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Biology 🧬 > cells + membranes > Flashcards

cells + membranes Flashcards

1
Q

plasma membrane

A

regulates movement of substances in and out of the cell
has receptors

made of phospholipids and proteins (carriers and channels)
glycoproteins and lipids
cholesterol

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2
Q

nucleus

A

surrounded by nuclear envelope containing nuclear pores
contains nucleolus
contains chromosomes (DNA on histones)

controls cells activities by
controlling transcription
contains DNA which has instructions to make protiens
pores allow substances to move between nucleus and cytoplasm
nucleolus makes ribosomes

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3
Q

mitochondria

A

double membrane (inner and outer)
inner membrane folded into cristae
inside is matrix
contains enzymes for respiration

site of aerobic respiration
where ATP released

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4
Q

chloroplast

A

found in plants and algae
double membrane

contains thylakoid membranes
stacked into grana
linked by lamellae (thin pieces of thylakoid membrane)
stroma - fluid (like cytoplasm)

site of photosynthesis
in stroma or grana

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5
Q

golgi apparatus and vesicles

A

fluid filled flattened sacs

processes and packages new lipids and proteins
makes lysosomes
makes vesicles

vesicles are fuid filled sacs in cytoplasm
stores lipids and proteins made by golgi
transports them out of cell

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6
Q

lysosomes

A

round surrounded by membrane
type of golgi apparatus

contains lysozymes
used to digest pathogens
break down worn out cell components

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7
Q

ribosomes

A

in cytoplasm or attached to RER

made of a small and large subunit
made of protein and rRNA
(no membrane)

site of proteinsynthesis

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8
Q

rough endoplasmic reticulum

A

fluid surrounded by membranes
has ribosomes on surface

folds and processes proteins
from ribosomes

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9
Q

smooth endoplasmic reticulum

A

same as RER but without ribosomes

synthesises and processes lipids

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10
Q

cell vacuole

A

in plant cells
membrane bound - tonoplast
in cytoplasm
contains sap

maintain pressure in cell to keep it rigid - no wilting

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11
Q

cell wall

A

rigid structure surround some
supports cells, keeps shape

plants and algae - cellulose
fungi - chitin
bacteria - murein

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12
Q

differences between prokaryotic and eukaryotic cells

A

DNA is circular not linear
DNA not is nucleus but free in cytoplasm
DNA not associated with proteins
have plasmids

have cell wall of murein

smaller ribosomes (70s)

no membrane bound organelles

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13
Q

structure of prokaryotic cells

A

plasma membrane
cell wall of murein (glycoprotein)

cytoplasm - no membrane bound organelles
just ribosomes (smaller)

plasmids - small loops of DNA
(not part of main circular DNA)

DNA free in cytoplasm
(no nucleus)
no histones (proteins)
circular

flagellum - makes cell move
capsule - made of smile to protect from attack

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14
Q

structure of a virus

A

acellular - not cells and not live
no plasma membrane
no cytoplasm
no ribosomes
survive and reproduce in host cells

core of genetic material (DNA or RNA)
capsid - protein coat round core
attachment proteins - stick out from capsid, allow to attach to host

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15
Q

cells to organs

A

tissues
a group of cells working together to perform a particular function

organs
different tissues working together

organ systems
organs working together to complete a function

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16
Q

how do prokaryotic cells replicate?

A

binary fission

  1. circular DNA and plasmids replicate
    (DNA once but plasmid many times)
  2. cell grows, DNA moves to opposite poles
  3. cytokenesis

= 2 daughter cells
one copy of DNA, variable number of plasmids

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17
Q

how do viruses replicate?

A

use attachment proteins to bind to complementary receptors in hosts

(different viruses have different attachment proteins, require different hosts, viruses only affect certain cells)

inject genetic material into host
uses hosts enzymes and ribosomes to replicate

18
Q

how to calculate magnification

A

size of image
over
size of real object

19
Q

optical microscopes

A

use light to form an image
low magnification - up to x1500
low resolution - 0.2 micrometres

20
Q

how to prepare a slide for an optical microscope

A

pipette small drop of water onto slide
use tweezer to place thin specimen
add a drop of stain
carefully lower cover slip, one side then the other to avoid air bubbles

21
Q

transmission electron microscopes

A

uses beam of electrons
transmitted through specimen
denser parts absorb more - darker

+ highest resolution - see internal organelles
- only used on thin specimins

22
Q

scanning electron microscopes

A

scan beam of electrons across specimen
knocks of electrons to form image

+ 3D
+ thick specimens
- lower resolution then TEMs

23
Q

light vs electron microscopes

A

electron requires vacuum
electron has more complex preparation
electron has higher magnification and resolution
electron requires dead specimens

(compared to optical)

24
Q

outline cell fractionation

A

homogenisation - breaking up cells
filtration - removing large pieces
utracentifugation - seperating organelles

25
Q

homogenisation

A

vibrating or grinding up cells

breaks up plasma membrane
releases organelles into solution

solution should be:
ice cold - reduce enzyme activity that break down organelles
isotonic - same water potential as organelles, stops damage from osmosis
buffer solution - maintain pH, prevent damage

26
Q

filtration

A

filtered through gauze
separate large debris
organelles pass through

27
Q

ultracentrifugation

A

used to separate organelles from solution made
pour in tube and put in centrifuge

  1. spin at low speed
    densest organelles flung to bottom
    eg nucleus
    = pellet
    rest of organelles stay suspended
    = supernatant
  2. supernatant drained of into another tube
    spun at higher speed
    densest organelles form pellet
    eg mitochondria
    (or chloroplasts then mitochondria in plant cells)

supernatant drained again
spun at faster speed
repeated to separate denser organelles

28
Q

how does temperature affect membrane permeability?

A

very cold, damages membrane = more permeable

lower temperature = less kintetic energy, less permeable, increases with temperature

0-45
- as temperatures increase, have more kinetic energy
- phospholipids more fluid, less closely packed = more permeable

above 45
- phospholipid bilayer melts, breaks down, more permeable
- water inside expands, more pressure on membrane
- proteins deform, cant control movement, more permeable

29
Q

fluid mosaic structure of a membrane

A

acts as a barrier between cell and environment
- controls which substances enter and leave, partially permeable

made of lipids, proteins and carbohydrates

phospholipids arrange in bilayer
fluid - constantly moving
mosaic - pattern of transport proteins

carbohydrates can join proteins and lipids = glycoproteins/lipids

30
Q

role of phospholipids in membrane

A

hydrophilic head
hydrophobic tails

centre = hydrophobic
doesn’t allow water soluble water stances though (eg ions)

31
Q

role of cholesterol in membrane

A

type of lipid

fit between phospholipids = more closely packed
less fluid and more rigid
= maintains shape and provide support

32
Q

what type of substances can move through the membrane

A

oxygen and CO2 - small so pass between phospholipids

non-polar/lipid soluble
- dissolve in hydrophobic bilayer

water soluble CAN’T
- due to hydrophobic tails

water can as small

33
Q

outline diffusion

A

simple - molecules diffuse directly through membrane

for larger or charged (polar):
FD - molecules diffuse through channel/carrier proteins

different proteins transport different molecules

carrier
- molecule binds to one side
- protein changes shape
- released on other

channel
- create pores for polar molecules

34
Q

factor affecting simple vs FD

A

simple:
- concentration gradient
- thickness of surface
- surface area (microvilli)

FD:
- concentration gradient
- number of channel/carrier proteins

35
Q

outline osmosis

A

movement of water from high to low water potential across partially permeable membrane

move directly across membrane, small molecules
more - means lower water potential (0=pure)

affected by:
water potential gradient
thickness of surface
surface area

36
Q

effects of osmosis on plant cells

A

placed in high water potential
- water enters by osmosis into vacuole
- creates pressure, plant cell turgid

lower water potential
- leaves by osmosis, vacuole shrinks
- pulls away from cell wall
(plasmolysis)

37
Q

effects of osmosis on animal cells

A

lower water potential
- water leaves, cells shrivels

high water potential
- water enters
- cells bursts

has no cell wall to support it (unlike plant)

38
Q

outline active transport

A

movement of molecules against gradient using ATP through carrier proteins

molecule binds to carrier
protein changes shape
released on other side

ATP binds and it hydrolysed
= ADP and Pi = energy

affected by:
- number of carrier proteins
- rate of respiration = ATP produced
- speed of individual carriers

39
Q

outline co-transport

A

concentration gradient of one molecule used to move another against its own
- through co-transporters

eg absorption of glucose with sodium in ileum

40
Q

co-transport of glucose

A

Na+ actively transported out of ileum epithelial cells into blood
by sodium potassium pump
= higher concentration of Na+ in lumen then epithelial cell

Na+ diffuse from lumen into epithelial
though co-transporter proteins
= glucose transported with sodium

increase concentration of glucose inside epithelial cells = diffuses into blood

Biology 🧬 (23 decks)

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