Membranes And Cell Divisions Flashcards
(75 cards)
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
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
3
Q
Who developed the fluid mosaic model and when
A
- singer and nicolson
- 1972
4
Q
What is the fluid mosaic model
A
Theory of cell membrane structure with proteins embedded in a sea of phospholipids
5
Q
Why is the plasma membrane fluid
A
Phospholipids and proteins are free to move
6
Q
Why is the plasma membrane a mosaic
A
Proteins are randomly arranged
7
Q
What is a glycolipid
A
Phospholipid with a chain of carbohydrate molecules attached
8
Q
What is a glycoprotein
A
Protein with a chain of carbohydrate molecules attached
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
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
11
Q
How thick is a cell surface membrane
A
5-10 nm
12
Q
What factors effect membrane permeability
A
Temperature - effects KE. Chance of collisions happening
Solvent concentration
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
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
15
Q
What affects the rate of diffusion
A
- temperature
- diffusion distance
- surface area
- size of diffusing molecule
- concentration gradient
16
Q
What is osmosis
A
The movement of water molecules across a partially permeable membrane down their water potential gradient
17
Q
What is water potential
A
Mesure of the tendency of water molecules to diffuse from one region to another
18
Q
What has the highest water potential
A
Pure water = 0
19
Q
Osmosis in animal cells
A
- lysis
- normal
- crenated
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
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
22
Q
Osmosis in plant cells
A
- turgid
- normal
- flaccid
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
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
25
What does it mean if a solution is hypertonic
More water leaves the cell
26
What does it mean if a solution if hypotonic
More water enters the cell
27
What does it mean if a solution is isotonic
Dynamic equilibrium
28
What is a glycoprotein
A carbohydrate chain attached to a protein molecule
29
Features of a carbohydrate molecule (oligosaccharide)
- very hydrophilic
- attract water with dissolved solutes
- helps the cell interact with its watery environment and obtain dissolved substances
30
What is the function of cholesterol in the plasma membrane
Mechanical stability and flexibility
31
What are the main functions of membrane proteins
- transport
- receptors
- anchorage
- cell recognition
- intracellular joining
- enzyme activity
32
What are the different types of cell transport
- active
- passive
33
Examples of passive transport
- simple/lipid diffusion
- facilitated diffusion
- osmosis
34
Examples of active transport
- active transport
- bulk transport
35
What is an active method of transport
Requires ATP produced during cellular respiration
36
What is passive method transport
- takes place as a result of concentration, pressure or electrochemical gradients.
- it involves no metabolic energy from the cell
37
What particles can pass through the plasma membrane
- gases (oxygen, carbon dioxide)
- hydrophobic molecules (benzine)
- small polar molecules (water, ethanol)
38
What particles can’t pass through the plasma membrane
- large polar molecules (glucose)
- charged molecules (ions, amino acids)
39
What is Fick’s law
Rate of diffusion is proportionally identical to (surface area x concentration gradient) / diffusion distance
40
What is bulk transport
Large macromolecules, like proteins and polysaccharides and even smaller cells, are transported by bulk transport using membrane vesicles
41
What is the word for into in bulk transport
Endo
42
What is the word for out in bulk transport
Exo
43
What is the word for liquids in bulk transport
Pino
44
what is the word for solids in bulk transport
Phago
45
What is endophagocytosis
Moving solids into a cell
46
What is a phosopholipid bilayer
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
What does the cell theory state
- 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
What are the three main phases of the cell cycle
- interphase
- mitosis
- cytokinesis
49
What happens during each stage of interphase
G1 - organelles replicate, cell size increases, protein synthesis
S - DNA replication occurs
G2 - spindle proteins synthesised
50
What are the different stages of mitosis
- prophase
- metaphase
- anaphase
- telophase
51
What happens in prophase
- 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
What happens in metaphase
- the pairs of chromatids attach to the spindle threads at the equator region
- they attach by their centromeres
53
What happens in anaphase
- 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
What happens in telophase
- 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
what happens in cytokineses
The cell splits to form two identical daughter cells
56
What is the formula for mitotic index
Cells in mitosis / total number of cells
57
What are the functions of meiosis
- form haploid gametes
- half chromosome number: sexual lifecycle
- introduce genetic variation
58
Where does meiosis take place
In the reproductive organs of both male (plants) and females (animals)
59
what is the product of meiosis
4 genetically varied daughter cells
- containing half the number of chromosomes
- haploid
- called gametes
60
What is a homologous chromosome
Structural unit consisting of a long thread of coiled DNA and protein. Same structure. One maternal and one paternal
61
What is a sister chromatid
Duplicated chromosomes attached by a centromere
62
What is a bivalent
Connected homologous chromosomes, forming a unit of 4 DNA molecules, essential for the equilibrium segregation of the chromosome pool
63
What happens in prophase 1
- 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
what is crossing over
Where non-sister chromatids wrap around each other and may swap sections so that alleles are shuffled
- creates a new combination of alleles
65
What happens in metaphase 1
- 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
What is independent assortment
- homologous chromosomes line up randomly in metaphase 1
- sister chromatids in metaphase 2
- new combination of maternal and paternal chromosomes
67
What happens in anaphase 1
- 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
What happens in telophase 1
- 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
What happens in prophase 2
- nuclear envelope breaks down
- chromosomes condense each containing two chromatids
- chromatids of each chromosomes are no longer identical
- spindles form
70
What happens in metaphase 2
- chromosomes attach, by their centromere, to the equator of the spindle
- chromatids of each chromosome are randomly arranged
71
What happens in anaphase 2
- 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
What happens in telophase 2
- nuclear envelope forms around each of the four haploid nuclei
73
How does meiosis cause genetic variation
- crossing over
- independent assortment
- random fertilisation
74
What is the importance of genetic diversity
- gives the organism a better chance of survival
- evolution
75
What causes genetic diversity
Genetic mutation
