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Cells Flashcards

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AP® Biology flashcards
1
Q

What is the nuclear envelope ?

A

Double membrane that surrounds nucleus, often has ribosomes on the surface.Controls entry and exit of materials in and out of nucleus and contains reactions taking place within nucleus.

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2
Q

What do nuclear pores do ?

A

Allow the passage of large molecules such as MRNA out of nucleus. typically about 3000 pores in a nucleus each 40-100 nm in diameter

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3
Q

What do chromosomes consist of ?

A

Protein bound linear DNA

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4
Q

What is the nucleolus ?

A

Small spherical region within nucleoplasm. Manufactures ribosomal RNA and assembles ribosomes.

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5
Q

What are the functions of the nucleus ?

A
  • protein synthesis, production of MRNA and TRNA
  • hold genetic material of the cell in the form of DNA
  • manufacture ribosomal RNA and ribosomes.
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6
Q

What is the structure and function of mitochondria ?

A

rod shaped organelles, 1 -10 micrometres in length. cc

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7
Q

What is the structure and function of chloroplasts?

A

Typically disc shaped, 2-10 micrometres long and 1 micrometre in diameter. They are the site of photosynthesis. Contain both dNA and ribosomes so can quickly manufacture proteins involved in photosynthesis

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8
Q

What is the chloroplast envelope ?

A

Double plasma membrane that surrounds the chloroplasts. Very selective on what can enter and leave chloroplasts.

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9
Q

What are the grana ?

A

Stacks of 100 disc like structures called thylakoids. Within the thylakoids there is the green pigment chlorophyll. The grana are where the light absorption stage of photosynthesis takes place.

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10
Q

What is the stroma ?

A

fluid filled matrix where the second stage of photosynthesis takes place ( sugar synthesis) within the stroma you can also find starch grains.

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11
Q

What is the structure and function of rough endoplasmic reticulum ?

A

Has ribosomes present on the outer surface of the membranes. Provide a large SA for synthesis of proteins and glycoproteins. Provide a pathway for the transport of materials throughout cell.

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12
Q

What is the structure and function of smooth endoplasmic reticulum?

A

Doesn’t have ribosomes on the surface. Synthesise store and transport lipids and carbs

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13
Q

What is the structure and function of golgi apparatus ?

A
  • consists of a stack of membranes which make up flattened sacs called cisternae, with small rounded hollow structures called vesicles. Forms glycoproteins, produce secretory enzymes, secrete carbs, transport, store and modify lipids and form lysosomes.
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14
Q

What are lysosomes and their structure ?

A
  • formed when the vesicles contained by the golgi apparatus contains enzymes such as proteases, and also contain lysosymes - enzymes that hydrolyse cell walls of certain bacteria. Up to 1 micrometre in diameter.
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15
Q

What are the function of lysosomes ?

A
  • break down material ingested by phagocytic cells
  • release enzymes to destroy material around a cell
  • digest worn organelles so the materials they were made from can be recycled
  • completely break down cells after they have died.
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16
Q

What is the structure of ribosomes and function ?

A
  • have two subunits, one large and one small, each of which contains ribosomal RNA and proteins
    Are the site of protein synthesis
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17
Q

What are the two types of ribosomes ?

A

80S, found in eukaryotic cells and around 25 nm in diameter
70S found in prokaryotic cells, mitochondria and chloroplasts slightly smaller in diameter.

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18
Q

What is the structure of the cell wall ?

A
  • consists of microfibrils of cellulose which have considerable strength
  • thin layer called the middle lamella which marks boundary between adjacent cell walls and sticks adj cells together.
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19
Q

What is the function of the cell wall ?

A
  • to provide mechanical strength to prevent cell from bursting due to osmosis.
  • to give strength to plant as a whole
  • to allow water to pass along it to contribute to movement of water throughout plant.
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20
Q

What do the cell walls of fungi contain ?

A

chitin, glycan and glycoproteins

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21
Q

What is the structure and function of a vacuole ?

A

A vacuole is a fluid filled sac bounded by a single membrane which contains a solution of mineral ions, sugars, amino acids, wastes and pigments
- Support herbaceous plants by making cells turgid
- sugars and amino acids can act as temp food store
- pigments may colour petals to attract pollinating insects

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22
Q

what does herbaceous mean ?

A

herbaceous plants have green stems not hard, woody stems

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23
Q

What are some key features of prokaryotic cells ?

A

No true nucleus, DNA not associated with proteins, DNA can be found in plasmids, no membrane bound organelles, no chloroplasts, smaller ribosomes, cell wall made of murein, may have a capsule ( outer mucilaginous ( sticky, viscous) layer)

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24
Q

What are some key features of eukaryotic cells ?

A

Distinct nucleus, DNA associated with histones ( proteins found in chromosomes) , no plasmids, membrane bound organelles, chloroplasts in plant and algae cells, larger ribosomes, cell wall made of cellulose and no capsule

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25
Q

What are some adaptations of chlroplasts for their function ?

A
  • contain DNA and ribosomes so proteins needed for photosynthesis can quickly be made
  • contain thylakoids with chlorophyll, chlorophyll captures light for photosynthesis
  • thylakoid stacks create large SA for light absorption
  • fluid of stroma has all enzymes needed to make sugars in second stage of photosynthesis
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26
Q

What are the negative aspects of an electron microscope ?

A

views non living specimens only, very expensive and has to be stored in specific conditions.

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27
Q

Which electron microscope has a higher resolution ?

A

TEM has a higher resolution than SEM

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28
Q

How does TEM work ?

A
  • beam of electrons focused onto specimen using condenser magnet
  • beam passes through thin section of specimen
  • parts that absorb electrons appear dark
  • parts that allow electrons to pass through appear bright
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29
Q

What are limitations of TEM

A
  • can’t study living organisms, complex staining process, specimen has to be very thin, image may contain artefacts ( structures that appear to be real but aren’t part of natural specimen) and 2D black and white image
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30
Q

How does SEM work ?

A

-electron beam directed onto surface of specimen from above ( specimen doesn’t have to be cut as thin)
-electrons bounce off surface, area scattered by specimen
- scatter pattern of the electrons produces 3D image ( image is in colour)

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31
Q

What is eyepiece graticule ?

A

glass disc with scale etched in placed in eyepiece lens

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32
Q

How to calibrate the eyepiece graticule?

A
  • line up graticule with stage micrometer
  • figure out how many divisions on EG correspond to length of stage micrometer ie 90 division = 0.24mm
  • now work out what one division on EG represents
  • calibration must be repeated at every new magnification
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33
Q

What is the total length of stage micrometer ?

A

1mm

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34
Q

What is the definition of resolution ?

A

Ability to distinguish between two points which are very close together

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35
Q

What is magnification ?

A

Ability to enlarge an object by a number of times

36
Q

What is meant by cell fractionation?

A

process where cells are broken up and the different organelles they contain are separated out

37
Q

What are the two processes in cell fractionation ?

A

homogenisation and ultracentrifugation

38
Q

Describe process of homogenisation

A

cell/tissue placed in homogeniser, which breaks it up into smaller pieces. these are released into cold, buffered solution. filtration then used to separate any cell debris, leaving filtrate containing a mixture of organelles

39
Q

Describe process of ultracentrifugation

A
  • centrifuge spins at a low speed initially, heaviest organelles ( nuclei) forced to bottom of tube where they form a pellet
  • fluid at top of tube ( supernatant) is removed and placed into another tube and spun at a higher speed
  • next heaviest organelles forced to bottom of tube
  • process continues so each increase in speed separates out more organelles
40
Q

Why should soluton be cold, buffered and have same water potential as tissue ?

A

buffered =pH stays the same so that enzymes/ proteins don’t denature
cold = to reduce enzyme activity
same water potential = to prevent any net osmosis

41
Q

outline role of organelles in production, transport and release of proteins

A
  • ribosomes synthesise proteins from amino acids
  • rough endoplasmic reticulum contains ribosomes on surface, provides large sA for synthesis of proteins and glycoproteins and pathway for transporting materials like proteins out of cell
  • golgi apparatus packages proteins in vesicles, carries them to cell surface membrane and releases them.
42
Q

Which is stronger ionic or covalent bonds ?

A

both very strong but covalent stronger

43
Q

Where can hydrogen bonding be found ?

A

found between bases of a nucleotide and in water

44
Q

How does hydrogen bonding work ?

A
  • in some molecules, electrons not evenly distributed, may spend more time in one position making a more negatively charged region on molecule
  • slightly positive charged and negatively charged regions on separate molecules attract, forms weak electrostatic bonds between mols
45
Q

What is a functional group?

A

A group of atoms which give a molecule specific properties

46
Q

What is general formula for an alkyl

A

CNH2N + 1

47
Q

What is an amine group vs an amino group

A

amine group contains a nitrogen atom with lone pair of electrons

amino group contains nitrogen atom bonded to two hydrogens

48
Q

What functional group does a carboxyl have

A

combination if hydroxyl ( OH) and carbonyl group ( C double bond O)

49
Q

What are tissues ?

A

A group of similar cells working together to perform a specific function

50
Q

What are organs ?

A

Different tissues working together for one majour function/outcome

51
Q

What is an organ system ?

A

Consists of different organs working together to achieve same goal

52
Q

What are the three main stages of the cell cycle ?

A

interphase, mitosis/meiosis and cytokinesis

53
Q

Describe interphase in detail

A

G1 - cell replicates its organelles to prepare for division. Also growth of cell and transcription/translation because replicating organelles require proteins

S - DNA synthesis stage

G2 - cell growth continues and replacing energy stores used in replication and also more transcription/translation

54
Q

What are the four stages of mitosis ?

A

prophase: chromosomes condense, spindle fibres form from centrioles, nuclear envelope disintegrates and nucleolus disappears

metaphase: chromosomes line up at equator of cell, spindle fibres attach to chromosomes at centromeres ( middle of chromosomes)

anaphase: chromosomes split into chromatids, each chromatid pulled to opposite end of cell by spindle fibres contracting

telephase: cell membrane folding in at equator, nuclear membrane reforms, chromosomes uncoil and nucleolus reappears

55
Q

When do cells enter G0

A

they enter G0 permanently if they are fully differentiated or if DNA is damaged
temporarily sometimes and then triggered to enter cell cycle again i B memory cells during infection

56
Q

Describe process of binary fission

A

cell replicates circular DNA and plasmids
cell grows larger , CDNA loops migrate to opposite poles of cell
cytoplasm starts to divide and new murein cell walls develop
cytoplasm fully divides into two daughter cells. each daughter cell has a copy of circular DNA along with plasmids

57
Q

State the different cell checkpoints

A
  • cell chekcs at key points that cell cycle should continue
  • if cell fails “checkpoint” will exit cycle and enter G0

G1 checkpoint: checks if cell has grown enough and for DNA damage

G2 checkpoint: same checks as G1

metaphase checkpoint: checks that chromosomes are assembled correctly on mitotic spindle so mitosis can occur ( mitotic spindle - segregates chromosomes during mitosis)

58
Q

What is cancer caused by ?

A
  • mutation in TP53 gene ( whose job it is to monitor and control cell cycle)
59
Q

What are the two types of tumors?

A
  • benign which are non cancerous and don’t spread
  • malignant which are cancerous and spread to different regions of body making them hard to remove
60
Q

Chemotherapy

A
  • disrupts cell cycle by preventing DNA replication is S phase and preventing metaphase by interfering with spindle formation
  • can also have an effect on normal cells but targets rapidly dividing cells more which is why hair is so often lost with chemo
61
Q

What is osmosis ?

A

movement of water molecules from an area of higher water potential to an area of lower water potential, across a selectively permeable membrane.

62
Q

What is difference between solute and solvent

A

solute is the substance that dissolves in a liquid while solvent is the liquid the solute dissolves in

63
Q

What is the difference between hypertonic and hypotonic solutions ?

A

hypertonic solution — the concentration of solute inside the cell is higher than outside

hypotonic solution — the concentration of solute is lower inside the cell than outside

64
Q

What is the definition of water potential

A

it is the pressure created by water molecules, measured in kilopascals

65
Q

what is the water potential of pure water under standard conditions ?

A

under 25 degrees celcius and 100 kPA pure water has a water potential of 0kPa, which is the highest water potential

66
Q

How does water move in osmosis ?

A

from a less negative water potential to a more negative water potential ie from -50 to -100 because it moves from high to low wp and -50 is a lerger num than -100.

67
Q

What happens if the water potential of the external solution is equal to the water potential within cell

A

no net osmosis, so state of cell remains normal as no water enters or exits

68
Q

What happens if the water potential of the external solution is lower than the water potential within cell

A

water exits the red blood cell, state of the cell: crenated and the appearance would be shrivelled as water exits the cell.

69
Q

What happens if the water potential of the external solution is higher than the water potential within cell

A

Water will enter the cell, state of the cell becomes swollen. red blood cell would burst due to no cell wall

70
Q

If water enters plant cell what happens ?

A

protoplast swells, condition of the cell: turgid

71
Q

If no water enters or leaves plant cell, what happens ?

A

No change in the protoplast, incipient plasmolysis takes place( the point in which 50 % of the cells become plasmolysed)

72
Q

What happens if water leaves the plant cell ?

A

protoplast shrinks, condition of cell: becomes plasmolysed

73
Q

What does the protoplast refer to ?

A

Basically refers to everything within the cell membrane, all the organelles.

74
Q

What is incipient plasmolysis ?

A

Happens when the water potential of the plant cell and that of its external solution are equal.It is when 50% of the cells become plasmolysed.

75
Q

What is facilitated diffusion ?

A

movement of substances ( passive) such as biological molecules or ions across a plasma membrane, by use of a transport protein. transport protein facilitates/ aids diffusion process.

76
Q

What is active transport ?

A

Active transport is the movement of molecules and ions into or out of a cell from a region of lower to higher concentration, against conc gradient.

Uses ATP because it is an active process and uses carrier proteins. each carrier protein is specific ( only transports one type of molecule or ion)

77
Q

What does active transport require ? ( important points to remember about it)

A

Hydrolysis of ATP
substances are moved against conc gradient
carrier proteins are required
very selective - carrier proteins carry molecules with complementary shapes

78
Q

Describe the process of direct active transport ?

A

intrinsic carrier proteins bind to the molecule or ion to be transported
binding occurs at complementary shaped receptor sites
ATP binds to the carrier protein on the inside of the cell.
ATP is hydrolyzed into ADP and phosphate molecule
phosphate attaches to carrier protein and causes it to change shape
shape change causes the carrier protein to transport the molecule or ion across the membrane, where it is released.
phosphate leaves carrier protein causing it to return to its previous shape. ADP and phosphate will later reform ATP during respiration.

79
Q

How does the sodium potassium pump work ?

A

ATP binds to pump on inside of cell
carrier protein undergoes conformational change
Na + binds to specifically haped binding sites on carrier protein
ATP is hydrolysed ( broken down using water)
carrier protein undergoes a confirmational change ( second time)
this allows NA + to exit cell and K + o bind to different binding site son the protein
The P leaves the pump
carrier protein undergoes a confirmational change
K + can now move into cell
The ADP and P diffuse into mitochondria to be reformed into ATP

80
Q

What is the role of the ileum and what cells bind the ileum ?

A

The role of the ileum is the absorption of digested food molecules. epithelial cells line the ileum.

81
Q

What are the two forms of active transport ?

A

co transport and direct active transport

82
Q

After digestion what happens to glucose concentration in the lumen of ileum ?

A

high concentration of glucose in the lumen of the ileum.

83
Q

How is the glucose moved down the concentration gradient ?

A

moves down the concentration gradient by facilitated diffusion, this is done by carrier proteins. First glucose diffuses into epithelial cells and then from epithelial cells into blood stream.

84
Q

What is the problem with this facilitated diffusion ?

A

problem with the facilitated diffusion is that the rate depends on the conc gradient of glucose. conc gradient falls as glucose moves into epithelial cells, so hence not all glucose can be absorb by FD.

85
Q

How are they also absorbed then and how does this work with co transport ?

A

so also absorbed by AT, first stage involves CP called Na p pump ( sodium potassium pump) transports Na + ions out of epithelial cells into BS by AT and K + ions into epith cells

we start off with low conc of sodium ions inside epithelial cells, lumen of ileum contains high conc of sod ions. this has created a conc grad
in memb of epith cell, there is a protein called sodium glucose co transporter.

sodium ions can diffuse down conc gradient into epith cell. simultaneously transporter also transports glucose into cell. glucose mols transported agst conc gradient, so AT hapeening.
energy for transport of glucose comes indirectly from conc gradient of na + ions.

86
Q

What are some adaptations of the ileum for co transport ?

A

epithelial cells contain many mitochondria which provide ATP needed for sodium potassium pump.

membrane of epithelial cells folded into a large num of microvilli. provide large SA for membrane which means more space for proteins for FD and AT

glucose molecules rapidly transported by BS, so steep conc gradient between epithel cells and blood ( for glucose) increases rate of diiffusion

87
Q
A

a level biology flashcards (15 decks)

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