3.2- Cells

Question 1

What do microscopes use to produce an image

Answer 1

waves

Question 2

what waves do the different microscopes use

Answer 2

optical - light waves
electron - electron beam

Question 3

define magnification

Answer 3

the ability to produce an enlarged image of an object

Question 4

define resolution

Answer 4

the ability to distinguish between 2 close points

Question 5

why do electron microscopes have a higher resolution

Answer 5

an electron beam has a shorter wavelength than a light wave (more likely to be deflected by small objects)

Question 6

how do transmission electron microscopes work (TEMs)

Answer 6

electromagnets focus beam of electrons transmitted through specimen
denser parts absorb more (look darker on image)

Question 7

advantages and disadvantages of TEMs

Answer 7

ADV - high resolution images, can see internal structure of organelles
DIS - only used on thin specimens

Question 8

how do scanning electron microscopes work (SEMs)

Answer 8

scan electron beam across specimen
knocks off electrons from specimen, gathered in cathode ray tube
forms an image

Question 9

advantages and disadvantages of SEMs

Answer 9

ADV - images show surface and can be 3D
can be used on thick specimens
DIS - lower reduction images than TEMs

Question 10

calculation for magnification

Answer 10

M = I/A
magnification = image size / real size

Question 11

how do you prepare a temporary mount of a specimen on a slide

Answer 11

pipettes small drop off water onto slide
use tweezers to place thin section of specimen on top of water
add stain
add cover slip - stand slip upright then carefully tilt and lower so it covers the specimen without any air bubbles

Question 12

what is the structure of the plasma membrane

Answer 12

made of lipids and protein
receptor molecules to respond to chemicals

Question 13

what is the function of the plasma membrane

Answer 13

regulates movement of substances

Question 14

what is the structure of the nucleus

Answer 14

surrounded by double membrane nuclear envelope - contains pores
chromosomes made from protein bound linear DNA
nucleolus

Question 15

function of nucleus

Answer 15

controls cell activity
instructions to make proteins
pores allow substances to move between nucleus and cytoplasm
nucleolus makes ribosomes

Question 16

structure of mitochondria

Answer 16

double membrane
inner is folded to form cristae
matrix containing respiration enzymes

Question 17

role of mitochondria

Answer 17

site of aerobic respiration

Question 18

structure of chloroplast

Answer 18

double membrane
contains thylakoid membranes
- thylakoid stacked form grana
grana linked by lamellae

Question 19

function of chloroplast

Answer 19

site of photosynthesis

Question 20

structure of golgi apparatus

Answer 20

fluid filled membrane bound flat sacs
vesicles are at the edge

Question 21

role of golgi apparatus

Answer 21

processes and packages new lipids and proteins
makes lysosomes

Question 22

structure of golgi vesicle

Answer 22

small fluid filled sac
surrounded by membrane

Question 23

role of vesicle

Answer 23

store lipids and proteins made by apparatus
transports out of cell

Question 24

structure of lysosome

Answer 24

round organelle
surrounded by membrane
no clear internal structure

Question 25

role of lysosomes

Answer 25

contain lysozymes used to digest invading cells or break down worn out components

Question 26

structure of ribosome

Answer 26

small organelle
free floating or attached to RER
made up of proteins and RNA

Question 27

role of ribosomes

Answer 27

protein synthesis

Question 28

structure of rough endoplasmic reticulum

Answer 28

membranes covered with ribosomes

Question 29

role of rough endoplasmic reticulum

Answer 29

fold and process proteins

Question 30

describe the process of cell fractionation

Answer 30

solution of cells in cold isotonic solution
homogenisation - break up plasma membrane
filtration - remove cell debris
ultracentrifugation - separates organelles

Question 31

order the organelles from lightest to heaviest

Answer 31

ribosomes
ER
lysosomes
mitochondria
nuclei

Question 32

how do bacteria divide

Answer 32

binary fission

Question 33

what is the cell surface membrane made of

Answer 33

phospholipid bilayer

Question 34

what is the function of the phospholipid bilayer

Answer 34

control entry / exit of lipid soluble substances
prevent water soluble substances from entry/exit
makes membrane flexible + self sealing

Question 35

function of proteins on the cell surface membrane

Answer 35

(on surface): mechanical support, act as cell receptors
(spanning): protein channels- allow water soluble ions to diffuse
carrier proteins- bind to ions, change shape, move molecules
help cells adhere

Question 36

function of cholesterol on the cell surface membrane

Answer 36

reduce lateral movement of other molecules
make membrane less fluid at high temp
prevent leakage of water/dissolved ions

Question 37

function of glycolipids

Answer 37

recognition sites
membrane stability
help form tissues

Question 38

function of glycoproteins on the cell surface membrane

Answer 38

recognition sites
help cells form tissues
cells recognise each other eg lymphocytes

Question 39

describe the fluid mosaic model

Answer 39

fluid - phospholipid molecules move freely so the shape is constantly changing
mosaic - proteins vary in shape and size across the cell surface

Question 40

define diffusion

Answer 40

the net movement of molecules from an area of high concentration to low concentration down a concentration gradient

Question 41

which molecules can move by simple diffusion

Answer 41

small
non polar

Question 42

which substances move by facilitated diffusion

Answer 42

large
polar