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Biology 1 > Cell biology > Flashcards

Cell biology Flashcards

1
Q

What are two reasons as to why no cells could be seen when looking through an eyepiece lens?

A
  • The magnification and resolution is too low
  • The microscope is not focussed
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2
Q

Compare the structure of a red blood cell to a plant cell.

A
  • RBCs have a biconcave disc shape whereas PCs have many shapes
  • RBCs contain haemoglobin but PCs do not
  • PCs contain chlorophyll, chloroplasts and a permanent vacuole whereas RBCs do not
  • RBCs are much smaller than PCs
  • Both have a cytoplasm
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3
Q

Explain why plant cells do not burst when placed into a beaker of water.

A

A plant cell has a cell wall (strengthened by cellulose) which prevents the cell from bursting when water moves in by osmosis as it can withstand this higher pressure, maintaining cells structure

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4
Q

What do aseptic techniques mean?

A

Techniques ensuring microorganisms being tested don’t escape/ get contaminated

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5
Q

RPA 2: What are aseptic techniques used?

A
  • Sterilising incoluating loop by passing through a flame
  • Sterilise petri dish before use
  • Secure lid of Petri dish with adhesive tape (not entire way round) and store upside down
  • Incubate at 25 degrees celcius
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6
Q

RPA 1: what is the general purpose of the coarse and fine focus knobs?

A

To give a more clear image/bring the image into focus.

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7
Q

RPA 2: how can you see which antiseptic is the most effective?

A

The one with the largest zone of inhibition as the most bacteria was killed there

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8
Q

Describe the function of muscle cells in the stomach.

A

Contract to churn food.

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9
Q

RPA 2: give one reason why a disinfectant may not be best for a given purpose.

A

It could be toxic/harmful and only works well on some bacteria/the bacteria tested.

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10
Q

RPA 1: why is a thin layer of onion used?

A

So light can pass through easily.

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11
Q

RPA 1: explain why iodine is added.

A

To add colour to internal structures so they can be seen clearly.

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12
Q

RPA 1: explain why the cover slip is lowered at an angle.

A

To make sure no air bubbles present which would disrupt view and so the cover slip doesn’t break.

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13
Q

Describe two differences between the transpiration and translocation.

A
  • Transpiration water and mineral ions move through xylem but translocation sugars move through phloem
  • Transpiration water only moves in one direction (continuous stream) whereas translocation sugars move in both directions through pores to different parts of the plant for storage/immediate use
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14
Q

Explain why larger organisms require exchange surfaces.

A

Smaller surface area to volume ratio so diffusion distance is too large so can’t get sufficient molecules. Exchange surfaces allow sufficient molecules to be transported into and out of cells for the organism’s needs.

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15
Q

RPA 1: what equipment is used to prepare the slide?

A
  • cover slip
  • dye / stain like iodine
  • pipette / dropper
  • forceps / tweezers
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16
Q

Compare the structure and function of the phloem and xylem.

A

Structure
- Phloem made of living cells whereas xylem is made of dead cells
- Xylem’s dead walls are strengthened by lignin whereas phloem doesn’t have lignin
- Phloem has pores (end walls) allowing sugars to travel in both directions whereas xylem doesn’t so water and mineral ions only travel in one direction in a continuous steam
- Both are made from cells and have a cytoplasm
Function
- Phloem transports dissolved sugars in translocation whereas xylem transports water and mineral ions in transpiration
- Both transport substances through the stem

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17
Q

Explain why less water is lost from a plant at night.

A

Guard cells are light sensitive so as there is lower light intensity the stomata is closed (by the guard cells)

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18
Q

Give 3 differences between eukaryotes and prokaryotes.

A
  • prokaryotes are smaller
  • prokaryotes do not have DNA enclosed in a nucleus but have a loop of DNA (no memory bound organelles)
  • prokaryotes have plasmids, eukaryotes don’t
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19
Q

Explain the 3 stages of mitosis.

A

Stage 1: interphase/growth stage
- DNA replicate to form X shaped chromosomes (two copies of each chromosome)
- sub cellular structures increase in number/replicate
Stage 2: mitosis
- chromosomes line up at centre of cell and one set of each chromosome pairs are pulled to opposite ends of the cell by cell fibres (nucleus also divides)
Stage 3: cytokinesis
- cytoplasm and cell membrane divide producing two genetically identical (daughter) cells with identical set of chromosomes in each

20
Q

Name three substances found in growth medium.

A
  • glucose
  • amino acids
  • ions
21
Q

Explain one way in which root hair cells are adapted to taking in water.

A

Increase surface area from root hairs so a faster rate of osmosis.

22
Q

Explain why the mean rate of water uptake is higher on a hot day than on a cold day.

A

More evaporation so more water lost therefore more water must be drawn up to replace water loss.

23
Q

Explain why root hair cells contain mitochondria

A

(aerobic) respiration is carried out in the mitochondria which releases energy that is required for active transport as mineral ions are going against their concentration gradient (from a low -> high concentration).

24
Q

Explain how a transplant of bone marrow cells can help to treat medical conditions.

A

Has stem cells which can differentiate into many types of cells that can cure diseases like paralysis.

25
Q

Give 3 differences between mitosis and meiosis

A
  • Mitosis produces 2 genetically identical cells but meiosis produces 4 non genetically identical cells
  • 1 cell division in mitosis but 2 in meiosis
  • Mitosis asexual meiosis sexual
26
Q

Why may a low concentration of oxygen lead to death?

A

Concentration gradient of oxygen will be less steep/more shallow (higher inside so oxygen may diffuse out) so less oxygen diffuses into organism meaning less aerobic respiration so less energy released. Therefore, less metabolism. Also, may anaerobically respire which releases lactic acid (that is toxic).

27
Q

Give 2 pros and cons of using embryos stem cells.

A
  • Can differentiate into mostly all specialised human cells so treats many diseases
  • Painless
  • Ethical objections as it harms the embryo
  • Risk of rejection and infection
28
Q

Give 2 pros and cons of using bone marrow stem cells.

A
  • Quick recovery
  • Can differentiate into many specialised human cells
  • Painful and risk of infection and rejection
  • Can’t treat as many diseases as embryos
29
Q

Give 2 pros of meristems

A
  • Protect rare plants from extinction
  • Crop plants with special features such as disease resistance can be cloned to produce large numbers of identical plants for farmers quickly and economically, increasing yield
30
Q

Describe how ions, water and sugar are obtained and transported through plants

A

Ions: by active transport from a low to high concentration (requiring energy from respiration) from the roots to be transported by the xylem
Water: by osmosis from a high to low water potential from roots to be transported by the xylem
Sugar: from photosynthesis moves up and down the plant stem through the phloem

31
Q

How is the small intestine adapted for efficient absorption? (5)

A
  • Villi in large quantities which increases surface area so a larger diffusion area
  • Villi thin so short diffusion distance
  • Capillary network provides a good blood supply which maintains a positive concentration gradient
  • Intestines are long to give ample time for absorption
  • Villi cells have many mitochondria for respiration for active transport
32
Q

Why do scientists use a temperature of 37 degrees but students use 25 degrees to incubate bacteria?

A

37 degrees is human body temperature so bacteria (microorganism) grows better and faster (in warm conditions) so results are given sooner whereas 25 degrees prevents growth of harmful pathogens

33
Q

Explain why bacterial cells burst if their cell wall is damaged?

A

Water will move into the cell by osmosis through a partially permeable membrane which cannot withstand high pressure of water as there is no cell wall

34
Q

RPA 2: Explain the purpose of each aseptic technique

A
  • Petri dishes and culture media must be sterilised before use to kill any existing bacteria
  • inoculating loops to transfer bacteria must first be sterilised by passing them through a flame to kill any existing bacteria
  • the lid of the Petri dish should be secured with adhesive tape to prevent unwanted bacteria entering but not all way around to prevent anaerobic bacteria growing and stored upside down to prevent moisture dripping on agar which disrupts growth
  • in school laboratories, cultures should generally be incubated at 25°C to prevent harmful pathogens growing
35
Q

Why may the mass of a potato not change in solution?

A

External concentration of solution = internal concentration inside potato.
This means there will be net movement of water in or out by osmosis

36
Q

How would you carry out the osmosis practical?

A
  • Cut potato chips with cork borers so they have an equal length
  • Measure initial mass with a balance and length with a ruler and record
  • Pour sugar/salt solutions of different concentrations into their labelled test tubes and use water as a control, ensure these are all same volume
  • Put in potato chips and leave for 24 hours
  • Remove potatoes and dry with paper towels
  • Measure final mass and length and record
  • Calculate change in mass and percentage change
37
Q

Explain how oxygen gets into mitochondria from the blood

A

Diffuses into body cell from a high to low concentration through the cell membrane

38
Q

What is the risk and how should you minimise risk of a sharp knife?

A

May cut yourself. Keep fingers away from blade.

39
Q

What is the risk and how should you minimise risk of using iodine?

A

Is an irritant so may cause allergic reaction/skin rash. Wear gloves and wash skin immediately after contact.

40
Q

What three differences would be seen in an onion cell viewed by an electron microscope compared to a light microscope?

A
  • Would be seen in black and white
  • Would be more magnified so more sub cellular structures would be seen
  • Higher resolution
41
Q

Describe how mitosis produces two genetically identical cells (4)

A
  • DNA replicates forming X shaped chromosomes and internal structures replicate
  • One set of chromosomes are pulled apart to opposite ends of the cell by cell fibres (nucleus also divides)
  • (Cytokinesis) cytoplasm and cell membrane divide forming two genetically identical daughter cells, the set of chromosomes in each new cell are identical
42
Q

RPA 2 [osmosis] : what are three sources of error

A
  • potatoes not dried properly
  • balance inaccurate
  • evaporation from tubes
43
Q

RPA [microbiology] : why must you incubate upside down?

A

Prevent moisture dripping onto agar, which disrupts growth.

44
Q

Define a specialised cell

A

Cells that are adapted and have differentiated to perform a particular function

45
Q

Describe how to make healthy lungs from a faulty gene using stem cells that aren’t rejected

A
  • take stem cells from patients bone marrow
  • fix the faulty gene
  • create an embryo using these stem cells
  • remove stem cells from embryo and allow them to differentiate into lung cells

Biology 1 (4 decks)

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