Cell Structure

Question 1

Name the parts of a light microscope

Answer 1

Eye piece, objective lens, stage, lamp, coarse-focusing knob, fine-focusing knob.

Question 2

How does a light microscope works?

Answer 2

Has two lenses- objective and eyepiece. Objective lens produces a magnified image which is magnified again by the eyepiece lens. The sample is illumination usually by a light source underneath the sample.

Question 3

Eye piece lens

Answer 3

Used to view image formed after light has passed through the objective lens

Question 4

Coarse focusing wheel

Answer 4

Wheel on a microscope that moves parts of the microscope to get the image into focus (bigger wheel)

Question 5

Fine focusing wheel

Answer 5

Wheel on a micrscope that moves parts of the micrscope a small amount to get the image into focus (smaller wheel)

Question 6

Objective lens

Answer 6

Alters the magnification

Question 7

Condenser lens

Answer 7

Used to control the illumination entering the objective lens

Question 8

What can you see with a light microscope

Answer 8

Nuclei, cytoplasm, cell membranes, cell wall

Question 9

How does an electron microscope work

Answer 9

Uses a beam of electrons to illuminate the specimen. Electrons have a much shorter wavelength than light so greater resolution can be achieved

Question 10

What is the magnification of electrn micrscopes

Answer 10

up to x500,000

Question 11

what can you see with an electron microscope

Answer 11

the cell ultrastructure

Question 12

Transmission electron microscope

Answer 12

electron bream is transmitted through the specimen. The final image is 2D. produces a cross sectional image. Has a resolving power of 0.5nm

Question 13

Scanning electron microscope

Answer 13

Electron beam scattered across the surface of an object which produces a 3D image. has a resolving power of 3-10nm

Question 14

What is the formula for magnification

Answer 14

Magnification = image size/actual size IAM triangle

Question 15

Define resolution

Answer 15

The degree to which its possible to distinguish between 2 objects that are very close together. The higher the resolution the greater detail you can see

Question 16

Advantages of light microscopes

Answer 16

cheap
easy to use
wide range of specimens can be viewed including live organisms

Question 17

disadvantages of light microscopes

Answer 17

specimen needs to be thin and transparent
max magnification - 1500
max resolution - 200nm

Question 18

advantages of TEM

Answer 18

greater resolution (0.05-1nm)
produces more detailed 2D images showing the cell ultrastructure
greater magnification - x500,000

Question 19

disadvantages of TEM

Answer 19

electron beams are deflected by air particles therefore sample needs to be in a vacuum which kills living cells
very expensive
requires a skilled operator

Question 20

advantages of SEM

Answer 20

high resolution (3-10nm)
Produces more detailed 3D images
Shows cell ultrastructure
Greater magnification x100,000
Produces 3D images that can show cell and tissue arrangements

Question 21

disadvantages of sem

Answer 21

has to be done in a vacuum which kills all living cells
very expensive
needs a skilled operator

Question 22

advantages of laser scanning confocal

Answer 22

wide range of specimens can be viewed including living organisms
can give 2d and 3d images
greater resolution
can focus at different depths within a specimen

Question 23

disadvantages of laser scanning confocal

Answer 23

specimen needs to be thin and transparent
requires a skilled operator

Question 24

how does a laser scanning confocal microscope work

Answer 24

moves a single spot of focused light across a specimen. this causes fluorescence from the components labelled with a dye. the emitted light from the specimen is filtered through a pinhole aperture. only light radiated from very close to the focal plane is detected

Question 25

what would light emitted from other parts of the specimen do on a laser scanning confocal microscope

Answer 25

reduce the resolution and cause blurring. this unwanted radiation does not pass through the pinhole and is not detected

Question 26

How are 2d and 3d images produced with a laser scanning confocal microscope

Answer 26

A spot illuminating the specimen is moved across the specimen and a 2d image is produced. A 3d image can be produced by creating images at different focal planes

Question 27

What can laser scanning confocal micrscopes be used for

Answer 27

currently used in the diagnosis of diseases in the eye and is also being developed for use in endoscopic procedures. since it can be used to see the distribution of molecules within cells its also used in the development of new drugs

Question 28

what are the rules for a good scientific drawing

Answer 28

title state magnification use a sharp pencil labels shouldnt have arrowheads white unlined paper use as much of the paper as possible smooth continuous lines no shading draw clearly defined structures ensure proportions are correct label lines should be parallel to the top of the page and drawn with a ruler

Question 29

how to calibrate a microscope

Answer 29

you do this by comparing a stage micro meter and eyepiece graticule to work out what one unit on the eyepiece graticule is in micrometres

Question 30

function of cell membrane

Answer 30

controls the exchange of materials between the internal cell environment and the external cell environment partially permeable formed from a phospholipid bilayer of phospholipids

Question 31

function of cell wall

Answer 31

found in plant cells not animal cells offer structural support plants - cellulose bacteria - peptidoglycan

Question 32

function of nucleus

Answer 32

present in all eukaryotic cells large and separated from cytoplasm by a double membrane (nuclear envelope) containing pores pores allow mRNA and ribosomes to travel out of the nucleus contains chromatin (material from which chromosomes are made) chromosomes are made of sections of linear dna tightly would around proteins called histones contains nucleolus which is the site of ribosome production

Question 33

function of mitochondria

Answer 33

site of aerobic respiration within all eukaryotic cells surrounded by double membrane with the inner membrane folded to form cristae the matrix formed by the cristae contains enzymes needed for aerobic respiration, producing atp small circular pieces of DNA (mitochondrial dna) and ribosomes are found in matrix

Question 34

function of chloroplasts

Answer 34

found in plant cells larger than mitochondria and surrounded by a double membrane site of photosynthesis membrane bound compartments called thylakpids containing chlorophyll stack to form structures called grant contain small circular pieces of DNA and ribosomes used to synthesise proteins needed in chloroplast replication and photosynthesis

Question 35

function of ribosomes

Answer 35

all cells freely in cytoplasm or as part of the rough endoplasmic reticulum in eukaryotic cells 80s ribosomes are found in eukaryotic cells 70s ribosomes are found in prokaryotic mitochondria and chloroplasts site of protein synthesis

Question 36

function of rough endoplasmic reticulum

Answer 36

found in plant and animal cells surface covered in ribosomes formed from continuous folds of membrane with nuclear envelope processes proteins made by ribosomes

Question 37

function of smooth endoplasmic reticulum

Answer 37

found in plant and animal cells no ribosomes on surface involved in the production processing and storage of lipids carbohydrates and steroids

Question 38

function of golgi apparatus

Answer 38

found in plant and animal cells flattened sacs of membrane similar to the SER modifies proteins and lipids before packaging them into golgi vesicles vesicles then transport proteins and lipids to their required destination proteins that go through the golgi apparatus are usually exported such as hormones like insulin, put into lysosomes or delivered to membrane bound organelles

Question 39

large permanent vacuoles

Answer 39

sac in plant cells surrounded by the tonoplast, selectively permeable membrane vacuoles in animal cells are not permanent and small

Question 40

function of vesicle

Answer 40

plant and animal cells membrane bound sac for transport and storage

Question 41

function of lysosomes

Answer 41

specialist forms of vesicles which contain hydrolytic enzymes (enzymes that break down biological molecules down) break down waste material such as worn out organelles used extensively by cells of the immune system and in apoptosis (programmed cell death)

Question 42

function of centriole

Answer 42

hollow fibres made of microtubules two centrioles at right angles to search other form a centrosome, which organises the spindle fibres during cell division not found in flowering plants and fungi

Question 43

function of microtube

Answer 43

found in all eukaryotic cells makes up the cytoskeleton of the cell ab 25nm in diameter made of alpha and beta tubulin combined to form dimers, the dimers are then joined into protofilaments 13 protofilaments in a cylinder make a microtubule

Question 44

function of cytoskeleton

Answer 44

provide support and movement of cell

Question 45

structure of microvilli

Answer 45

specialised animal cells cell membrane projections increases surface area to increase the rate of exchange of substances