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A Level Biology > Membranes And Cell Divisions > Flashcards

Membranes And Cell Divisions Flashcards

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1
Q

What are the roles of the membranes within cells and at the surface

A
  • partially permeable barriers between the cell and its environment, between organelles and the cytoplasm and within organelles
  • sites of chemical reactions
  • sites of cell communication (cell signalling). Release chemicals
  • contain receptors for these chemical signals
  • regulates transport of materials in and out of the cell
  • may contain enzymes involved in specific metabolic pathways
  • have antigens so the organisms immune system can recognise the cell as being self and not attack it
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2
Q

How can molecules pass through a partially permeable membrane

A
  • very small molecules simply diffuse through the cell membrane
  • some substances dissolve in the lipid bilayer and pass through
  • other substances pass through special protein channels or are carried by carrier proteins
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3
Q

Who developed the fluid mosaic model and when

A
  • singer and nicolson
  • 1972
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4
Q

What is the fluid mosaic model

A

Theory of cell membrane structure with proteins embedded in a sea of phospholipids

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5
Q

Why is the plasma membrane fluid

A

Phospholipids and proteins are free to move

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6
Q

Why is the plasma membrane a mosaic

A

Proteins are randomly arranged

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7
Q

What is a glycolipid

A

Phospholipid with a chain of carbohydrate molecules attached

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8
Q

What is a glycoprotein

A

Protein with a chain of carbohydrate molecules attached

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9
Q

What are the different components of the plasma membrane

A
  • phospholipid : hydrophobic phosphate head, hydrophilic fatty acid tail
  • glycoprotein
  • proteins: channel, carrier, intrinsic, extrinsic
  • olygocarbohydrate
  • glycolipid
  • cholesterol
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10
Q

What are the different types of proteins in the plasma membrane

A

Channel proteins - contain pores to allow ions with electrical charges to pass through
Carrier proteins - change their shape to carry specific molecules across the membrane
Other proteins can attach to carrier proteins and act as enzyme, receptor or antigen sites for complementary-shaped signalling chemicals

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11
Q

How thick is a cell surface membrane

A

5-10 nm

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12
Q

What factors effect membrane permeability

A

Temperature - effects KE. Chance of collisions happening
Solvent concentration

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13
Q

What is diffusion

A

The net movement of molecules from an area of high concentration to low concentration across a partially permeable membrane
Does not require ATP

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14
Q

What is facilitated diffusion

A

Movement of molecules from an area of high concentration to low concentration across a partially permeable membrane via protein channels or carriers.
Does not require ATP

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15
Q

What affects the rate of diffusion

A
  • temperature
  • diffusion distance
  • surface area
  • size of diffusing molecule
  • concentration gradient
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16
Q

What is osmosis

A

The movement of water molecules across a partially permeable membrane down their water potential gradient

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17
Q

What is water potential

A

Mesure of the tendency of water molecules to diffuse from one region to another

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18
Q

What has the highest water potential

A

Pure water = 0

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19
Q

Osmosis in animal cells

A
  • lysis
  • normal
  • crenated
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20
Q

What does it mean when an animal cells is in lysis

A
  • higher water potential: more water coming into cell then out
  • lower concentration
    Cell will burst
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21
Q

What does it mean if an animal cell is crenated

A
  • low water potential: more water leaving then coming in
  • high concentration
    Cell will shrivel
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22
Q

Osmosis in plant cells

A
  • turgid
  • normal
  • flaccid
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23
Q

what does it mean if a plant cell is turgid

A
  • high water potential: more water in than out
  • lower concentration
    Cell will burst
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24
Q

what does it mean if a plant cell is flaccid

A
  • lower water potential: more water leaving than entering
  • higher concentration
    Cell will shrivel
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25
Q

What does it mean if a solution is hypertonic

A

More water leaves the cell

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26
Q

What does it mean if a solution if hypotonic

A

More water enters the cell

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27
Q

What does it mean if a solution is isotonic

A

Dynamic equilibrium

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28
Q

What is a glycoprotein

A

A carbohydrate chain attached to a protein molecule

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29
Q

Features of a carbohydrate molecule (oligosaccharide)

A
  • very hydrophilic
  • attract water with dissolved solutes
  • helps the cell interact with its watery environment and obtain dissolved substances
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30
Q

What is the function of cholesterol in the plasma membrane

A

Mechanical stability and flexibility

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31
Q

What are the main functions of membrane proteins

A
  • transport
  • receptors
  • anchorage
  • cell recognition
  • intracellular joining
  • enzyme activity
32
Q

What are the different types of cell transport

A
  • active
  • passive
33
Q

Examples of passive transport

A
  • simple/lipid diffusion
  • facilitated diffusion
  • osmosis
34
Q

Examples of active transport

A
  • active transport
  • bulk transport
35
Q

What is an active method of transport

A

Requires ATP produced during cellular respiration

36
Q

What is passive method transport

A
  • takes place as a result of concentration, pressure or electrochemical gradients.
  • it involves no metabolic energy from the cell
37
Q

What particles can pass through the plasma membrane

A
  • gases (oxygen, carbon dioxide)
  • hydrophobic molecules (benzine)
  • small polar molecules (water, ethanol)
38
Q

What particles can’t pass through the plasma membrane

A
  • large polar molecules (glucose)
  • charged molecules (ions, amino acids)
39
Q

What is Fick’s law

A

Rate of diffusion is proportionally identical to (surface area x concentration gradient) / diffusion distance

40
Q

What is bulk transport

A

Large macromolecules, like proteins and polysaccharides and even smaller cells, are transported by bulk transport using membrane vesicles

41
Q

What is the word for into in bulk transport

A

Endo

42
Q

What is the word for out in bulk transport

A

Exo

43
Q

What is the word for liquids in bulk transport

A

Pino

44
Q

what is the word for solids in bulk transport

A

Phago

45
Q

What is endophagocytosis

A

Moving solids into a cell

46
Q

What is a phosopholipid bilayer

A

The two layers of phospholipids arranges in such a way that the your hydrophobic fatty acid tails are facing inwards and their hydrophilic polar heads are facing outwards

47
Q

What does the cell theory state

A
  • new cells are always formed by division of old cells
  • the life of a cell from one division to the next is called the cell cycle
48
Q

What are the three main phases of the cell cycle

A
  • interphase
  • mitosis
  • cytokinesis
49
Q

What happens during each stage of interphase

A

G1 - organelles replicate, cell size increases, protein synthesis
S - DNA replication occurs
G2 - spindle proteins synthesised

50
Q

What are the different stages of mitosis

A
  • prophase
  • metaphase
  • anaphase
  • telophase
51
Q

What happens in prophase

A
  • the chromosomes that have been replicated in S phase of interphase and consists of two identical sister chromatids shorten and thicken as the DNA supercoils
  • nuclear envelope breaks down
  • tubulin treads form
52
Q

What happens in metaphase

A
  • the pairs of chromatids attach to the spindle threads at the equator region
  • they attach by their centromeres
53
Q

What happens in anaphase

A
  • the centromere of each pair of chromatids splits
  • motor proteins pull each sister chromatids of a pair in opposite directions towards opposite poles
  • the chromatids now called chromosomes form a V shape
54
Q

What happens in telophase

A
  • the separated chromosomes reach the poles
  • new nuclear enveloped forms around each set of chromosomes
  • cell now contains two nuclei each genetically identical to each other
55
Q

what happens in cytokineses

A

The cell splits to form two identical daughter cells

56
Q

What is the formula for mitotic index

A

Cells in mitosis / total number of cells

57
Q

What are the functions of meiosis

A
  • form haploid gametes
  • half chromosome number: sexual lifecycle
  • introduce genetic variation
58
Q

Where does meiosis take place

A

In the reproductive organs of both male (plants) and females (animals)

59
Q

what is the product of meiosis

A

4 genetically varied daughter cells
- containing half the number of chromosomes
- haploid
- called gametes

60
Q

What is a homologous chromosome

A

Structural unit consisting of a long thread of coiled DNA and protein. Same structure. One maternal and one paternal

61
Q

What is a sister chromatid

A

Duplicated chromosomes attached by a centromere

62
Q

What is a bivalent

A

Connected homologous chromosomes, forming a unit of 4 DNA molecules, essential for the equilibrium segregation of the chromosome pool

63
Q

What happens in prophase 1

A
  • chromatin condenses and each chromosome supercoils
  • nuclear envelope breaks down
  • spindle threads of tubulin proteins form from the centriole in animal cells
  • the chromosomes come together in their homologous pairs
  • crossing over occurs
64
Q

what is crossing over

A

Where non-sister chromatids wrap around each other and may swap sections so that alleles are shuffled
- creates a new combination of alleles

65
Q

What happens in metaphase 1

A
  • pairs of homologous chromosomes attach along the equator of the spindle
  • each attach to a spindle thread by its centromere
  • homologous pairs are arranged randomly
  • arrange in independent assortment
66
Q

What is independent assortment

A
  • homologous chromosomes line up randomly in metaphase 1
  • sister chromatids in metaphase 2
  • new combination of maternal and paternal chromosomes
67
Q

What happens in anaphase 1

A
  • members of each pair of homologous chromosomes are pulled apart by motor proteins that drag them along the tubulin threads of the spindle
  • centromeres do not divide
  • each chromosome consists of two chromatids
  • crossed over areas separate from each other, resulting in swapped areas of chromosomes and allele shuffling
68
Q

What happens in telophase 1

A
  • two new nuclear envelopes form around each set of chromosomes and the cell divides by cytokinesis
  • each new nucleus contains half the original number of chromosomes
  • each chromosome consists of two chromatids
69
Q

What happens in prophase 2

A
  • nuclear envelope breaks down
  • chromosomes condense each containing two chromatids
  • chromatids of each chromosomes are no longer identical
  • spindles form
70
Q

What happens in metaphase 2

A
  • chromosomes attach, by their centromere, to the equator of the spindle
  • chromatids of each chromosome are randomly arranged
71
Q

What happens in anaphase 2

A
  • centromeres divide
  • chromatid from each chromosome are pulled apart by motor proteins
  • pulled along the tubulin of the spindle to each pole
  • chromatids are randomly segregated
72
Q

What happens in telophase 2

A
  • nuclear envelope forms around each of the four haploid nuclei
73
Q

How does meiosis cause genetic variation

A
  • crossing over
  • independent assortment
  • random fertilisation
74
Q

What is the importance of genetic diversity

A
  • gives the organism a better chance of survival
  • evolution
75
Q

What causes genetic diversity

A

Genetic mutation

A Level Biology (13 decks)

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