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Cells Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Eukaryotic and prokaryotic?

A

. Eukaryotic= DNA is in nucleus, contains membrane bound specialised organelles
prokaryotic= DNA free in cytoplasm , no organelles

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2
Q

Structure + function of cell surface membrane?

A

Structure= fluid mosaic phospholipid bilayer with extrinsic and intrinsic proteins
Function= isolates cytoplasm for extra cellular environment. Selectively permeable,to regulate transport of substances. Involved in cell recognition

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3
Q

Structure and function of nucleus?

A

Structure= surrounded by nuclear envelope, a semi permeable double membrane. Nuclear pores allow substances to enter. Dense nucleolus made of RNA and proteins assembles ribosomes
Function= contains DNA coiled around chromatin into chromosomes. Controls cellular processes e.g semi conservative replication

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4
Q

Structure and function of mitochondria?

A

Structure= surrounded by double membrane folded inner membrane forms cristae. Fluid matrix- contains mitochondrial DNA, lipids, proteins
Function= site of aerobic respiration to produce ATP

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5
Q

Structure and function of chloroplast?

A

Structure= vesicular plastid with double membrane. Thylakoids- flattened discs stack to form grana. Intergranal lamellae- tubes attached to thylakoids in adjacent grana. Stroma- fluid filled matrix
Function= site of photosynthesis to convert solar energy to chemical energy

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6
Q

Structure and function of Golgi apparatus?

A

Structure= planar stack of membrane bound, flattened sacs cis face aligns with rER. molecules are processed in trans face via exocytosis
Function:
-modifies+ packages proteins for export
- synthesises glycoproteins

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7
Q

Structure and function of lysosome?

A

Structure= sac surrounded by single membrane embedded H+ pump maintains acidic conditions, contains digestive hydrolase enzymes, glycoprotein coat protects cell interior
Function= digests contents of phagosome. Exocytosis of digestive enzymes

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8
Q

Structure and function of ribosome?

A

Structure= formed of protein + rRNA. Free in cytoplasm or attached or ER
Function= site of proteinsynthesis via translation.

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9
Q

Structure and function of endoplasmic reticulum ( ER)?

A

Structure= cisternae- network of tubules + flattened sacs extends from cell membrane through cytoplasm + connects to nuclear envelope
Function= rough ER- many ribosomes attached for proteinsynthesis + transport. Smooth ER- lipid synthesis

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10
Q

Structure and function of cell wall?

A

Structure= bacteria- made of polysaccharide murein. Plants- made of cellulose micro fibrils
Function= provides strength and support

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11
Q

Structure and function of cell vacuole?

A

Structure= surrounded by single membrane- tonoplast. Contains cell sap- mineral ions, water
Function= control turgor pressure. Absorbs + hydrolyses potentially harmful substances to detoxify cytoplasm

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12
Q

Cell adaptations?

A

. Folded membrane- increase surface area
. Many mitochondria- lots of ATP for active transport
. Walls one cell thick- reduces distance of diffusion pathway

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13
Q

Role of plasmids in prokaryotes?

A

. Small ring of DNA that carries non essential genes

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14
Q

Role of flagella in prokaryotes?

A

. Rotating tail propels

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15
Q

Role of capsule in prokaryotes?

A

Polysaccharide layer:
- prevents desiccation
- acts a food reserve
- sticks cells together

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16
Q

Why are viruses referred to as particles not cells?

A

They’re acellular and non living so no cytoplasm, can’t self reproduce, no metabolism

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17
Q

Structure of a viral particle?

A

. Linear genetic material + viral enzymes
. Surrounded by capsid
. No cytoplasm

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18
Q

Structure of an enveloped virus?

A

. Surrounded by matrix protein
. Matrix surrounded by envelope
. Attachment proteins on surface

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19
Q

Role of capsid on viral particles?

A

. Protect nucleic acid from degradation by restriction endonucleases
. Surface sites enable viral particle to bind + enter host cells

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20
Q

Role of attachment proteins on viral particles?

A

. Enable viral particle to bind to complementary sites on host cell- enter via endosymbiosis

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21
Q

How could a student prepare tissue for an optical microscope?

A

. Obtain thin section of tissue
. Place in a drop of water
.stain on a slide to make structures visible
. Add coverslip using mounted needle

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22
Q

How do transmission electron microscopes work?

A

. Pass a high energy beam of electrons through thin slice of specimen
.more dense structures appear darker as more e- are absorbed
.focus image on photographic plate using magnetic lenses

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23
Q

+/- do TEM?

A

+:
. E- have shorter wavelength than light= High resolution
. High magnification
-:
. Requires a vacuum- can’t show living structures
. Colourless image

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24
Q

How do scanning electron microscopes work?

A

. Focus a beam of e- onto specimens surface using electromagnetic lenses
. Reflected e- hit a collecting device + are amplified to produce and image on a photographic plate

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25
Q

+/- do SEM?

A

+:
. 3D image
. E- have shorter wavelength than light= high resolution
-:
. Vacuum needed
. Colourless image.
. Only shows outer surface

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26
Q

Magnification?

A

Factor by which image is larger than actual specimen

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27
Q

Resolution?

A

Smallest separation distance at which 2 separate structures can be distinguished

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28
Q

how to use an eyepiece graticule and stage micrometer to measure the size of a structure.?

A

1.Place micrometer on stage to calibrate eyepiece graticule.
2. Line up scales on graticule and micrometer. Count how many graticule divisions are in 100um on the micrometer.
3. Length of 1 eyepiece division = 100um / number of
divisions
4. Use calibrated values to calculate actual length of structures.

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29
Q

what happens during cell fractionation and ultracentrifugation?

A
  1. Mince and homogenize tissue to break open cells & release organelles.
  2. Filter homogenate to remove debris.
  3. Perform differential centrifugation:
    a) Spin homogenate in centrifuge.
    b) The most dense organelles in the mixture form a pellet.
    c) Filter off the supernatant and spin again at a higher speed.
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30
Q

why are fractionated cells kept in a cold, buffered, isotonic solution?

A

cold: slow action of hydrolase enzymes.
buffered: maintain constant pH.
isotonic: prevent osmotic lysis/ shrinking of organelles.

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31
Q

State what the cell cycle is and outline its stages.

A

cycle of division with intermediate growth periods
1. interphase
2. mitosis or meiosis (nuclear division)
3. cytokinesis (cytoplasmic division)

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32
Q

what happens during interphase?

A

G1: cell synthesises proteins for replication e.g. tubulin for spindle fibres & cell size doubles
S: DNA replicates = chromosomes consist of 2
sister chromatids joined at a centromere
G2: organelles divide
9O
www.pmteducation
000O PMTEducation

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33
Q

Purpose of mitosis?

A

produces 2 genetically identical daughter cells for:
• Growth
• Cell replacement/ tissue repair
• Asexual reproduction

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34
Q

what happens during prophase?

A
  1. Chromosomes condense, becoming visible.
    (X-shaped: 2 sister chromatids joined at centromere)
  2. Centrioles move to opposite poles of cell (animal cells) & mitotic spindle fibres form.
  3. Nuclear envelope & nucleolus break down = chromosomes free in cytoplasm.
35
Q

what happens during metaphase?

A

Sister chromatids line up at cell equator, attached to the mitotic spindle by their centromeres.

36
Q

what happens during anaphase?

A

requires energy from ATP hydrolysis
1. Spindle fibres contract = centromeres divide.
2. Sister chromatids separate into 2 distinct chromosomes & are pulled to opposite poles of cell (looks like ‘V’ shapes facing each other).
3. Spindle fibres break down.

37
Q

what happens during telophase?

A
  1. Chromosomes decondense, becoming invisible again.
  2. New nuclear envelopes form around each
    set of chromosomes = 2 new nuclei, each
    with 1 copy of each chromosome.
38
Q

procedure for a root tip squash experiment?

A
  1. Prepare a temporary mount of root tissue.
  2. Focus an optical microscope on the slide. Count total number of cells in the field of view and number of cells in a stage of mitosis.
  3. Calculate mitotic index (proportion of cells undergoing mitosis).
39
Q

What are tumour suppressor genes?

A

Genes that code for proteins to trigger apoptosis (programmed death of damaged cells)/ slow cell cycle (acts between G1 & S in interphase so damaged DNA cannot replicate).

40
Q

What are proto-oncogenes?

A

Genes that code for proteins to stimulate cell cycle to progress from one stage to the next.

41
Q

How can mutation to tumour suppressor genes & proto-oncogenes cause cancer ?

A

• Tumour suppressor: no production of a protein needed to slow the cell cycle.
• Proto-oncogenes: form permanently-activated oncogenes.
• Disruption to cell cycle → uncontrolled cell division → tumour.

42
Q

How do prokaryotic cells replicate?

A

Binary fission:
1. DNA loop replicates. Both copies stay attached to cell membrane. Plasmids replicate in cytoplasm.
2. Cell elongates, separating the 2 DNA loops.
3. Cell membrane contracts & septum forms.
4. Cell splits into 2 identical progeny cells, each with 1 copy of the DNA loop but a variable number of plasmids.

43
Q

how viruses replicate?

A
  1. Attachment proteins attach to receptors on host cell membrane.
  2. Enveloped viruses fuse with cell membrane or move in via endocytosis & release DNA/ RNA into cytoplasm OR viruses inject DNA/ RNA.
  3. Host cell uses viral genetic information to synthesise new viral proteins/ nucleic acid.
  4. Components of new viral particle assemble.
44
Q

the fluid mosaic model of membranes?

A

Fluid: phospholipid bilayer in which individual phospholipids can move = membrane has flexible shape.
Mosaic: extrinsic & intrinsic proteins of different sizes and shapes are embedded.

45
Q

role of cholesterol & glycolipids in membranes?

A

• Cholesterol: steroid molecule in some plasma membranes; connects phospholipids & reduces fluidity to make bilayer more stable.
• Glycolipids: cell signalling & cell recognition.

46
Q

functions of extrinsic and transmembrane proteins in membranes?

A

extrinsic:
• binding sites/ receptors e.g. for hormones
• antigens (glycoproteins)
• bind cells together
• involved in cell signalling
Intrinsic:
electron carriers
(respiration/photosynthesis)
• channel proteins (facilitated diffusion)
• carrier proteins (facilitated diffusion/ active transport)

47
Q

functions of membranes within cells?

A

• Provide internal transport system.
• Selectively permeable to regulate passage of molecules into / out of organelles.
• Provide reaction surface.
• Isolate organelles from cytoplasm for specific metabolic reactions.

48
Q

Name and explain 3 factors that affect membrane permeability?

A

• Temperature: high temperature denatures membrane proteins / phospholipid molecules have more kinetic energy & move further apart.
• pH: changes tertiary structure of membrane proteins.
• Use of a solvent: may dissolve membrane.

49
Q

how colorimetry could be used to investigate membrane permeability?

A
  1. Use plant tissue with soluble pigment in vacuole. Tonoplast &
    cell-surface membrane disrupted = 1 permeability = pigment
    diffuses into solution.
  2. Select colorimeter filter with complementary colour.
  3. Use distilled water to set colorimeter to 0. Measure absorbance/ % transmission value of solution.
  4. high absorbance/
50
Q

osmosis?

A

Water diffuses across semi-permeable membranes from an area of higher water potential to an area of lower water potential until a dynamic equilibrium is established.

51
Q

What is water potential (4)?

A

• pressure created by water molecules measured in kPa
• 4 of pure water at 25°C & 100 kPa: 0
• more solute = 4 more negative

52
Q

How does osmosis affect plant and animal cells?

A

• osmosis INTO cell:
plant: protoplast swells = cell turgid
animal: lysis
• osmosis OUT of cell:
plant: protoplast shrinks = cell flaccid
animal: crenation

53
Q

simple diffusion?

A

• Passive process requires no energy from ATP hydrolysis.
• Net movement of small, lipid-soluble molecules directly through the bilayer from an area of high concentration to an area of lower concentration (i.e. down a concentration gradient).

54
Q

facilitated diffusion?

A

Passive process
Specific channel or carrier proteins with complementary binding sites transport large and/ or polar molecules/ ions (not soluble in hydrophobic phospholipid tail) down concentration gradient
© www.meducatie O0 PMTEducation

55
Q

Explain how channel and carrier proteins work?

A

Channel: hydrophilic channels bind to specific ions = one side of the protein closes & the other opens
Carrier: binds to complementary molecule = conformational change releases molecule on other side of membrane; in facilitated diffusion, passive process; in active transport, requires energy from ATP hydrolysis

56
Q

Name 5 factors that affect the rate of diffusion?

A

• Temperature
• Diffusion distance
• Surface area
• Size of molecule
• Difference in concentration (how steep the concentration gradient is)

57
Q

State Fick’s law?

A

surface area x difference in concentration / diffusion distance

58
Q

active transport?

A

Active process: ATP hydrolysis releases phosphate group that binds to carrier protein, causing it to change shape.
Specific carrier protein transports molecules/ ions from area of low concentration to area of higher concentration (i.e. against concentration gradient).

59
Q

co-transport?

A

Movement of a substance against its concentration gradient is coupled with the movement of another substance down its concentration/ electrochemical gradient.
Substances bind to complementary intrinsic protein: symport: transports substances in same direction antiport: transports substances in opposite direction e.g. sodium-potassium pump.

60
Q

Explain how co-transport is involved in the absorption of glucose / amino acids in the small intestine?

A
  1. Na* actively transported out of epithelial cells & into bloodstream.
  2. Na* concentration lower in epithelial cells than lumen of gut.
  3. Transport of glucose/ amino acids from lumen to epithelial cells is ‘coupled” to facilitated diffusion of Na* down electrochemical gradient.
61
Q

What is an antigen?

A

• Cell-surface molecule which stimulate immune response.
• Usually (glyco)protein, sometimes (glyco)lipid or polysaccharide.
• Immune system recognises as “self” or “non-self” = enables identification of cells from other organisms of same species, pathogens, toxins & abnormal body cells.

62
Q

How does phagocytosis destroy pathogens?

A
  1. Phagocyte moves towards pathogen via chemotaxis.
  2. Phagocyte engulfs pathogen via endocytosis to form a phagosome.
  3. Phagosome fuses with lysosome (phagolysosome).
  4. Lysozymes digest pathogen.
  5. Phagocyte absorbs the products from pathogen hydrolysis.
63
Q

Explain the role of antigen-presenting cells (APCs)?

A

Macrophage displays antigen from pathogen on its surface (after hydrolysis in phagocytosis).
Enhances recognition by T, cells, which cannot directly interface with pathogens/ antigens in body fluid.

64
Q

the 2 types of specific immune response?

A

• cell-mediated
• humoral

65
Q

process of the cell-mediated response?

A
  1. Complementary TH lymphocytes bind to foreign antigen on APC.
  2. Release cytokines that stimulate:
    a) clonal expansion of complementary T, cells (rapid mitosis: become memory cells or trigger humoral
    response.
    b) clonal expansion of cytotoxic T cells (T.): secrete enzyme perforin to destroy infected cells.
66
Q

process of the humoral response?

A
  1. Complementary T, lymphocytes bind to foreign antigen on antigen-presenting T cells.
  2. Release cytokines that stimulate clonal expansion (rapid mitosis) of complementary B lymphocytes.
  3. B cells differentiate into plasma cells.
  4. Plasma cells secrete antibodies with complementary variable region to antigen.
67
Q

What is an antibody?

A

proteins secreted by plasma cells
Quaternary structure: 2 light chains’ held together by disulfide bridges, 2 longer ‘heavy chains’.
Binding sites on variable region of light chains have specific tertiary structure complementary to an antigen.
The rest of the molecule is known as the constant region.

68
Q

How do antibodies lead to the destruction of a pathogen?

A

Formation of antigen-antibody complex results in agglutination, which enhances phagocytosis.

69
Q

What are monoclonal antibodies?

A

Antibodies produced from a single clone of B cells.

70
Q

What are memory cells?

A

• Specialised TH B cells produced from primary immune response.
• Remain in low levels in the blood.
• Can divide very rapidly by mitosis if organism encounters the same pathogen again.

71
Q

Contrast the primary and secondary immune response?

A

secondary response:
• Faster rate of antibody production.
• Shorter time lag between exposure & antibody production.
• Higher concentration of antibodies.
• Antibody level remains higher after the secondary response.
• Pathogen usually destroyed before any symptoms.

72
Q

What causes antigen variability?

A
  1. Random genetic mutation changes DNA base sequence.
  2. Results in different sequence of codons on mRNA
  3. Different primary structure of antigen = H-bonds,
    ionic bonds & disulfide bridges form in different places in tertiary structure.
  4. Different shape of antigen.
73
Q

Explain how antigen variability affects the incidence of disease?

A

• Memory cells no longer complementary to
antigen = individual not immune = can catch
the disease more than once.
• Many varieties of a pathogen = difficult to develop vaccine containing all antigen types.

74
Q

Compare passive and active immunity.
Give examples of both types?

A

• both involve antibodies
• can both be natural or artificial
99sg
passive natural: antibodies in breast milk/ across placenta passive artificial: anti-venom, needle stick injections active natural: humoral response to infection active artificial: vaccination

75
Q

Explain the principles of vaccination?

A
  1. Vaccine contains dead/ inactive form of a pathogen or antigen.
  2. Triggers primary immune response.
  3. Memory cells are produced and remain in the bloodstream, so secondary response is rapid & produces higher concentration of antibodies.
  4. Pathogen is destroyed before it causes symptoms.
76
Q

What is herd immunity?

A

Vaccinating large proportion of population reduces available carriers of the pathogen.
Protects individuals who have not been vaccinated e.g. those with a weak immune system.

77
Q

Suggest some ethical issues surrounding the use of vaccines?

A

• production may involve use of animals
• potentially dangerous side-effects
• clinical tests may be fatal
• compulsory vs opt-out

78
Q

Describe the structure of HIV?

A

• Genetic material (2 x RNA) & viral enzymes (integrase & reverse transcriptase) surrounded by capsid.
• Surrounded by viral envelope derived from host cell membrane.
• GP120 attachment proteins on surface.

79
Q

How does HIV result in the symptoms of
AIDS?

A
  1. Attachment proteins bind to complementary CD4
    receptor on Ty cells.
  2. HIV particles replicate inside Ty cells, killing or damaging them.
  3. AIDS develops when there are too few T, cells for the immune system to function.
  4. Individuals cannot destroy other pathogens & suffer from secondary diseases/ infections.
80
Q

Why are antibiotics ineffective against viruses?

A

Antibiotics often work by damaging murein cell walls to cause osmotic lysis. Viruses have no cell wall.
Viruses replicate inside host cells = difficult to
destroy them without damaging normal body cells.

81
Q

Suggest the clinical applications of monoclonal antibodies?

A

• Pregnancy tests by detecting HCG hormones in urine.
• Diagnostic procedures e.g. ELISA test
• Targeted treatment by attaching drug to antibody so that it only binds to cells with abnormal antigen e.g. cancer cells due to specificity of tertiary structure of binding site.

82
Q

Explain the principle of a direct ELISA test?

A

detects presence of a specific antigen
1. Monoclonal antibodies bind to bottom of test plate.
2. Antigen molecules in sample bind to antibody. Rinse excess.
3. Mobile antibody with ‘reporter enzyme’ attached binds to antigens that are ‘fixed”’ on the monoclonal antibodies. Rinse excess.
4. Add substrate for reporter enzyme. Positive result: colour change.

83
Q

Explain the principle of an indirect ELISA test?

A

detects presence of an antibody against a specific antigen
1. Antigens bind to bottom of test plate.
2. Antibodies in sample bind to antigen. Wash away excess.
3. Secondary antibody with ‘reporter enzyme’ attached binds to primary antibodies from the sample.
4. Add substrate for reporter enzyme. Positive result: colour change.

84
Q

Suggest some ethical issues surrounding the use of monoclonal antibodies?

A

• Production involves animals.
• Drug trials against arthritis & leukaemia resulted in multiple organ failure.

Biology (7 decks)

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