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Biology > 3.2 Cells > Flashcards

3.2 Cells Flashcards

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1
Q

What is the cell surface membrane?

A

*double layer of phospholipids + larger proteins within bilayer

•controls movement in and out of cell

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2
Q

What is the structure of the nucleus?

A

•nuclear envelope= in + out
•nuclear pores= pass MRNA out
•chromosomes
•nucleolus

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3
Q

What is the function of the nucleolus?

A

Site of rRNA production, making ribosomes

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4
Q

What is the function of the nucleus?

A

•DNA replication
•transcription (mRna)
•genetic code for each cell

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5
Q

What is the structure of mitochondria?

A

•double membrane:
Inner is cristae which +SA for enzymes
•fluid centre is matrix
•loop of mitochondrial DNA: codes for enzymes for respiration

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6
Q

What is the function of mitochondria?

A

aerobic respiration to release ATP energy

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7
Q

What is chloroplast?

A

(Site of photosynthesis)
•double membrane
•thylakoids (stacks of flattened discs) with chlorophyll for light dependent reaction
•fluid stroma-enzymes for light independent reaction

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8
Q

What is the structure of the Golgi body?

A

•folded membrane stacked= cisternae
•vesicles pinch off from cisternae

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9
Q

What is a golgi vesicle?

A

Lipids + proteins are packed in special membrane bound parcels and transported

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10
Q

What is the function of the Golgi body?

A

•+ carb to protein= glycoprotein
•form lysosomes
•modify + pack proteins and lipids in vesicles

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11
Q

What are lysosomes?

A

*bags of digestive enzymes (hydrolytic enzymes)

•hydrolyses pathogens in phagocytosis
•breaks down dead cells (autolysis)
•exocytosis: release enzymes to outside to destroy material
•digest worn out organelles to reuse materials

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12
Q

What are ribosomes?

A

*subunits= rRNA + protein
80S = eukaryotic
70S = pro
Not membrane bound

•site of protein synthesis

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13
Q

What is the structure of endoplasmic reticulum?

A

•rough+smooth ER have folded membranes (cisternae)
•rough has ribosomes on cisternae

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14
Q

What does the rough endoplasmic reticulum do?

A

Modifies and transports proteins and glycoproteins

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15
Q

What does the smooth endoplasmic reticulum do?

A

Synthesis + storage of lipids, carbs, cholesterol and steroid hormones

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16
Q

What is the cell wall for plants and fungi?

A

(Provides structural strength)
Plants: micro fibrils of cellulose polymer
Fungi: chitin (N-containing polysaccharide)

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17
Q

What is the structure of the permanent vacuole?

A

•filled with fluid surrounded by single membrane (tonoplast)
•solution of mineral salts, sugars and amino acids, waste and pigments

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18
Q

What is the function of the vacuole?

A

•turgid: support
•temporary store of amino acids and sugars (food)
•pigment colours petals to attract pollination
•absorbs and hydrolyses potentially harmful substances

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19
Q

Why are prokaryotic cells different to eukaryotic cells?

A

•cytoplasm lacks membrane bound organelles
•smaller ribosomes (70S)
•single circular DNA free in cytoplasm
•DNA not associated with proteins
•cell wall that contains murein (glycoprotein)

+:
•plasmids
•capsule surrounds cell
•flagella

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20
Q

What is a virus and it’s structure?

A

(Acellular (no cells) and non-living)
•genetic material: RNA or DNA
•protein capsid
•attachment proteins identify + attach to host cells
•some have lipid envelope

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21
Q

How do viruses invade + hijack host cells?

A

1)attachment proteins bind to host cells receptor
2) DNA or RNA injected into host cell
3)host cell divides as normal + virus is replicated

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22
Q

What is magnification?

A

How much larger the image size is compared to actual size

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23
Q

What is resolution?

A

The smallest distance between 2 entities that can still be seen as separate entities

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24
Q

How do you use an optical (light) microscope? + Advantages

A

Beam of light is condensed using lens to form an image.
•alive + dead cells viewed
•easy sample preparation (no damage)
•cheaper and portable

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25
Q

Why does a light microscope have a lower resolution?

A

Longer wavelength of light

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26
Q

Why does TEM have the highest resolution?

A

Beam of e- have a much shorter wavelength

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27
Q

How is a transmission EM used?

A

•Beam of e-pass though very thin sample in vacuum.
•Focused using an electromagnet.
•absorbs e- = darker
Shows a detailed internal structure of organelles

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28
Q

How is a scanning EM used?

A

•e- beamed at surface
•e- knocked off sample + scattered= collected and amplified
3D outside surface structure

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29
Q

What are the disadvantages of an electron microscope?

A

•expensive
•complex sample preparation where it can alter and damage cells (artefacts)
•dead only = vacuum as e- absorbed so won’t reach specimen
•only black and white

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30
Q

How is an eyepiece graticule set up?

A

Eyepiece graticole is calibrated using a stage micrometer

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31
Q

How is ultracentrifugation carried out?

A

1) cells homogenised (broken up) in a cold, isotonic + buffered solution
2) homogenised mixture filtered to remove cell debris+unbroken cells
3) filtrate is put in centrifuge at low speed
4) densest organelle form pellets
5)supernatant spun at higher speed for more pellets

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32
Q

What is the order of collected pellets in a centrifuge? (Densest to least)

A

1) nuclei
2) i. chloroplast
2) ii. mitochondria
3) ER
4) ribosomes

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33
Q

Why must the homogenised mix be in a cold solution?

A

Reduces hydrolytic enzyme activity so organelles won’t be digested

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34
Q

Why must the homogenised mix be in an isotonic solution?

A

No osmosis in or out so the organelles won’t burst nor shrink

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35
Q

Why must the homogenised mix be in a buffered solution?

A

To keep Ph constant so fast organelles proteins + enzymes won’t be denatured

36
Q

What is a cell membrane?

A

•phospholipid bilayer:
Hydrophobic tails face inwards
Hydrophilic head faces outwards
•partially permeable: allows any lipid soluble substances + very small substances e.g CO2

37
Q

Why is a cell membrane described as a fluid mosaic?

A

• phospholipid molecules constantly moving
• composed of different molecules arranged as mosaic e.g proteins, cholesterol

38
Q

What is the function of cholesterol in the cell membrane?

A

•Restricts movement of phospholipids = less fluid + more rigid
This helps to maintain shape of animal cells

39
Q

What are extrinsic proteins used for? ( + e.g with use )

A

•Mechanical support
•glycoproteins + glycolipids which are used for cell recognition/signalling such as receptors

40
Q

What are integral/intrinsic proteins used for and e.g?

A

•transport molecules across membrane
•channel and carrier proteins

41
Q

How do channel proteins function?

A

Form tubes that fill with water to allow water soluble ions through membrane by facilitated diffusion
•selective as it opens only in presence of certain ions

42
Q

How do carrier proteins function?

A

Bind to larger molecules like glucose and amino acids and will change shape to transport to other side

43
Q

How is a temporary mount of tissue prepared for optical microscope?

A

1.Obtain thin tissue
2.place tissue in a drop of water
3.stain tissue on slide
4.add coverslip using mounted needle to avoid air bubbles

44
Q

What is facilitated diffusion and what does it recquire?

A

Large, polar molecules can diffuse down the concentration gradient via channel and carrier proteins. It is a passive process

45
Q

What is diffusion and what can move into membrane by diffusion?

A

1)Net movement of particles down a concentration gradient until equilibrium is reached. It is a passive process.
2)lipid soluble and small substances can move in

46
Q

What is osmosis?

A

Movement of water form area of high to low water potential across partially permeable membrane. From a less negative to a more negative water potential

47
Q

What is water potential and what does a lower pressure (kPa) for water potential mean?

A

1) pressure created by water molecules (KPa)
2)It has less water and is more concentrated with solutes
3) water= 0KPa and more concentrated become more negative

48
Q

What is active transport and how does it work?

A

•Movement of particles against concentration gradient using ATP energy and a carrier protein

1)molecule binds to complimentary shape on protein
2) ATP bind to protein, hydrolysed to ADP +Pi
3)attached Pi causes protein to change shape + release molecule inside
4) when Pi is released carrier protein reverts to original shape

49
Q

What is a co-transporter and how does it function?

A

•type of carrier protein
•it will bind to 2 molecules at a time
•conc. gradient of one is used to move another against its conc. gradient

50
Q

How does the co-transport of glucose and sodium ions in the ileum work?

A

1.Na+ actively transported out of epithelial cell into blood by Na-K pump= lower conc. of Na+ in epithelium than ileum lumen (conc. gradient made)

2.Na+ can move down conc. in ileum to epithelium using co-transport protein.

  1. Glucose or AA will also bind to con-transport protein and move down
    conc. gradient to epithelium

4.glucose and AA can move down conc. gradient from epithelium to blood by facilitated diffusion

51
Q

What affects rate of active transport?

A

•speed of individual carrier proteins
•no. of carrier proteins
• rate of respiration= ATP

52
Q

What affects the permeability of a membrane?

A

• temperature: high will denature membrane protein/increases fluidity of phospholipid bilayer/damage membrane
•Ph: changes tertiary structure membrane
•solvent: May dissolve membrane

53
Q

How is a colorimeter used?

A

1) select colorimeter filter with complimentary colour
2)use distilled water to set it to 0
3) measure absorbance or % transmission of solution
4) high absorbance/ low transmission = more pigment in solution

54
Q

What affects diffusion rate?

A

• concentration gradient
• surface area
• temperature
• diffusion distance
• size of molecule

55
Q

What does a serial dilution do and why is it advantageous?

A

•Step by step dilution to produce different concentrations
•ad: makes very low concentration without measuring out small volumes, improving accuracy

56
Q

What formulas are needed for dilution series calculations?

A

C1+V1=C2+V2
V2=V1 + volume of water to dilute

C1+V1: conc. and volumes of stock solution
C2+V2: conc. and volumes of solutions made

57
Q

What are non specific responses to pathogens?

A

•skin: physical barrier + sebum
•tears: lysozymes
•Mucus traps dirt+microbes and cilia beats it away
•platelets produce clots
•phagocytes
•HCl in stomach

58
Q

What are phagocytes?

A

Neutrophils (blood) attracted to chemicals by chemoattraction
Macrophages (tissues) recognise foreign atigen

(Bind, engulf and digest pathogens)

59
Q

What is the process of phagocytosis?

A

1.attracted to chemicals/debris and recognise foreign antigens
2.Receptors bind + engulf pathogen by endocytosis = phagosome (enclosed vesicle)
3.lysosome fuse with phagosome = phagolysosome
4.lysosomes release hydrolytic enzymes= digest pathogens by hydrolysis
5.macrophage (only) will present antigen on cell surface membrane (APC)

60
Q

Why is a thin sample needed for an optical microscope?

A

•let light through
•single layer of cell viewed

61
Q

What happens to a cell when placed in a hypotonic solution?

A

It will gain water by osmosis down the water potential gradient, from a less negative water potential to a more negative water potential across a partially permeable membrane
*plant cell is plasmolysed
*animal cell lysis

62
Q

What stimulates the immune response?

A

•pathogens
•cells from other organisms/transplants
•abnormal cells/cancer
•toxins

63
Q

What is the definition of an antigen?

A

Protein molecule present on cell surface membrane that stimulates an immune response by specific lymphocytes

64
Q

What is the cell mediated response?

A

•specific T-H activated by APC
•T-H are cloned by mitosis and differentiate:
*cytotoxic T cells (T-C)
*T-memory cells
*activate B-lymphocytes
*stimulate phagocytosis

65
Q

What is the humoral response?

A

•TH cells bind to antigen on APC
•specific T-H cells activate specific B-cells by releasing cytokines
•B cells clone by mitosis and differentiate (clonal selection)
•into plasma B cells and memory B cells
•plasma B cells release specific antibodies complementary to antigen causing agglutination

66
Q

What do cytotoxic ‘killer’ T cells do?

A

They release perforin which makes holes on the cell surface membrane of APC and cause osmotic lysis

67
Q

What is an antibody? (Structure + function)

A

•4 Polypetide chains joined by disulfide bridges (2 heavy/2 light)
•constant region: allows it to bind to WBC
•2 antigen binding sites to form antigen antibody complex (variable region)

•agglutination: clump up pathogens allowing quick + more phagocytosis

68
Q

What is antigen variability?

A

DNA mutates in gene that codes for antigen. Antigen changes shape so previous memory cells are ineffective as no longer complementary to the new antigen (unrecognisable)

69
Q

What is passive immunity?

A

1.antibody introduced from outside source
2.short term as antibodies broken down
3.fast acting (antidote)
E.g natural: breast milk
artificial: injection

70
Q

What is active immunity?

A

1.involves memory cells
2.antibody made by plasma cells
3.long term immunity
4.can take time to develop

E.g natural: infection
artificial: vaccines

71
Q

What is a vaccine?

A

•weak or dead pathogen (antigen)
•antigens on macrophages activate specific B cells to clone and differentiate into plasma + memory B cells
————————————————
•(during secondary immune response)memory B cells: divide rapidly into plasma cells to make large no. of antibodies rapidly = no symptoms

72
Q

What is herd immunity?

A

Majority of people are immune so unvaccinated people are less likely to come in contact with infected people

73
Q

What is the structure of HIV?

A

•RNA and reverse transcriptase in capsid
•viral envelope: made of membrane of host’s cell membrane
•glycoprotein: attach to TH cells receptors

74
Q

How does HIV replicate in TH cells?

A

•HIV glycoprotein will bind to TH cells receptors
•HIV protein capsid fuses with TH cells membrane, allows RNA + enzymes to enter
•reverse transcriptase copies viral RNA into a DNA copy= moves to TH cell’s nucleus (DNA) (retrovirus)
•viral DNA transcribed into mRNA= viral proteins made to assemble new HIV
•released by “budding off”

75
Q

When does HIV develop to AIDS?

A

AIDS is when HIV virus in TH cells interfere with normal functioning of immune system= left vulnerable to cancer and infections (immune system destroyed)

76
Q

Why are antibiotics ineffective against viruses?

A

•Viruses don’t have cell walls that can be attacked by antibiotics
•no mechanism (protein synthesis/ respiration) that can be targeted

77
Q

What are monoclonal antibodies used for and what are its ethical considerations?

A

•medical diagnosis e.g pregnancy/cancer
•target medicine to specific cell types by attaching drug to antibody

:
•deliberate induction e.g of cancer to animals
•testing/treatments have been dangerous

78
Q

How does the ELISA test work and what does it tell you?

A

(If patient has antibody or antigens to specific disease)

1.testing wells lined with immobilised antibodies
2.sample added to well
3.wash to remove unbound antigens
4.enzyme-linked antibodies added bind to antigen
5.wash to remove unbound E-L antibodies
6.substrate added, changes colour if enzyme is present (antigen present)

79
Q

What does the rate of colour change depend on in the ELISA test?

A

It is directly proportional to the amount of enzyme present (which is proportional to amount of antigen present)

80
Q

What is the interphase part of the cell cycle?

A

(G1, S, G2)
•cell grows
•organelles and DNA replicated
•ATP content increases as energy needed for cell division

81
Q

What are the steps in mitosis?

A
  1. Prophase: •chromosomes condense (short/fat), nuclear envelope breaks
    •centrioles move to poles (spindle fibres)

2.Metaphase: •chromosomes move to middle
•spindle fibres attach to centromere and chromatid

3.Anaphase: •centromere divides, separates sister chromatids to poles (ATP used)

4.Telophase: •chromosomes longer and thinner, nuclear envelope reforms
•cytokinesis: division of cytoplasm

82
Q

What is caused by uncontrolled cell division and how can it be stopped?

A

•cancers/tumours (caused by random mutations)

•drugs to stop DNA replication so cannot enter S phase
•radiation/drugs damage DNA and cell kills itself when detected
•prevent spindle fibre formation so inhibits metaphase / anaphase

83
Q

What is the process of binary fission in prokaryotic cells?

A

•replication of circular DNA and plasmids
•(cell grows larger and circular DNA to poles)
•cytoplasm divides, murein cell wall forms= 2 daughter cells with circular DNA and variable no. of plasmids

84
Q

Why do monoclonal antibodies bind to one specific antigen?

A

•produced from single clone of plasma B cells
•specific primary/tertiary structure (variable site)
•complementary shape to one antigen

85
Q

Why are many fields of views used during experiments?

A

•ensures there’s a representative sample

86
Q

Why do we push down hard in coverslip but not sideways in mitosis practical?

A

•to squash tissues to get a single layer of cells so light can pass through
•prevent rolling together of cells/avoid breaking chromosomes

87
Q

Why do we push down hard in coverslip but not sideways in mitosis practical?

A

•to squash tissues to get a single layer of cells so light can pass through
•prevent rolling together of cells/avoid breaking chromosomes

Biology (8 decks)

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