Exam 2 of Cell Bio (ch 11, 12,15,9)

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Cell membrane is

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Biology

100 Terms

1

Cell membrane is

semi-permeable, forms selective barriers, and allows cells to maintain their own aqueous environment

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2

Do both eukaryotes and prokaryotes have cell membranes?

YESSSS

Eukaryotes have INTERNAL membranes as well though

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3

What is the cell membrane made of?

Phospholipid bilayer and proteins

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4

Phosphatidylcholine

common phospholipid in membrane; amiphatic

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5

Unsaturated phospholipids

KINKY = more fluid (less packed)

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6

Saturated phospholipids

Straight = less fluid (packed/rigid af)

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7

Purpose of phospholipid bilayers in the membrane

form stable compartments (polar on outside, nonpolar on inside)

Allows for membrane fluidity

Forms a CLOSED system of the cell

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8

Cholesterol

major component of membranes; rigid ring REDUCES membrane flexibility/fluidity

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9

Organelle membranes have 2 sides:

cytosolic (outside) and internal side (lumen)

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10

Transporter proteins

move phospholipids around in membranes

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11

Membrane assembly in ER

Phospholipid synthesis adds to cytosolic side of bilayer (UNEVEN)

Scramblase transfers phospholipids RANDOMLY to make growth even

Bilayer growth is SYMMETRIC

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12

Membrane addition in golgi

NOT random

Phospholipid compositions are different on lumen side vs cytosolic side (distinct sides)

Flippase causes bilayer to be ASYMMETRIC

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13

Functions of membrane proteins

receive information

Import and export small molecules

Movement and expansion

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14

Types of membrane proteins

Transporters/channels

Anchors (adhere cell)

Receptors

Enzymes

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15

Membrane proteins associate differently with membrane due to

amino acid side chains

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16

Types of membrane protein associations

Transmembrane (span membrane)

Monolayer-associated (attach to 1 side of membrane)

Lipid Linked (linked to membrane via lipids)

Protein attached (proteins anchor proteins to membrane)

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17

Transmembrane proteins

typically form a pore (hydrophobic on outside facing bilayer and hydrophilic on inside to make a tunnel for molecules to come into cell)

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18

protein stabilization in lipid bilayer is due to

protein-protein interactions:

-Cell cortex barriers

-cell to cell adhesion

-extracellular matrix

-diffusion (tight junctions)

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19

proteins can be regionally restricted by

tight junctions

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20

tight junctions

pinch and hold cell to restrict protein movement

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21

eukaryotic cells have membrane modifications (carbohydrate) that aid in

cell signaling

cell recognition

cell to cell association

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22

Types of membranes in cells

Bilayer (cell membrane) or intracellular membranes

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23

Solutes cross membrane based on

size, charge, and solubility

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24

Na+ and Cl- are higher (inside/outside) cell?

OUTSIDE

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25

K+ and anions are higher (inside/outside) cell?

INSIDE

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26

Small nonpolar molecules (hormones, O2, steroids) pass through membrane

easily

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27

Small uncharged polar molecules (H2O) pass through membrane

fairly easily

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28

Larger uncharged polar molecules (amino acids, nucleotides) pass through membrane

not easily

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29

Ions pass through membrane

not easily- usually require help

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30

Simple diffusion

movement of solutes from high conc → low conc (no energy)

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31

channels

movement of solutes from high conc → low conc (no energy- passive trasnport)

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32

transporters

movement of solutes from high conc → low conc (no energy-passive transport )

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33

Pumps

movement of solutes from low conc → high conc (energy- ACTIVE transport)

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34

Inside of cell is (neg/pos)?

NEGATIVE

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35

Outside of cell is (neg/pos)?

POSITIVE

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36

Sodium/Potassium pump

requires energy; pumps 3 Na+ out of cell and 2 K+ in to cell

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Ouabain

inhibits Na/K pump by preventing K+ from binding

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38

Symport

moves molecules in same direction (glucose-Na)

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39

antiport

moves molecules in different directions (Na/K pump)

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40

Uniport

moves 1 solute down its concentration gradient

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41

Glucose-Na+ symport

moves Na+ and glucose into cell

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42

Purpose of membrane bound organelles in eukaryotes

-establish compartments within cell

-compartments allow for specialized functions

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43

Double membrane organelles in eukaryotes

nucleus, mitochondria,

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44

How might nucleus double membrane have formed?

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45

Protein sorting purpose

proteins are transported to their appropriate location(s)

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46

Types of protein sorting

nuclear, across membranes, vesicles

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47

Nuclear sorting

requires energy; protein remains folded

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Across membrane sorting

requires energy; protein is unfolded

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49

vesicles sorting

requires energy; protein remains folded

-pass through nuclear pore

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50

Purpose of signal sequences

determine where protein is transported to

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no signal sequence

protein stays in cytosol

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is signal sequence removed at end?

yes- once protein reaches final destination

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53

Protein translocators

transport proteins across membranes

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54

Nuclear pore structure

have disordered regions that form a mesh

-large molecules cannot pass easily, but small molecules can

-large molecules require receptors and energy (GTP) to cross

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55

Nuclear localization signal

directs protein from cytosol to nucleus (signal sequence)

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How receptors work in nuclear pore

receptors bind target protein

protein links to nuclear pore fibrils

protein crosses pore

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57

How do proteins enter mitochondria?

series of recognition interactions:

-signal sequence on protein binds to receptor on mitochondria surface

-protein translocator helps protein cross outer membrane (protein is unfolded)

-protein translocator helps protein cross inner membrane (unfolded)

-cleave signal sequence

-chaperone proteins help protein refold

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58

How do proteins enter ER?

-Signal recognition proteins (SRP) bind to ribosome/ER complex

-SRP receptor recognizes SRPs

-translocator proteins bring protein(s) into ER

-Translation occurs in ER

-Transfer polypeptide across bilayer

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59

How do vesicles work?

They have phospholipid bilayers, so they can FUSE with plasma membranes on either side

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60

Endocytosis

bring things in

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Exocytosis

take things out

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How can proteins be modified in ER?

Sugar monomers add to amino acid of protein

-aid in recognition, protection, and/or holding

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63

What happens if a protein is misfolded?

try to fix it or degrade it

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64

Purpose of golgi?

final modifications to proteins and ship proteins off to their location(s)

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65

Two main exocytosis pathways in golgi

constitutive secretion and regulated secretion

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constitutive secretion

UNREGULATED exocytosis; always happening

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regulated secretion

REGULATED exocytosis; needs a signal in order for exocytosis to begin

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68

Endocytic

plasma membrane pinches inside

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69

Endomembrane system

package, label, and ship proteins; ER, Golgi, peroxisomes, lysosomes, endosomes

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70

Endosomes have 3 pathways

recycling, degradation, and transcytosis

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71

recycling

early endosomes return to membrane

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72

degradation

endosomes travel to lysosome to be degraded

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transcytosis

endosomes move to other area of membrane

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74

Endocytic pathways (do/do not) require receptor mediation

DO

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75

Purpose of lysosomes

degrade material via enzymatic digestion

-acidic (high H conc) due to H+ pump

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What happens to degraded materials?

transported out to cytosol

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77

3 ways lysosomes receive content

phagocytosis, endocytosis, and autophagy

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78

phagocytosis

eating

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autophagy

old organelles are sent to lysosome and recycled back to cell (recycles parts of self)

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80

Ways that genetic variation is generated?

Mutation within gene

Mutation in regulatory DNA

Gene duplication and divergence

Exon Shuffling

Transposition

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81

Exon shuffling

moving exons around within 2 different genes `

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transposition

move portion of gene and insert it into new gene

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83

mutations can be

neutral

beneficial

harmful

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84

horizontal transfer

lateral gene transfer between organisms

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85

germ line cell

gametes

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86

heritable mutations are exchanged via

germ-line cells

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87

transposon

chromosomal segment that can undergo transposition

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88

transposase enzyme

enzyme that binds to transposon to catalyze its movement to another part of genome

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89

~50% of human genome

mobile gene elements

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90

effects of exon rearrangement during transposition?

impacts coding for proteins and gene expression

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91

two major retrotransposon groups in humans

L1 elements and Alu sequences

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92

Similarities in retrotransposon groups

have RNA intermediate

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93

reverse transcriptase

RNA → DNA

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94

what do transposons and retrotransposons have in common with viruses?

Overtake cell machinery to make copies

Can have DNA or RNA genomes

Can impact eukaryotes and prokaryotes

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95

Retrovirus

RNA virus that utilizes reverse transcriptase

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96

Exons

stay

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97

Introns

spliced out

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98

Receptor for SARS-CoV-2

ACE2

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99

Primary entry points for COVID19

endosomal or cell surface

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100

Glycocalyx

physical barrier around cell; protects cell by preventing viruses from binding to it

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