Cell Structure And Division

Question 1

Function of a Cell wall in Plants and Fungi

Answer 1

Function: Provides cell with protection to withstand hydrostatic pressure and permeability to allow osmosis of water molecules

Question 2

Characteristics of cell wall in Plants and Algae

Answer 2

Plants-made of microfibrils of cellulose polymer(the monomer is polysaccaride)
Fungi-made of chitin(nitrogen containing polysaccharide)

Question 3

Functions of the Golgi Apparatus?

Answer 3

Add carbohydrates to proteins to make glycoprotein
Transports,modifies and stores lipids
Secretes carbohydrates
Forms lysosomes

Question 4

What is Plasmodesmata?

Answer 4

Specialised channels in the wall of 2 connecting plant cells which allow communication and transport of materials

Question 5

Structure of chloroplasts and organelles?

Answer 5

Has own DNA and ribosomes to easily manufacture proteins
Has a chloroplast envelope
Thylakoids contains chlorophyll
Membranes= large SA for attachment of chlorophyll

Question 6

Function and structure of Mitochondria

Answer 6

Double membrane
Cristae- extensions of inner membrane providing large SA for enzymes for proteins
Site of AR and where ATP is made

Question 7

Vacuole function and structure?

Answer 7

Fluid filled sac bounded by one membrane called a tonoplast
Contains solution of mineral salts
Makes cells turgid and provide protection
Stores sugars and amino acids

Question 8

What is a nuclear envelope

Answer 8

A double membrane surrounding the nucleus,continuous with endoplasmic reticulum.
Ribosomes on surface

Question 9

What is nucleolus?

Answer 9

Small sphere in nucleus which is the site of rRNA production and makes ribosomes

Question 10

Nucleus function?

Answer 10

Site of DNA replication and transcription
Contains genetic code for making each cell
Contains genetic material
Contains pores to allow RNA to move between nucleus and cytoplasm

Question 11

What is the Rough endoplasmic Reticulum?

Answer 11

Contains folded membranes called cisternae
Has proteins on outer surface
Where protein synthesis occurs
Provides a large SA for proteins and glycoprotein
Provide a pathway for transport of materials

Question 12

What is the Smooth endoplasmic reticulum?

Answer 12

Synthesis and storage of carbohydrates and lipids
Contains lots of tubules which increases SA for storage of key enzymes

Question 13

What are lysosomes and function?

Answer 13

Bags of different enzymes(contains lysozymes)
Hydrolyse phagocytic cells
Autolysis-break down cells
Exocytosis-release enzymes to outside of cells to destroy material
Digest worn out organelles for reuse
Fuse with the vesicle

Question 14

What is the plasma membrane?

Answer 14

Found in all cells
Controls the exit and entrance of molecules
Phospholipid layer-molecules embed within and attach on the outside

Question 15

What is binary fission?

Answer 15

Method of cell division by prokaryotes involving replication of circular DNA and plasmids

Question 16

What is the cytoskeleton?

Answer 16

Protein filaments in cells helping to maintain its shape and structure

Question 17

What are viruses?

Answer 17

They are acellular,non living particles
Size:20 to 300nm

Question 18

Characteristics of Viruses?

Answer 18

Contains DNA or RNA
Can only multiply through a host cell
Capsid-protein coat protecting DNA
Lipid envelope-surrounds capsid
Attachment proteins-allow virus to attach to host cell

Question 19

Function of Ribosomes?

Answer 19

Where protein synthesis occurs
70s-small ribosomes found in eukaryotic cells
80s-found in eukaryotic cells

Question 20

What is cell fractionation?

Answer 20

A technique to separate out the different components/organelles of the cell

Question 21

What is homogenisation?

Answer 21

Cells are broken up by a homogeniser(to break organelles)

Question 22

Stage 1 of Cell Fractionation?

Answer 22

Place in cold temperature-to reduce enzyme activity that could damage and cause enzymes to denature and to prevent digestion
Isotonic-so cells do not burst or shrivel by osmosis to prevent lysis
Buffered-to maintain constant pH and prevent damage

Question 23

Stage 2 of Cell Fractionation?

Answer 23

Is Homogenisation-add tissue into a test tube and use a homogeniser to break organelles

Question 24

Stage 3 of cell Fractionation?

Answer 24

The homogenate is FILTERED to remove any insoluble material such as cell walls and connective tissue

Question 25

Stage 4 of Cell Fractionation

Answer 25

Ultracentrifugation: The filtrate is placed in a centrifuge and spun at a low speed This causes large organelles to be collected at the bottom of the tube The fluid at the top(supernatant)and large organelle is removed Repeat process at higher speeds to get smaller organelles

Question 26

Compare DNA and mRNA

Answer 26

DNA is double stranded but RNA is single stranded,DNA is longer DNA has non coding sequences but RNA does not

Question 27

What is magnification?

Answer 27

How many times larger image size is compared to object size

Question 28

What is resolution?

Answer 28

Minimum distance between 2 objects at which a microscope can distinguish them as separate entities

Question 29

Light Microscopes characteristics?

Answer 29

Radiation:Light Max resolution:200nm Max Mag:1500x

Question 30

Benefits and costs of Light microscope?

Answer 30

Cheap Low mag Poor resolution Colour images Can view living samples

Question 31

What is the Laser Scanning Microscope?

Answer 31

Radiation:Laser Resolution:20nm Mag:1500x Image:3D

Question 32

What is a TEM and characteristics?

Answer 32

Radiation:Beam of electrons Focused by: Magnets Mag: 100000x Resolution:0.5nm A live specimen cannot be used as its placed in a vacuum Image:2D

Question 33

What's an SEM and characteristics?

Answer 33

Radiation:Electrons Radiation focused by:Magnets Mag:200000x Resolution:0.2nm Cannot be used to view a live specimen Image:3D

Question 34

What is the Centrosome and functions?

Answer 34

A microtubule organising centres of eukaryotic cells Contains 2 centrioles Involved in creating and extending microtubules that contribute to the cytoskeleton Involved in the formation of mitotic fibres

Question 35

What is the centrioles?

Answer 35

Cylindrical microtubule Forms flagella and cilia Involved in the formation of mitotic spindle during cell division

Question 36

What is the eyepiece graticule and its function?

Answer 36

Small piece of glass with a measurement scale on surface inside microscope eyepiece This allows for precise measurements and analysis of microscopic measurements

Question 37

What is the eyepiece graticule and its function?

Answer 37

Small piece of glass with a measurement scale on surface inside microscope eyepiece This allows for precise measurements and analysis of microscopic measurements

Question 38

Explain why some organisms cannot be viewed with an optical microscope(2)

Answer 38

Requires a greater resolution Because wavelength of light is too long

Question 39

Explain why biologists use a blender and then filter(2)

Answer 39

Breaks open cells and produces a homogenate Remove unbroken cells and larger debris

Question 40

Describe how to mount a piece of plant tissue to observe starch grains?(4)

Answer 40

Add drop of water to slide Place thin section on slide Add iodine Lower coverslip at an angle

Question 41

What are prokaryotes?

Answer 41

Single celled organisms with no nucleus

Question 42

What are eukaryotes?

Answer 42

Complex multicellular organisms with a nucleus

Question 43

Explain the Principles and limitations of TEM

Answer 43

Principles: Electrons enter through thin specimen Denser parts absorb more electrons Electrons have a short wavelength giving it a high resolution Limitations: Thin specimen required Only 2D images Cannot view living cells