2.1.1 - Cell structure

Question 1

What is cell theory

Answer 1

The theory that all living organisms are made up of one or more cells and that cells only arise via the division of pre-existing cells.

Question 2

What does microscopy allow?

Answer 2

the ability to observer and investigate the many different cells types and the various different cell structures.

Question 3

What is an artefact

Answer 3

Structures visible on an image that having been formed during the sample preparation, which aren’t actually present in the cell, ie are bubbles or mesosomes

Question 4

light microscope energy source

Answer 4

Visible light

Question 5

how does a light microscope work

Answer 5

lenses made of glass bend light that has passed through the specimen such that you see a magnified image

Question 6

thickness of light microscope specimens

Answer 6

thin/flat

Question 7

why must light microscopes have thin/flat specimens

Answer 7

so the light can pass through the specimen into you eyes

Question 8

advantages of light microscope (6)

Answer 8

we can see true colours
living processes can be seen
inexpensive to buy and maintain
easy sample preparation
sample preparation less likely to cause artefacts
straightforward

Question 9

why are stains used (2)

Answer 9

cell = colourless, so the stains make specific parts visible
contrast

Question 10

how to calculate overall magnification of light microscope

Answer 10

magnification of eyepiece lens x magnification of objective lens

Question 11

light microscope magnification

Answer 11

x1500

Question 12

light microscope resolution

Answer 12

200nm

Question 13

laser scanning confocal microscope energy source

Answer 13

ultraviolet light

Question 14

why does an LSCM have a higher resolution that light microscope

Answer 14

ultraviolet light has a shorter wave length than visible light.

shorter wave length = higher resolution

Question 15

how to prepare specimen for LSCM

Answer 15

cell treated with antibodies which bind to specific proteins
the antibodies have floutesecnt dyes attaches, which absorbs light from the laser and re-emits the light of a specific wavelength

or

cells can be genetically modified to produce fluorescent proteins which reveal their own location.

Question 16

LSCM, how does it work

Answer 16

laser scans across the specimen in a fixed plain, illumination only a single point at a time
high resolution, but 2D ‘slice’
many slices can be put into a computer programme to create a 3D image.

Question 17

LSCM advantages

Answer 17

it can show the precise location of one or more specific types of protein at different depths within a cell.
if the cell in prepared appropriately, living cells can be viewed, and changed over time can be tracked, such as the position and length of spindle fibres during cell division.

Question 18

TEM and SEM energy source

Answer 18

beam of electrons, which is then picked by electromagnetic which are used as lenses

Question 19

how does a TEM work/ preparation

Answer 19

thin section of cell is stained with a heavy metal such as gold. the electron beam passes through the specimen and onto a detector, but the are where the heavy metals atom are the electrons can’t pass through and are blocked, providing contrast to the image

Question 20

TEM image description

Answer 20

Flat, but extremely detailed due to high resolution, artificially coloured, 2D

Question 21

TEM magnification

Answer 21

x500000

Question 22

TEM resolution

Answer 22

0.5 nm

Question 23

how does a SEM work/ preparation

Answer 23

thin section of cell is stained with a heavy metal such as gold. the electron beam is directed across the surface specimen, and where the heavy metal is the electrons are reflected of the surface of the cell and create an image on the detector

Question 24

SEM image description

Answer 24

Surface view of a cell where the image has a 3D appearance

Question 25

SEM magnification

Answer 25

x100000

Question 26

SEM resolution

Answer 26

5nm

Question 27

advantages of electron microscopes

Answer 27

very high resolution and magnification

Question 28

disadvantages of electron microscopes

Answer 28

black and white image produces, however artifical colours can be added using a computer, and the components must be digitally enhanced for non-experts to interpret the image sample preparation is technically demanding much training and practice is needed very large and not portable very expensive to buy and maintain vacuum must be maintained so the electron beam isn't scattered by gas particles, meaning the cell is dead the sample preparation is generally more likely to form artefacts than light microscopes

Question 29

disadvantages of light microscopes

Answer 29

low resolution and magnification

Question 30

what do you call the outer most membrane?

Answer 30

plasma membrane or cell surface membrane

Question 31

what are the three types of slide preparations for light microscopy, and which is the most effective

Answer 31

1. Smear 2. Squash 3. Sectioning (most effective)

Question 32

Describe smear preparation

Answer 32

spreading the sample evenly across a microscope slide, so it forms a thin layer, (so light can pass through) add colour stain if needed add coverslip on top of the specimen

Question 33

advantages of smear preparation

Answer 33

Living cell can be viewed

Question 34

Describe squash preparation

Answer 34

tissue is placed onto a slide add stain if needed place coverslip of specimen and gently press down gently to spread out / squash the sample into a thin layer

Question 35

advantages of squash preparation

Answer 35

living cells can be viewed

Question 36

describe sectioning preparation

Answer 36

tissue is first fixed and preserved using formaldehyde embedded in solid wax or resin very thinly sliced with a device called a microtome place onto a slide and stain if needed place coverslip over the specimen

Question 37

disadvantages of sectioning preparation

Answer 37

living cells CANNOT be viewed

Question 38

example of smear preparation

Answer 38

blood

Question 39

example of squash preparation

Answer 39

root tip in which is undergoing mitosis

Question 40

Why do we use stains

Answer 40

enables cells or cell components to become visible which were previously invisible . provides contrast between structures so different component or cell types can be distinguished from one another enable identification of cell types, organelles or specific biological molecules

Question 41

give an example of a stain used in light microscopy

Answer 41

methylene blue - Binds to DNA, so nucleus looks blue

Question 42

give an example of a heavy metal used in electron microscope

Answer 42

Gold

Question 43

1mm is how many micrometers

Answer 43

1000um

Question 44

1mm is how many nano meters

Answer 44

1000000nm

Question 45

1um is how many nano meters

Answer 45

1000 nm

Question 46

Magnification definition

Answer 46

The number of times larger the size of an image is compared to the real object

Question 47

what is the magnification triangle

Answer 47

Question 48

Resolution defintion

Answer 48

The ability to distinguish two close points as sepatate objects

Question 49

why is it not worthwhile to magnify above x1500 with a light microscope

Answer 49

The resolution of the LM is not high enough to make it useful to magnify above x1500; no further detail would be seen in the image. The resolution of the LM is 200nm, limited by the long wavelength of light

Question 50

ultrastrucutre definition

Answer 50

fine details of cell structure

Question 51

organelle definition

Answer 51

a cell component with a specific structure and function

Question 52

eukaryote cell

Answer 52

A cell with a nucleus and other membrane bound organelles.

Question 53

eukaryote cell size

Answer 53

10-100um

Question 54

prokaryote definition

Answer 54

cells without a membrane bound nucleus or organelles.

Question 55

prokaryote size

Answer 55

1-2um

Question 56

cell wall materials

Answer 56

prokaryotes - peptidoglycan fungi - chitin plant- cellulose protocists - cellulose cell wall

Question 57

how would you describe the shape of endoplasmic reticulum and what is the funciton of each type

Answer 57

membrane bound flatted tubes called cisterna with an internal space called the lumin containing specific proteins. rer - proteins synthesis ser - lipid synthesis

Question 58

how would you describe the shape of the golgi, and what is its function

Answer 58

membrane bound flatted discs called cisternae with a lumin containg specialsed ezumes. role - modify proteins and packaging into secratory vesicles creates lysosomes.

Question 59

lysosomes shape and function

Answer 59

spherical membrane-bound organelle containing hydrolytic enzymes such as protease. digest old/faulty organelles digestion of engulfed pathogens THE MEMBRANE IS IMPORTANT BECAUSE IT ENSURE THAT THE HYDROLYTIC ENZYMES DO NOT LEAK OUT AND CASUE DAMGE TO THE CELL.

Question 60

mitochondria shape and function

Question 61

chloroplast design and function

Answer 61

double membrane structure fluid within is called the stroma, contains many enzymes needed in photosynthesis thylakoid membranes contain chlorophlyll msny thylakoid are in a blob shape called the granum

Question 62

vacuole function

Answer 62

membrane enclosed compartment storage role maintains cell turgor - water moves into the vacuole via osmosis, increases vacuole volume, prssure exerted against cell wall which cant expand therfore cell becomes turgid

Question 63

centrioles design and function

Answer 63

short cylinder-shaped strucutre at a right angle to each other made of microtubles only in animal cells

Question 64

flagella

Answer 64

cell movement 9 +2 arrangement of microtubles an extenision of the plasma membrnae

Question 65

cytoskeleton deffinition

Answer 65

a network of protein strands found in the cytoplasm of te cytoskeleton

Question 66

microtubles

Answer 66

made of tubulin - transport vesicle and organelle movements - movement of chlorplast centrioles - organise spindle fibres during cell division - cell movement via a flagella

Question 67

microfillaments

Answer 67

very fine threads of actin give the cell mechanical strength and determines the cell shape

Question 68

nucleolus function

Answer 68

production of RNA