B1 Flashcards
Cell structure and transport
1
Q
How many times can light microscopes magnify, what is their resolving power (usually), and what are their benefits/disadvantages ?
A
- magnification = up to 2000x
- resolving power = 200 nm
- can observe live specimens
- cannot magnify as much as an electron microscope
- cheap, portable and easy to use
2
Q
How many times can electron microscopes magnify, what is their resolving power (usually), and what are their benefits/disadvantages ?
A
- up to 2 000 000x
- resolving power = 0.2 nm
- can magnify much more than light microscopes
- have to be kept in special conditions to work, are expensive, large and heavy
- cannot observe live specimens, as specimens must be frozen first
3
Q
Convert 1 metre to micrometres and nanometres
A
- 1 000 000 micrometres
- 1 000 000 000 nanometres
4
Q
Convert 1 millimetre into micrometres and nanometres
A
- 1000 micrometres
- 1 000 000 nanometres
5
Q
Give the formula for finding magnification using image size and real size
A
magnification = image/real
6
Q
How large is the average animal cell ?
A
10 - 30 micrometres
7
Q
What are the structures present in an animal cell and what do they do ?
A
- cell membrane
[] controls which materials enter and exit the cell - nucleus
[] carries all genetic information of the cell
[] gives instructions to the cell for all cellular activities - cytoplasm
[] site of all chemical reactions in a cell
[] jelly-like substance - ribosomes
[] where proteins are produced/synthesised - mitochondria
[] where aerobic respiration takes place
8
Q
What is the size of the average plant cell ?
A
10 - 100 micrometres
9
Q
What are the structures present in a plant (palisade) cell and what do they do ?
A
- cell membrane
[] controls which materials enter and exit the cell - nucleus
[] carries all genetic information of the cell
[] gives instructions to the cell for all cellular activities - cytoplasm
[] site of all chemical reactions in a cell
[] jelly-like substance - ribosomes
[] where proteins are produced/synthesised - mitochondria
[] where aerobic respiration takes place - cellulose cell wall
[] strengthens and supports the cell - permanent vacuole
[] filled with cell sap to keep cells rigid to support the plant - chloroplasts
[] filled with green pigment called chlorophyll that absorbs sunlight for photosynthesis
10
Q
What is a eukaryotic cell ?
A
- animal, fungi, protista or plant cell
- large (10-100 micrometres)
- contain cytoplasm, cell membrane and a nucleus where DNA is stored
11
Q
What is a prokaryotic cell ?
A
- bacteria and other prokaryotes
- small (0.2 - 2 micrometres)
- have a cytoplasm, cell wall (not cellulose) and DNA loops/plasmids that are free-floating within the cell, not enclosed in a nucleus
12
Q
What are the structures present in a bacteria cell and what do they do ?
A
- SOME have a flagellum/flagella
[] long whip-like protein that allows the bacterium to move around - DNA loop
[] all main genetic information of the cell - plasmids
[] smaller DNA loops that code for VERY specific functions like antibiotic resistance - cell wall
[] strengthens and supports cell - SOME have a slime capsule
[] extra protective layer for the cell - cytoplasm
[] site of all cellular chemical reactions - cell membrane
[] controls what goes in/out of the cell - (small) ribosomes
[] protein synthesis - NO MITOCHONDRIA; TOO BIG TO FIT INSIDE
13
Q
Describe how to set up the onion cell practical using a light microscope
A
- if microscope has mirror, set up full light source in front of mirror so mirror reflects the light up into the stage and all that can be seen from the eyepiece is a white circle
- if has its own light source, switch it on
- check that the objective lens used first is the lowest magnification
- lower the stage all the way down
- remove a very thin (1 cell thick) piece of onion tissue from an onion with a scalpel or tweezers
- get glass slide and only touch the edges to prevent oils from skin dirtying the glass
- place thin layer of onion tissue (1 cell thick) on the glass slide
[] ensure there are no wrinkles and it is laid down flat to maximise clarity of cell image
[] stain the tissue with iodine (iodine colours the starch in the plant tissue blue-black) to maximise clarity of the image - place glass cover slip over top, again touching only the edges
[] lay down flat so no air bubbles - place prepares specimen on stage and secure with clips
- raise the stage as close as possible to the eyepiece without the objective lens touching the slide
- slowly focus the image by incrementally using the coarse and fine focus dials
- if want to change magnification, lower the stage all the way, change the objective lens then restart the process of raising the stage as close as possible then finely focusing
14
Q
What are the structures present in an algal cell ?
A
- permanent vacuole
- light sensitive spot
- mitochondria
- nucleus
- flagella
- cell wall
- cell membrane
- ribosomes
- chloroplasts
15
Q
Describe the functions and adaptations of a red blood cell
A
- biconcave shape created by the lack of nucleus
[] more space to carry oxygen molecules
[] however means can’t reproduce via mitosis, so adult stem cells replenish supply over one’s life - contain haemoglobin, a red pigment which allows oxygen to bind to the cell
16
Q
Describe the functions and adaptations of a nerve cell
A
- lots of dendrites to connect with other nerve cells and thus effectively transmit impulses around the body
- long axon to carry impulses further quicker
- synapses
[] use neurotransmitters to allow electrical impulses to effectively carry on between different nerves - myelin sheath for insulation of the axon
[] speeds up nerve impulses, increasing the efficiency of the nervous system
17
Q
Describe the functions and adaptations of a sperm cell
A
- has acrosome at its head
[] filled with digestive enzymes to break down the egg and allow fertilisation - lots of mitochondria for energy to travel long distances
- whip-like tail to propel itself towards the egg
- large nucleus carrying the paternal genetic information
18
Q
Describe the functions and adaptations of a muscle cell
A
- special proteins make muscle fibres contract by sliding over each other
- many mitochondria for energy to contract and relax muscles accordingly
- store glycogen to be converted back into glucose when a quick supply of glucose is needed for respiration for energy to move
[] speeds up response of the muscles to nervous system’s impulses
19
Q
Describe the functions and adaptations of a root hair cell
A
- no chloroplasts because is underground so no sunlight available for photosynthesis
[] saves plant’s resources - close to xylem for easy water transport
- huge surface area for efficient osmosis
- large vacuole to speed up osmosis by increasing ion concentration in the cell
- many mitochondria
[] active transport of mineral ions into root hair cell
20
Q
Describe the functions and adaptations of a photosynthetic cell
A
- chloroplasts with chlorophyll to maximise light absorption for photosynthesis
- cells are in continuous layers in leaves and the outer layer of stems, maximising area of plant that can photosynthesise and thus increasing food/resources for the plant
- large vacuole, keeps leaf spread out and rigid to capture as much sunlight as possible
21
Q
Describe the functions and adaptations of a xylem cell
A
- transports water and mineral ions from the roots of the plant to the shoots and leaves by diffusion
- xylem cells are dead, meaning they have no organelles or cell walls between cells
[] less resistance for more efficient flow of water and ions - lignin strengthens the outside of the hollow dead cells
- support the plant stem through their high rigidity (due to lignin)
22
Q
Describe the functions and adaptations of a phloem cell
A
- transports sugars and organic compounds via active transport
- cells are alive but lose many of their internal structures to transport more efficiently and with less resistance
[] supported by companion cells which supply energy via having many mitochondria for active transport - cell walls on the ends of the cells break down into sieve plates to allow nutrients and compounds through
23
Q
Describe a method for estimating/measuring the image size of cells using a microscope
A
- arrange specimen so one full row of full cells spans the eyepiece’s diameter
- count and note how many full cells there are
- remove the specimen and place a clear ruler there instead
- refocus if necessary
- see how many mm span the diameter
- convert to micrometres by multiplying by 1000, then divide by number of full cells to get average cell length in micrometres
24
Q
What is diffusion ?
A
- movement of particles from areas of high concentration to areas of low concentration
- no energy needed
- particles move DOWN a concentration gradient
25
Q
Which factors affect the rate of diffusion ?
A
- surface area
[] higher SA = higher rate of diffusion - temperature
[] higher temp = higher rate of diffusion as particles have more energy to move quicker - short diffusion distance (makes more effective and easy)
- high concentration gradient
[] a higher proportion of particles will move towards the area of low concentration than backwards
26
Q
Name biological examples of diffusion
A
- gas exchange in lungs
- diffusion of waste products out of a cell via the cell membrane
- selective reabsorption
- (de)oxygenation of red blood cells
27
Q
What is osmosis ?
A
- the movement of water from an area of high concentration OF WATER to an area of low concentration of water ACROSS A SEMI-PERMEABLE MEMBRANE
- does not require energy, as water moves DOWN the concentration gradient in this case
28
Q
What does isotonic mean ?
A
of the same ion concentration
29
Q
What does hypertonic mean ?
A
of a higher ion concentration
30
Q
What does hypotonic mean ?
A
of a lower ion concentration
31
Q
When can osmosis cause problems in cells/organisms ?
A
if concentration gradients are not carefully monitored, the hypotonic water will flood into the hypertonic cells
[] too much water makes the cell burst
32
Q
What is cellular osmoregulation ?
A
- regulation of a cell’s water content via osmosis
- if cytoplasm is too dilute after a chemical reaction, surrounding fluids outside the cell automatically become hypertonic to the cytoplasm, and water leaves the cell via the cell membrane to restore normal water levels
- if cytoplasm is too concentrated after a chemical reaction, surrounding bodily fluids outside the cell automatically become hypotonic to the cytoplasm, and water moves into the cell via the cell membrane to restore normal water levels
33
Q
What is osmosis used for in plant cells ?
A
- creating turgor pressure, keeping the cell rigid as a result
[] cell does not burst like an animal cell thanks to reinforcement of the cell wall - need the fluid surrounding cells to be hypotonic to the cytoplasm to maintain the concentration gradient so that water goes INTO the cell rather than out
[] if cell loses too much water, becomes flaccid - bad for plant as leaves shrivel and cannot catch as much light to photosynthesise with
[] if loses even more water, then plasmolysed (cytoplasm and cell vacuole shrink)
[] if a cell becomes plasmolysed the cell membrane pulls away from the cell wall and the cell dies quickly - usually only seen in a lab
34
Q
Describe the method for the osmosis required practical
A
- prepare potato cylinders of the same mass and diameter, using a corer and a mass balance to check these dimensions are accurate
[] record initial masses and diameters - prepare three beakers
[] one with salt/sugar solution in it
[] one with pure/distilled water
[] one with solution that is isotonic to the potato - place a cylinder in each beaker
[] wait for 20 minutes - remove each and pat dry gently to remove excess outer liquid
[] weigh each again and record against their initial masses
[] calculate difference in mass - should find that the cylinder in the salt/sugar solution lost mass (as water would have left the potato, hypotonic to the solution), the cylinder in isotonic solution stayed (roughly) the same mass, and the cylinder in pure water gained mass (water moved into potato, which is hypertonic to the pure water)
35
Q
What is active transport ?
A
- the movement of particles against a concentration gradient, from an area of low concentration to high concentration
- requires energy
36
Q
What happens to the SA:volume ratio as an object gets larger, and what does this mean for material exchange in organisms ?
A
- SA decreases, volume increases, overall ratio decreases
- as an organism gets larger, it is harder and more inefficient to exchange materials via osmosis or diffusion, as surface area is outweighed by volume
37
Q
Describe 4 adaptations to make material exchange more efficient, and give 3 real-life examples
A
- large surface area
- short diffusion distance or thin membrane for osmosis
- efficient blood/fluid supply to maintain steep concentration gradient
- ventilation to maintain steep concentration gradient
- alveoli
- root hair cells
- small intestine’s walls/membrane (many villi, only 1 cell thick, good blood supply)
