLY mitosis. (PROPHASE)

61
Q

What is the mitotic spindle?

A

A BIPOLAR array of microtublues. Involved in seperation of chromosomes and materials.

62
Q

What is a spindle pole?

A

has a centrosome and other components. Has three types of microtubules,

ASTRAL microtubules

KINETOCHORE microtubules

INTERPOLAR microtubules

63
Q

What is ASTRAL microtubules?

A

from spindle pole to cell cortex. Helps ANCHOR spindle poles.

64
Q

What is KINETOCHORE microtubules?

A

From spindle pile to CHROMOSOME (attach to kinetochore)

65
Q

What is INTERPOLAR microtubules?

A

From spindle pole to interpolar microtubule coming from other spindle

66
Q

How does a cell know when it is time to proceed from metaphase to anaphase?

A

In metaphase, ALL CHROMOSOMES SHOULD BE ATTACH TO KINETOCHORE MICROTUBULES.
-prevent improper sorting during cell division

The metaphase to anaphase transition checkpoint sense if there is no free kinetochore remaining. APC/C

67
Q

What drugs target the mitotic spindle assembly? (cancer therapy)

A

PACLITAXEL AND DOCETAXEL
- bind and stabilize microtubles, prevents assembly of mitotic spindle
-trigger metaphase-anaphase checkpoint arrest

68
Q

What types are passive transport? (2)

A
  1. channel mediated (continous pore)
  2. transporter-mediated
69
Q

What types are active transport? (3)

A
  1. coupled transporter
  2. ATP-driven pump
  3. light-driven pump
70
Q

What happens to the membrane when charged solutes are transported by passive transport?

A

created a electrochemical gradient (membrane potential)

Helps molecules move by faciliated diffusion

71
Q

What are the conformational states during passive transport?

A

Outward-open

occluded

inward-open

72
Q

What are the 3 couples transporter pump?

A

Uniport- only 1 molecule in

Symport- 2 molecules can go in same direction

Antiport- 2 molecules can go in opposite directions

73
Q

What does Na+ glucose symporter do?

A

recover glucose from extracellular medium before excretion.

Glucose is passivly diffused by the electrochemical gradient of Na+

74
Q

What does ATP-Driven pumps do?

A

membrane transport enzymes that use energy released by ATP HYDROLYSIS to drive transport

75
Q

What are the types of ATP-driven pumps? (4)

A
  1. P-type-transport IONS
  2. ABC transporter- Transport small molecules
  3. V-type proton pump- transport H+ and CONCUSME ATP
  4. F-type ATP synthase- transport H+ and makes ATP
76
Q

How does P-type Na+ K+ pump work?

A

Exchange 3 Na+ to 2K+
IT IS ELECTROGENIC
drives electrical currect accross the membrane

77
Q

What does P-type Na+ K+ control ?

A

CONTROL OSMOLARTIY

the Na+ electrochemical gradient draw Cl- and balanced the inter and extracellular

78
Q

What are the gating mechanisms of ion channels? (4)

A

Voltage gated

Ligand-gated(extracellular)

Ligand-gated (intracellular)

mechanically gated

79
Q

What are the functions of channels?

A

regulate electrical signals in neurone

regulate neuron to neuron communication

muscle contraction and senses

leaf-closing response

MEMBRANE POTENTIAL

80
Q

How does a K+ channel select K+ and excludes Na+?

A

Bc there’s a bacterial K+ channel

Four subunits
-negative charges on CYTOSOLIC side allows +ve ions to pass

-Vestibule is a hydrating area (H2O bound ions)

-Pore helix also selects for +ve ions

-Selectivity filter allows only K+ to pass

81
Q

What is an action potential?

A

signal is a change in MEMBRANE POTENTIAL that goes a long the length of the neuron

82
Q

What is the process of an action potential?

A

short, local DEPOLARIZATION of the plasma membrane that migrates along the axon

MORE POSITIVE OR NEUTRAL MEMBRANE POTENTIAL

controled by VOLTAGE GATED CATION CHANNELS

83
Q

What is happing to the electrochemical gradients during action potential>

A

Before AP: Lots of Na+ OUTSIDE
Lots of K+ INSIDE

During AP: Na+ rush IN
Na+ channels openning

84
Q

How is membrane polarity reestablished?

A

Voltage gated Na+ channels INACTIVATION
DELAYED VOLTAGE GATED K+ CHANNELS

k+OUT and Na+ INN CELL

85
Q

What are the types of glial cell

A

Schwann cells enclose PERIPHERAL NERVES

Oligodendrocytes enclose nerves of the CNS

86
Q

What is a neuronal synapse

A

neurons form contact sites with other neurons

permind UNIDIRECTIONAL chemical communication between cells

87
Q

Whats happens when an action potential is activated? (6 steps)

A
  1. It activates voltage-gated Ca+2 channels to open the presynaptic neurone.

Ca+2 cause secretion of ACETYLCHOLINE

  1. ACETYLCHOLINE binds and OPENS acetylcholine receptors, causing Na+ to enter and DEPOLARIZE Cell
  2. nearby voltage-gated Na+ channels open to further DEPOLARIZE and speak action potential in MUSCLE CELL
  3. plasma membrane voltage-gated Ca+2 channels open ALLOWING Ca+2 to enter cells
  4. Sarcoplasmic reticulum voltage gated Ca+2 channels open to release stored Ca+2 into cytosol
  5. VERY LARGE SPIKE IN CYTOSOLIC CA+2 CAUSES MUSCLES TO CONTRACT
88
Q

What are the 2 membrane transport proteins?

A

Channels

Carriers or permeases (Active and Passive)

89
Q

Are all membrane transport proteins MULTIPASS INTEGRAL membrane proteins?

A

YES

90
Q

What is the electrochemical gradient?

A

A net driving force that consist of concentration and ELECTRON POTENTIAL DIFFERENCE

91
Q

What can remove integral membrane proteins?

A

DETERGENTS

92
Q

What can remove peripheral membrane proteins?

A

CHANGES IN PH AND SALT

93
Q

What is a P-type pump?

A

Self-phosphorylate and transports ions

MAINTAIN ION GRADIENTS ACCROSS MEMBRANWS

94
Q

wHAT are membrane rafts?

A

PARTS OF MEMBRANE ENRICHED IN SPECIFIC LIPIDS: SATURATED LIPIDS AND CHOLESTORL

95
Q

What are two examples of membrane proteins?

A

Bacteriorhodopsin, and GLYCOPHORIN

96
Q

What is the partial repolarization stage?

A

Closing Na VOLTED gated channels

97
Q

What is complete repolarization stage?

A

Closing K+ VOLTED gated channels
Activity of the sodium-potassium pump
K+ leak channels

Cell Biology Midterm 1 (3 decks)

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