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Cells Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What are the distinguishing features and general structure of eukaryotic cells?

A

Distinguishing Features:
Cytoplasm containing membrane-bound organelles.
DNA enclosed in a nucleus.
General Structure:
Eukaryotic cells have a nucleus, cytoplasm, and various organelles like mitochondria, ribosomes, endoplasmic reticulum (rER and sER), Golgi apparatus, and lysosomes.

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2
Q

Describe the structure and function of the rough and smooth endoplasmic reticulum (rER and sER).

A

rER:
Ribosomes on surface.
Synthesizes and processes proteins, which are folded and transported within the rER.
Packages proteins into vesicles for transport to the Golgi apparatus.
sER:
Lacks ribosomes.
Synthesizes and processes lipids, such as cholesterol and steroid hormones.

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3
Q

Describe the structure and function of the nucleus.

A

Structure:
Contains genetic information in the form of DNA.
Nucleolus within the nucleus produces ribosomes.
Function:
Stores genetic information which codes for proteins.
Site of DNA replication and transcription (produces mRNA).

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4
Q

What are ribosomes and what is their function?

A

Structure:
Composed of ribosomal RNA and protein, with two subunits.
Not membrane-bound.
Function:
Site of protein synthesis (translation).

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5
Q

Describe the structure and function of the Golgi apparatus and Golgi vesicles.

A

Golgi Apparatus:
Modifies proteins (e.g., adding carbohydrates to produce glycoproteins) and lipids (e.g., glycolipids).
Packages proteins and lipids into Golgi vesicles.
Produces lysosomes.
Golgi Vesicles:
Transport proteins and lipids to their required destinations, such as the cell surface membrane.

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6
Q

What are lysosomes and what is their function?

A

Structure:
Membrane-bound organelles containing hydrolytic enzymes (lysozymes).
Function:
Break down pathogens or worn-out cell components via hydrolysis.

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7
Q

Describe the structure and function of mitochondria.

A

Structure:
Double membrane-bound organelle with inner folds called cristae.
Contains its own DNA and ribosomes.
Function:
Site of aerobic respiration, producing ATP for energy.
Powers processes like protein synthesis, vesicle movement, and active transport.

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8
Q

What is the structure and function of the cell vacuole in plants?

A

Structure:
A membrane-bound organelle filled with cell sap (water, sugars, amino acids, pigments, and waste chemicals).
Function:
Maintains turgor pressure to prevent wilting.
Stores nutrients and waste products.

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9
Q

Describe the structure and function of the cell wall in plants, algae, and fungi.

A

Structure:
Composed mainly of cellulose in plants/algae, and chitin in fungi.
Function:
Provides mechanical strength and prevents the cell from changing shape or bursting under osmotic pressure.

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10
Q

Describe the structure of viruses.

A

Structure:
1. Nucleic acids surrounded by a capsid (protein coat)
2. Attachement proteins allow attachment to specific host cells
3. No organelles eg cytoplasm,ribosomes
4. some are also surrounded by a lipid enevlope , e,g HIV

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11
Q

Describe how viruses replicate

A
  1. Attachment proteins attach to complementary receptors on host cell
  2. Inject viral nucleic acid (DNA/RNA) into host cell
  3. infected host cell replicates virus particles:
    a. nucleic acid replicated
    b. cell produces viral protein/capsid/enzymes
    c. virus assembled then released
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12
Q

What is the structure and function of chloroplasts in plants and algae?

A

Structure:
Contain chlorophyll, a double membrane, and internal stacks of thylakoids (grana).
Function:
Absorb light energy for photosynthesis, producing organic substances like carbohydrates and lipids.

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13
Q

How are eukaryotic cells organized in complex multicellular organisms?

A

Tissue: Group of specialized cells with a similar structure working together to perform a specific function.
Organ: Aggregations of tissues performing specific functions.
Organ System: Group of organs working together to perform specific functions.

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14
Q

What are the distinguishing features and general structure of prokaryotic cells?

A

Distinguishing Features:
Lacks membrane-bound organelles.
Genetic material not enclosed in a nucleus.
Structure:
Contains a single, circular DNA molecule free in the cytoplasm.
Has smaller ribosomes (70S), a cell wall made of murein, and may have plasmids, capsules, and flagella.

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15
Q

Compare the structure of eukaryotic and prokaryotic cells.

A

Eukaryotic Cells:
Have membrane-bound organelles, a nucleus, and DNA associated with histone proteins.
Larger ribosomes (80S).
Cell wall in plants, algae, and fungi, made of cellulose or chitin.
Prokaryotic Cells:
Lack membrane-bound organelles and nucleus.
DNA is short, circular, and not associated with proteins.
Smaller ribosomes (70S).
Cell wall present, made of murein.

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16
Q

What are the principles and limitations of different types of microscopes?

A

Optical Microscope:
Uses light; limited resolution (200nm) and magnification (x1500).
Can view living specimens and show color.
Transmission Electron Microscope (TEM):
Uses electrons; high resolution (1nm) and magnification (x1,000,000).
Only dead specimens, produces 2D images.
Scanning Electron Microscope (SEM):
Electrons deflect off surface; high resolution, 3D images.
Only dead specimens, no internal structures visible.

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17
Q

Describe and explain the principles of cell fractionation and ultracentrifugation as used to seperate cell components

A
  1. Homegenise tissue (blend) , distrupting cell membrane , opening up cells and releasing its contents (organelles)
  2. Place in a cold , isotonic,buffered solution :
    * cold to reduce enzyme activicty
    * isotonic so water doesn’t move in or out of organelles by osmosis -so they don’t burst
    * buffered to keep pH constant - so enzymes don’t denature
  3. Filter homegenate - remove large unwanted debris eg connective tissue
  4. Ultacentrifugation - seperates organelles in order of mass/density.
    - centrifuge homgentate at high speed
    - remove pellet of heaviest organelle and respin supernatant at a higher speed
    - repeat at increasing speeds until seperated out.
    * order of organelles: nuclei,chloroplasts/mitochondria,lysosome,ER, ribosomes
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18
Q

Describe the stages of the cell cycle in eukaryotic cells.

A
  1. Interphase :
    * DNA replicates semi conservatively .
    * Leading to 2 chromatids (identical copies) joined at centromere
    * number of organelles & volume of cytoplasm increases
  2. Mitosis:
    * Nucleus divides
    * to produce 2 nuclei with identical copies of DNA produced by parent cell
  3. Cytokinesis:
    * Cytoplasm and cell membrane divide
    * to form 2 new genetically identical daughter cells
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19
Q

Describe the behaviour of chromosomes &role of spindle fibres in mitosis . (describe the stages of mitosis) PMAT

A

1 . Prophase :
* chromosomes condense , become shorter/thicker
* they appear as 2 sister chromatids joined by chromatids
* centrioles move to the opposite poles forming spindle network
2. Metaphase :
* spindle fibres attach to chromosomes by their centromeres
*chromosomes align along the equator
3. Anaphase :
* spindle fibres shorten /contract
* centromere divides
*Pulling chromatids from each pair to opposite poles of the cell
4. Telophase :
* chromosomes uncoil ,becoming longer/ thinner
*Nuclear envelopes reform = 2 nuclei
* Spindle fibres / centrioles break down

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20
Q

Explain the importance of mitosis in the life of an organism

A
  • Growth of multicellular organisms by increasing cell number
  • Replacing cells to repair damaged tissue
    *Asexual reproduction
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21
Q

Why do some eukaryotic cells not undergo the cell cycle ?

A
  • Within multicellular organisms , not all cells retain the ability to divide (eg. neurons)
  • Only cells that do retain this ability go through the cell cycle
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22
Q

How do prokaryotic cells replicate by binary fission?

A

DNA replicates (including plasmids).
Cell grows, DNA moves to opposite poles.
Cytoplasm divides, producing two daughter cells with identical circular DNA but varying plasmid numbers.

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23
Q

Describe the arrangements of components of a cell membrane

A

*Phospholipids form a bilayer -fatty acid tails face inwards ,phosphate heads face outwards.
* Proteins
- Integral proteins span bilayer eg. channel and carrier proteins
- peripheral proteins on the surface of membrane
* Glycolipids (lipids with polysaccharide attached ) found on exterior surface
* Glycoproteins (proteins with polysaccharide chains attached )found on exterior surface
* Cholesterol (sometimes present) bonds to phospholipd hydrophobic fatty acid tails

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24
Q

Explain the arrangement of Phospholipids in a cell membrane

A

*Bilayer ,with water present on either side
* Hydrophobic fatty acid tails repelled from water so point away from water
*Hydrophilic phosphate heads attracted to water so point to water

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25
Q

Explain the role of cholesterol in cell membrane

A
  • Restricts movement of other molecules making up membrane
  • so decreases fluidity and permeability thus increasing rigidness
26
Q

Describe how movement across membrane occurs by simple diffusion

A
  • Phospholipid Bilayer is fluid - membrane can bend for vesicle formation /phagocytosis
  • Glycoproteins/glycoproteins act as receptors/antigens - involved in cell signalling /recognition
27
Q

What factors affect the rate of movement across cell membranes?

A

Surface Area: Larger surface area increases the rate.
Protein Channels/Carriers: More proteins increase facilitated diffusion and active transport rates.
Concentration Gradient: A steeper gradient increases the rate of diffusion and osmosis.
Water Potential Gradient: Affects osmosis rate.

28
Q

Explain the limitations of imposed by the nature of the phospholipid bilayer

A
  • Restricts movement of water soluble / polar and larger substances eg. Na and glucose
  • Due to hydrophobic fatty acid tails in interior of bilayer
29
Q

Explain the role of carrier and channel proteins in facilitated diffusion

A
  • Shape/charge of protein determines which substances move
  • channel proteins facilitate diffusion of water-soluble substances
  • hydrophilic pore filled with water
    -May be gated (can open and close)
  • Carrier Proteins facilitate diffusion of slightly larger substances
  • Complementary substance attaches to binding site
  • protein changes shape to transport substance
30
Q

Describe how movement across membranes occurs by osmosis

A
  1. Water diffuses
  2. from an area of high to low water potential /down a water potential gradient
  3. through a partially permeable membrane
  4. Passive - doesn’t require energy from ATP/respiration
31
Q

Describe how movement across membrane occurs by active transport

A
  • substances move from an area lower conc. to an area of higher conc. against a conc. gradient
    *requiring of ATP and specific carrier proteins
32
Q

Describe the role of carrier proteins and the importance of they hydrolysis of ATP in active transport

A
  1. Complementary substance binds to a specific carrier protein
  2. ATP binds , hydrolysed into ADP+pi, releasing energy
  3. carrier protein , changes shape ,releasing substance on side of higher concentration
  4. Pi released -protein returns into original shape
33
Q

describe an example that illustrates co - transport

A

Absorption of sodium ions and glucose (or amino acids) by cells lining the mammalian ileum:
1. ● Na+ actively transported from
epithelial cells to blood (by
Na+/K+ pump)
● Establishing a conc. gradient
of Na+(higher in lumen than epithelial cell)
2. ● Na + enters epithelial cell down
its concentration gradient with glucose against its concentration gradient
● Via a co-transporter protein
3. ● Glucose moves down a conc. gradient into blood via facilitated diffusion
The movement of sodium can be considered indirect / secondary active transport, as it is reliant on a concentration gradient established by active transport.

34
Q

Describe how surface area, number of channel or carrier proteins and differences in gradients of concentration or water potential affect the rate of movement across cell membranes

A

● Increasing surface area of membrane increases rate of movement
● Increasing number of channel / carrier proteins increases rate of facilitated diffusion / active transport
● Increasing concentration gradient increases rate of simple / facilitated diffusion and osmosis
● Increasing concentration gradient increases rate of facilitated diffusion
○ Until number of channel / carrier proteins becomes a limiting factor as all in use / saturated
● Increasing water potential gradient increases rate of osmosis

35
Q

Explain the adaptations of some specialised cells in relation to the rate of transport across their internal and external membranes

A

● Membrane folded eg. microvilli in ileum → increase in surface area
● More protein channels / carriers → for facilitated diffusion (or active transport - carrier proteins only)
● Large number of mitochondria → make more ATP by aerobic respiration for active transport

36
Q

What is an antigen ?

A

● Foreign molecule / protein / glycoprotein / glycolipid
● That stimulates an immune response leading to production of antibody

37
Q

How are cells identified by the immune system?

A

● Each type of cell has specific molecules on its surface (cell-surface membrane / cell wall) that identify it
● Often proteins → have a specific tertiary structure (or glycoproteins / glycolipids)

38
Q

What types of cells and molecules can the immune system identify?

A
  1. Pathogens (disease causing microorganisms) eg. viruses, fungi, bacteria
  2. Cells from other organisms of the same species (eg. organ transplants)
  3. Abnormal body cells eg. tumour cells or virus-infected cells
  4. Toxins (poisons) released by some bacteria
39
Q

Describe phagocytosis of pathogens (non-specific immune response)

A

1 Phagocyte attracted by chemicals / recognises (foreign) antigens on pathogen
2 Phagocyte engulfs pathogen by surrounding it with its cell membrane
3 Pathogen contained in vesicle / phagosome in cytoplasm of phagocyte
4 Lysosome fuses with phagosome and releases lysozymes (hydrolytic enzymes)
5 Lysozymes hydrolyse / digest pathogen

40
Q

What does phagocytosis lead to ?

A

Phagocytosis leads to presentation of antigens where antigens are displayed on the phagocyte cell-surface
membrane, stimulating the specific immune response (cellular and humoral response).

41
Q

Describe the response of T lymphocytes to a foreign antigen (the cellular
response)

A

T lymphocytes recognise (antigens on surface of) antigen presenting cells eg. infected cells, phagocytes
presenting antigens, transplanted cells, tumour cells etc.
Specific helper T cells with complementary receptors (on cell surface) bind to antigen on
antigen-presenting cell → activated and divide by mitosis to form clones which stimulate:
● Cytotoxic T cells → kill infected cells / tumour cells (by producing perforin)
● Specific B cells (humoral response - see below)
● Phagocytes → engulf pathogens by phagocytosis

42
Q

Describe the response of B lymphocytes to a foreign antigen (the humoral
response)

A

B lymphocytes can recognise free antigens eg. in blood or tissues, not just antigen presenting cells.
1. Clonal selection:
● Specific B lymphocyte with complementary receptor (antibody on cell surface) binds to antigen
● This is then stimulated by helper T cells (which releases cytokines)
● So divides (rapidly) by mitosis to form clones
2. Some differentiate into B plasma cells → secrete large amounts of (monoclonal) antibody
3. Some differentiate into B memory cells → remain in blood for secondary immune response

43
Q

What are antibodies?

A

● Quaternary structure proteins (4 polypeptide chains)
● Secreted by B lymphocytes eg. plasma cells in response to specific antigens
● Bind specifically to antigens forming antigen-antibody complexes

44
Q

Explain how antibodies lead to the destruction of pathogens

A

● Antibodies bind to antigens on pathogens forming an antigen-antibody complex
○ Specific tertiary structure so binding site / variable region binds to complementary antigen
● Each antibody binds to 2 pathogens at a time causing agglutination (clumping) of pathogens
● Antibodies attract phagocytes
● Phagocytes bind to the antibodies and phagocytose many pathogens at once

45
Q

Explain the differences between the primary & secondary immune response

A

● Primary - first exposure to antigen
○ Antibodies produced slowly & at a lower conc.
○ Takes time for specific B plasma cells to be
stimulated to produce specific antibodies
○ Memory cells produced
● Secondary - second exposure to antigen
○ Antibodies produced faster & at a higher conc.
○ B memory cells rapidly undergo mitosis to
produce many plasma cells which produce
specific antibodies

46
Q

What is a vaccine?

A

● Injection of antigens from attenuated (dead or weakened) pathogens
● Stimulating formation of memory cells

47
Q

Explain how vaccines provide protection to individuals against disease

A
  1. Specific B lymphocyte with complementary receptor binds to antigen
  2. Specific T helper cell binds to antigen-presenting cell and stimulates B cell
  3. B lymphocyte divides by mitosis to form clones
  4. Some differentiate into B plasma cells which release antibodies
  5. Some differentiate into B memory cells
  6. On secondary exposure to antigen, B memory cells rapidly divide by mitosis to produce B plasma cells
  7. These release antibodies faster and at a higher concentration
48
Q

Explain how vaccines provide protections for populations against disease

A

● Herd immunity - large proportion of population vaccinated, reducing spread of pathogen
○ Large proportion of population immune so do not become ill from infection
○ Fewer infected people to pass pathogen on / unvaccinated people less likely to come in contact
with someone with disease

49
Q

Explain the effect of antigen variability on disease and disease prevention

A

● Antigens on pathogens change shape / tertiary structure due to gene mutations (creating new strains)
● So no longer immune (from vaccine or prior infection)
○ B memory cell receptors cannot bind to / recognise changed antigen on secondary exposure
○ Specific antibodies not complementary / cannot bind to changed antigen

50
Q

Describe the structure of a HIV particle

A
  • RNA
  • Lipid Envelope
    *Reverse transcriptase
    *capsid
    *Attachment Proteins
51
Q

Describe the replication of HIV in helper T cells

A

Describe the replication of HIV in helper T cells
1. HIV attachment proteins attach to receptors on helper T cell
2. Lipid envelope fuses with cell-surface membrane, releasing capsid into cell
3. Capsid uncoats, releasing RNA and reverse transcriptase
4. Reverse transcriptase converts viral RNA to DNA
5. Viral DNA inserted / incorporated into helper T cell DNA (may remain latent)
6. Viral protein / capsid / enzymes are produced
a. DNA transcribed into HIV mRNA
b. HIV mRNA translated into new HIV proteins
7. Virus particles assembled and released from cell (via budding)

52
Q

Explain how HIV causes the symptoms of acquired immune deficiency
syndrome (AIDS

A

● HIV infects and kills helper T cells (host cell) as it multiplies rapidly
○ So T helper cells can’t stimulate cytotoxic T cells, B cells and phagocytes
○ So B plasma cells can’t release as many antibodies for agglutination & destruction of pathogens
● Immune system deteriorates → more susceptible to (opportunistic) infections
● Pathogens reproduce, release toxins and damage cells

53
Q

Explain why antibiotics are ineffective against viruses

A

Viruses do not have structures / processes that antibiotics inhibit:
● Viruses do not have metabolic processes (eg. do not make protein) / ribosomes
● Viruses do not have bacterial enzymes / murein cell wall

54
Q

What is a monoclonal antibody?

A

Antibody produced from genetically identical / cloned B lymphocytes / plasma cells
● So have same tertiary structure

55
Q

Explain how monoclonal antibodies can be used in medical treatments

A

● Monoclonal antibody has a specific tertiary structure / binding site / variable region
● Complementary to receptor / protein / antigen found only on a specific cell type (eg. cancer cell)
● Therapeutic drug attached to antibody
● Antibody binds to specific cell, forming antigen-antibody complex, delivering drug
Some monoclonal antibodies are also designed to block antigens / receptors on cells.

56
Q

Explain how monoclonal antibodies can be used in medical diagnosis

A

● Monoclonal antibody has a specific tertiary structure / binding site / variable region
● Complementary to specific receptor / protein / antigen associated with diagnosis
● Dye / stain / fluorescent marker attached to antibody
● Antibody binds to receptor / protein / antigen, forming antigen-antibody complex
Examples vary, eg. pregnancy tests. You’ll need to interpret information in the question on how these work.

57
Q

Explain the use of antibodies in the ELISA (enzyme-linked immunosorbent
assay) test to detect antigens

A

Direct ELISA
1. Attach sample with potential antigens to well
2. Add complementary monoclonal antibodies with enzymes attached → bind to antigens if present
3. Wash well → remove unbound antibodies (to prevent false positive)
4. Add substrate → enzymes create products that cause a colour change (positive result)
OR sandwich ELISA
1. Attach specific monoclonal antibodies to well
2. Add sample with potential antigens, then wash well
3. Add complementary monoclonal antibodies with enzymes attached → bind to antigens if present
4. Wash well → remove unbound antibodies (to prevent false positive)
5. Add substrate → enzymes create products that cause a colour change (positive result)

58
Q

Explain the use of antibodies in the ELISA test to detect antibodies

A

Indirect ELISA
1. Attach specific antigens to well
2. Add sample with potential antibodies, wash well
3. Add complementary monoclonal antibodies
with enzymes attached → bind to antibodies if
present
4. Wash well → remove unbound antibodies
5. Add substrate → enzymes create products that
cause a colour change (positive result)

59
Q

Suggest the purpose of a control well in the ELISA test

A

● Compare to test to show only enzyme causes colour change
● Compare to test to show all unbound antibodies have been washed away

60
Q

Discuss some general ethical issues associated with the use of vaccines and
monoclonal antibodies

A

● Pre-clinical testing on / use of animals - potential stress / harm / mistreatment
○ But animals not killed & helps produce new drugs to reduce human suffering
● Clinical trials on humans - potential harm / side-effects
● Vaccines - may continue high risk activities and still develop / pass on pathogen
● Use of drug - potentially dangerous side effects

61
Q

Suggest some points to consider when evaluating methodology relating to
the use of vaccines and monoclonal antibodies

A

● Was the sample size large enough to be representative?
● Were participants diverse in terms of age, sex, ethnicity and health status?
● Were placebo / control groups used for comparison?
● Was the duration of the study long enough to show long-term effects?
● Was the trial double-blind (neither doctor / patient knew who was given drug or placebo) to reduce bias?

62
Q

Suggest some points to consider when evaluating evidence and data
relating to the use of vaccines and monoclonal antibodies

A

● What side effects were observed, and how frequently did they occur?
● Was a statistical test used to see if there was a significant difference between start & final results?
● Was the standard deviation of final results large, showing some people did not benefit?
● Did standard deviations of start & final results overlap, showing there may not be a significant difference?
● What dosage was optimum? Does increasing dose increase effectiveness enough to justify extra cost?
● Was the cost of production & distribution low enough?

biology (4 decks)

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