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A Level Biology > Chapter 3.2 (cells) > Flashcards

Chapter 3.2 (cells) Flashcards

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1
Q

organelles found in a eukaryotic cell?

A
  • cell surface membrane
  • nucleus
  • mitochondria
  • ribosomes
  • Golgi apparatus and vesicles
  • RER & SER
  • lysosomes

P- chloroplast
P- cell wall
P- permanent large vacuole

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2
Q

Function of the cell surface membrane?

A

Hold cell together
Selectively permeable (in/out control)
Maintain homeostasis
(Compartmentalisation of internal organelles)

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3
Q

Function of the nucleus?

A

Retain genetic material (DNA/chromosomes)
Act as control centre - producing mRNA & tRNA
Manufacture ribosomes RNA and ribosomes

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4
Q

Function of the mitochondria?

A

Site of AEROBIC respiration
Production of ATP from respiratory substances

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5
Q

Function of chloroplast?

A

Harvest sunlight and photosynthesis

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6
Q

Function of Golgi apparatus and vesicles?

A

Add carbs + protein -> glycoproteins
Produce secretory enzymes
Secrete carbs
Transport, modify and store lipids
Form lysosomes

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7
Q

Function of lysosomes?

A

Hydrolyse materials ingested by phagocytic cells
Exocytosis (Release enzymes outside cell)
Digest old organelles
Autolysats (break down dead cells)

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8
Q

Function of ribosomes?

A

Site of protein synthesis

At RER proteins -> out of cell
In cytoplasm proteins-> inside cell

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9
Q

Function of SER?

A

Synthesise, store, transport lipids & carbs
(Steroid synthesis)

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10
Q

Function of RER?

A
  • provide large SA to synthesises proteins & glycoproteins
  • pathway for minerals throughout cell
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11
Q

Function of cell wall?

A

Provide mechanical strength to prevent cell bursting under pressure from water via osmosis

Controls growth and shape
Provides protection

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12
Q

Function of permanent large vacuole?

A

Acts as temporary storage for sugars and amino acids
Support against turgor pressure

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13
Q

Which organelles have a double membrane?

A

Nucleus
Cell surface membrane
Mitochondria
Chloroplast

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14
Q

Organelle Cristae found in ?

A

Mitochondria

(Folded inner membrane)

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15
Q

Organelle grana found in?

A

Chloroplast

(Stacks found inside)

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16
Q

Organelle stroma found ?

A

Chloroplast

(Liquid filling)

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17
Q

Organelle thylakoid found?

A

Chloroplast

(Membrane)

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18
Q

Organelle cisternae found?

A

Golgi

(Flattered sacs)

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19
Q

Organelle with small and large sub units?

A

Ribosome

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20
Q

organelle tonoplast found ?

A

Permanent cell vacuole

(Membrane)

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21
Q

Differences in prokaryotic and eukaryotic cells?

A

Pro are smaller

Pro lack membrane bound organelles

Pro have smaller ribosomes

Pro have no nucleus (circular dna instead)

Pro have cell walls made out of murein (glycoprotein) not cellulose

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22
Q

Features of prokaryotic cell?

A

-flagella
- capsule (slime layer)
-cell wall
- cell membrane
- cytoplasm
-ribosomes
-plasmid
- Circular DNA

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23
Q

Are viruses living?

A

No viruses are acellular and non-living

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24
Q

Structure of virus particle?

A

Genetic material (RNA or DNA)
Capsid
Attachment proteins

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25
Q

Def specialised cell

A

Cell that had differentiated obtaining specific adaptions to carry out a specific function

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26
Q

Def magnification

A

How many times bigger the image produced is that the real-life object you are viewing

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27
Q

Def resolution

A

The ability to distinguish between objects that are close together

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28
Q

Calc for magnification?

A

Magnification. =. Image size
___________________
Actual size

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29
Q

Def of cell fractionation

A

Process where cells are broken up and different organelles they contain are separated out to be analysed

2 stages= Homogenisation & ultracentrifugation

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30
Q

process of cell fractionation & ultracentrifugation?
+ give reasons for why

A
  1. Tissue cut into small pieces and placed in cold, isotonic, buffered solution
    (reduces enzymatic action that could break down cell)
  2. Ground into smaller pieces using homognizer
    ( to release organelles)
  3. Homogenate is filtered
    ( remove large particles/ complete cells)
  4. Suspension of homogenate placed in centrifuge
  5. Spun at slow speeds to separate large fragments and supernatant liquid
  6. Larger fragments removed and supernatant re-spun at faster speed
    (Different spin speeds separate different cells)
  7. Continue this and smaller and smaller fragments will be separated.
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31
Q

Convert mm to micrometer

A

1mm = 1,000 μm

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32
Q

Convert millimetres to nanometres

A

1mm = 1,000,000 nm

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33
Q

3 types of microscopes

A

Light microscope
Transmission electron microscope (TEM)
Scanning electron microscope (SEM)

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34
Q

Compare the 3 microscopes on
1) magnification
2) resolution
3) specimens (dead/alive)
4) type of view (section/ external)
5) staining

A

See notes

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35
Q

Disadvantages of electron microscopes

A
  1. Complex preparation produces artefacts (errors) that are difficult to identify and distinguish
  2. Specimens must be dead to be observed
  3. Cannot be viewed directly
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36
Q

Phases of the cell cycle? (Mitosis)

A

interphase
- G1 (gap 1)
- S phase (DNA synthesis)
- G2 (gap 2)
Mitosis

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37
Q

what happens in G1 phases? — of cells cycle (mitosis)

A

G1 first growth phase
- protein synthesis
- increase volume of cytoplasm
- increase organelles

If cells don’t divide they exit the cycle at this stage and entre G0

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38
Q

what happens in S phases? — of cells cycle (mitosis)

A

S Phase
- DNA replication/ synthesis
- histone proteins synthesised

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39
Q

what happens in G2 phases? — of cells cycle (mitosis)

A

G2 phase second growth phases
- proteins synthesised
- increased energy stores
- chromosomes begin to condense prior to nuclear division
- increase volume of cytoplasm
- increase organelles

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40
Q

The sub phases of mitosis (the cell cycle)?

A

1) Prophase
2) Metaphase
3) Anaphase
4) Telophase

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41
Q

What happens during PROPHASE (mitosis)?

A
  • Chromosomes become visible as shorten and thicken
  • nuclear envelope breaks open
  • spindle fibres start to form

(- centrioles move to opposite ends of cell)

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42
Q

what happens during the METAPHASE? (Mitosis)

A
  • chromosomes can be seen as X shaped structures (2 chromatids joined at the centre)
  • chromosomes line up along equator (middle of cell)
  • chromosomes attached to the spindle fibres at centromere
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43
Q

What happens during during ANAPHASE? (Mitosis)

A
  • microtubes in spindle fibres contract pulling chromatids to opposite poles of cell
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44
Q

What happens during TELOPHASE? (Mitosis)

A

-groups of chromatids form two new nuclei + chromosomes uncoil
- cytokinesis > division of cytoplasm to produce two new cells

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45
Q

Prokaryotic cell division

A

Eukaryotic cells - cell cycle (mitosis)
Bacteria cells - binary fission

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46
Q

When does cancer form?

A

Mitosis is a controlled process. Uncontrolled cell division can lead to formation of tumours and cancer

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47
Q

Process of binary fission

A
  • replication of circular DNA + plasmids
  • division of cytoplasm to produce 2 daughter cells, each with a single copy of circular DNA ans a variable number of copies of plasmids
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48
Q

How do viruses replicate?

A

Being non-living viruses don’t do cell division.

1) LYTIC CYCLE
After injecting their genetic information, host cell replicates the virus particles

2) LYSOGENIC CYCLE
Injected genetic material but the DNA stays hidden inside host cell’s DNA until triggered to go into the lytic cycle

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49
Q

Calculation for mitotic index

A

MI= number of cells with condensed chromosome (in cell cycle)
_____________________________________________________________. X 100
Total number of compete cells

50
Q

Cell membrane structure
(Simple)

A

Phospholipid bilayer

Cholesterolin the fatty acid tail sections
Integral proteins that span the entire bilayer
Peripheral proteins that anchored at phosphate head layer
glycolipids that come out of the top of the bilayer

51
Q

Why is cell membrane structure described as Fluid Mosaic membrane

A

FLUID
- components aren’t in fixed shapes/positions they are constantly moving

MOSAIC
- all components are different shapes and sides yet still fit tightly together

52
Q

Structure & function of glycolipids
(In membrane structure)

A

STRUCTURE:
(Similar to phospholipid-) 2 fatty acids, glycerol + Sugar head

FUNCTION:
Electrical insulation and cell signalling

53
Q

Structure & function of cholesterol
(In membrane structure)

A

STRUCTURE:
Different from phospho and glyco lipids

FUNCTION:
Acts in the hydrophobic section of bilayer:
Maintain/ regulate membrane fluidity

54
Q

Structure & function of peripheral proteins
(In membrane structure)

A

STRUCTURE:

Normal primary, secondary,tertiary structures of proteins
Anchored into phosphate heads (easily removed by altering pH)

FUNCTION:
Anchors cytoskeleton to it

55
Q

Structure & function of integral proteins
(In membrane structure)

A

STRUCTURE:
Normal primary, secondary,tertiary structures of proteins
Embedded into hydrophobic part of bilayer (spans entire membrane)

FUNCTION:
Transports substances through it

56
Q

Functions of the membrane?

A

1) transport
2) compartmentalisation of cells
3) cell communication
4) cell recognition
5) cell adhesion

57
Q

Substances that can pass straight through the surface membrane?

A

Must be:
-non polar/ hydrophobic
- small (E.g O2, steroid, CO2)
- lipid soluble

Triglycerides, proteins, glucose = too large

58
Q

Def of simple diffusion

A

The net movement of particles from area of high conc. to area of lower conc. down the conc. gradient

59
Q

Factors effect simple diffusion?

A
  1. Steepness of concentration gradient
  2. Size of particles
  3. Temperatures
  4. Surface area of membrane
  5. Distance across
60
Q

What is facilitated diffusion?

A

Similar to diffusion, it occurs down a concentration gradient, but it differs as special protein channels & carrier proteins are envolved

61
Q

Protein channels

A

A protein that forms a pore in a cell membrane and allows the facilitated diffusion of charged particles

62
Q

Role of

A
63
Q

Carrier proteins

A

A protein in cell membrane that allows the facilitated diffusion of large molecules

64
Q

Role of

A
65
Q

Def of osmosis?

A

The passage of water from a region where it has higher water potential to a region of lower water potential through a selectively permeable membrane.

66
Q

Def of solute

A

Any substance that is dissolved in a solvent to form a solution

67
Q

Unit of water pressure

A

KiloPascals (kPa)

68
Q

Def of active transport?

A

The movement of molecules or ions into or out of a cell from a region of lower conc. to a region of higher conc. against the conc. gradients using ATP and carrier proteins

69
Q

Describe active transport processes of single molecule/ ion

A
  • carrier protein on membrane binds to molecule/ion to be transported (at receptor site)
  • inside cell ATP bind to protein and is hydroylsised into ADP &Pi releasing energy causing protein to change shape and open to opposite side of membrane
  • molecule/ ion released
  • Pi released from protein causing it to revert to original shape ready to repeat
70
Q

Explain the Sodium- potassium pump

A

Active transport example
3 Na+ ions removed &
2 K+ actively taken in

Carrier proteins require energy from ATP for this movement.
This is used to set up conc. gradients & create nerve impulses

71
Q

When is co-transport done in the body?

A

-absorption of amino acids/ glucose into ileum epithelial cells

72
Q

Process of absorption of glucose in the ileum (epithelial cells)

A

1) Na+ actively transported with use of ATP out of epithelial cells and K+ ions are drawing in- sodium potassium pump using carrier proteins

2) creates high conc. Na+ in lumen of intestine than inside cell

3) Na+ diffuse into cells (through symport co-transport proteins) carrying either amino acid/glucose molecule into cell with them into epithelial cell

4) the glucose/amino acid pass into the blood by facilitated diffusion by carrier proteins in the basal membrane

73
Q

Draw a diagram to show absorption of glucose into the epithelial cells (ileum) from the small intestine

A

See notes

74
Q

Def osmosis

A

The passage of water for a region where of higher water potential to a region of lower water potential through a selectively permeable membrane

75
Q

What is water potential of pure water

A

Water potential (Ψ ) -ability for H2O molecules to move

Pure water has Ψ of 0
In a concentration solution Ψ is a negative value

76
Q

Osmosis in animal cells and plant cells what would happen?

A

If too much water moves into an animal cell by osmosis they will swell and burst

Water is stored in the vacuole. Vacuole pushes against cells wall= turgid this prevent them wilting.
Cells with vacuoles completely away from cell wall = plasmolysed

77
Q

Def these in terms of water potential
i) hypotonic solution
ii) isotonic solution
Iii) hypertonic solution

A

Hypotonic - solution with Higher water potential. [ water moves out of cell]
isotonic - solution with identical water potential
hypertonic - solution with lower water potential [ water moves into cell]

78
Q

Def of antigen

A

Marker molecule that can be detected by antibodies and trigger an immune response
(Specific to each cell/pathogen)

79
Q

Def of antigen

A

Marker molecule that can be detected by antibodies and trigger an immune response
(Specific to each cell/pathogen)

80
Q

Def of antibody
+what is another name for it

A

A protein found in the blood that is produced by plasma cells (B. Cells) which binds to antigens as part of the immune response

Also called Immunoglobulin proteins

81
Q

Structure of antibody

A

Protein made of 4 polypeptide chains forming a Y shaped structure
- 2 heavy chains
- 2 light chains
Constant regions and variable regions
Disulfide bridges between polypeptide chains

82
Q

Variable and control regions of antibody

A

Variable - contain unique sequence of amino acids part of antibody that binds to antigens

Constant - always have same amino acid sequence - heavy chain constant regions bind to receptors on some types of white blood cells

83
Q

Explain how it is possible
Each B cell produces a specific antibody which binds to only one specific antigen

A
  • variable regions of each antibody has a unique order of amino acids in that regions that form the antigen-binding site
  • different antibody proteins will fold into unique tertiary 3D shape
  • each antigen-binding site will have a complementary shape specific to only one type of antigen molecule
84
Q

Functions of antibodies in immune response

A
  1. Agglutination
    Each antibody can bind to 2 antigens this clumps together microbes making them easier for phagocytes to engulf.
  2. Opsonisation
    Constant regions of antibody bind to receptor on macrophage, microbe ingested by phagocytosis forming phagosome, lysosome fused with phagosome releasing chemicals and hydrolytischem enzymes to destroy pathogen
  3. Destruction by complement
    The constant regions of the heavy change binds to and activities complement which are proteins in the plasma that punch holes in bacterial cell membranes
85
Q

What are non-specific immune responses?

A
  • inflammatory response
  • blood clotting
    Phagocytosis
86
Q

Explain the process of phagocytosis

A

1) contact and binding between receptor molecule and antigen on foreign matterial
2) pseudopodia (feet) form on phagocyte and ingestion of bacteria by endocytosis
3)formation of a phagosome( vesicle) plasma membrane surround the bacterium pinches and forms phagosome
4) lysosome fuses with phagosome to form vesicle = phagolysosome
5) lysosome containers hydrolytic enzymes that digest bacteria and break molecules down
6) products of digestion
- absorbed
- released by exocytosis
- presented on phagocyte’s surface

87
Q

Phagocytosis vs. Pinocytosis

A

Phagocytosis
- for solid matter (cell eating)

Pinocytosis
- for liquid matter (cell drinking)

88
Q

Structure of HIV particle

A

Virus particle
- core contains RNA (genetic material)
- core contains proteins including enzyme reverse transcriptase
- outer protein coating = capsid
- extra outer layer = envelope
Attachment protein

89
Q

Describe replication of HIV in human s

A

HIV replicates inside Helper T-cells
1) protein on HIV binds to CD4 protein most frequently on helper T-cells
2) protein capsid fuses with cell membrane and releases RNA into T-cell along with enzymes
3) HIV reverse transcriptase converts virus’s RNA into DNA stand
4) Made viral DNA moved and inserted into helper T-cell’s DNA
5) HIV DNA creates mRNA using cell’s enzymes - this mRNA makes viral proteins & RNA
6) cell’s protein synthesis makes HIV particles which bind to cell surface membrane of Hkeper T-cell and form lipid envelope
7) viral particles go to infect new cells

90
Q

How is someone with aids affected by the illness?

A

HIV causes aids by killing/ interfering with function of Helper T-Cells
Without these T-cells the immune system cannot stimulate B-cells to produce antibodies or cytotoxic T-cells that kill infected cells
As a result
- more susceptible to infections
- normal infections can be serious or deadly

91
Q

Why are antibiotics ineffective against viral diesease/

A

1) Virus rely on host ells to carry out metabolic activities so lack their own metabolic structures and pathways which antibiotics usually target

2) viruses have proteins coats rather than more in cell walls therefore cannot break through and get into particle

3) no site for antibiotics to bind when viruses are within host cells

92
Q

What are antibodies also known as

A

Immunoglobulin proteins
Produced by B-cells in response to antigens during immune response

93
Q

Structure of an antibody

A

Protein made up of 4 polypeptide chains ( 2 heavy and 2 light) forming a Y-shaped structure help together with disulphide bridges

There are variable regions and contrast regions

94
Q

Why do antibodies contain variable and constant regions?

A

Variable regions - unique sequence of amino acids that bind to specific antigen
Constant regions- always the same (heavy chain) so region can bind to repertory on some types of white blood cells

95
Q

Label the structure of antibody

A

See notes

96
Q

Explain how it is possible to produce a specific antibody that only binds to one specific antigen?

A
  • variable regions of each antibody has a unique order of amino acids (primary structure) in the region that forms that antigen binding site
  • different antibody proteins will fold into different 3D shapes (each has a unique tertiary strucutre)
  • each antigen-binding site will have a complementary shape specific to only one type of antigen molecule.
97
Q

Ways in which antibodies destroy pathogens + describe mechanism of each one

A

1) AGGLUTINATION
Each antibody can bind to 2 antigens this clumps them together making it easier for phagocytes to engulf them

2) OPSONISATION
Constant region of antibody binds to receptors on macrophage, microbe then ingested by phagocytosis

3) DESTRUCTION BY COMPLEMENT
Constant region of heavy change binds to and activates complements- these are proteins in plasma that punch holes in bacteria cell membranes

98
Q

Where are T-lymphocytes produced?

A

In bone marrow

99
Q

What are MHC molecules?
+ how do they work with T-cells

A

MHC- are protein marker found on cel surface which presents antigen in infected and abnormal cells to signal T-cells to attack

100
Q

Describe production of helper T-cells

A

1) macrophage presents antigen on MHC molecule and T-cell binds to become helper T-cell
2) divides by mitosis to produce clone identical T-cells
3) activated T-helper cells facilitate activity of other immune cells
4) activated T-cells produce cytokines (interleukins) to stimulate phagocytosis also stimulate mitosis of B-cells

101
Q

What do cytotoxic T-cells do (killer)

A

These cells identify abnormal/infected cells.
When attached it releases a glycoprotein called perforin
Perforin destroys cells by creating holes in the membrane

102
Q

Def of colonial selection

A

The process of matching the antigens on an antigen presenting cell with the antigen receptors on B and T- lymphocytes

103
Q

def of clonal expansion

A

The production of many genetically identical daughter cells through cell division of the activated B or T- lymphocyte after clonal selection

104
Q

Def of herd immunity

A

A type of disease immunity that occurs when a large proportion of a population are vaccinated against a disease which prevents the spread of the diseases to unvaccinated individuals

105
Q

Def of monoclonal antibodies

A

Identical antibodies that have been produced by an immune cell that has been cloned from a patent cell

106
Q

Describe Humoral response used to produce antibodies

A

1) surface antigens of invading pathogens are complementary to a receptor (antibody) on B-cell and binds
2) B-cell activated causing it to engulf antigen by endocytosis and digest it
3) displaying the antigen fragments bound to its unique MHC molecules
4) helper T-cells attach to antigen and MHC on B-cells activating it
5) cytokines secreted by T-cell help B- cell to divide by mitosis and mature into producing clone plasma cell.
6) plasma cells produce & secrete specific antibody into the blood
7) the antibodies attach to antigens on the pathogen and destroy it in a variety of ways
8) some B-cells develop into memory cells that circulate in the blood and tissue fluid for future infections ( secondary immune response)

107
Q

The role of Helper T-cells in the immune response

A

They release cytokines that stimulate:
- maturation of B-lymphocytes
- production of memory B-cells
- Activation of Cytotoxic T cells which destroy foreign cels using performing
- increased rate of phagocytosis

108
Q

What is a vaccine?

A

A suspension of antigens that are intentionally put into the body to induce artificial active immunity. It results in a specific immune response where antibodies were released by plasma cells

109
Q

How do vaccines induce long-term immunity?

A

Memory cells are made. The immune system remembers the antigen when reencountered and produces antibodies to it, in what is a faster, stronger secondary response

110
Q

What is herd immunity?

A

A sufficient large proportion of the population has been vaccinated (and therefore immune)
Which makes it difficult for a pathogen to spread within that population

Those people not immunised (children or those with weakened immune system) are protected and unlikely to contract it as levels of diseases are low.

the proportion of the population that needs to be vaccinated in older to achieve herd immunity is different for each disease

111
Q

Challenges with eradication of diseases? (with vaccines)

A

Some pathogens are complicated, vaccines are not possible
Some people don’t want vaccinations
Lack of public health facilities e.g fewer trained personnel
Unstable political situation

112
Q

Challenges with eradication of diseases? (with vaccines)

A

Some pathogens are complicated, vaccines are not possible
Some people don’t want vaccinations
Lack of public health facilities e.g fewer trained personnel
Unstable political situation

113
Q

What are the advantages and disadvantages of vaccines

A

Advantages:
- can give a lifetime of protection (very effective)
- generally harmless (do not cause disease themselves)

Disadvantage
- poor response in some individuals
- antigenic variation (variations in antigens on cell surface)
- antigenic concealment

114
Q

What is the ethics behind vaccines?

A

They use animals
Can be side effects
Testing for vaccines can be unethical
Herd immunity
Expensive vaccines and diseases that are almost eradicated
Individual health risks versus protecting the population

115
Q

Describe the difference between active and passive immunity
(5 marks)

A

In active immunity the body produces its own antibodies by plasma cells to stimulate immune response. Whereas, passive immunity happens without bodies own immune response (for example when babies are given antibodies by mother through breast milk)

Active immunity is slower acting but lasts longer response. Passive immunity is faster acting as antibodies already present but shorter response as only acts while antibodies last.

116
Q

Process used to produce monoclonal antibodies

A
  1. Immunise mouse with antigen
  2. Immune response occurs, antigen-specific B-cells selected and divide by mitosis
  3. Spleen removed and B-cells isolated
  4. B-cells and myeloma cells grown together and fuse forming hybridomas
  5. Hybridomas which secrete correct antibodies are identified and cultured
  6. Monoclonal antibodies harvested from culture and purified
117
Q

Uses of monoclonal antibodies

A

1) to treat diseases
By binding to and blocking action of certain molecules
e.g HER-2 receptor which cause growth of breast cancer cells

2) to diagnose disease/ pregnancy/ research
By binding to specific molecules
*monoclonal antibodies which bind to hCG (only produced by implanted embryo) used in pregnancy testing kits

118
Q

Explain why monoclonal antibodies can be used to treat and diagnose disease
(5 marks)

A

Antibodies have variable regions that bind to complementary shaped antigen. These antibodies bind to one specific target molecule and inhibits that action of target molecules that cause disease

In diagnostics, antibodies bind to specific target molecules produced as a result of the disease, it prevents false positive results.

119
Q

The process of the ELISA Tests
(Testing antigen)

A

1) antigen is bound to the bottom of the reaction vessel
2) blood plasma sample is added to the reaction vessel
- antibodies complementary to antigen bind to bound antigen = primary antibodies
3) the vessel is washed out to remove any unbound antibodies
4) secondary antibodies with enzymes attached bind to the primary antibodies
5) reaction vessel rewashed to remove any unbound secondary antibodies (this prevents false positives)
6) solution containing enzyme’s substrate is added which reacts with the enzyme attached to secondary antibodies.
If secondary antibodies are present and attached then colour product produced so there is a colour change

120
Q

How do phagocytosis lead to prevention of antigens

A

Phagosome fuses with lysosome
Pathogen gets destroyed by hydrolytic enzymes
Pathogen antigen displayed on the cell membrane

121
Q

Describe how the presentation of a virus antigen leads to the secretion of an antibody against this virus antigen

A

Helper T-cell binds to the antigen
This helper t-cell stimulates specific B-cell
B-cell divides by mitosis
Forming plasma cells that release antibodies

122
Q

Role of cytokines in immune response

A
  • maturation of B-lymphocytes into plasma cells
  • production of memory cells
  • activation of cytotoxic t-cells
  • increases the rate of phagocytosis

A Level Biology (10 decks)

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