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Bio PPQs > Cells > Flashcards

Cells Flashcards

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Biology 101 flashcards
1
Q

Explain why it is not possible to determine the identity of certain internal structures using an optical microscope

(2 marks)

A
  • Resolution too low
  • Because wavelength of light is too long
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2
Q

Describe the role of one named organelle in digesting bacteria

(3 marks)

A
  • Lysosomes
  • Fuse with vesicle
  • Release hydrolytic enzymes
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3
Q

Suggest one explanation for the faster rate of plasmid replication in cells growing in a culture with a high amino acid concentration

(2 marks)

A
  • Amino acids used in protein synthesis
  • So more enzymes/ DNA polymerase
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4
Q

Contrast how an optical microscope and transmission electron microscope work and contrast the limitations of their use when studying cells

(6 marks)

A
  • TEM use electrons and optical use light
  • TEM allows greater resolution
  • TEM allows smaller organelles to be observed
  • TEM only view dead specimens and optical can view live specimens
  • TEM does not show colour and optical can
  • TEM requires thinner specimen
  • TEM requires more complex preperation
  • TEM focuses using electromagnets and optical uses glass lens
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5
Q

Describe how a sample of chloroplasts could be isolated from leaves

(4 marks)

A
  • Homogonise cell tissue (in a blender) to break open cells and filter
  • In ice cold, isotonic and buffered solution
  • Centrifuge and remove nucleus
  • Centrifuge at a higher speed, chloroplasts settle out
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5
Q

Outline the role of organelles in the production, transport and release of proteins from eukaryotic cells

(4 marks)

A
  • DNA in nucleus is code for protein
  • Ribosomes on rough endoplasmic reticulum produce protein
  • Mitochondria produce ATP for protein synthesis
  • Golgi apparatus packages/ modifies proteins
  • Vesicles/ RER transports
  • Vesicles fuse w cell surface membrane
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6
Q

Contrast the structure of an animal cell and a prokaryotic cell

(5 marks)

A

Animal vs prokaryotic
- Animal is bigger than prokaryotic
- Mitochondria vs no mitochondria
- Golgi body vs no golgi
- No cell wall vs murein cell wall
- No capsule vs capsule
- Linear DNA vs circular DNA
- Animal has larger ribosomes than prokaryotic

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8
Q

Suggest why a centrifuge is spun at a higher speed to obtain mitochondria

(1mark)

A
  • Mitochondria is less dense than nucleus
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9
Q

No organelles are visible in the cytoplasm of a red blood cell viewed under a TEM. Explain why

(1 mark)

A
  • Cytoplasm of red blood cell filled with haemoglobin
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10
Q

Suggest an explanation for the appearance of the cell-surface membrane as two dark lines under a TEM

(3 marks)

A
  • Membrane has phospholipid bilayer
  • Stain binds to phosphate
  • On inside and outside of membrane

  • In any question about cell-surface membrane, write about phospholipid bilayer
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11
Q

Describe how you could make a temporary mount of a plant tissue to observe the position of starch grains in the cells when using an optical microscope

(4 marks)

A
  • Add a drop of water glass slide
  • Obtain a thin section of plant tissue and place on slide
  • Stain with iodine in potassium iodide
  • Lower cover slip using mounted needle
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12
Q

Describe binary fission in bacteria

(3 marks)

A
  • Replication of circular DNA
  • Replication of plasmids
  • Division of cytoplasm
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13
Q

Suggest and explain how two environmental variables could be changed to increase the growth rate of a prokaryotic cell

(4 marks)

A
  • Increased conc of glucose
  • Increased respiration
    …
  • Increased conc of oxygen
  • Increased respiration
    …
  • Increased temp
  • Increased enzyme activity
    …
  • Increased conc of phosphate
  • Increased ATP
    …
  • Increased conc of nucleotides
  • Increased DNA synthesis

(4 max)

Mark in pairs

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14
Q

Name the first three phases of mitosis and describe the role of spindle fibres and behaviour of chromosomes during each phase

(5 marks)

A
  • Prophase and metaphase and anaphase
  • In prophase chromosomes condense
  • In metaphase centromeres attach to spindle fibres
  • In metaphase chromosomes line up at equator of cell
  • In anaphase centromeres divide
  • In anaphase spindle fibres contract/ shorten
  • In anaphase, chromatids pulled to opposite poles of cell

(5 max)

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15
Q

During the preperation of a slide of onion cells, a student used only the first 5mm from the tip of an onion root, and pressed down firmly on the cover slip. Explain why he did this

(2 marks)

A
  1. Where dividing cells are found/ where mitosis occurs
  2. Single/ thin layer of cells are spread out so light passes through
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16
Q

Describe and explain what a student should do when counting cells to make sure the mitotic index they obtained for an onion root tip is accurate

(2 marks)

A
  • Examine large number of fields of view/ many cells
  • To ensure a representative sample
    OR
  • Repeat count
  • To ensure figures are accurate
    OR
  • Count only whole cells
  • To standardise counting

(2 max)

  • When writing answers about accuracy, use key words such as representative, reliable and remember ideas about repeatability and counting things many times
17
Q

When preparing cells for observation, a scientist placed them in a solution that had a slightly higher water potential than the cytoplasm which moved chromosomes apart. Suggest how it did this

(2 marks)

A
  • Water moves into cell/ cytoplasm by osmosis
  • Cell/ cytoplasm gets bigger

Reject chromosomes expand

18
Q

Describe two aseptic techniques a scientist would have used when transferring a sample of broth culture onto an agar plate and explain why each is important

(4 marks)

A
  • Keep lid on petri dish/ open it as little as possible
  • To prevent unwanted bacteria contaminating the dish
    OR
  • Wear gloves/ mask/ wash hands
  • To prevent contamination from bacteria on hands
    OR
  • Use sterile pipette/ flame the loop
  • To maintain a pure culture of bacteria
19
Q

Describe the appearance and behaviour of chromosomes during mitosis

(5 marks)

A

Prophase:
- Chromosomes coil/ condense
- Appear as two sister chromatids joined at centromere
Metaphase:
- Chromosomes line up at equator
- Chromosomes attached to spindle fibres
- By their centromere
Anaphase:
- Centromere splits
- Sister chromatids are pulled to opposite poles
Telophase:
- Chromatids unwind/ uncoil

20
Q

When preparing a slide of tissue from an onion root tip, she made sure to push down hard on the cover slip, but not to push the cover slip sideways. Explain why

(2 marks)

A
  • Push hard - spread tissue so it is thin and light can shine through
  • Not push sideways - avoid rolling cells together/ breaking chromosomes
21
Q

Name and describe five ways substances can move across the cell-surface membrane into a cell

(5 marks)

A
  • Simple diffusion of small non-polar molecules down conc. gradient
  • Facilitated diffusion down a concentration gradient via protein channel/ carrier
  • Osmosis of water down a water potential gradient via aquaporin
  • Active transport against concentration gradient via protein carrier using ATP
  • Co-transport of 2 different substances using a carrier protein
22
Q

How does the movement of Na+ out of a cell allow the absorption of glucose into the cell

(2 marks)

A
  • Maintains a concentration gradient for Na+
  • Na+ moving in by facilitated diffusion brings glucose with is
23
Q

Describe and explain two features you would expect to find in a cell specialised for absorption

(2 marks)

A
  • Folded membrane/ microvilli so large surface area
  • Large no. of carrier/ channel proteins so fast rate of absorption
  • Large no. of mitochondria so more ATP for active transport
  • Membrane-bound digestive enzymes so maintains a conc. gradient

(2 max)

  • REMEMBER TO TALK ABOUT ATP WHEN TALKING ABOUT ACTIVE TRANSPORT
24
Q

The movement of substances accross cell membranes is affected by membrane structure. Describe how

(5 marks)

A
  • Phospholipid (bilayer) allows movement/ diffusion of non-polar/ lipid soluble substances
  • Phospholipid (bilayer) prevents movement/ diffusuion ofr polar/ charged substances
  • Carrier proteins allow active transport
  • Channel/ carrier proteins allow facilitated diffusion
  • Shape/ charge of the channel/ carrier determines which substances move
  • Number of channels/ carriers determines how much movement
  • Membrane surface area determines how much movement/ diffusion
  • Cholesterol affects fluidity/ permeability

(5 max)

  • Remember that proteins have specific tertiary structures, so only specific molecules can bind to the specific receptor proteins.
25
Q

Give two similarities in the movement of substances by diffusion and by osmosis

(2 marks)

A
  • Movement down a gradient/ from high to low conc.
  • Passive/ do not use energy from ATP
26
Q

Sodium ions from salt are absorbed by cells lining the gut using carrier proteins, which actively transport one sodium ion into the cell in exchange for one proton. Use knowledge of transport across membranes to suggest how it does this.

(3 marks)

A
  • Cotransport
  • Uses ATP
  • Sodium ion and proton bind to protein
  • Protein changes shape to move Na+ and H+ across membrane

(3 max.)

  • Asking about how cotransport works- don’t let terminology confuse you
27
Q

Describe how a phagocyte destroys a pathogen present in the blood

(3 marks)

A
  • Engulfs
  • Forms a vesicle and fuses with lysosome
  • Enzymes digest/ hydrolyse
28
Q

Give 2 types of cell other than pathogens that can simulate an immune response

(2 marks)

A
  • Cells from other organisms/ transplants
  • Abnormal/ cancer/ tumour cells
  • Cells infected by virus
29
Q

Describe and explain the role of antibodies in simulating phagocytosis.

Do not include details about the process of phagocytosis

(2 marks)

A
  • Bind to antigen
  • Cause clumping/ agglutination
30
Q

What is an antigen?

(2 marks)

A
  • Foreign protein
  • That stimulates an immune response
31
Q

What is an antibody?

(2 marks)

A
  • A protein specific to an antigen
  • Secreted by plasma cells
32
Q

Describe the difference between active and passive immunity

(5 marks)

A
  • Active involves memory cells, passive does not
  • Active involves production of antibody by plasma cells
  • Passive involves antibody introduced into body from outside/ vaccine
  • Active long term, because antibody produced in response to antigen
  • Passive short term, because antibody is broken down
  • Active can take time to work, passive is fast acting
33
Q

When a vaccine is given to a person, it leads to the production of antibodies against a disease-causing organism.

Describe how

(5 marks)

A
  • Vaccine contains antigen from pathogen
  • Macrophage presents antigen on surface
  • T cell with complementary receptor protein binds to antigen
  • T cell stimulates B cell
  • With complementary antibody on its surface
  • B cell secretes large amounts of antibody
  • B cell divides to form clone, all secreting same antibody
34
Q

What is a monoclonal antibody?

(1 mark)

A
  • Antibodies with same tertiary structure
    OR
  • Antibodies produced from cloned plasma B cells
35
Q

Describe the role of antibodies in producing a positive result in ELISA test

(4 marks)

A
  • First antibody binds to antigen
  • Second antibody with enzyme attached is added
  • Second antibody attaches to antigen
  • Substrate added and colour changes
36
Q

Describe how HIV is replicated once inside Th cells

(4 marks)

A
  • RNA converted into DNA using reverse transcriptase
  • DNA inserted into T cell DNA
  • DNA transcribed into (HIV m)RNA
  • Translated into new HIV proteins
37
Q

Describe how HIV is replicated

(4 marks)

A
  • Attachment proteins attach to receptors on Th cell
  • RNA enters cell
  • Reverse transcriptase converts RNA to DNA
  • Viral protein produced
  • Virus assembled and released from cell

Bio PPQs (7 decks)

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