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MCAT Prep > U7: F2 Cells > Flashcards

U7: F2 Cells Flashcards

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1
Q

main building block of cell membranes

A

phospholipids

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2
Q

components of phospholipids

A
  1. phosphate head
  2. glycerol backbone (holds fatty acid tails to phosphate heads)
  3. fatty acid tails
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3
Q

the head of a phospholipid is

A

hydrophilic

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4
Q

the tail of a phospholipid is

A

hydrophobic

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5
Q

amphipathic means

A

molecule has a hydrophilic and hydrophobic part

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6
Q

the inside of the phospholipid bilayer is

A

hydrophobic

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7
Q

what can pass through the cell membrane?

A

small, nonpolar molecules pass quickly through passive diffusion (gases)
small, polar molecules pass through slowly (water, ethanol)
large, nonpolar molecules pass through slowly (benzene)

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8
Q

what kinds of things do not pass through the cell membrane?

A

large, polar molecules (like glucose)
charged molecules (Na+, Cl-, amino acids)

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9
Q

which conformation presents more kinks in the phospholipid membrane?

A

cis

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10
Q

what 3 components make up the cell membrane?

A

phosopholipids, cholesterol, and proteins

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11
Q

what makes cholesterol relatively stable?

A

multiple rings in the structure

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12
Q

what is cholesterol’s role in the cell membrane relative to temperature?

A

when temperature is low - cholesterol helps increase fluidity
when temperature is high - cholesterol helps reduce fluidity

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13
Q

what forms do proteins take in the cell membrane?

A

integral membrane proteins (embedded in cell membrane)
peripheral proteins (sit on top of membrane)

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14
Q

what are the roles that proteins serve in the cell membrane?

A

can act as receptors or help transport molecules

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15
Q

what molecule binds lipids or proteins?

A

carbohydrates
use the prefix glyco- to signify this (glycoproteins or glycolipids)

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16
Q

fluid mosaic model

A

top view of the cell membrane that looks like a mosaic
called fluid because proteins and phospholipids can move around

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17
Q

_____ comprise 75% of the cell membrane’s mass

A

proteins

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18
Q

lipid bound protein

A

protein embedded in the intermembrane space and do not serve much of a purpose

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19
Q

channel proteins

A

allow molecules, like ions, to pass into the cell without using any energy
ions flow DOWN concentration gradient (high to low)

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20
Q

carrier proteins

A

carries substances into or out of the cell
can go AGAINST concentration gradient
uses energy/ATP

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21
Q

glycoproteins are for

A

signaling (allows cells to recognize other cells)

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22
Q

what 3 factors affect membrane fluidity?

A
  1. temperature
  2. cholesterol
  3. unsaturated vs saturated fatty acids
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23
Q

fluidity of the membrane at low vs high temperature

A

low temp = low fluidity (phospholipids crystallized and packed)
high temp = high fluidity (phospholipids have gaps)

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24
Q

how does cholesterol affect fluidity at high and low temperatures?

A

at low temperature, it inserts itself to increase distance between phospholipids to increase fluidity
at high temperature, it inserts itself to attract phospholipids and decrease fluidity

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25
Q

saturated vs unsaturated fatty acids effects on cell membrane fluidity

A

saturated (single bonds) – lower fluidity (neat and tight)
unsaturated (double bonds) – higher fluidity (bent nature causes distance between phospholipids)

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26
Q

transbilayer diffusion

A

phospholipid on outer leaflet moves to inner leaflet or vice versa
uncatalyzed, slow

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27
Q

lateral diffusion

A

phospholipid moves side to side
happens fast and often, uncatalyzed

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28
Q

catalyzed movement of phospholipids

A

both use ATP
flippase - flips from outer leaflet to the inside using protein catalyst called flippase
floppase - flips from inner leaflet to outter leaflet
scramblase (doesnt require ATP) - flips one to the inside and one to the outside at the same time quickly

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29
Q

potassium has a large concentration _______ the cell whereas sodium has a large concentration _______ the cell

A

inside; outside

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30
Q

primary active transport

A

directly uses ATP for energy to transport molecules

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31
Q

symport

A

both molecules move in the same direction into the cell

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32
Q

antiport

A

molecules move in different directions into and out of the cell

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33
Q

secondary active transport

A

energy is used indirectly to transport molecules into the cell (uses gradient already set up)

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34
Q

vesicle

A

small pocket of cell membrane that surrounds a molecule for transport

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35
Q

endocytosis

A

the ingestion of large particles and uptake of fluids or macromolecules in small vesicles
uses a lot of energy

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36
Q

exocytosis

A

a process by which the contents of a cell vacuole are released to the exterior through fusion of the vacuole membrane with the cell membrane

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37
Q

types of passive transport

A

diffusion
osmosis
facilitated diffusion
filtration

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38
Q

facilitated diffusion

A

protein channel binds target molecule and changes conformation to allow molecule inside the cell without an input of energy

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39
Q

solvent vs solute

A

solvent is what does the dissolving
solute is what is being dissolved

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40
Q

diffusion

A

spreading of molecules from high concentration areas to low concentration areas

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41
Q

hypertonic solution

A

more solute than solvent

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42
Q

hypotonic solution

A

more solvent than solute

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43
Q

osmosis

A

water as a solvent diffusing through a membrane from high concentration of water to low concentration of water

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44
Q

in exocytosis, what does the vesicle do?

A

merge with the cell membrane to release its contents

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45
Q

what molecules use exocytosis a lot?

A

neurotransmitters

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46
Q

phagocytosis

A

process where a cell binds to the item it wants to engulf on the cell surface and draws it inward while engulfing it

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47
Q

phagocytosis often happens in what context?

A

when immune cells are trying to destroy something like a virus or an infected cell

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48
Q

what are 4 common cell surface receptors that phagocytize?

A

opsonin receptors
scavenger receptors
toll like receptors
antibodies

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49
Q

opsonin receptors

A

used to bind bacteria or particles coated with immunoglobulin G antibodies by the immune system

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50
Q

scavenger receptors

A

bind to molecules produced by bacteria by recognizing the extracellular matrix of proteins that surround bacteria

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51
Q

toll-like receptors

A

bind to specific molecules produced by bacteria by binding to a bacterial pathogen to recognize bacteria and activate an immune response

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52
Q

antibodies

A

molecules that bind to specific antigens - molecules that act like a pathogen warning because they help alert the immune system

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53
Q

steps of phagocytosis (simple)

A
  1. cell and virus come into contact with each other (accident, chemotaxis, cytokines)
  2. virus binds to surface receptors on macrophage
  3. use pseudopods to surround particle and enclose it in membrane
  4. surrounded virus is enclosed in bubble like structure called phagosome in the cytoplasm
  5. phagosome fuses with lysosome to become phagolysosome (breaks down virus)
  6. phagolysosome lowers pH to break down virus
  7. once contents have neutralized, phagolysosome forms residual body that contains waster products and discharges it from the cell
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54
Q

K+ inside (and outside) the cell are bound to

A

anions to neutralize the cell
(like proteins or Cl-)

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55
Q

what drives potassium out of the cell? what drives potassium into the cell?

A

out of the cell: concentration gradient
into the cell: membrane potential created when K+ leaves

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56
Q

when potassium moves out of the cell, what happens on the inside of the cell?

A

the anions are left behind and creates a negative charge inside the cell

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57
Q

what is the equilibrium potential for K+?

A

point at which K in = K out
~ -92 mV

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58
Q

tight junctions

A

connect cells with an impermeable layer
bladder, intestines, kidneys

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59
Q

desmosomes

A

connections that hold two cells together via the cytoskeleton but there is a space for ions and water to flow inbetween cells
intestines, skin

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60
Q

gap junction

A

two cells are connected by a tube like structure
allow ions and water to pass from cell to cell, also transmits action potentials
cardiac muscle and neurons

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61
Q

membrane receptors

A

integral protein that communicates with the outside environment

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62
Q

what kind of receptors do neurons use?

A

ligand gated ion channels

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63
Q

ligand gated ion channels

A

transmembrane ion channels that open or close in response to binding of a ligand
allosteric binding

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64
Q

what comprises the largest known class of membrane receptors?

A

G Protein coupled receptors (GPCR)

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65
Q

GPCR’s have how many alpha helices?

A

7 transmembrane alpha helices

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66
Q

G protein

A

able to bind GTP and GDP, important for GPCR

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67
Q

all G proteins are

A

heterotrimeric (3 subunits)

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68
Q

subunits of G-protein

A

alpha, beta, gamma

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69
Q

what subunits of the g protein are attached to the cell membrane and how?

A

lipid anchors, alpha and gamma

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70
Q

GPCRs are inactive when

A

GDP is bound to the alpha subunit

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71
Q

the conformational change after ligand binding of GPCR causes the alpha subunit to

A

be attached to GTP instead of GDP, and separate itself from the other subunits

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72
Q

steps of GPCR ligand binding

A
  1. ligand binds to GPCR
  2. GPCR undergoes conformational change
  3. alpha subunit exchanges GDP for GTP
  4. alpha subunit dissociates and regulates target proteins
  5. target protein relay signal via 2nd messenger
  6. GTP hydrolyzed to GDP
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73
Q

example of GPCR in the body

A

epinepherine binds to GPCR (adrenergic receptor)
alpha subunit regulates adenylate cyclase, and turn ATP to cAMP
cAMP is the second messenger that increases heart rate, dilates blood vessels, and degrades glycogen to glucose

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74
Q

enzyme linked receptor

A

catalytic receptors
binding of a ligand triggers enzymatic activity of the receptor

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75
Q

what is a common example of an enzyme linked receptor

A

receptor tyrosine kinases (RTKs)

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76
Q

receptor tyrosine kinases

A

tyrosine is on the intracellular enzymatic portion
kinase transfers phosphate groups from ATP to intracellular proteins to activate them

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77
Q

RTKs occur

A

in pairs

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78
Q

after the ligand binds to RTKs,

A

the RTKs associate to form a cross-linked dimer

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79
Q

what happens when the cross-linked dimer is formed?

A

the tyrosines are phosphorylated because the association triggers kinase activity
cross-phosphorylation happens

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80
Q

after cross phosphorylation, what happens?

A

different proteins can come and attach themselves to the enzymatic portion of the receptor (intracellular)

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81
Q

the binding of proteins to RTKs can lead to

A

signal transduction and regulate gene transcription

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82
Q

RTKs are mostly known for

A

binding growth factors for cells

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83
Q

if someone’s RTKs are dysfunctional, what can occur?

A

cell growth can be unregulated and lead to cancer or not grow at all

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84
Q

RTKs signal usually travels to the

A

nucleus

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85
Q

What are the defining characteristics of a eukaryotic cell vs a prokaryotic cell?

A

Eukaryotic cells are compartmentalised, contain organelles (membrane bound), have a nucleus, and divide by mitosis

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86
Q

How do prokaryotes replicate?

A

Binary fission (make two copies of everything in the cell and just divide into two)

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87
Q

Mitochondria

A

Organelle where cellular respiration occurs and energy is created

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88
Q

Endoplasmic reticulum

A

Continuous Folded compartment where protein synthesis occurs
mRNA is translated at the E.R.

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89
Q

Endoplasmic reticulum

A

Continuous Folded compartment where protein synthesis occurs
mRNA is translated at the E.R.

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90
Q

Golgi apparatus

A

Sends proteins to other parts of the cell (like secretion or to another organelle)

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91
Q

Lysosome

A

Environment inside lysosome is ve **

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92
Q

Peroxisome

A

Organelle that reduces reactive oxygen species into nontoxic forms

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93
Q

Where do proteins and mRNA enter or exit the nucleus?

A

Nuclear pores

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94
Q

Nucleolus

A

Center of the nucleus that contains very densely packed DNA where ribosome assembly occurs
Where ribosomal rna is assembled into a ribosome which is transported to the cytoplasm

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95
Q

Nucleolus

A

Center of the nucleus that contains very densely packed DNA where ribosome assembly occurs
Where ribosomal rna is assembled into a ribosome which is transported to the cytoplasm

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96
Q

The outer membrane of the nucleus is continuous with

A

The membranes of the endoplasmic reticulum (share interior space)

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97
Q

The outer membrane of the nucleus is continuous with

A

The membranes of the endoplasmic reticulum (share interior space)

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98
Q

Nuclear envelope

A

Refers to the combination of inner and outer membranes and nuclear pores that encloses the nucleus

99
Q

Mitochondrial membranes

A

Outer membrane (permeable to smaller molecules)
Inner membrane (not permeable to small molecules
- includes lots of folds called Christa connected by Cristae junctions

100
Q

The matrix of the mitochondria is located

A

Inside the inner membrane

101
Q

Where does glycolysis occur?

A

Cytoplasm

102
Q

Where does the PDC occur?

A

In the matrix
Pyruvate is converted to acetyl CoA

103
Q

Where does the Krebs cycle occur? What about the ΕΤC?

A

Matrix
On the inner membrane

104
Q

order of enzymes in the electron transport chain

A

NADH dehydrogenase
cytochrome Q (succinate dehydrogenase for FADH2)
cytochrome reductase
cytochrome C
cytochrome oxidase

105
Q

while the electron transport chain is transferring electrons, what is happening at the same time?

A

ATP synthase funnels H+ into the cell to create concentration gradient while simultaneously pushing ADP and P together in an axel way

106
Q

what is the main difference between the smooth and rough endoplasmic reticulum?

A

the rough ER has ribosomes, but the smooth does not

107
Q

rough endoplasmic reticulum role(s)

A

site of protein synthesis

108
Q

smooth endoplasmic reticulum role(s)

A

synthesizes lipids (cell membrane, steroids)
metabolizes carbohydrates
detoxifying drugs

109
Q

what is the difference between proteins translated in the cytoplasm vs the rough ER?

A

cytoplasm: end in the nucleus, peroxisomes, cytoplasm, or nucleus
RER: secreted, become integral proteins in the cell membrane, end in ER, golgi apparatus, or lysosomes

110
Q

post translational modifications happen in

A

the rough ER

111
Q

secretory pathway

A

molecules that enter this pathway have a signal sequence detected in translation so that it gets pushed to the rough ER
goes from the ER-golgi apparatus to the lysosome or cell membrane

112
Q

golgi apparatus role(s)

A

modifies proteins made in the RER
sorts and sends proteins to proper destination
synthesizes certain macromolecules for secretion

113
Q

layers of the golgi apparatus

A

cis-stack (closest to ER)
medial stack
trans stack (furthest from ER)

114
Q

where can proteins that use the secretory pathway end up?

A

in the lysosome (for recycling and breakdown)
the cell membrane for secretion or integration

115
Q

lysosome role(s)

A

digest various molecules and substances via autophagy and crinophagy

116
Q

autophagy

A

“self-eating”
lysosome digests molecules that part of the cell itself or other cells
ex: organelles that are no longer functional, macrophages of immune system

117
Q

crinophagy

A

lysosome digests excess secretory products
ex: extra hormones that need to be broken down

118
Q

after the lysosome breaks down molecules, what happens?

A

it releases the contents (building blocks/most basic parts) into the cytoplasm for reuse

119
Q

what are the enzymes in the lysosomes?

A

acid hydrolases
(require acidic environment to function)

120
Q

what is the environment inside the lysosome like? why?

A

acidic (~ 5)
safety mechanism for the cell - if it were to burst and the acid hydrolases escaped, the cell is about pH 7.2 so they will not function and the organelles will not get eaten

121
Q

peroxisomes role(s)

A

lipid breakdown, detoxification
**protect cell from damage of peroxides - contains catalase which breaks down hydrogen peroxide into water and oxygen

122
Q

what types of animal tissues are made from eukaryotic cells?

A

epithelial
connective
muscle
nervous

123
Q

epithelial tissue

A

inner and outer lining
ex: outer layer of skin, outer and inner layer of organs, lines inside of cavities

124
Q

endocrine and exocrine glands are made of

A

epithelial tissue

125
Q

exocrine glands release their substances where?

A

directly to the target organ

126
Q

endocrine glands release their substances where?

A

directly into the bloodstream, like hormones

127
Q

forms of epithelial tissue

A

simple (one layer)
stratified (2+ layers)

128
Q

where can you find simple epithelium?

A

places where substances need to diffuse from different places
ex: alveoli of the lungs to diffuse O2 and CO2

129
Q

where can you find stratified epithelium?

A

in places that need to resist chemical or mechanical stress
ex: esophagus (acts as protective layer)

130
Q

epithelial cells are attached to

A

basement membrane (made of fibers, like collagen)

131
Q

is epithelial tissue vascular or avascular?

A

avascular

132
Q

how do epithelial tissues get their nutrients?

A

via the basement membrane, which is semi-permeable

133
Q

endothelium

A

epithelial lining of tissues like blood vessels and lymphatic vessels

134
Q

connective tissues role(s)

A

support tissues
connects tissues
separates different tissues from each other

135
Q

types of connective tissues

A

areolar
adipose
fibrous
blood
osseous
hyaline cartilage

136
Q

examples of connective tissues

A

bone, cartilage, blood, lymph, adipose, membranes covering the brain and spinal cord

137
Q

what are the characteristics of connective tissues?

A

cells, ground substance, fibers
matrix = ground substance + fibers

138
Q

areolar tissue

A

binds different tissues together
provides flexibility and cushioning

139
Q

adipose tissue

A

fat tissue
provides cusioning, stores energy
DOES NOT CONTAIN FIBERS

140
Q

fibrous connective tissue

A

strong tissue that provides support and shock absorption for bones and organs
found in dermis, tendons, and ligaments

141
Q

blood

A

no fibers
matrix = plasma

142
Q

osseous tissue

A

bone tissue
osteocytes = cells
matrix = bone mineral / hydroxyapatite

143
Q

hyaline cartilage

A

chondrocytes = cells
found in surfaces of joints

144
Q

cytoskeleton role(s)

A

provides structural support
helps with movement
helps with transport of substances within the cell

145
Q

the cytoskeleton is made of

A

microtubules, intermediate filaments, and microfilaments
(all made of protein)

146
Q

microtubules

A

diameter of ~25nm
involved in mitotic spindle, make up cilia, make up flagella, help with transport of substances

147
Q

intermediate filaments

A

diameter of ~10nm
provide structural support to the cell and help resist mechanical stress to help cell retain shape
like mattress springs

148
Q

microfilaments

A

diameter ~7nm
help with movement of the entire cell from within (like cell division)

149
Q

what are microfilaments made of?

A

actin, which joins to become an actin polymer, which combine to form actin filaments

150
Q

how are microfilaments dynamic?

A

they can lengthen and shorten via actin polymerization and actin depolymerization, respectively

151
Q

what are intermediate filaments made of?

A

made of several different proteins that twist to form filaments

152
Q

what are microtubules made of?

A

alpha tubulin and beta tubulin dimers

153
Q

what are microtubules bound to?

A

microtubule organizing center (MToc)

154
Q

what are the different types of microtubule organizing centers?

A

centrosome
basal body

155
Q

centrosome

A

organelle found near nucleus of the cell that contains 2 centrioles (rods)

156
Q

centrioles are made up of

A

9 triplets

157
Q

how many microtubules are required to make a centriole?

A

27 (9x3)

158
Q

what are microtubules role in mitosis?

A

makes up mitotic spindle which connect to kinetichore fibers on the chromosomes
helps pull chromosomes apart to form 2 identical cells

159
Q

what are basal bodies?

A

the MToc for cells that have cilia or flagella

160
Q

what are basal bodies made of?

A

microtubules connected by nexin and dynein (use ATP)
- called the 9+2 arrangement because there are 9 pairs of microtubules surrounding 1 PAIR of microtubules

161
Q

important function of microtubules

A

form network to connect soma to synaptic terminal of a neuron

162
Q

what two proteins are found in neurons and help shuttle things down the microtubules?

A

kinesin and dynein

163
Q

what kinds of things are shuttled down the microtubule path of the neuron?

A

synaptic vesicles that contain neurotransmitters proteins
lipids
organelles

164
Q

kinesin and dynein can transport substances down the axon in which direction?

A

both directions

165
Q

abiogenesis

A

theory that life formed from spontaneous generation
disproved by discovery of binary fission

166
Q

cell theory major tenets

A

the cell is the basic unit of strucutre in life
all living organisms are composed of cells
all cells come from pre-existing cells

167
Q

what were the first organisms to appear on earth?

A

archaea

168
Q

types of extremophiles

A

thermophiles (heat)
halophiles (salt)
methanogens (swamp gas)

169
Q

flagellin

A

makes up flagella of a bacteria

170
Q

prokaryotes lack

A

membrane bound organelles (like nucleus or mitochondria)

171
Q

bacterial chromosomes are made of

A

circular double stranded DNA

172
Q

how do bacteria obtain nutrients?

A

from their enviroment using the flagella

173
Q

bacterial shapes and names

A

sphere = coccus
bacillus = oval
spirochete = squiggle

174
Q

the stain of bacteria is only located on

A

the outer layer of bacteria

175
Q

what is the difference between gram positive and gram negative bacteria?

A

gram positive stays purple because the peptidoglycan layer is much larger in gram positive so it stays purple when wiped

176
Q

steps of binary fission

A

origin of replication opens and replication begins
cell elongates & origins move towards cell ends as DNA is copied
septum forms down the middle
cell pinches in two

177
Q

differences between DNA replication in bacteria vs eukaryotes

A

bacteria does not form mitotic spindles and replication occurs at the same time as dna separation, unlike mitosis

178
Q

criteria for something to be “alive”

A
  1. maintain homeostasis
  2. different levels of organization
  3. reproduction
  4. growth
  5. use energy
  6. response to stimuli
  7. adapt to environment
179
Q

4 defining characteristics of viruses

A
  1. size - very small
  2. shape - capsid protein coat (can be icosahedral, helical, spherical)
  3. nucleic acid (can be single stranded DNA or double stranded RNA)
  4. type of host - obligate intracellular parasite (must utilize host cell to replicate)
180
Q

how do bacteriophages inject themselves into bacteria?

A

complex shape with a head, sheath, and tail (injects like a needle)

181
Q

how do viruses infect eukaryotic cells?

A

they utilize receptors on the eukaryotic cell membrane to trick them into letting them in via receptor mediated endocytosis

182
Q

why do some viral cells contain an envelope?

A

gives them extra shape to be able to fuse into the cell membrane and inject the virus
“direct fusion”

183
Q

3 ways that viruses inject themselves into cells

A
  1. bacteriophage injection
  2. no envelope: trick receptors into letting them in
  3. envelope: directly fuse with membrane
184
Q

lytic viral replication

A

DESTROYS cell
after virus infects host cell, virus replicates until cell breaks open to release virus into environment, and continues to create as many virus cells as possible

185
Q

lysogenic viral replication

A

(provirus) virus is repressed in host cell in a dormant phase, and waits for bacteria to replicate with it in there until not repressed, so bacteria excises viral dna, which is then able to replicate and proceed to lyse the cell and continue on

186
Q

retrovirus

A

enveloped ssRNA that contains 3 special proteins - reverse transcriptase, integrase, protease

187
Q

steps of retrovirus

A

insertion of retrovirus
uncoating of envelope
reverse transcriptase create dsDNA
integrase creates sticky ends (cuts off 3’ ends) and integrates viral DNA into nucleus of host cell
follows lysogenic pathway
protease cleaves to form mature viral cells

188
Q

what about retroviruses is dangerous?

A

they are regularly transcribed with other DNA and do not have a dormant phase

189
Q

subviral particles

A

smaller than virus
nonliving infectious agents
types: viroids and prions

190
Q

viroids

A

single strand of circular RNA
catalytic RNA - can self cleave to create more viroids
ex: hepatitis D

191
Q

prions

A

proteinaceous infectious particles
no genetic material, only made of proteins
made of beta sheets (normal proteins are made of alpha helix) = made of same proteins, different conformations
changes alpha helices to beta sheets

192
Q

what phase do cells usually spend most of their time in?

A

interphase (growing phase)
*except cancer cells

193
Q

what phase the cell actively divide?

A

mitosis

194
Q

stages of interphase

A

G1(or to G0)
S
G2

195
Q

G1 phase

A

growth phase that is the longest phase
most of cell’s life
make organelles and proteins

196
Q

G0 phase

A

branches off of G1 and is a phase where there is no more cell division
example: neurons

197
Q

S phase

A

synthesis phase
dna replication where we go from 23 pairs to 36 pairs of chromosomes

198
Q

G2 phase

A

growth phase where microtubules are made and the cell is prepared for mitosis

199
Q

mitosis

A

process by which the cell divides
final stage of the cell cycle
products enter G1 phase and continue through cycle again or enter G0 phase

200
Q

checkpoints of the cell cycle

A

between G1 & S
between G2 & M

201
Q

what proteins regulate the cell cycle?

A

cyclin-dependent kinases (+ P group to (in)activate enzymes)
cyclin

202
Q

what enzyme is always present in the cell?

A

CDKs (cyclin dependent kinases), but they are inactive

203
Q

what is the role of cyclin in the cell?

A

specific cyclins are made at specific times in the cell cycle and this will ACTIVATE CDKs

204
Q

what cyclins are made in the G1 phase?

A

cyclinD
cyclinE

205
Q

what binds with cyclin D and cyclin E? where does this occur?

A

CDK2-E
CDK4-D
occurs at first checkpoint

206
Q

what occurs at the first checkpoint?

A

CDK2-E and CDK4-D are formed
CDK4-D phosphorylates Rb protein to allow DNA replication to occur (Rb inhibits DNA replication)

207
Q

what cyclin is made in the S phase? what does this bind to?

A

cyclin A
CDK2-A

208
Q

what is CDK2-A responsible for?

A

activating DNA replication in the S phase

209
Q

what cyclin is made in the G2 phase? what does it bind to? what is its purpose?

A

cyclin B
CDK1-B
activates mitosis

210
Q

p53

A

“guardian of the genome”
binds DNA directly to produce proteins that block cell cycle progression
ex: p21 which inhibits CDK

211
Q

Rb is produced from a

A

tumor suppressor gene

212
Q

what occurs if the tumor-suppressor genes malfunction?

A

cancer

213
Q

human diploid and human haploid

A

diploid = 46
haploid = 23

214
Q

phases of mitosis

A

interphase
prophase
metaphase
anaphase
telophase
cytokinesis

215
Q

interphase

A

formation of bivalent chromosome - dna strand of chromosome is copied and attached to the original strand at the centromere

216
Q

prophase

A

centrosomes move to opposite ends
bivalent chromosomes pack into tight packages
mitotic spindle is formed
nuclear envelope dissolves

217
Q

metaphase

A

each chromosome lines up in a single file line at the center of the cell
mitotic spindles attach to each chromatid

218
Q

anaphase

A

mitotic spindles pry each chromatid apart and drag them to opposite ends of the cell

219
Q

telophase

A

membranes form around the 2 new groups of chromosomes and the spindles are disassembled
at this point: there are 2 nuclear membranous groups of 46 chromosomes

220
Q

cytokinesis

A

creates two clones of original cell
each with 46 monovalent chromosomes

221
Q

sister chromatids are attached at

A

the centromere

222
Q

what else is replicated in the S phase?

A

centrosome

223
Q

where are centrioles located?

A

in the centrosomes

224
Q

where do spindle fibers attach?

A

kinetochores

225
Q

what is the main difference between mitosis and meiosis?

A

mitosis produces 2 diploid cells (2n)
meiosis produces 4 haploid cells (n)
mitosis = somatic cells
meiosis = gametes (sex cells)

226
Q

germ cells can undergo

A

mitosis to produce more germ cells
meiosis to produce gametes

227
Q

phases of meiosis (overview)

A

meiosis I: homologous pairs separated
meiosis II: sister chromatids separated

228
Q

diploid number of germ cells

A

4

229
Q

in each round of meiosis division, what stages occur?

A

prophase
metaphase
anaphase
telophase

230
Q

prophase I

A

chromosomes condense and pair up with its homologue partner
crossing over occurs at this point

231
Q

what assists sister chromatids with crossing over of homologues?

A

synaptonemal complex

232
Q

chiasmata

A

cross shaped structure where homologues are linked after crossover

233
Q

metaphase I

A

homologue pairs line up at metaphase plate

234
Q

anaphase I

A

homologues separate to opposite ends of the cell
sister chromatids stay together

235
Q

telophase I

A

newly formed cells are haploid and each chromosome has 2 non-identical sister chromatids
nuclear membranes begin to form again
unraveling

236
Q

prophase II

A

starting cells are haploid cells from meiosis I
chromosomes condense

237
Q

metaphase II

A

chromosomes line up at metaphase plate

238
Q

anaphase II

A

sister chromatids separate to opposite ends of the cell

239
Q

telophase II

A

unraveling
newly forming gametes are haploid, with each chromosomes containing just one chromatid

240
Q

does meiosis always produce 4 gametes?

A

No
spermatogenesis usually generates 4 functional gametes
oogenesis usually only produces 1 functional egg cell because only 1 of the cells at the end of meiosis I proceed down egg cell pathway while the other becomes a polar body

241
Q

what are the ways that meiosis “mixes and matches” genes

A

crossing over and random orientation of homologue pairs

242
Q

what is a main difference between mitotic anaphase and meiosis anaphase I?

A

mitosis: sister chromatids are pulled apart
meiosis anaphase I: sister chromatids stay together, its the homologous PAIRS that get pulled apart

243
Q

what is different between anaphase I and anaphase II?

A

the sister chromatids SPLIT in anaphase II

MCAT Prep (5 decks)

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