Biology As Unit 1 Part 2

Front 1

Meaning of resolution power

Back 1

Ability to distinguish points that are close together allowing fine details to be seen

Front 2

Why does an electron microscope have a higher resolving power than a light microscope?

Back 2

Electron microscope has a shorter wavelength

Front 3

What is the water potential of distilled water?

Back 3

0

Front 4

What property does a cell surface membrane have which allows osmosis to take place?

Back 4

Selectively permeable
Does not allow solute molecules through

Front 5

What are artefacts?

Back 5

Features visible in a micrograph which may not actually be present in the cell due to the distorting of cell contents during preparation

Front 6

How is the genetic material in a bacterial cell different from the genetic material in an animal cell?

Back 6

Bacteria: prokaryote -> circular plasmid not associated with histone proteins
Animal: eukaryote -> linear chromosomes associated with proteins

Front 7

Explain why triglycerides are not polymers

Back 7

substituent compounds (glycerol and three fatty acids) not identical monomer units

Front 8

Describe the structure of a phospholipid molecule and explain how phospholipids are arranged in a plasma membrane

Back 8

Phosphate group with two fatty acid tails
Phosphate head is hydrophilic and so positions itself on the outside to the internal and external environments of the plasma membrane.
Phospholipid bilayer allows hydrophobic fatty acid tails to position themselves inwards away from any water.
Phospholipids formed by condensation reactions

Front 9

Explain how an electron microscope works

Back 9

Electron beam is focused using electromagnets which illuminate the specimen producing an image when focused onto a fluorescent screen

Front 10

What is the radiation medium in a light microscope vs electron microscope?

Back 10

Light: air
Electron: vacuum

Front 11

What can a light microscope vs electron microscope show?

Back 11

Light: living or dead tissues
Electron: ultrastructure of dead cells

Front 12

How can you measure a microorganism in a microscope?

Back 12

Use a graticule or a stage micrometer

Front 13

Which kind of electron microscope requires a very thin specimen?

Back 13

Transmission Electron Microscope

Front 14

What is the difference in the way that electrons beams are detected via a fluorescent screen in a transmission electron microscope vs scanning electron microscope?

Back 14

Transmission: electron beam goes through thin sample and hits fluorescent screen
Scanning: electron beam hits surface of sample, the fluorescent screen detects secondary electrons due to excitation of the primary electron beam

Front 15

Why must a vacuum be used in an electron microscope?

Back 15

Allow electron beam to travel in straight lines otherwise it would interfere with the air

Front 16

Why does staining help in the preparation of samples for electron microscopes?

Back 16

(heavy metals) Adds electron density to sample giving contrast between different structures

Front 17

What is the point of cryofixation and fixation in the preparation of samples for electron microscopes?

Back 17

Preserve specimen taking a snapshot close to its native state to prevent further deterioration wit the minimal of artefacts

Front 18

What is an antigen?

Back 18

Protein usually on the cell wall which triggers an immune response

Front 19

What is an antibody?

Back 19

Protein produced by B-lymphocytes which binds to a specific antigen due to complementary tertiary structures

Front 20

What are B-lymphocytes responsible for?

Back 20

Humoral response responsible for the production and release of antibodies in response to an antigen

Front 21

What are T-lymphocytes responsible for?

Back 21

Cell-mediated immune response where the T-lymphocytes bind to antigen-carrying cells and as a result destroy them and/or activate a humoral response (B-lymphocytes)

Front 22

What are B-lymphocytes?

Back 22

A type of white blood cell which mature in the bone marrow

Front 23

Where does the humoral response take place?

Back 23

In the blood and in tissue fluid

Front 24

How come each B-lymphocyte has a unique plasma membrane?

Back 24

B-lymphocytes differentiate so that each one has its own specific antibody inserted into its plasma membrane

Front 25

Describe the humoral response process

Back 25

B-lymphocyte's antibody receptor binds with complementary specific antigen stimulating the B-lymphocyte to secrete antibodies and undergo mitosis to form B-lymphocyte clones called plasma cells. These plasma cells secrete more specific antibodies and also produce memory cells for that particular antigen until all antigens are destroyed.

Front 26

Describe the cell-mediated response process

Back 26

T lymphocyte binds with complementary antigen receptor on an antigen-presenting cell.
This stimulates the T-lymphocytes to undergo mitosis and form clones to secrete cytotoxic cells, phagocytes, B-lymphocytes and suppressor cells

Front 27

Once stimulated (by what process?) what does the T-lymphocyte secrete?

Back 27

Cell-mediated immune response
Cytotoxic cells -> destroys specific antigen-carrying cells
Phagocytes -> engulf cels
B-Lymphocytes -> forms plasma and memory cells
Suppressor cells->turn off immune response by halting antibody production.

Front 28

Describe and explain some non-specific defense mechanisms. What is the advantage of these?

Back 28

Skin: thick continuous keratin layer which can be washed and flaked to prevent a build up of bacteria
Eyes: lysozyme in tears breaks down bacterial cell walls
Phagocytosis: Phagocytes engulf pathogen by surrounding it and releasing lytic enzymes
Immediate effect

Front 29

Describe and explain the effect of passive natural immunity

Back 29

Antibodies travelling from mother to foetus via placenta.
Short term effect because no memory cells involved

Front 30

Describe and explain the effect of active natural immunity

Back 30

Body exposed to pathogen (antigen) triggering an immune response leading to the manufacture of antibodies and memory cells so that there is a long term effect reducing response time for future exposures of the same antigen.

Front 31

Describe and explain the effect of passive artificial immunity

Back 31

Inject ready made antibodies so no memory cells made

Front 32

Describe and explain the effect of active artificial immunity

Back 32

Inject weakened form of antigen (vaccine) stimulating an immune response leading to the production of antibodies and memory cells so that there is a long term effect reducing response time for future exposures of that particular antigen

Front 33

Describe how T-cells and antibodies are produced with the help of macrophages

Back 33

Macrophage engulfs pathogen with antigen molecules in their membranes. Macrophage presents these antigens on its own membrane and as a result helper T-cells incorporate these antigens into their own protein structures .
These activated helper T-cells then stimulate B-cells which then divide to form clones of antibody-secreting plasma cells and memory cells.

Front 34

What are monoclonal antibodies?

Back 34

Antibodies produced from a single group of genetically identical B-cells

Front 35

How are monoclonal antibodies used to treat cancer?

Back 35

Monoclonal antibodies produced with a certain complementary shape to bind specifically to tumour markers (antigens only found on cancer cells). Once bound the monoclonal antibodies release the anti-cancer drugs which are attached to them.

Front 36

How are monoclonal antibodies used in pregnancy tests?

Back 36

Test strip layered with immobilised monoclonal antibodies complementary to hormone hCG present in the urine of pregnant women. Once bound an antigen-antibody complex is formed and so any non-bound will be washed off leaving a blue plate identifying a positive result.

Front 37

When is the primary immune response triggered?

Back 37

When a foreign antigen penetrates into the body for the first time

Front 38

Why is the primary immune response slow?

Back 38

No pre-existing B-cells with complementary antibodies for particular antigen.

Front 39

What is meant by someone being "immune"?

Back 39

Memory cells which recognise that particular antigen are present and so can bind to the antigen.
Memory B-cells divide into plasma cells producing more antibodies with a complementary shape to the foreign antigen.
Memory T-cells divide to destroy these antigen-carrying cells.

Front 40

What happens during the primary response?

Back 40

B-cells increase in number dramatically to produce more antibodies with a complementary shape to the antigen. During this time the infected person will show symptoms because the process is slow. After this exposure T and B lymphocytes produce memory cells. Memory T-cells recognise that particular antigen next time. Memory B-cells record the specific antibodies required with a complementary shape to the antigen needed to bind with the antigen

Front 41

How does a vaccine work?

Back 41

Contains foreign antigens which stimulate an immune response involving T and B lymphocytes to produce the memory cells needed to recognise a future exposure to that same foreign antigen.

Front 42

What is the advantage of vaccines?

Back 42

Makes you immune to a particular pathogen without actually causing disease-showing symptoms.

Front 43

What is herd immunity?

Back 43

Reducing the occurrence of a disease by implementing vaccines to a great proportion of a population.

Front 44

What is the effect of herd immunity?

Back 44

Even those in the population who are not vaccinated are less likely to catch the disease - little spread of disease.

Front 45

What are the disadvantages of taking a vaccine orally?

Back 45

Weakened foreign antigens present may be broken down by enzymes in the gut or may not be absorbed into the bloodstream because molecules may be too big.

Front 46

What is the advantage of injecting a vaccine?

Back 46

Antigens supplied straight into the bloodstream and so the process is quicker and more efficient than the oral method.

Front 47

Why are booster vaccines given?

Back 47

Given after many years to make sure that memory cells are produced.

Front 48

How does antigenic variation affect the second immune response?

Back 48

Memory cells produced from first exposure's immune response will not recognise the new foreign antigens. As a result, the second immune response actually acts like a primary response.

Front 49

Why does antigenic variation make it difficult to develop vaccines?

Back 49

New strains formed when antigens change. Once the immune system involving B and T cells are triggered the memory cells from the previous infection will not recognise these new foreign antigens and as a result every time we are infected with a new strain our immune system produces a primary response. Therefore, we suffer the symptoms every time.

Front 50

What are plasma cells?

Back 50

Clones of B-cells which secrete antibodies specific to a particular antigen

Front 51

What are the 2 functions of antibodies?

Back 51

1. Surround the pathogen, coating it via agglutination to make it easier for phagocytes to engulf and prevent the pathogen from entering host cells.
2.Bind to toxins produced by pathogen - neutralising and inactivating them

Front 52

State the 6 simple steps of the immune system

Back 52

1.Foreign antigens trigger an immune response
2. Phagocytes engulf pathogens
3. Phagocytes activate T-cells
4. Helper T-cells activate B-cells
5. B-cells divide into plasma cells
6. Plasma cells make antibodies to a specific antigen