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A-Level Bio > Unit 2: Cells > Flashcards

Unit 2: Cells Flashcards

1
Q

What are the 6 similarities between prokaryote and eukaryote cells?

A

Chromosomes, DNA, ribosomes, cytoplasm, plasma membrane, sometimes cell walls and a vacuole.

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2
Q

What are the 8 components a prokaryotic cell has that a eukaryotic cell does not?

A

Nucleoid, circular DNA, simpler DNA, no membrane bound organelles, smaller, binary fission, unicellular, anaerobic and aerobic.

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3
Q

What are the 8 components that a eukaryotic cell has which a prokaryotic cell does not?

A

Nucleus, linear DNA, complex DNA, membrane bound organelles, larger, mitosis and meiosis, multicellular and aerobic.

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4
Q

What is created from Mitosis and Meiosis?

A

Mitosis - 2 identical copies created
Meiosis - 4 with 1/2 DNA to create gametes

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5
Q

What do plasma membranes do?

A

They control the passage of substances across exchange surfaces by passive/active transport.

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6
Q

What are Plasmodesmata?

A

Small channels directly connecting the cytoplasm of neighbouring plant cells to each other, creating living bridges.

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7
Q

What is Chitin?

A

A large polysaccharide made from chains of modified glucose. It’s found in exoskeletons of insects, fungi cell walls and structures in invertebrates and fish.

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8
Q

What does a nuclear envelope consist of?
What does it have?

A

Two lipid bilayer membranes, an inner nuclear membrane and an outer nuclear one.
It has many nuclear pores that allow materials to move by cytosol and the nucleus.

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9
Q

What features do bacteria cells have?

A

Single circular DNA free in the cytoplasm, has 1 or more plasmids and flagella, a capsule surrounding the cell and they replicate by binary fission.

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10
Q

What are viruses?

A

Non living and acellular.

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11
Q

Where are CSM or PM?
What do they contain?
What do they control?
What do receptor molecules do?

A

Outside of animal cells or inside cell wall of others.
Contains lipids & proteins.
Controls in and out movements.
Receptor molecules to respond to chemicals (hormones.)

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12
Q

What is the nucleus surrounded by?
What does it contain?
What do pores allow it to do?
What does the nucleolus make?

A

A large organelle surrounded by a nuclear envelope.
Contains chromosomes (linear DNA.)
Pores allow substances to move between cytoplasm and nucleus.
The nucleolus makes ribosomes.

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13
Q

What does the mitochondrian have?
What does it contain?

A

Has a double membrane, the inner one is folded to form cristae.
Contain enzymes for aerobic respiration.
More are found in cells needing a lot of ATP.

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14
Q

What are chloroplasts?
Surrounded by?

A

Small flat structures in plant/algal cells.
Surrounded by double membrane and inside has Thylakoid membranes.

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15
Q

What is lamellae?

A

A thin, flat thylakoid membrane.

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16
Q

What is the function of the Golgi Apparatus?
Makes?

A

fluid filled flat sacs which process and package lipids/proteins.
it makes lysosomes.

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17
Q

What are the Golgi vesicles?
Stores?

A

Small fluid filled sacs by the Golgi Apparatus, outside of the apparatus.
Stores lipids/proteins made by G.A and transports them out.

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18
Q

What are lysosomes?
Digests?

A

digests invading/unwanted parts of the cell. membrane bound organelle which secretes hydrolytic enzymes (lysozymes)

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19
Q

What is the Rough Endoplasmic Reticulum?

A

A system of membranes with ribosomes on the outer surface, transports and synthesises proteins and glycoproteins made by the ribosomes.

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20
Q

What is the smooth endoplasmic reticulum?

A

A system of membranes with no ribosomes on the outer surface. Site of synthesis, transportation and storage of lipids and carbohydrates.

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21
Q

What is the function of cell wall?

A

provides rigidity to the cell and stops the cell from bursting by exerting inward pressure to prevent osmosis.
this enables turgidity which makes parts of the plant semi-rigid.

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22
Q

What is the vacuole?
Contains?
Surrounded by?
Keeps it?
Isolates?

A

A membrane bound organelle in cytoplasm.
Contains sap.
Surrounded by a tonoplast (a membrane.)
Keeps it ridged & helps maintain pressure.
Isolates unwanted chemicals inside the cell.

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23
Q

What happens in G0?

A

When a cell will leave the cycle and quit dividing. Either in a temporary resting period or a more permanent one. Example of the latter is a neuron as it has reached an end stage and no longer divides.

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24
Q

What happens in G1?

A

Cells increase in size, produce RNA and synthesise protein. G1 checkpoint ensures everything is ready for DNA synthesis.

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25
Q

S phase?

A

DNA replication occurs here.

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26
Q

What happens in G2?

A

The cell continues to grow and produces new proteins.
At the end, another control checkpoint determines if the cell can now process to enter M and divide.

27
Q

What happens in Mitosis phase?

A

Cell growth & protein production stop. Cell is focussed on divided into 2 similar daughter cells.
Shorter than interphase.
Lasts approximately 1/2 hours.
Checkpoint in the middle of mitosis (metaphase CP) that ensures the cell is ready to complete cell division.

28
Q

What is the function of the nucleus?

A

Controls the cells activities by controlling the transcription of DNA.

29
Q

What is the structure of DNA/Chromosomes?

A

Packaged into thread-like structures called chromosomes. Each chromosome is made up of DNA tightly coiled many times around histones (proteins) that create its structure.

30
Q

What happens when the cell is not dividing?

A

Chromosomes are not visible in the cell’s nucleus. During cell division, DNA making up chromosomes becomes more tightly packed and is visible.

31
Q

What occurs in Interphase?

A

Divided into G1, S & G2. The cell functions normally but also prepares to divide.
DNA is unravelled, copied and doubled.
Organelles are replicated and the amount of ATP is increased.

32
Q

How long does interphase usually last?

A

12-24 hours in mammalian tissue.

33
Q

What is the cell wall made of in fungi and plants/algae?

A

Chitin in fungi.
Cellulose in plants.

34
Q

what are cristae?

A

the folded inner membrane of the mitochondria, site of oxidative phosphorylation.

35
Q

what are grana?

A

Stacks of thylakoid found in the chloroplast

36
Q

what are thylakoids?

A

flattened sacs in the chloroplast, containing chlorophyll. site of light dependent reaction of photosynthesis.

37
Q

what is a glycoprotein?

A

A protein attached to a carbohydrate chain on the cell-surface membrane.

38
Q

What are two functions of cholesterol embedded in the cell membrane?

A

reduce fluidity and permeability of the cell membrane, increases rigidity of the cell membrane,

39
Q

what is a glycoprotein?

A

a protein attached to a carbohydrate chain on the cell surface membrane

40
Q

What is the function of the phospholipid bilayer?

A

it allows diffusion of lipid soluble molecules and prevents the passing through of water soluble molecules.

41
Q

what is the function of glycoproteins?

A

to act as recognition sites for hormones and neurotransmitters, as well as helping cells to attach to form tissues

42
Q

what are plasmids

A

small loops of DNA that are separate from the main DNA molecule which contain genes that can be passed between prokaryotes

43
Q

what does the capsule do

A

protects bacteria from drying out and from attack by cells of the immune system of the host organism

44
Q

what is the flagellum

A

the long hair-like structure that rotates to enable movement for the prokaryote

45
Q

describe and explain the first step of treatment for a tissue in cell fractionation

A

the tissue must be placed in a cold, isotonic, and buffered solution.
cold to reduce enzyme activity that might break down organelles
isotonic to prevent shrinking/bursting via osmosis
buffered to prevent pH fluctuation which would alter organelle structure or affect enzymes

46
Q

explain the process of homogenation

A

cells are broken up by a homogeniser which releases organelles from the cell, the resultant fluid is the homogenate.
the homogenate is then filtered to remove any complete cells or large debris

47
Q

explain the process of ultracentrifugation

A

the tube of filtrate is placed in the centrifuge and spun at a low speed.
the heaviest organelles (nuclei) are forced to the bottom of the tube and form a pellet.
the fluid at the top (supernatant) is removed, leaving just the sediment.
the supernatant is transferred to another tube and spun at a faster speed so the next heaviest organelles are forced to the bottom.
the process is continued so at each increase in speed, the next heaviest organelle is separated out.

48
Q

describe the order of organelles sedimented out in centrifugation

A

nuclei - chloroplasts - mitochondria - lysosomes - endoplasmic reticulum - ribosomes

49
Q

describe how red blood cells are specialised

A

biconcave and have no nucleus to increase their surface area so more oxygen can be transported

50
Q

describe how neurones are specialised

A

they have a cell body which hosts most of the cellular structures where most protein synthesis occurs
extensions of the cytoplasm form dendrites (receive signals) and axons (transmit signals) allowing the neurone to communicate
the axon has a fatty sheath which speeds up nerve impulses and is long to extend communication quicker

51
Q

describe how muscle cells are specialised

A

they have layers of protein filaments which slide over each other to cause muscle contraction
high density of mitochondria to provide energy for contraction
fuse during development to contract in unison

52
Q

how is a sperm cell specialised to their function

A

the head is haploid so it can fuse to form a diploid
head contains digestive enzymes to break down the outer layer of an egg cell
packed with mitochondria to release energy for tail movement

53
Q

describe how a root hair cell is specialised to its function

A

thin hairs to increase the surface area
thinner walls to decrease diffusion pathway
a vacuole permanently having a higher concentration than the soil water so maintains a water potential gradient
mitochondria for active transport of mineral ions

54
Q

describe how xylem vessels are specialised

A

no top/bottom walls so hollow for a continuous stream
dead to allow free movement of water
walls lignified for support

55
Q

describe how phloem vessels are specialised

A

joined end to end with holes for sap to flow easily through
very few sub cellular structures to aid the flow of materials
made of loving cells which are supported by companion cells

56
Q

describe the function of glycolipids

A

to act as recognition sites
help maintain stability of the membrane
helps cells attach to one another

57
Q

why don’t most molecules freely diffuse across the membrane

A

they aren’t soluble in lipids and cannot pass through the bilayer
they are too large to pass through channels in the membrane
have the same charge as protein channels so are repelled
polar so cannot pass through non-polar tails

58
Q

explain the fluid-mosaic model of the CSM

A

the fluid part represents the individual phospholipid molecules that move giving a flexible moving structure
the mosaic part represents the proteins embedded which vary like mosaics

59
Q

explain co-transport and absorption of glucose in the ileum

A
  • sodium ions are actively transported out of epithelial cells by the sodium potassium pump, into the blood. this takes place on one type of protein carrier molecule found in the CSM of the epithelial cells
  • this maintains a higher concentration of sodium ions in the lumen of the intestine than inside the epithelial cells
  • sodium ions diffuse into epithelial cells down this gradient through a different type of protein carrier (co-transport) in the CSM. As sodium ions diffuse in through this second carrier protein they carry either amino acid molecule or glucose into the cell with them
  • the glucose and amino acids pass into the blood plasma by facilitated diffusion
60
Q

define osmosis

A

the passage of water from a region of higher water potential to a region where there is a lower water potential through a selectively permeable membrane

61
Q

what does adding solute do to water potential

A

the more solute added, the lower the WP

62
Q

what happens if a RBC is placed in a solution with a lower WP and what if in pure water

A

water will leave by osmosis and the cell shrinks and shrivels
in pure water, it will absorb water by osmosis and burst known as haemolysis

63
Q

explain direct active transport

A

the carrier proteins span the plasma membrane and bind to the molecule/ion that needs to be transported on one side of the membrane
the mc/ion binds to the receptor sites on the carrier protein
on the inside of the cell, ATP binds to the protein so it splits into ADP and a phosphate. this causes the protein molecule to change shape and opens the opposite side of the membrane
the mc/ion is released to the other side of the membrane
the phosphate is then released which causes the protein to return to the orignal shape and the process can repeat

A-Level Bio (12 decks)

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