Cell structure

Question 1

What is homogenation

Answer 1

• when cells get broken down and the cells organelles get released
• the resultant fluid is homogenate which gets filtered to remove any debris

Question 2

What is ultracentrifugation

Answer 2

a process where fragments from filtered homogenate get separated in a centrifuge

Question 3

What is the use of a cold isotonic buffer

Answer 3

cold - reduce enzyme activity

buffer - so that pH doesn’t fluctuate and result in organelle structure

Question 4

What is the process of ultracentrifugation

e.g. isolating chloroplasts from a lettuce leaf

Answer 4

• sample is cut up in cold buffered solution
• further broken down in a homogeniser
• homogenised sample (tissue) is spun in a ultracentrifuge at low speed
• heavy organelles (nuclei) forced to the bottom of the tube forming a thin sediment
• the fluid on top, called the supernatant is removed and put in another tube, leaving just the sediment of nuclei
• the supernatant gets spun in the centrifuge at medium speed
• the next heaviest organelles like mitochondria are forced to the bottom of the tube
• this process is continued till the next heaviest organelle is sedimented at higher speeds

Question 5

What is the formula for magnification

Answer 5

magnification = size of observed / size of real

Question 6

Compare Light, Transmission Electron and Scanning Electron Microscopes

Answer 6

LM 500nm:
-low resolution
- short wavelengths of light
TEM 10nm:
- beam of electron pass through thin non living specimen
- specimen has to be prepared which can result in limitations of resolution
SEM 2nm:
-same limitations as the TEM however higher resolution and non living specimen doesn’t need to be as thin

Question 7

Evaluate the use of Electron Microscopes to study cells

Answer 7

Advantages - higher resolution and magnification

Disadvantages - very large and are costly to make/use

Question 8

Eukaryotes VS Prokaryotes

Answer 8

Eukaryotes: Prokaryotes:

• linear DNA -circular DNA
• introns -no introns
• nucleus -no nucleus
• membrane bound organelles -non membrane bound
• 80’s ribosomes -70’s ribosomes
• divide my mitosis/meiosis -divide by binary fission
• cell wall made from murein -cell wall cellulose/chitin

Question 9

Describe the structure of a nucleus

Answer 9

• nuclear envelope
• nuclear pours
• nucleocytoplasm
• chromosomes of protein bound linear DNA

Question 10

Describe the structure of a mitochondrion

Answer 10

• outer membrane
• inner membrane
• cristae (extensions on the inner membrane)
• matrix

Question 11

Describe the structure of a chloroplast

Answer 11

• outer membrane
• inner membrane
• thylakoids (light dependent reaction)
• granum (stacks of thylakoids)
• stroma (light independent reaction)

Question 12

What are the functions of the Rough and Smooth Endoplasmic Reticulum

Answer 12

RER: ribosomes present on its outer membrane

• provides large surface area for the synthesis of proteins and glycoproteins
• provide pathway for transport of materials e.g. proteins throughout the cell

SEM: lacks ribosomes and is tubular

• synthesise, store and transport lipids
• synthesise, store and transport carbohydrates

Question 13

What are the functions of the Golgi Apparatus

Answer 13

• processes triglycerides
• add carbohydrates and proteins to form chylomicrons
• packaged for exocytosis into lymph capillary

Question 14

How do cells become specialised

Answer 14

by differentiation the genes needed for the role of the cell get expressed

Question 15

What is a tissue

Answer 15

a collection of similar cells that perform a specific function

Question 16

What is an organ

Answer 16

a collection of tissues that perform a variety of functions

Question 17

What is an organ system

Answer 17

a group of organs the work together as a unit to perform a function more efficiently

Question 18

What are 3 organ systems

Answer 18

• digestive system
• respiratory system
• circulatory system

Question 19

What is the use of Pillus and Capsule of a bacterium

Answer 19

pillus - bacterial adhesion and conjunction

capsule - protects bacterium from other cells

Question 20

Structure of a virus

Answer 20

• they are acellular, non living particles
• contain nucleic acid enclosed in a protein coat called a capsid
• have attachment proteins that allow virus to bind to host cells

Question 21

What is mitosis

Answer 21

the devision of a cell that results on 2 daughter diploid cells being genetically identical to the parent cell

Question 22

What is Interphase

Answer 22

when a cell is getting ready to divide and the S, G1, G2 and DNA replication stages take place

Question 23

What are the 4 stages of Mitosis

Answer 23

Prophase - centrioles move towards poles and spindles begin to form
Metaphase - chromosomes line up along the equator and spindles attach to the centromeres
Anaphase - chromosomes separate and chromatids get pulled towards the poles
Telophase - nuclear envelope forms around the chromosomes which uncoil into chromatin
-followed by cytokinesis, the devision of the cytoplasm

Question 24

How do prokaryotic cells divide (bacteria)

Answer 24

binary fission:

• the circular DNA and plasmids replicate
• cell membrane begins to grow between the 2 circular DNA molecules dividing the cytoplasm into two
• new cell wall forms between the two forming 2 new identical daughter cells

Question 25

How is cancer similar to mitosis

Answer 25

its a process where cells divide however cancer cells have no restriction to how much they can replicate also they damage surrounding cells

Question 26

How could a drug prevent the growth of a tumour

Answer 26

preventing the DNA from replicating by inhibiting metaphase of mitosis by interfering with spindle formation