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chapter 1: cell biology Flashcards

(59 cards)

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1
Q

semi-permeable membrane

A

certain materials may cross, charged/large materials cant typically cross

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2
Q

selective (ref: membranes)

A

regulate materials that can cross

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3
Q

passive transport

A

movement of materials along concentration gradient (high to low concentration), as materials move down concentration gradient it doesnt require energy (atp hydrolysis)

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4
Q

3 main types passive transport

A

simple diffusion
osmosis
facilitated diffusion

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5
Q

active transport

A

movement of materials against concentration gradient (low to high concentration), as against gradient- requires ATP

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6
Q

two main types active transport

A

primary (direct)
secondary (indirect)

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7
Q

diffusion

A

net movement of molecules from region of high to low concentration

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8
Q

equilibrium by diffusion

A

directional movement of molecules (passive) and continues till molecules are evenly dispersed

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9
Q

diffusion in membranes

A

small non polar (lipophilic) molecules diffused freely across membranes

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10
Q

rate of diffusion affected by

A

temperature, molecular size, steepness of gradient

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11
Q

osmosis

A

net movement of water molecules across semi permeable membrane from region of low to high solute concentration (until equilibrium reached)

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12
Q

water = universal solvent

A

associates with + dissolves polar or charged molecules (solutes)

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13
Q

because solutes cannot cross a cell membrane unaided

A

water will move to equalise two solutions

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14
Q

at higher solute concentration

A

there are less free water molecules in solution as water = associated with the solute

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15
Q

osmolarity

A

measure of solute concentration as defined by n.o of osmoles of a solute per litre of solution (osmol/L)

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16
Q

solutions categories based on relative osmolarity

A

hypertonic, isotonic, hypotonic

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17
Q

hypertonic

A

higher relative osmolarity, high solute concentration: gains water

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18
Q

hypotonic

A

low relative osmolarity, low solute concentration: loses water

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19
Q

isotonic

A

same osmolarity, same solute concentration: no net water flow

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20
Q

facilitated diffusion

A

passive movement of molecules across membrane via membrane protein aid

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21
Q

facilitated diffusion used by

A

molecules unable to freely cross phospholipid bilayer (large molecules, polar molecules, ions), mediated by channel/carrier proteins

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22
Q

carrier protein

A

integral glycoproteins that bind solute +have conformational change to translocate solute across membrane

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22
Q

carrier protein binding

A

via attachment similar to enzyme-substrate

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23
Q

movement against concentration gradient (carrier protein)

Study These Flashcards
A

in presence of ATP, carrier proteins move against concentration gradient

24
which is faster transportation? carrier or channel proteins
channel
25
channel protein
integral lipoproteins containing pore via which ions may cross from one side of membrane to othwe
26
channel protein transport
ion selective and regulate passage og ions in response to stimuli
27
axons of nerve cells
transmit electrical impulses by translocating ions, creating voltage difference across membrane
28
at rest, sodium-potassium pump (ref:axons)
expels sodium ions from nerve cell, while potassium ions accumulated within
29
when neuron fires (ref:axons)
these ions swap locations via facilitated diffusion via sodium/potassium channels
30
potassium channels
integral proteins w hydrophilic inner pore via which potassium ions may be transported
31
potassium channel comprised of
four transmembrane sub units, while inner pore contains selectivity filter at narrowest region, restricting passage of alternative ions
32
depending on transmembrane voltage
potassium channels typically are voltage gated and cycle between open and closed formation
33
active transport
uses energy to move molecules against concentration gradient
34
energy (for active transport) generated by
1. direct hydrolysis ATP (primary active transport) 2. indirectly coupling transport w another molecule moving along its gradient (secondary)
35
active transport involves use of
carrier proteins (called protein pumps due to use of energy)
36
in active transport
1. specific solute binds to protein pump on one side of membrane 2. hydrolysis (to ADP + Pi) of ATP causes conformational change in protein pump 3. solute is translocated across membrane against gradient + released
37
at rest sodium potassium pump
expels sodium ions from nerve cell while potassium ions accumulate within
38
when neuron fires
sodium + potassium ions swap locations by faciltated diffusion by sodium/potassium channels
39
sodium potassium pump
integral protein exchanges 3 sodium ions (moves out of cell) with two potassium ions (into cell)
40
steps of sodium potassium pump
1. 3 sodium ion bind to intracellular site on S-P pump 2. phophate group transferred to pump via hydrolysis of ATP 3. pump conformational change, translocating sodium across membrane 4. conformational change exposes two potassium binding site on extracellular surface of pump 5. phosphate group released, causing pump to return to original state, translocating potassium across membrane completing ion exchange
41
vesicles
membranous containers that transport materials used in secretion
42
endoplasmic reticulum
membranous network responsible for synthesising secretory materials
43
smooth er
involved in lipid synthesis and plays role in carbohydrate metabolism
44
rough er
embedded w ribosomes and synthesises proteins for extracellular use
45
materials transported from er when
membrane bulges and buds to create vesicle surrounding material
46
golgi apparatus
vesicle (post er) transported to golgi apparatus and fuses to internal (cis) face of complex
47
material movement in golgi apparatus
materials move via vesicles from internal cis face to external trans face materials may be structurally modified in gogi apparatus materials sorted in golgi will either be secreted externally or transported to lysosome
48
plasma membrane
vesicles containing materials for extracellular use transported to plasma membrane, vesicle will fuse w cell membrane and materials expelled into extracellular fluid
49
materials sorted by golgi apparatus may be either
released immediately into extracellular fluid (constitutive secretion stored within intracellular vesicle for delayed release in response to cellular signal (regulatory secretion)
50
membrane in cell
is principally held together by weak hydrophobic associations between fatty acid tails of phospholipids (weak association = fluidity/flexibility) this allows breaking and reforming of bilayer allowing big materials to enter w/o having to cross membrane (active process- ATP)
51
Endocytosis
process by which large substances (or large amounts of small substances) enter cell w/o crossing membrane
52
What happens in endocytosis?
an invagination (=surface folds in on itself to form cavity) of the membrane forms a flask-like depression which envelopes extracellular material invagination sealed off to form intracellular vesicle containing material
53
two types of endocytosis
phagocytosis and pinocytosis
54
phagocytosis
the process by which solid substances are ingested (+usually transported to lysosome)
55
pinocytosis
process by which liquids/dissolved substances are ingested (allows faster entry via protein channels)
56
exocytosis
process where large substances (or large amounts of small substances) exit cell without crossing membrane
57
what happens in exocytosis
vesicles (typically from golgi) fuse w plasma membrane expelling contents to extracellular environment the process adds vesicular phospholipids to cell membrane, replacing those. lost when vesicles are formed in endocytosis
58
endocytosis vs exocytosis
endo: process where large substances/large amounts of small substances enter cell w/o crossing membrane exo: where large substances/large amounts of small substances exit cell w/o crossing membrane endo: enter exo: exit

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