Cell Membranes Flashcards

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1
Q

cell membrane

A

controls what goes in and out of the cell

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2
Q

phospholipid

A

phosphate head- negatively charged, polar, hydrophilic
glycerol molecule
2 fatty acid chains - no charge, non polar, hydrophobic

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3
Q

phospholipid bilayer

A

arranged with hydrophilic head on the outside and hydrophobic tails on the inside

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4
Q

water

A

polar molecule
partially positive- hydrogen
partially negative- oxygen

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5
Q

polar molecules

A

polar (charged) molecules like PL are attracted to water
they are soluble in water as they form h bonds with water
hydrophobic group together in water as they are non polar

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6
Q

non polar

A

hydrophobic - not charged
are not soluble in water because they are not attracted to water molecules + clump together
are soluble in non polar liquid eg oil will mix with more oil

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7
Q

PL bilayer functions

A

allows lipid soluble (non polar) molecules in and out of the cell
prevents water soluble (polar) molecules in and out of cell
makes membrane flexible

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8
Q

proteins

A

interspersed throughout membrane
span the membrane from one side to the other- transmembrane
on the inside (intrinsic) or the outside (extrinsic)

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9
Q

transmembrane protein

A

facilitated diffusion uses carrier and channel proteins
protein channels- have a hole/ channel all the way through to allow polar molecules (water soluble)

carrier proteins- span membrane and help transport ions or larger substances eg glucose + amino acids by changing shape

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10
Q

carrier proteins

A

some are involved in diffusion and do not require ATP to change shape

some are involved in active transport and require ATP to move molecules against conc gradient from low to high

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11
Q

glycoproteins and glycolipids

A

proteins/ lipids with branches of sugars attached
carbohydrate (sugar) portion extends to the outside of the cell

both- act as recognition sites
help cells attach/adhere together to form tissue
GP- acts as receptors to receive chemicals eg NT and hormones

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12
Q

cholesterol

A

found within PLB of eukaryotic cells, in cell surface membrane
provides stability to cell membrane as it prevents too much lateral movement of other molecules in membrane

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13
Q

permeability of PL

A

only small non polar molecules can diffuse through easily
they are soluble in non polar fatty acid tails

charged ions and polar molecules do not diffuse through easily as they are not soluble in fatty acid tails
polar molecules are only soluble in polar substances eg water
-transported using protein channels and carrier molecules

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14
Q

fluid mosaic model

A

fluid- individual phospholipid molecules can move so it is flexible
mosaic- proteins and phospholipids interspersed in the membrane vary in shape and size

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15
Q

active transport

A

requires ATP from aerobic respiration- mitochondria
uses carrier proteins- molecule attaches, protein changes shape, moves molecule across membrane and releases it on other side

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16
Q

co transport

A

type of carrier protein that bind two molecules at a time and the conc gradient of one molecule is used to move the other molecule against its conc gradient
eg in ileum cell

17
Q

water potential

A

more water= higher wp
pure water = high wp of 0
more solute= more negative wp
water moves down wp gradient by osmosis

18
Q

hypertonic

A

solution has high conc of solute and less water
lower wp
cells in hypertonic solution lose water and become plasmolyse

19
Q

hypotonic

A

solution has low conc of solute and more water
high wp
cells in hypotonic solution gain water and become turgid

20
Q

isotonic

A

solution same concentration of solute as that in a cell

21
Q

plant cells

A

lose water = flaccid
lose water and cell membrane pulls away from cell wall= plasmolyse
gain water = turgid

22
Q

animal cells

A

gain too much water + burst= lyse (swell)

lose too much water= shrink

23
Q

water movement

A

water cannot usually move through membrane as it is a dipole and is polar
can sometimes slip through small gaps
aquaporins- channel proteins for water

24
Q

root cells

A

adapted for absorption of water and mineral ions
specialised shape that increases surface area so rate of water uptake by osmosis is greater
thin walls so shorter diffusion pathway
permenent vacuole containing cell sap which ensures high wp gradient is maintained

25
Q

epithelial cells

A

microvilli- (folded sections of membrane) to increase surface area so rate of diffusion is greater
have lots of mitochondria to provide ATP for active transport of substances

26
Q

cell membranes adapted for rapid uptake

A

membrane folded increases surface area for faster diffusion
large number of protein channels/carriers for facilitated diffusion
large number of carrier proteins for active transport
large number of carrier/channel proteins for active transport