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A-levels > Biology UNIT 2-Cells & Cell structure > Flashcards

Biology UNIT 2-Cells & Cell structure Flashcards

1
Q

What is a Eukaryotic cell?

A

A cell that contains a nucleus surrounded by a plasma mebrane. The nucleus contains DNA surrounded by histone proteins.
There are also a number of other specialised membrane bound organelles.

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2
Q

What is the structure and function of the chloroplasts?

A

Structure:
Has a doubled membrane. Inner membrane is folded into lamellae.
Inner membrane contains a continuous network of Thylakoids (containing photosynthetic pigments)
Function:
Site of photosynthesis.

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3
Q

What is the structure and function of Microvilli?

A

Structure:
Have a plasma membrane, cytoplasm and a cellular fluid. Also contain microfiliments called Actin.
Function:
Increase surface area of cells to absorb more nutrients and aids in cellular adhesion,

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4
Q

What is the structure and function of the Nucleus?

A

Structure:
Largest Organelle occupying 10% of the cell.
Has a double membrane with the outer membrane having continuous rough ER.
Nuclear envelope to separate genetic material and the cytoplasm,
Nucleolus is central containing Chromatin.
Function:
Controls a cells growth, movement and reproduction.
Contains the DNA and genetic material of the cell.

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5
Q

What is the structure and function of the mitochondria?

A

Structure:
Present in all eukaryotic cells.
Has double membrane with outer membrane being fairly permeable and inner membrane strictly permeable to Oxygen and ATP.
Inner membrane is folded into a shelf called Cristae.
Has a Matrix with proteins and enzymes contained within it.
Function:
Produce ATM from respiration
Help maintain calcium ion levels
Help in building parts of blood and hormones.

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6
Q

What is the structure and function of Lysosomes?

A

Structure:
Surrounded by a membrane of phospholipids separating internal and external areas of the organelle.
Have a sac/bag like structure full of digestive enzymes (lytic enzymes)
Function:
To digest organic waste
remove warn out cells

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7
Q

What is the structure and function of the cell wall?

A

Structure:
Made of cellulose and other polysaccharides.
Has 3 layers (Plasma membrane, Primary cell wall, middle lamella)
Function:
Protects the cell
regulates life cycle of plant organisms
provides structural support
separates inner and outer environments of the cell
Prevents water loss.

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8
Q

What is the structure and function of the vacuole?

A

Permanent organelle in plants, can be in animal cells,
Structure:
Cell membrane surrounding a body of fluid
Function:
could store nutrients or food or waste products to prevent contamination. Helps keeps plants turgid

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9
Q

What is the structure and function of the Golgi apparatus?

A

Structure:
Made of several flattened membrane sacs called cisternae.
One end is set to synthesise proteins from the ER.
Has secretory vesicles which release proteins.
Function:
Modify sort and package proteins for secretion. Creates lysosomes and transport lipids around the cell.

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10
Q

What is the structure and function of ribosomes?

A

Structure:
60% RNA and 40% proteins,
found in both prokaryotic and eukaryotic cells
can be freely suspended in the cytoplasm or joined to the end of rough ER.
Function:
To make proteins which are needed for growth and repair. They are required for protein synthesis.

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11
Q

What is the structure and function of the cell surface membrane?

A

Structure:
Plasma membrane separates the cell interior from the exterior environments.
Consists of a phospholipid bilayer with embedded proteins.
Cell membrane is selectively permeable to ions, organic molecules.
Function:
Passive osmosis and diffusion of small molecules and ions.
Absorbing molecules by engulfing them. (Endocytosis).

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12
Q

What is the structure and function of the Endoplasmic Reticulum?

A

Structure:
2 types, (rough ER and Smooth ER)
Rough ER is stubbed due to outer membrane is covered with ribosomes.
Both ER form a network of flattened sacs called cisternae,
Phospholipid membrane which encloses the cisternal space.
Function:
Rough ER transports proteins created by ribosomes to the golgi and folds proteins in the cisternae.

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13
Q

What is the structure and function of Cilia?

A

Structure:
Tiny hairs with microtube pairs and filaments.
Function:
Moves substances/liquid along the surface of the cell.

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14
Q

What is the structure and function of flagella?

A

Structure:
Tail filled with mitochondria to provide energy.
Function:
Helps the cell to move using energy and to move liquid past easily.

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15
Q

What is a specialised cell?

A

Specialised cells can be differentiated for a particular function. The number of organelles will differ depending on that function.

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16
Q

How do you calculate the actual size of an image and the magnification?

A

Actual size= Image size / magnification

Magnification= Image size / Actual size

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17
Q

What is a prokaryotic cell?

A

A cell with no true nucleus/ They do not contain membrane bound organelles and are in general much smaller than a eukaryotic cell.

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18
Q

What are the features of a eukaryotic cell?

A

Contains membrane bound organelles.
True nucleus
Tend to be bigger
Often multi-cellular

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19
Q

What are the features of a prokaryotic cell?

A 
No true nucleus
Lacks membrane bound organelles
uni-cellular
Asexually reproduce
No Cytoplasm
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20
Q

What are prokaryotic cell walls made from?

A

Peptidoglycan

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21
Q

What is gram positive and gram negative bacteria?

A

Gram positive- Thick cell walls containing many layers of peptidoglycan and teichoic acids.

Gram Negative- Relatively thin cell walls consisting of a few layers of peptidoglycan surrounded by a second lipid membrane containing liopolysaccharides and lipoproteins.

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22
Q

What is the origin of a virus?

A

Uncertain!!!

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23
Q

What are the 5 Kingdoms?

A 
Animalia
Plantae
Fungi
Prokaryotae
Protoctista
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24
Q

Which of the 5 kingdoms do viruses fit into?

A

None- as viruses show no/tiny amounts of characteristics to define a living organism.

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25
Q

What are the characteristics of a virus?

A

Obtigates intercellular parasites.
Small (nanometers in size)
Contain a single type of nucleic acid. (either DNA or RNA)
Contain a protein coat (capsid)
May contain a host
Multiply inside living cells using bio synthetic machinery of the host.

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26
Q

What the the different types (morphological types) a virus can be classified as?

A

Helical
Polyhedral/cubic
enveloped
complex

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27
Q

What are the 5 major steps in viral replication?

A 
Attachment
Penetration
Nucleic acid and protein synthesis.
Assembly of virons (virus particles)
Release/egress
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28
Q

Define a parasite.

A

An oragnism which lives in or off another organism (host) and benefits by deriving nutrients at the other organisms expense.
(viruses are a type of parasite)

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29
Q

What does the virus do once inside the host cell?

A

Makes use of the cells enzymes to reproduce.
some take over the machinery of the host cell immediately.
They make large numbers of new virus particles which are then released ready to infect new cells.

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30
Q

What is the genetic material of a virus?

A

May contain DNA or RNA

The type of genetic material depends on the function/nature of the specific virus.

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31
Q

What is a bacteriophage?

A

A virus that attacks bacteria.
DNA is coated by proteins.
DNA is long thread with 150 genes packed into the head.
Larger than most other viruses.

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32
Q

How does a bacteriophage attack bacteria?

A

Attacks the surface of the bacteria using its tail.
DNA is injected into the bacteria where it proceeds to replicate,
The new viral DNA enables the manufactoring and assembly of new viral heads and tails.
After 30 mins the bacterium bursts open releasing 300+ viruses which repeat the process.

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33
Q

Define magnification size.

A

Magnification- How much bigger the image is in comparison to the actual size of the sample.

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34
Q

Define Resolution.

A

Resolution- How well a microscope distinguishes between two points which are close together.

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35
Q

How do you calibrate the eyepiece gratitude on a microscope?

A

1) place the stage micrometer on the microscope stage.
2) Line up the divisions on the eyepiece with those on the micrometer.
3) work out the length of one eyepiece graticule unit in micrometeres
4) repeat for each of the objective lenses on the microscope.

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36
Q

What is staining?

A

Biological material is not coloured (often) so chemicals can be bound to a specimen allowing it to be seen.
(Eg. Acetic Orcin stains DNA red)

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37
Q

What is sectioning?

A

Specimens are embedded into wax and then thin sections are cut without changing the structure of the specimen. (prevents distortion)

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38
Q

How does a Transmission Electron Microscope Work?

A

Beam of electrons are passed through the specimen and dispersed by the structures.
The scattered electrons are then captured on a photographic film.

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39
Q

How does a Scanning Electron Microscope Work?

A

Specimen is coated in a very thin metal layer.
Beam of electrons is bounced off the surface and onto a photographic plate.
Allows a 3D image to be produced.

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40
Q

What is etching?

A

Specimens are coated with a very thin layer of heavy metal in order to be looked at under a SEM.

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41
Q

What is freeze Fracture?

A

The specimen is frozen rapidly and then cracked on a plane through the tissue.
The Fracture occurs along weak portions of the tissue such as the cell membranes and organelles.

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42
Q

What are the advantages and disadvantages of using Electron Microscopes?

A

Adv- Higher magnification and resolution so better detailed images.

DisAdv- Very expensive and require training to use. Can only look at dead organisms.

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43
Q

What are the advantages and disadvantages of using optical microscopes?

A

Adv- Cheap, simple to use and can view living organisms up to 1500x magnification.

DisAdv- Lower resolution and magnification.

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44
Q

What is cell fractionation?

A

The separation of different parts of the cells in order to study cell structure and function.

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45
Q

Why is the chopped tissue homogenised in a cold, isotonic and buffered solution?

A

Cold- Reduce enzyme activity.
Isotonic- Prevents organelles shrivelling/bursting.
Buffered- Maintains a constant pH.

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46
Q

What are the main steps in cell frationation?

A

1) tissue is cut into small pieces.
2) Made smaller by a homogeniser.
3) homogenate is filtered to remove any large cells such as cell membrane and wall.
4) suspension of homogenate is placed into a test tube and centrifuged at high speeds.
5) slower speeds = larger fragments becomes sediment pellets and removed from the supernatant.
6) re-spun at a faster speed for longer = smaller organelles
7) repeat until the organelles have been removed.

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47
Q

What is a lipid?

A

A mixed group of hydrophobic compounds composed of Carbon, Hydrogen and oxygen, (FATS)

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48
Q

What are the main functions of lipids?

A 
Storage.
Production of metabolic water
thermal insulation
electrical insulation
water proofing
hormone production
buoyancy.
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49
Q

What is the backbone of lipids?

A

Glycerol molecule. (3 Carbon groups with 3 Alcohol groups)

(CH2OH)3

50
Q

What is a fatty acid?

A

Long molecules with a hydrophillic head and non-polar hydrophobic tail.

51
Q

What is the structure of a fatty acid?

A

CH3(CH2)nC00H

52
Q

What are the properties of saturated fatty acids?

A 
No C=C double bonds.
Fatty acids form straight chains
high melting points
tend to be in warm blooded animals.
solid at room temperature
53
Q

What are the properties of unsaturated fatty acids?

A

Have c=c double bonds
fatty acids form bent chains
low melting point
liquid at room temperature

54
Q

What characteristic of a lipid enables us to be able to do an emulsion test?

A

Lipids do not dissolve in water but do dissolve in ehtanol.

55
Q

What are the steps in an emulsion test?

A

1) Shake test sample with 4cm^3 of ethanol.
2) decant the liquid into a test tube of water leaving behind any undissolved substances.
3) lipids dissolved in ethanol will produce a white precipitate in water forming a cloudy white emulsion.
4) add sudan III dye to stain the lipids red.

56
Q

What are triglycerides?

A

Lipids made from 1 gycerol molecule and 3 fatty acid molecules.
bonded by an ester bond
formed via condensation reaction
hydrophobic and therefore insoluble.

57
Q

What is the structure of a triglyceride?

A

(CH2COOR)-(CHCOOR)-(CH2COOR)

58
Q

What is a phospholipid?

A

Lipids made from 1 glycerol molecule bonded to 3 fatty acids molecules however the 3rd fatty acid is replaced by a phosphate group head.

59
Q

What are the properties of a phospholipid?

A

Fatty acid tails are hydrophobic
Phosphate heads are hydrophillic.
contain saturated and unsaturated fats so they have control over fluidity of membranes which is easier.
can form phospholipid bilayers.

60
Q

What is the structure of a phospholipid?

A

(CH2COOR)-(CHCOOR)-Pi

61
Q

what are the roles of the plasma membrane?

A

Isolates the cytoplasm from the external environment.
Regulates the exchange of substances
communicates with other cells
membranes are mainly made of phospholipids
identification

62
Q

What does the phospholipid bilayer do?

A

Acts as a barrier between 2 aqueous solutions.
hydrogen bonds form between the phospholipid heads and the watery environments in and out of the cell.
Phospholipids are not bonded to each other which makes the double layer fluid.
Cholesterol is embedded in the membrane making it stronger and less fluid.

63
Q

What is the role of channel proteins?

A

They have small openings so molecules can diffuse through them.

64
Q

What is the role of carrier proteins?

A

they are the binding site on a protein surface which grabs certain molecules and pulls them into the cell.

65
Q

What is the role of receptor proteins?

A

molecular triggers that set off cell responses.

E.g the release of hormones or opening of channel proteins

66
Q

What is the role of cell recognition proteins?

A

They are ID tags to identify cells to the bodies immune system (antigens)

67
Q

What is the role of Enzymatic proteins?

A

They carry out metabolic reactions

68
Q

What are the components of the cell surface membrane?

A 
Phospholipds
proteins
cholesterol
glycolipids
glycoproteins
69
Q

What are the functions of phospholipids in the cell surface membrane?

A

Allow lipid soluble substances to enter and leave the cell.
Prevent water soluble substances from entering and leaving the cell.
Make the membrane flexible and self sealing.

70
Q

What are the functions of proteins in the cell surface membrane?

A

Peripheral (globular) proteins- provides structural support
Protein channels- channels to transport water soluble substances across
Carrier proteins- allow active transport across the membrane
receptor proteins- identifies cells
Globular proteins- also acts as receptors (eg hormones)

71
Q

What are glycolipids?

A

made up of a carbohydrate covalently bonded with a lipid.

the carbohydrate portion extends from the phospholipid bilayer into the watery environment,

72
Q

What are glycoproteins?

A

Carbohydrates chains attached to many extrinsic proteins on the out surface of the cell membrane.

73
Q

what are the functions of cholesterol in the cell surface membrane?

A

Adds strength
reduce lateral movement of other molecules including phospholipids.
makes the membrane less fluid at higher temperatures.
prevent the leakage of water and dissolved ions from the cell.

74
Q

What are functions of glycolipids in the cell surface membrane?

A

Act as recognition sites.
help maintain the stability of the membrane.
helps cells attach to one another and therefore form tissues.

75
Q

What are the functions of glycoproteins in the cell surface membrane?

A

Act as recognition sites
help cells to attach to one another to form tissues.
allows cells to recognise one another.

76
Q

What is the function of the cytoskeleton in the cell surface membrane?

A

3D network of fibrous proteins to provide structural support.

77
Q

Define Flaccid and turgid.

A

Flaccid- Something that is weak/soft.

Turgid- something that is swollen, bloated, puffed or inflated

78
Q

Define Hypotonic and Hypertonic,

A

Hypotonic- Having a low osmotic pressure in comparison to a particular fluid,

Hypertonic- Having a high osmotic pressure in comparison to a particular fluid.

79
Q

Define Isotonic.

A

An isotonic solution has the same osmotic pressure/water potential either side of the membrane.

80
Q

Define gross movement and net movement.

A

Gross movement- The overall direction of flow of everything.

Net movement- the overall direction of flow of a substance (E.g water in osmosis)

81
Q

Define plasmolysis.

A

the process in which cells lose water in a hypertonic solution.

82
Q

Define osmosis.

A

The movement of water through a partially permeable membrane from an area of higher water potential to an area of lower water potential.

83
Q

define solute, solvent and solution.

A

Solute- a dissolved substance in a solution
Solvent- the dissolving substance in a solution.
Solution- A type of homogenous mixture in which a solute is spread uniformly by a solvent.

84
Q

Define tugor pressure

A

The pressure of water pushing the plasma membrane against the cell wall of a plant cell.

85
Q

Define water potential.

A

The measure of the relative tendency of water to move from one area to another.

86
Q

Define osmotic pressure.

A

The volume of water drawn through a semi-permeable membrane.

87
Q

Define diffusion.

A

The movement of particles from an area of higher concentration to an area of lower concentraion.

88
Q

What is ficks law?

A

The relationship between factors; concentration, surface area and exchange surface

rate of diffusion = (surface area x concentration gradient) / Thickness of exchange surface.

89
Q

Define active transport

A

The movement of molecules or ions against the concentration gradient from areas of lower concentration to higher concentrations. This process requires energy from ATP hydrolysis and also to be carried out through carrier proteins.

90
Q

What is passive transport?

A

Transport that doesn’t require external energy input.

such as diffusion or osmosis.

91
Q

What are the steps in active transport?

A

1) carrier proteins in membrane bind to molecule.
2) molecule binds to receptor sites on protein.
3) ATP binds to protein on inside of the cell and splits to ADP + Pi. this causes the molecule to change shape.
4) Molecule ion is released to other side of the membrane.
5) Pi group released from protein (reverting shape back to original)
6) Pi recombines with ADP to form ATP molecule during respiration.

92
Q

Explain how the sodium potassium pump works.

A

Na+ ions are removed from the cell/organelle whilst k+ ions are taken into the cell from surroundings.
3 Na+ ions are removed so protein changes shape to be more affinitive to k+ ions.
2 K+ ions are then taken into the cell by carrier proteins.

93
Q

Define Cytosis.

A

The transporting of large substances across a membrane.

Endocytosis- Taking substances into cells
Exocytosis- cells secrete a substance for use.
Pinocytosis- Taking in liquids into cells.

94
Q

What is a pathogen?

A

A disease causing organism

95
Q

What is an Antigen?

A

A complex molecule usually a protein or carbohydrate that induces an immune response when introduced into the body/ detects a non-self antigen.

96
Q

What is an Antibody?

A

A type of Quaternary protein that serves as a vital body immune defence.

97
Q

What are the steps in Phagocytosis?

A

1) Phagocyte is attracted to the pathogen by chemoattractants in waste material left behind by pathogen.
2) Moves towards the pathogen along a concentration gradient.
3) Pahgocyte binds to the pathogen.
4) A Phagosome starts to form
5) Lysosomes migrate to the phagosome formed by engulfing the bacteria.
6) Lysosomes move towards the englufed bacteria.
7) Lysosomes relase Lytic enzymes into the phagosome where they break down bacteria.
8) Phagocyte recycles the broken down material of the bacteria.

98
Q

What is cell mediated immunity?

A

Part of the specific (adapted) immunity.

Once a pathogen is broken down via a phagocyte, it will present an antigen on the surface of its membrane.
T-cells bind to the antigen via a specific & complementary binding site.
T-Cells the go through many mitotic divisions to produce more T-cells (clones). There are 4 different populations of T-Cells produced.

99
Q

After T-cell mitosis what are the 4 populations formed?

A

Cytotoxic T-cells- directly destroy pathogen infected cells by puncturing the membrane.
Helper T-cells- stimulates the release of T&B-cells
Suppressor T-cells- Inhibits T&B-cells.
memory T-cells- remembers antigens for future encounters.

100
Q

What does the Humoral immune system involve?

A

The Bloodstream!

101
Q

what are the steps in a Humoral immune response?

A

1) B-lymphocyte (B-cell) binds to an antigen and takes the antigen in.
2) B-cell processes and then presents the antigen on the cell surface membrane.
3) T-helper cell with the specific complementary binding site binds to the antigen on the cell surface membrane.
4) This causes the B-cell to divide by mitosis into many clones of 2 populations. (plasma cells & memory cells)

102
Q

What are the differences between passive and active immunity?

A

Passive:
Does not involve memory cells.
Antibodies introduced into body via external source.
Short term immunity as antibodies given get broken down.
Fast response.

Active:
Involves memory cells.
Production of antibodies by plasma cells.
Long term immunity as antibodies produced as a response to antigen.
Takes time to develop.

103
Q

What is in a vaccine?

A

Antigens of a pathogen.
Viral protein coats.
Part of bacterial antigens.

104
Q

What is the basic primary response to a vaccine to produce memory T-cells and Memory B-cells

A 
Cell mediated Immunity:
-phagocytosis
-Antigen presenting cells
-T-cell binding
-T-cell division
Followed by...
Humoral Immunity:
-B-cell binds to antigen.
-T-helper cell binds to antigen
-B-cell division
Final products are T/B Memory cells
105
Q

What is the purpose of a vaccine?

A

To give our body the primary response to create T-memory and B-memory cells so that our secondary response (to the pathogen) is rapid and large to that specific antigen.

106
Q

Give and example of antigenic variability.

A

Influenza Virus:

  • RNA keeps mutating
  • therefore antigens constantly change shape
  • so body cannot flight it easily.
107
Q

What is HIV and AIDS?

A

HIV- Human Immunodeficiency Virus
AIDS- Acquired Immune Deficiency Syndrome

The HIV Virus causes AIDS.

108
Q

How does HIV infect cells?

A

1) HIV virus attaches to host cell membrane and releases RNA and enzymes into the cell.
2) RNA is converted into DNA by Reverse transcriptases.
3) Viral DNA passes through nuclear pores
4) Viral DNA hides in the host cell DNA/ genome.
5) All daughter cells are infected with the viral DNA.

109
Q

How does HIV cause AIDS?

A

-Targets T-helper cells and destroys them.
so there are less T-cells in the body
so cannot as easily recognise disease and pathogens.
so the body cannot fight simple pathogens.
Therefore the immune system is not working properly.
AIDS is therefore caused by HIV.

110
Q

How is being HIV positive different to having AIDS?

A

you can have the HIV virus (being HIV positive) but it is dormant and does not attack T-cells. so the immune system is not damaged and therefore does not have AIDS.

111
Q

What are the properties of antibiotics?

A

-Inhibits enzymes.
-Makes holes in cell walls of bacteria.
therefore water can move into bacteria cell cause them to lyse.
-Causes bacteria to clump together so phagocytes can easily engulf them.

112
Q

What are monoclonal antibodies?

A

Antibodies produced by a specific B-cell so all antibodies will have the same specific complementary binding site.

113
Q

How are monoclonal Antibodies made?

A
  • Immunise animal for immune response to occur with B-cells producing antibodies for specific antigen.
  • Remove blood containing the antibodies and fuse it with tumour cells (cancer cells).
  • Hybridomas form which can divide a lot and only produce the specific antibody.
114
Q

What is ELISA?

A

Enzyme Linked Immunosorbent Assay.

115
Q

What is the purpose of direct ELISA?

A

Trying to Identify if there are antigens in the serum (blood) and if the person has the pathogen.

116
Q

What is the purpose of indirect ELISA?

A

To identify if there is a specific antibody to an antigen in the serum/blood and therefore determine whether they have recently had a disease.

117
Q

What are the steps in Direct ELISA?

A

1) Antibodies specific to antigen are stuck on the bottom of the microtitre plate.
2) Antigens are added and if complementary will bind to the antibodies. The microtitre plate is then rinsed.
3) Enzyme linked antibodies are added where they bind to the antigens if specific. Microtitre plate is re rinsed.
4) Enzyme substrates added and if they bind to the enzyme then a colour change occurs. If the colour change happens then the pathogen is present in the blood/serum.

118
Q

What are the steps in Indirect ELISA?

A

1) Antigens specific to antibodies are stuck on the bottom of the microtitre plate.
2) Serum is added to the blate and if this contains the specific and complementary antibodies, then they will bind to the antigens. the plate is then rinsed.
3) Enzyme linked antibodies are added which if complementary will bind to newly bound antibodies. Plate is then rinsed.
4) Enzyme substrates added and if they bind to the enzyme then a colour change occurs. If the colour change happens then the antibody to the antigen is present in the serum/blood.

119
Q

What is Binary Fission?

A

The way in which prokaryotic cells divide since they do not undergo mitosis.

120
Q

What are the steps in binary fission?

A

1) Circular DNA molecule is replicated and then both copies attach to the plasma membrane. Plasmids also replicate.
2) Plasma membrane between the poles begins to grow.
3) Pinching occurs at the equator of the cell.
4) New cell wall forms between the 2 DNA molecules.

121
Q

How are Plasmids distributed during binary fission?

A

Plasmids do not bind to the membrane so when the cells split the distribution of plasmids may not be 100% even, and therefore the two daughter cells may not be genetically identical.

A-levels (23 decks)

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