Cells

Question 1

Magnification equation

Answer 1

Size of image / size of real object

Question 2

What is resolution?

Answer 2

The minimum distance apart that two objects can be in order for them to appear as separate items

Question 3

In cell fractionation the solution must be…

Answer 3

Cold- reduce enzyme activity
Same water potential as tissue- so organelles don’t burst or shrink because of osmosis
Buffered- so pH doesn’t fluctuate

Question 4

Ultracentrifugation process

Answer 4

Tube of filtrate placed in centrifuge and spun on slow speeds
Heaviest organelles (nuclei) falls to the bottom forming a pellet
The fluid left (supernatant) is removed and then spun again at higher speeds
Next heaviest organelle falls (mitochondria)
Process continued

Question 5

Compare light and electron microscopes

Answer 5

Light has a lower resolution as as it has a longer wavelength

Question 6

What are limitations of the transmission electron microscope?

Answer 6

TEM must be in a vacuum
Only dead specimen can be observed
Specimen must be extremely thin

Question 7

What is the nucleus?

Answer 7

Contains hereditary material and controls cell activity
Nuclear envelope- double membrane surrounding nucleus
Nucleoplasm- jelly-like material that makes up the the bulk of the nucleus

Question 8

What is the mitochondria?

Answer 8

Site of aerobic respiration
Double membrane controls entry and exit
Cristae extensions of inner membrane
Matrix makes up remainder of mitochondria and makes enzymes

Question 9

What are chloroplasts?

Answer 9

Where photosynthesis takes place.
Grana are stacks of thylakoids these contain the pigment chlorophyll and are where 1st stage of photosynthesis takes place. The stroma is where the 2nd stage of photosynthesis takes place

Question 10

What is the rough endoplasmic reticulum?

Answer 10

Ribosomes I’m the outer surface which provides:
Large SA for synthesis of proteins and provides a pathway for transporting materials

Question 11

What is the smooth endoplasmic reticulum?

Answer 11

Used for synthesis, store and transport of both lipids and carbohydrates

Question 12

What is the fiction of the Golgi apparatus?

Answer 12

Form glycoproteins (carbohydrate+proteins)
Produces secretory enzymes
Secrete carbohydrates
Form lysosomes

Question 13

What are lysosomes?

Answer 13

They hydrolyse material ingested by phagocytic cells and completely break down cells

Question 14

What are ribosomes?

Answer 14

Site of protein synthesis
80s- found in eukaryotic cells
70s- found in prokaryotic cells

Question 15

Compare prokaryotic and eukaryotic cells

Answer 15

P-no true nucleus E-distinct nucleus with nuclear envelope
P-DNA not associated with proteins E-DNA associated with histones(proteins)
P-no membrane-bound organelle E- membrane bound organelles
P- DNA can be circular E- DNA is linear
P-70s ribosomes E- 80s ribosomes

Question 16

What is the structure of a virus?

Answer 16

Attachment proteins on the outside
Lipid envelope outside then matrix
RNA and reverse transcriptase in capsid

Question 17

What are the mitosis stages?

Answer 17

Prophase, metaphase, anaphase, telophase and cytokinesis

Question 18

What happened in prophase?

Answer 18

Chromosomes become visible
Spindle fibres develop from centrioles called spindle apparatus
Nucleolus disappears and nuclear envelope breaks down
Chromosomes drawn to equator by spindle fibres

Question 19

What happens in metaphase?

Answer 19

Chromosomes made of two chromatids
Chromatids joined by centromere
Chromosomes pulled along spindle apparatus on the equator

Question 20

What happens in anaphase?

Answer 20

Centromeres divide and spindle fibres pull chromatids apart
Chromatids move to opposite poles

Question 21

What happens in telophase?

Answer 21

Nuclear envelope and nucleolus reforms and spindle fibres disintegrate

Question 22

What molecules are in the cell membrane?

Answer 22

Phospholipids, proteins, cholesterol, glycolipids and glycoproteins

Question 23

What is the fluid mosaic model?

Answer 23

The cell membrane is fluid because individual phospholipids can move around
It is mosaic because the proteins are embedded

Question 24

What is diffusion?

Answer 24

The net movement of molecules from a region of high concentration to one of low concentration
Facilitated diffusion uses protein channels and carrier proteins

Question 25

What is osmosis?

Answer 25

The passage of water from a region of high water potential to one of low water potential through a selectively permeable membrane

Question 26

What happened to cells at different water potentials?

Answer 26

High water potential causes cells to swell and burst (turgid) Equal water potential causes no change (incipient plasmolysis) Low water potential causes cells to shrink (plasmolysed)

Question 27

What is active transport?

Answer 27

Movement of molecules from a region of low concentration to one of high concentration using ATP and carrier proteins

Question 28

The process of co-transport of glucose

Answer 28

Sodium ions actively transported out of epithelial cells by sodium-potassium pump Higher conc of sodium in lumen instead of epithelial cells Sodium diffuses into epithelial cells down conc gradient carrying glucose with it Glucose pass into blood by facilitated diffusion

Question 29

What happens in phagocytosis?

Answer 29

The phagocyte is attracted to the pathogen and moves towards it on a conc gradient. The receptors on the membrane of the phagocyte attach to chemicals on the surface of the pathogen. Lysosomes within phagocyte migrate towards phagosome (engulfed bacteria). Lysosome releases lysozymes into phagosome to hydrolyse bacterium. Products from this are absorbed.

Question 30

What is the function of B lymphocytes?

Answer 30

Surface antigens of invading pathogen are taken up by B lymphocytes. It processes the antigens and puts them on its surface. Helper T cells attach to the antigens activating B cell. B cell divides by mitosis to clone plasma cell. This secretes specific antibodies to fit antigens on pathogens to destroy them. B cells can also develop into memory cells.

Question 31

What if the function of t lymphocytes?

Answer 31

Pathogens are taken in by phagocytes. The phagocyte puts antigens from pathogen on its surface. Receptors on specific helper T cells fit onto the antigens. This activates the T cells to divide by mitosis and form clones which can: develop into memory cells, stimulate phagocytes, stimulate B cells to divide and activate cytotoxic T cells

Question 32

What are monoclonal antibodies?

Answer 32

An antibody that can be isolated and cloned

Question 33

How can monoclonal antibodies target medication to specific cells?

Answer 33

Monoclonal antibodies are produced that are specific to antigens on cancer cells. They are given to a patient and attach themselves to receptors on cancer cells. They attach to the surface and block chemical signals that stimulate their uncontrolled growth.

Question 34

What are the different types of immunity?

Answer 34

Passive- antibodies that are in individuals from an outside source Active- stimulating the production of antibodies. There are two types: natural active which is from an individual being infected by disease Artificial active is from vaccinations

Question 35

How does HIV replicate?

Answer 35

HIV enters bloodstream. A protein on HIV readily binds to CD4. Protein capsid fuses with cell membrane. The RNA and enzyme from HIV enter helper T cell. HIV reverse transcriptase converts virus RNA to DNA. This DNA moves into helper T cells nucleus and creates mRNA. mRNA creates HIV using protein synthesis and BIV breaks away from helper T cell