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Biology A level > Unit 2 - Cell Structure > Flashcards

Unit 2 - Cell Structure Flashcards

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1
Q

Resolution definition

A

The distance at which two objects can be distinguished as separate

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2
Q

How an optical microscope works

A

Light passes through the specemin then through the lense to create a magnified image

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3
Q

How a TEM microscope works

A

Beam of electrons transmitted through specemin
Denser parts absorb more electrons- making them look darker
Detected on screen

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4
Q

How a TEM microscope works

A

Electron gun produces a beam of the electrons
Only some penetrate through the specemin
They then show up on the electron photomicrograph

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5
Q

How an SEM works

A

Directs a beam of electrons onto the surface of a specimen from above
Beam is then passed back in a regular pattern by the contours of the specemin
Computer forms a 3D image of the specemin

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6
Q

Electron microscope points (POS and NEG)

A 
Cells killed 
Hard to prepare and train 
Artefacts occur 
Only in Black and White 
Better resolution 
Higher Magnification
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7
Q

Light microscope points

A

Easy to prepare and train people
Worse resolution
Limited magnification

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8
Q

Cell fractionation process

A

1) Tissue is placed in a cold isotonic buffered solution
2) Homogenisation- Tissue is placed in homogeniser
3) Filtration- Homogenate is filtered to remove solids
4) Ultra centrifugation- Pellet and supernatant

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9
Q

Functions of the nucleus

A

Contains cells hereditary material

Controls cell behaviour

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10
Q

Mitochondria functions

A

Sites of aerobic respiration

Responsible for production of ATP

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11
Q

Function of chloroplasts

A

Carry out photosythesis

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12
Q

Smooth endoplasmic reticulum functions

A

Sythesise store and transport lipids

Synthesise store and transport carbohydrates

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13
Q

Roles of Rough ER

A

Provide a large surface area for synthesis of proteins and glycoproteins
Synthesise, store and transport carbohydrates

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14
Q

Golgi apparatus functions

A

transporting, modifying, and packaging proteins and lipids
Form lysosomes

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15
Q

Lysosome functions

A

Hydrolyse material ingested by phagocytic cells
Exocytosis- Releasing enzyme to the outside of the cell
Digest worn out organelles
Autolysis- Breaks down cell after death

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16
Q

Ribosome function

A

Where protein synthesis occurs

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17
Q

Cell wall function

A

Provides mechanical strength- Stops cell bursting
Gives strength to plant as a whole
Allows water to pass through

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18
Q

Vacuoles Functions

A

Supports plants
Food store
Colour petals

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19
Q

Cell surface membrane function

A

Acts as a differentially permeable layer- controls movement in and out of the cell

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20
Q

Capsule definition

A

Secreted slime which protects the bacteria from immune system cells and helps them stick together.

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21
Q

Role of Circular DNA in prokaryotic cells

A

Contains genetic material for the cell to replicate.

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22
Q

Flagellum definition

A

Long, hair-like structure which rotates to aid movement

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23
Q

Plasmid definition

A

Small circle of DNA which is used in diverse conditions, able to replicate independently from the main DNA.

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24
Q

Prokaryotes can be defined by…

A

Lacking membrane-bound organelles (Mitochondria Lysosomes and Chloroplasts)
Smaller ribosomes
Cell wall made of muerin

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25
Q

Virus definition

A

An acellular non-living protein shell containing either DNA or RNA.

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26
Q

Stages of Mitosis in order

A 
Interphase 
Prophase 
Metaphase 
Anaphase 
Telophase
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27
Q

Interphase

A

DNA replication

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28
Q

Prophase

A

Nucleolus fuses
Centrioles duplicate and move to poles, forming spindle fibres
Chromosomes become shorter and thicker
Nuclear membrane breaks down

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29
Q

Metaphase

A

Chromosomes line up on equator

Spindle fibres attach to centromeres

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30
Q

Anaphase

A

Spindle fibres contract
Centromere divides separating sister chromatids
The sister chromatids are pulled to opposite poles

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31
Q

Telophase

A

Spindle fibres disintegrate
Each chromatid is now a chromosome
Nuclear membrane reforms around each group of chromosomes
Cytokenisis- Cell divides at waist

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32
Q

Preparing a stained temporary mount

A

1) Put specemin on tile and remove thin piece of tissue
2) Add a drop of water to the slide
3) Put tissue at centre of microscope slide- make sure its not folded
4) Add stain
5) Lower an edge of coverslip onto stain- use the mounted needle held vertical with the coverslip leaning on it to slowly lower the coverslip onto the specemin.

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33
Q

Describe how to use an eyepiece graticule to calculate the distance across a transverse section of a leaf

A

1) put slide with leaf onto stage + determine which mag is appropriate
2) Replace with stage micrometer
3) Insert eyepiece graticule
4) Calculate length of each EPU
5) Put sample slide back on stage
6) Count how many EPU’s it is and multiply it by the ratio

34
Q

Methods of preventing cell division for cancer

A
  • Prevent spindle formation

- Prevent production of enzymes

35
Q

Prokaryotic cell division

A
  • Circular DNA and plasmids replicate independently
  • Circular DNA attaches to the cell membrane and the cell elongates
  • Circular DNA moves to opposite ends of the cell
  • The cell membrane grows, dividing the cytoplasm into two
  • New cell walls form between the DNA, dividing into two daughter cells
36
Q

Viral replication

A
  • Virus attackes to host cell receptor proteins
  • Genetic material is released
  • Genetic material and proteins are replicated by the host cell
  • Viral components assemble
  • Replicated viruses released from host cell
37
Q

Functions of the Phospholipid bilayer

A

Allow lipid soluble substances to enter and leave
Prevents water- soluble substances from entering and leaving the cell
Makes the membrane flexible and self-sealing

38
Q

The functions of the membrane are to

A
  • Provide structural support
  • Act as a channels transporting water soluble substances across the membrane
  • Allow active transport across the membrane through carrier proteins
  • Form cell- surface receptors (glycolipids)
  • Act as receptors, for example hormones
39
Q

The functions of cholesterol are

A
  • To reduce lateral movement of other molecules including phospholipids
  • Make the membrane less fluid at higher temperatures
  • Prevents leakage of water and dissolved ions from the cell
40
Q

The function of glycolipids in the membrane

A
  • Act as recognition sites
  • Help maintain the stability of the membrane
  • Help cells attach to each other and form tissues
41
Q

The functions of glycoproteins

A
  • Act as recognition sites
  • Help cells to attach to one another and form tissues
  • Allows cells to recognise one another
42
Q

Fluid mosaic model

A

Fluid- The induvidual phospholipid molecules can move relative to one another, this gives the membrane a flexible structure that is constantly changing shap.
Mosaic- The proteins embedded vary in shape, size and pattern

43
Q

Diffusion

A

The net movement of molecules or ions from a region where they are more highly concerntrated to one where their concerntration is lower until evenly distributed.

44
Q

Diffusion

A

The net movement of molecules or ions from a region where they are more highly concerntrated to one where their concerntration is lower until evenly distributed.

45
Q

Osmosis definition

A

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

46
Q

Hypotonic definition

A

When the solute concerntration is lower than the concerntration inside the cell

47
Q

Hypertonic solution

A

A solution in which the solute concerntration is higher than the concerntration inside the cell. (low water concerntration)

48
Q

How do pathogens cause disease?

A

By producing toxins

By causing damage to host cells/ tissues

49
Q

Physical Barriers to pathogens

A
  • Tears
  • Nasal Hairs
  • Blood clots
  • Stomach acid
50
Q

Phagocytosis steps

A

The phagocyte is atteacted to the pathogen by chemical products- moves toward pathogen
Receptor on phagocyte binds to pathogen
Phagosome is formed and lysosomes move toward the pathogen
Lysosomes release their lysozymes into the phagosome- pathogen is hydrolysed
The hydrolysis products will be absorbed/ presented on the surface/ relaesed (exocytosis)

51
Q

Antigen definition

A

Any part of an organism or substance that is recognised as non-self and triggers an immune response

52
Q

Antibody definition

A

They are proteins that are secreted by B lymphocytes in response to a non- self antigen

53
Q

Humoral response

A
  • There is a B cell that has a antibody complemetary to every antigen
  • There is a B cell that has an antibody specific to the pathogens antibody- the two bind
  • The B cell takes in the antigen and is presented on the surface by a molecule called MHC
  • T cell that binds to the B cell antigen stimulates it to divide
  • (Clonal expansion)- B cell divides to produce daughter cells
  • Most are plasma cells which synthesise and realease antibodies
  • Memory cells are produced- these remain dormant in the blood
54
Q

Ways that antibodies work

A

Agglutination- Clumping pathogens
Antitoxins- Neutralises toxins
Lysis- Digests bacterial membrane, killing the bacterium
Opponisation- Coats the pathogen in protein- iddentifying them as foreign cells

55
Q

Cell mediated response

A

Pathogens invade body cells or are ingested by phagocytes
Phagocyte/ infected cell places antigens from pathogens on its surface
Receptors on certain T cells are specific
This stimulates other T cells to divide rapidly by mitosis and form a clone
The cloned T cells:
Develop into memory cells
Stimulate phagocytosis
Stimulate B cells
Become cytotoxic T cells/ memory cytotoxic T cells

56
Q

Give examples of passive (natural and artificial) and active (natural and artificial) immunity

A

Natural Passive- Antibodies in mothers milk
Artificial Passive- Antivenom
Natural Active-Response in infection
Artificial Active- Vaccination

57
Q

3 types of vaccine

A

Dead pathogen with unaffected antigens
Weakened pathogen- Attenuation
Using purified antigens

58
Q

Features of a successful vaccination programme

A
  • Economically avaliable to immunise all the vulnerable population
  • Few side effects
  • Means of producing and storing it
  • Means of administering it
  • Must be possible to vaccinate vast majority for herd immunity
59
Q

Reasons why a vaccination programme may not work

A
  • Defective immune systems
  • Induvidual may develop disease immediately after vaccination
  • Pathogen mutates- antigen variability
  • Too many strains to make a vaccine
  • Pathogen may hide from immune system
  • Induviduals may reject based on personal/ beliefs
60
Q

Structure of HIV

A
  • A core that contains RNA and some proteins (also reverse transcriptase)
  • An outer protein coat called a capsid
  • An extra outer layer called an envelope
  • Attachment proteins on envelope
61
Q

HIV replication

A

Attatchment protein attaches to a receptor molecule on the cell membrane of the host helper T cell
The capsid is released into the cell, where it uncoats and releases genetic material
Reverse transcriptase is used to make a complementary strand of DNA from the viral RNA template
Double stranded DNA is made and inserted into human DNA
Host cell enzymes are used to make viral proteins from viral DNA
The viral proteins are assembled into new viruses which bud from the cell

62
Q

Why do antibiotics not work against viruses

A

Antibiotics kill bacteria by interfering with their metabolic reations
Viruses don’t have their own enzymes and ribosomes
Antibiotics can’t inhibit them

63
Q

Uses of monoclonal antibodies and an example

A

Targeting cells- During cancer treatment

Medical diagnosis- Pregnancy testing

64
Q

ELISA test outline

A
  • Antigen is bound to bottom of the well
  • Sample is added- any complementary antibodies will bind
  • Secondary antibody will bind to primary antibody
  • Dye that is complementary to the enzyme bounded to secondary antibody will bind if it is present
65
Q

Nucleus structure features

A 
Double membrane 
Outer membrane continuous with ER
Nuclear pores
Nucleoplasm 
Nucleolus- Manufacures ribosomal RNA
66
Q

Mitochondria structural features

A

Double membrane
Cristae- Large SA for attachment of enzymes and proteins
Matrix

67
Q

Chloroplast structural featurre

A

Double membrane
Grana- Stacks of thykaloids containing chlorophyl- high SA
Stroma- Fluid filled matrix- second step of photosynthesis
Contain DNA and 70 S ribosomes- quick manufacture of proteins

68
Q

Structural features of both types of ER

A

3D system of sheet-like membranes
Continuous with outer membrane of nucleus
Network of tubules and cisternae

69
Q

Golgi structural features

A

Stack of membranes- cisternae

Rounded vescicles

70
Q

What are ribosomes made of

A

RNA and a protein

71
Q

Cell wall structural features

A

Consists of microfibrils of polysaccaride cellulose
Embedded in a matrix
Thin middle lamella layer- cements adjacent cells together

72
Q

Vacuole structure

A

SIngle membrane
Tonoplast membrane
Contains mineral salts, sugars and amino acids

73
Q

Features of good diagram

A 
Solid cel outline 
Not too much detail 
No crossing lines
No hanging lines
Not over casual 
Dont scetch 
In pencil 
No shading 
Title 
Magnification
74
Q

Difference between cytokinesis in plant and animal cells

A

In Animal cells:

  • Cell membrane is pulled inwards across the centre of the cell
  • This separates/ pinches off the cytoplasm into two halves

In plant cells:

  • Vesicles fuse to extend the cell membrane across the cytoplasm
  • New cell walls develop
75
Q

Order of phases in interphase

A

G1
S
G2
Mitosis

76
Q

Cancer treatment aims

A

Preventing spindle formation

Preventing production of enzymes

77
Q

Co transport in illeum

A

Sodium potassium pump pumps potassium ions into the cell by active transport
This decreases the conc gradient for sodium ions in the lumen of the ileum
Sodium ions move down conc gradient by facilitated diffusion into cell
Sodium-glucose transporter proteins carry the glucose with the sodium into the cell
Glucose then diffuses out of the cell and into blood by facilitated diffusion

78
Q

Antigenic variability

A

An organism frequently changes antigens on their surface

79
Q

Ethical issues vaccines + Monoclonal antibodies

A
  • Vaccines require animal testing in some instances which some disagree with
  • Testing vaccines on humans might make them take risks
  • Some people wont take up the vaccine because of side effects but are still protected by herd immunity
  • Difficult decisions have to be made about who gets what vaccine

Monoclonal antibodies are often sourced from animals and involve animal rights issues

80
Q

Difference between T + B cells reacting to respective antigens

A

T Cells reacts to antigen presenting cell
B cell reacts to free antigen

T cell stimulates immune response (releases cytokines)
B cell reacts by releasin antibodies

81
Q

Why might people have concerns about vaccinations

A

Side effects
Ethical concerns regarding use of animal testing
Ethical concerns around use of embryonic stem cells in testing

82
Q

What is a vaccine

A

Cotains weakened pathogen
Stimulates production of B cells
Artificial immunity

Biology A level (13 decks)

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