Topic 2-Cell structure

Question 1

Name all the structures in a eukaryotic cell

Answer 1

Cell-surface membrane
nucleus
mitochrondria
Chloroplasts
gogli apparatus and golgi vesicles
lysosomes
ribosomes
rough endoplasmic reticulum
smooth endoplasmic reticulum
ribosomes
cell wall
cell vacuole

Question 2

Give the formula to calulate magnification

Answer 2

maginification= size of image÷size of real object

Question 3

Define magnification

Answer 3

the number of times bigger the image/ drawing compared to the object /real size

Question 4

Define cell fractionation

Answer 4

The process where cells are broken up and different organelles they contain are seperated out.

Question 5

Describe what is done to the tissue before cell fractionation occurs

Answer 5

Placed in a cold, buffered solution of the same water potential.

Question 6

Why is the solutuion the tissue is placed in cold?

Answer 6

To reduce enzyme activity that might break down the organelles.

Question 7

Why is the solutuion the tissue is placed in of the same water potential?

Answer 7

To prevent organelles bursting or shrinking as a result of osmotic gain or loss of water.

Question 8

Why is the solutiuon the tissue is placed in buffered?

Answer 8

So that pH does not fluctuate. Any cvhanges to pH could alter the structure of the organelles or affect the functioning of enzymes.

Question 9

Name the 5 structures the nucleus consists

Answer 9

Nuclear envelope
Nuclear Pores
Nucloplasm
Chromosomes
Nucleolus

Question 10

Describe function and structure of nuclear envelope

Answer 10

-is a double membrane surrounding the nuclues
-outer membrane is continuous with endoplasmic reticulum
-often had ribosomes on its surface
-controls the entry and exit of materials in and out of nucleus -contains reactions taking place within it

Question 11

Describe the function of the nuclear pores

Answer 11

-Allows the passage of large molecules such as messanger RNA out of the nucleus.

Question 12

Describe the structure and function of the nucleoplasm

Answer 12

The granular, jelly-like material that makes up the bulk of the nucleus.

Question 13

Describe the structure and function of the nucleolus

Answer 13

-A small spherical region within the nucloplasm
-Manufactures ribosomal RNA and assombles the ribosomes
-May be more than one nucleolus

Question 14

Chromosomes consist of ….

Answer 14

Protein bound, Linear DNA

Question 15

Describe the function of the cell-surface membrane

Answer 15

It is selectively permeable so controls passage of substances, it has receptors on its surface allowing cell to cell signalling

Question 16

Describe the structure of the nucleus

Answer 16

It consisters of a nuclear envelope which has a double membrane and pore, inside there is the nucloplasm and the nucleolus which is the dense region, There is also protein bound linear DNA i the forms of condensed chromstion and highly condenses chromosomes

Question 17

What are ribosomes made of ?

Answer 17

Ribosomal RNA and protein (two subnits)

Question 18

Describe the function and structure of rRER

Answer 18

Ribosomes on surface synthesise protiens, Proteins are Processes/ folded/ transported into the rER. Proteins packed into vesicles for transport to Golgi appartus

Question 19

Describe the function of the sER

Answer 19

It synthesises and processes lipids (e.g cholestral)

Question 20

Describe the stucture of Golgi apparatus and Goldi vesicles

Answer 20

Goldi apparatus- Flattened membrane sacs
Golgi Vesicle - Small ,membrane

Question 21

Describe the function of the golgi apparatus

Answer 21

It modifies proteins and lipids to produce e.g glycolipids/proteins, It also packages proteins/ .ipids into golgi vesicles
Produces lysosmes

Question 22

Describe the function of the Golgi vesicles

Answer 22

They transport proteins/ lipids to their required destination by moving to and fusing with cell- surface membranes

Question 23

Describe the structure of lysosmes

Answer 23

Spherical membrane bound organelles that consist of a membrane containing hydrolytic enzymes

Question 24

Describe the function of lysosmes

Answer 24

To release hydrolytic enzymes (lysozomes)
To break dow and hydrolyse pathogens or worn oyt cell components

Question 25

Desribe the structure of mitochondria

Answer 25

It consists of an outer membrane Cristae- inner membran fold Matrix- containing small 70s ribosmes & circular DNA

Question 26

Describe the structure of chloroplasts in plants and algae

Answer 26

It is a double membrane with stomata containing: Thylakoid membrane small 70s ribosomes Circular DNA Starch granuels/ Lipid droplets It has Lamella- Thykkaloid linking grana Grana- STacks of thykaloid

Question 27

What is the function of chloroplasts for plants and algae

Answer 27

Absorbs light energy for photosynthesis and produes organic substances like carbohydrates and lipids

Question 28

Wat is the cell wall composed of in plants, algae and fungi

Answer 28

Composed mainly of cellulose -Plants & Algae Composed of chitin- Fungi

Question 29

Describe the function of the cell wall in plants, algae and fungi

Answer 29

It provude mechanical strength to the cell This preventds the cell chaging shape or bursting under pressure due to osmosis

Question 30

Describe the structure of the cell vacuole in plants

Answer 30

Has a tonoplast membrane and cell sap

Question 31

Describe the function of the cell vacuole in plants

Answer 31

It mantains turgor pressure in cell stopping the plant from witling and contains cells sap to store sugars amino acids, pigments and any waste chemicals

Question 32

What are the distinguishing features of prokaryotic cells?

Answer 32

Cytoplasm lacking membrane bound organelles so its getic material is not enclosed in a nucleus

Question 33

Desribe the structure of prokaryotic cells

Answer 33

Contains cell- surface membran/ cell wall/ cytoplasm/ small ribosomes and circukar DNA always It sometimes contains Capsule/ Plasmids and Flagella

Question 34

Draw and descrive the general structure of a virus particle

Answer 34

Nucleic acids surrounded by a capsid Attachment proteins allow attachment to specific host cells No cytoplasm, ribosomes, cell wall, cell-surface membrane etc. Some also surrounded by a lipid envelope eg. HIV

Question 35

What is resolution?

Answer 35

A minimum distance apart 2 objects can be to be distinguished as seperate objects

Question 36

Compare the principles and limitations of optical microscopes, transmission electron microscopes and scanning electron microscopes

Answer 36

OP focuses using glass lense, TEM&SEM use electromagnets OP passes light through specimen and different structure absorb diff wavelength TEM & SEM pass elecrons through specimen so denser parts absorb more and appear darker. OP & TEM create 2D image of a cross section SEM generates 3D image of a surface OP has low resolution due to long waveL of light TEM had very high resolution SEM has high resolution both due to short wavelength of electrons OP cannot see internal structure of orbanelles or ribosomes, TEM can and SEM cannot OP sepcimen must be thin TEM must be very thin, SEM dont need to be thin OP can view living organisms, TEM & SEM only dead/ dehydrated in a vacuum OP low magnification SEM & TEM high magnification OP can show colour, TEM & SEM cannot show any colour

Question 37

How do you turn mm into um?

Answer 37

x1000

Question 38

How to convert micrometre (um) to nanometre?

Answer 38

x1000

Question 39

Describe how the size of an object viewed with an optical microscope can be measured

Answer 39

You can line up the eyepience graticule with the stage micrometre Calibrate the eyepiece graticule- use stage micrometre to calculate size of divisions on the eyepiece graticule Take micrometre away and graticle to measure how many divisions make up the object Calculate the size of the object by multiplying number of divisions by size of division Recalibrate eyepiece graticule at different magnifications

Question 40

Describe and explain the priciples in cell fractination and ultracentrifugation as used to seperate cell components

Answer 40

The tissue is homogenised using a blender- this dirupts cell membrane, breaking open cells and releasing contents/organelles It is placed in a cold, isotonic, buffered solution - this reduces enzymic activty so organelles are not damaged- isotonic so water dosent move in and out of cell by osmosis as there is no water potential- Buffered to keep pH constant so enzymes dont denature Homogenate is filtered- Removes large/ unwanted debris Ultracentrifugation seperates organelles by density and mass - centrifuge homogenate in a tube at high speed- Removes pellet of heaviest organelle and respin supernatant at a higher speed- Repeat at increasing speed until seperated out

Question 41

What is the order in which organelles are seperated out in ultracentrifugation?

Answer 41

Nuclei-Chloroplasts/mitochondria-lysosomes-ER-ribosomes

Question 42

What is importance of fluidity in cell membrane

Answer 42

Phagocytosis vesicles