Cells

Question 1

What is the resolution of an optical microscope? Why is this low

Answer 1

0.2ym

Low because of long wavelength of light

Question 2

What is the magnification equation?

Answer 2

Magnification = image size/ size of real object

Question 3

Give the conversions between mm ym and nm

Answer 3

Mm x 1000 = ym

Ym x 1000 = nm

Question 4

What is resolution of a microscope?

Answer 4

Minimum distance apart that two objects are distinguishable

Question 5

Why must a solution involved in cell fractionation be: iostonic, cold, buffered

Answer 5

Cold reduces enzyme activity
Isotonic means the same water potential prevents bursting of organelles
Buffered means stops pH changes which effect enzyme reactions

Question 6

Describe how cell fractionation occurs

Answer 6

Cell broken by homogeniser forming the homogenate
Filter homogenate to remove debris
Centrifuge homogenate slowly, heaviest organelle i.e. Nucleus resides at bottom remove this as a pellet
Re centrifuge faster removes next heaviest
So on

Question 7

Give the advantages of electron microscopes

Answer 7

Shorter wavelengths

Charge allows electrons to be focused

Question 8

How does a transmission electron microscope work? What is produced?

Answer 8

Electron gun fires electrons at sample from below, electrons either pass through or are absorbed, pass through hit the sensor which gives a black colour
Produce a 2D black and white image called a photo micrograph

Question 9

What are the limitations of both types of electron microscope?

Answer 9

Needs to be in a vacuum, means living things cant be monitored.
Complex staining process
Black and white
Very thin sample required (TEM)

Question 10

How does a scanning mircoscope work?

Answer 10

Electrons reflected of the sample to and picked up by sensors allowing a 3D image to be produced

Question 11

TEM or SEM has the highest magnification and resolution?

Answer 11

TEM

Question 12

What is a eye piece graticule?

Answer 12

Eye piece that allows you to measure things direct from the microscope, calibrate to a stage micrometer which shows measurements at paticular magnification.

Question 13

Describe these five features of the nucleus:
Nuclear enevelope
Nuclear pores
Nuclearplasm
Chromosomes
Nucleolus

Answer 13

Nuclear enevelope is double membrane surronding the nucleus can be connected to Endoplasmic reticulum
Nuclear pores are small holes in the membrane allows RNA through
Nucleoplasm is the cytoplasm
Nucleolus are smaller dark areas within the nucleus where rRNA and ribosomes are made

Question 14

Describe the structure of the mitochondria

Answer 14

Double membrane
Cristae extentions of inner membrane provide large SA
Matrix where enzymes are etc in middle

Question 15

Describe the structure if the cholorplast

Answer 15

Double membrane
Grana are stacks of thylakoids, cholorphyll resides in thylakoids
Stroma is the fluid

Question 16

Differentiate between the structures of rough and smooth endoplasmic reticulums

Answer 16

Rough - associated ribosomes (hence rough) large SA for protin synthesis which is a pathway for proteins to move within the cells
Smooth - synthesises and store lipids and carbohydrates

Question 17

What is the role of the Golgi apparatus?

Answer 17

Modifies proteins from rough ER 
Adds carbohydrates 
Produces secratory proteins
Secretes carbohydrates 
Forms lysosomes

Question 18

What are cell walls in fungi made of?

Answer 18

Chitin

Question 19

What is the role of the vacuole?

Answer 19

Single membrane bound fluid sac
Makes plants turgid
Temporary food store

Question 20

Describe the build up of prokaryotic cells

Answer 20

Cell walls made of murein
Have a capsule around them
Cell surface 70s membranes 
Synthesise proteins 
Circular DNA strand with plasmids

Question 21

Describe a virus

Answer 21

Acellular particle
Nucleic acids which it injects inti a host
Inside a capsid protein
Has attachment proteins that identify host cells