cells + membranes

Question 1

plasma membrane

Answer 1

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

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

Question 2

nucleus

Answer 2

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

Question 3

mitochondria

Answer 3

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

site of aerobic respiration
where ATP released

Question 4

chloroplast

Answer 4

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

Question 5

golgi apparatus and vesicles

Answer 5

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

Question 6

lysosomes

Answer 6

round surrounded by membrane
type of golgi apparatus

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

Question 7

ribosomes

Answer 7

in cytoplasm or attached to RER

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

site of proteinsynthesis

Question 8

rough endoplasmic reticulum

Answer 8

fluid surrounded by membranes
has ribosomes on surface

folds and processes proteins
from ribosomes

Question 9

smooth endoplasmic reticulum

Answer 9

same as RER but without ribosomes

synthesises and processes lipids

Question 10

cell vacuole

Answer 10

in plant cells
membrane bound - tonoplast
in cytoplasm
contains sap

maintain pressure in cell to keep it rigid - no wilting

Question 11

cell wall

Answer 11

rigid structure surround some
supports cells, keeps shape

plants and algae - cellulose
fungi - chitin
bacteria - murein

Question 12

differences between prokaryotic and eukaryotic cells

Answer 12

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

Question 13

structure of prokaryotic cells

Answer 13

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

Question 14

structure of a virus

Answer 14

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

Question 15

cells to organs

Answer 15

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

Question 16

how do prokaryotic cells replicate?

Answer 16

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

Question 17

how do viruses replicate?

Answer 17

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

Question 18

how to calculate magnification

Answer 18

size of image
over
size of real object

Question 19

optical microscopes

Answer 19

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

Question 20

how to prepare a slide for an optical microscope

Answer 20

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

Question 21

transmission electron microscopes

Answer 21

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

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

Question 22

scanning electron microscopes

Answer 22

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

+ 3D
+ thick specimens
- lower resolution then TEMs

Question 23

light vs electron microscopes

Answer 23

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

(compared to optical)

Question 24

outline cell fractionation

Answer 24

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

Question 25

homogenisation

Answer 25

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

Question 26

filtration

Answer 26

filtered through gauze separate large debris organelles pass through

Question 27

ultracentrifugation

Answer 27

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

Question 28

how does temperature affect membrane permeability?

Answer 28

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

Question 29

fluid mosaic structure of a membrane

Answer 29

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

Question 30

role of phospholipids in membrane

Answer 30

hydrophilic head hydrophobic tails centre = hydrophobic doesn't allow water soluble water stances though (eg ions)

Question 31

role of cholesterol in membrane

Answer 31

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

Question 32

what type of substances can move through the membrane

Answer 32

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

Question 33

outline diffusion

Answer 33

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

Question 34

factor affecting simple vs FD

Answer 34

simple: - concentration gradient - thickness of surface - surface area (microvilli) FD: - concentration gradient - number of channel/carrier proteins

Question 35

outline osmosis

Answer 35

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

Question 36

effects of osmosis on plant cells

Answer 36

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)

Question 37

effects of osmosis on animal cells

Answer 37

lower water potential - water leaves, cells shrivels high water potential - water enters - cells bursts has no cell wall to support it (unlike plant)

Question 38

outline active transport

Answer 38

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

Question 39

outline co-transport

Answer 39

concentration gradient of one molecule used to move another against its own - through co-transporters eg absorption of glucose with sodium in ileum

Question 40

co-transport of glucose

Answer 40

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