year 1 random Flashcards
learn it!
1
Q
what is diffusion?
A
the net movement of particles from a region of higher concentration to a region of lower concentration. it continues until movement is equal in both directions (equilibrium)
2
Q
factors affecting the speed of diffusion
A
temperature
distance
difference in concentration
surface area
3
Q
why would temperature decrease speed of diffusion
A
particles moving at high speeds are constantly colliding which slows down their overall movement. The more collisions that take place the slower the rate of diffusion.
4
Q
what is facilitated diffusion
A
diffusion through protein channels in the membrane. involves movement down a concentration gradient (passive transport)
5
Q
what is the phospholipid bilayer a barrier to without channel proteins
A
polar molecules and ions
6
Q
what is facillitated diffusion affected by
A
affected by all factors which affect simple diffusion alongside the number of channel proteins present
7
Q
what is endocytosis
A
the process of substances entering the cell via bulk transport
8
Q
what is the process of endocytosis (step by step)
A
- cell surface bends inwards when comes into contact with material to be transported
- membrane enfolds the material until membrane fuses
- this forms a vesicle
- vesicle moves into cytoplasm and detached from membrane to transfer material for further processing eg bacteria to lysosomes
9
Q
what ways can molecules move across membranes
A
simple diffusion facilitated diffusion osmosis (water only) bulk transport (endo/exocytosis) active transport (against a concentration gradient)
10
Q
what roles do cell membranes have
A
separate contents of cells from the surrounding environment
separate different areas within cells from each other
allow for compartmentalisation which allows for different potentially incompatible reactions to take place at the same time
allows to set up specific conditions for specific cellular reactions
allow chemical gradients to be maintained
protect vital cell components
allow for efficient cell communication
11
Q
define what is meant by the term organ
A
a collection of tissues adapted to perform a particular function eg heart
12
Q
define what is meant by the term tissue
A
made up of a collection of differentiated cells which have specialized functions. each tissue is adapted for a particular function within an organism.
13
Q
define what is meant by an organ system
A
composed of a number of organs working together to carry out a major body function eg digestive system
14
Q
describe chromatin
A
DNA accessible for transcription so genetic info can be translated
DNA usually packed loosely within nucleus
found in all non dividing cells in process of interphase
15
Q
what are chromosomes
A
DNA that is easily segregated and transported without damage
the DNA cannot be transcribed
temporary packaging of tightly wound and condensed DNA.
16
Q
what are homologous chromosomes
A
the same size
contain the same genes
contain sister chromatids
17
Q
what is exocytosis
A
the bulk transport of substances out of the cell
18
Q
what is the process of exocytosis (step by step)
A
vesicles are formed with material inside
vesicles move towards the plasma membrane to fuse with it
the contents of the vesicle are released to the outside of the cell
19
Q
what is bulk transport
A
a form of ACTIVE TRANSPORT. large molecules and whole cells are too large to move through channel or carrier proteins so move in or out of the cell via bulk transport.
20
Q
describe the step by step process of active transport when using a carrier protein
A
- the molecule to be transported binds to receptors in the channel of the carrier protein on the outside of the cell
- on the inside of the cell ATP binds to carrier protein and is hydrolysed into ADP and inorganic phosphate
- phosphate binds to carrier protein thus changing the proteins shape , opening up to the inside of the cell
- molecule released to inside of cell
- phosphate molecule released and recombined with ADP to form ATP
- carrier protein forms to original shape
21
Q
describe osmosis
A
passive process
net movement of water from solution with high water potential to a solution of lower water potential down a water potential gradient.
will continue until there is equal movement in both directions (equilibrium)
22
Q
what ways can a solution be described in relation to a cell
A
solution is either isotonic hypertonic or hypotonic to a cell
23
Q
define hypertonic
A
solution has a lower water potential outside of the cell can lead to crenation
24
Q
define hypotonic
A
solution has a higher water potential outside of the cell can lead to cell lysis
25
define isotonic
think lucozade solution has same water potential outside of the cell
26
What happens at checkpoint G1
G1 -nutrient levels growth factors and DNA damage checked if fails goes to G0
27
what factors effect membrane structure and permeability and how do they do this
Temperature when increased phospholipids will have more kinetic energy and thus move more. this increases the membranes fluidity to the point where it starts to loose its structure. at higher temperatures this means the cell can break down completely. there is also an increase in permeability due to the change in tertiary structure of membrane proteins carrier and channel proteins thus become denatured
Solvents water is a polar solvent this allows for interactions that keep the bilayer intact. organic solvents are less polar and will dissolve membranes less concentrated solutions do not dissolve membranes but there presence disrupts the membrane
28
describe plasma membrane structure
phospholipid bilayer forms majority of cell surface membrane. phospholipids have hydrophilic head and hydrophobic tail. hydrophilic heads form inner and outer surface of membrane. hydrophobic fatty acid tails form a hydrophobic core inside the membrane. their are intrinsic and extrinsic proteins within the membrane. the fluid mosaic model models the membranes properties and structure.
29
what is an adaptation of the plasma membrane structure?
phospholipids suited to aqueous environment both inside the cell and outside the cell, this is because hydrophilic heads can interact with water
30
what are channel proteins?
An intrinsic protein
Involves passive transport for polar ions and molecules.
Held in position by interactions between hydrophobic core of plasma membrane and hydrophobic r groups on the outside of proteins.
31
what are the intrinsic proteins found in the plasma membrane?
channel
carrier
glycoproteins
lipids
32
what are extrinsic proteins?
proteins that are only present on one side of the bilayer (usually have hydrophobic r groups on outer surfaces) interact with polar heads or intrinsic proteins. some can move between layers an example would be cholesterol
33
what are carrier proteins?
proteins in plasma membrane which involve both the passive and active transport into cells and change shape in order to let substances in
34
what are glycolipids?
lipids with an attached sugar chain. they act as cell markers like antigens which can be recognised as self and non-self.
35
what are glycoproteins?
proteins with an attached sugar chain. these play a role in cell adhesion and receptors for chemical signals playing a part in cell communication. when a chemical binds to a receptor it causes a direct response or a cascade of events.
36
what is cholesterol?
a lipid with a polar and non polar end it regulates fluidity of membranes, positioned in between phospholipids. cholesterol also adds stability by the polar end interacting with heads while non polar end interacts with tails. this pulls them together without making them too rigid. prevents phospholipid molecules grouping too closely and crystallizing.
37
what is meant by the fluid mosaic model?
it describes the fact that proteins occupy various positions on the membrane and that phopholipids are free to move in their layer relative to each other. the membrane is therefore flexible. proteions are also embedded in the membrane which vary in shape size and position, proteins have to be in particular positions for chemical reactions.
38
Basic principles of meiosis including interphase
In interphase chromosomes replicate
In meiosis 1 homologous chromosomes separate
In meiosis 2 sister chromatids separate
In both meiosis 1 and 2 PMAT is followed
39
Describe interphase in terms of activity
```
Chromatin unwinds
Chromosomes replicate
Centrioles replicate
Nucleus present
Protein synthesis
Cell growth
ATP production
Transcription and translation of DNA
```
40
Describe prophase in terms of activity (mitosis)
Chromatin condenses coiling to form chromosomes
Can clearly see chromosomes
Nucleus disappears
Spindle fibres attach to centromeres
41
Describe metaphase in terms of activity (mitosis)
Chromosomes align at metaphase equator/plate
Nuclear envelope disappears
Spindle fibres attached to centromeres
42
Describe anaphase in terms of activity (mitosis)
Sister chromatids separate and move to poles resulting in < shape
Nuclear membrane not present
Spindle fibres contract so pull sister chromatids to opposite poles centromeres divide
43
Describe independent assortment in metaphase 1 meiosis
Orientation of each homologous pair is random and independent of other pairs
Maternal and paternal chromosomes can face either pole
The fact that chromosomes could be in any combination in which pole chromosomes are facing is random is known as independent assortment
This results in genetic variation
44
More detail of prophase 1 meiosis key terms
Bivalent
Chiasmata
Recombination
Two homologous chromosomes pair up to form a bivalent
Crossing over of genetic material between non sister chromatids can occur at chiasmata where chromatids become entangled
The crossing over results in physical exchange of genetic material and new gene combinations are formed on chromatids this is known as recombination
45
Reasons for mitosis TOAD
Tissue repair and replacement
Organism growth so multicellular organisms can derive new cells
Asexual reproduction in plants
Development of embryos from zygotes
46
Reasons for meiosis GERR
Genetic variation
Ensures that produced organisms in sexual reproduction have correct number of chromosomes
Repairs genetic defects
Reprograms gametes helping fertilised egg grow
47
Describe telophase and the activity that occurs mitosis
Chromatids form into chromosomes at opposite poles
Spindle fibres detach from chromosomes
Nuclear envelope reforms at each pole
Enters cytokinesis forming two identical daughter cells
48
What happens at checkpoint G2
G2 -cell size correct replication checked if fails DNA is repaired and cell is allowed to continue growing
49
What happens at metaphase checkpoint
Metaphase- chromosome spindle fibre attachment checked if fails waits for spindle fibres to attach to chromatids
50
What happens at G0
G0 -non dividing stage cells leave cell cycle entering can be temporary or permanent usually aged damaged or dormant cells re enter but cells that have reached their max differentiation do not re enter the cell cycle
cells enter from G1
51
describe function disadvantage usefulness of a TEM transmission electron microscope
function - looking at a thin cross section of an object (eg cell) for looking at internal structure
disadvantage - can't view living things and is costly
useful for - looking at high resolution objects and relationships between structures
52
describe function disadvantage usefulness of a SEM scanning electron microscope
function - looking at the surface of objects at high resolution
disadvantage - costly and cant view living organisms
useful for - looking at objects in 3D and surfaces
53
describe function disadvantage usefulness of a confocal scanning laser microscope
function - allows us to look at thon slices of a sample while keeping it intact and label with fluorescence
disadvantage - low resolution only what is fluorescent can be viewed. fluorescences can cause artefacts
useful for - looking at living cells relationships between cells and highlighting individual components
54
what is the function of a vacuole
to continue turgor pressure help support and act as a reservoir of waste including salts sugars and pigments
55
describe function disadvantage usefulness of a compound light microscope
function - use visible light to illuminate a thin section of sample
disadvantage - lower resolution than electron microscope
useful for - viewing living organisms cells tissues and allows foe an overview of a sample
56
describe key features of a prokaryotic cell
No nucleus has a single strand of DNA (circular plasmid)
Can have flagella
Is smaller than eukaryotic cell 0.1 to 10 micrometres
Single celled
Reproduction via binary fission
Organelles not membrane bound
57
describe function disadvantage and usefulness of a light stereomicroscope
function - illuminates surface of sample
disadvantage - lower resolution than compound light microscope
useful for - looking at living surfaces
58
what is endosymbiosis explain the process
Two independent bacteria
One engulfs the other
One now lives inside the other
Mutualism between the process
Internal bacteria passed on from generation to generation
Bacteria has more potential to become complex due to this process
59
Explain the reproduction of prokaryotes
Binary fission
Circular DNA copied in response to replication signal
Two DNA loops attach to the membrane
Membrane elongates allowing for two cells to be formed
60
how can we support the idea that mitochondria were once prokaryotes
```
Would of existed as an internal bacteria which got passed on and as it did so evolved more complexly
Mitochondria has
Double membrane
DNA genome inside
Similar reproduction process
Not all organelles membrane bound
```
61
Function of mitochondria
Formation of ATP
| Provides energy for aerobic respiration within cells
62
Function of a chloroplast
Photosynthesises (transfers light into energy)
| Has pigment that absorbs light
63
Function of ribosome
Protein synthesis
64
Function of plasma membrane
Controls exchange between cell and the environment
Selectively permeable
Has receptors for cell recognition and communication
65
Function of nucleus
Controls activities of cell
Contains genetic information that can be transmitted to next generation
Involved in transcription
66
overall role filaments and tubules
```
Provide strength and support to cell
Determine cell shape
Involved in movement of organelles
Help hold organelles in place
Can make up centrioles and spindle fibres
```
67
Process of protein synthesis within eukaryotic cell
Synthesised via translation of genetic code in the cytoplasm (involves mRNA)
Ribosomes produce the protein
Ribosomes attached to the RER
RER lumen proteins fold up into the correct 3D shape and undergo additions like sugar chains
Transport vesicle created round protein to go to golgi
Golgi apparatus each compartment adds and takes away components modifying the protein
Secretory vesicle out of golgi
68
function of cytoplasm
site of chemical reactions
69
function of golgi apparatus
Process molecules and proteins
Used in secretion of ^^
Involved in lysosome formation
70
function of cell wall
Gives cell its shape strength and support
Prevents cell lysis during osmosis
Fully permeable
71
function of rough ER
Protein synthesis via ribosomes attached
| Transport of proteins
72
function of smooth ER
makes and transports lipids steroids hormones
73
function of nucleolus
produces ribosomes
74
key aspects of intermediate filaments
Stability main function anchoring organelles
In between microfilaments and microtubules (8-12 nm)
Consist of entwined dimers of various proteins
Add mechanical strength helping to maintain the integrity of cytoskeleton
75
key aspects of microfilaments
Provide contractile motion when interact with myosin
Solid
Composed of protein ACTIN
Involved in cytokinesis forming two daughter cells
Support cell movement have FALSE HANDS
Smallest out of IF MT (7nm)
76
key aspects of microtubules
Largest out of IF MF (25 nm)
Made up of globular tubulin proteins
Polymerise to form hollow tubes which form a scaffold to determine the shape of a cell (centrioles)
Act as roads for vesicles and organelles
Form hollow tubulin subunits forming cilia flagella and spindle fibres
Help separate chromosomes in cell division
77
describe the cytoskeleton
An elaborate network of fine protein filaments
Made of protein filaments and tubules (fibres within the cell)
Helps cells maintain their shape and internal organisation giving an internal framework to the cell
Provides mechanical support enabling cells to carry
out TRANSPORT DIVISION and MOVEMENT
Eukaryotes cytoskeleton consists of MF IF MT
78
What could happen to the protein once in the secretory vesicle (3 paths)
1. transported to plasma membrane vesicle membrane and plasma membrane fuse to perform exocytosis (contents released to extracellular matrix)
2. vesicle held at plasma membrane to be released upon specific signal
3. quality control misfolded protein transported to lysosome where digestive enzymes degrade it
79
describe the key features of a eukaryotic cell DORA
D - linear
O - has a true nucleus and organelles membrane bound
R - mitosis and meiosis
A - larger than prokaryotic cell 10-100 micrometers
Performs more complex functions like making multicellular organisms
80
function of lysosomes
contains digestive enzymes to breakdown undigested material
| acts as waste bin/quality control
81
what contains RNA not DNA
ribosome
82
structures that can penetrate the walls of adjacent plant cells are called what
plasmodesmata
83
what cell structure does not have an envelope
mitochondrion
84
what is the purpose of a sucrose solution
prevents organelles changing structure via osmosis
85
what organelle always contains DNA
mitochondria
86
what would be found in an animal cell undergoing mitosis but not in a plant cell undergoing mitosis
centriole
87
interphase G1
Increase in cytoplasm volume
Proteins are synthesised for organelle production
Replication of organelles
88
interphase S phase
DNA is replicated to produce new set of chromosomes
89
interphase G2
Increase in cytoplasm volume
Errors in DNA checked for
Final growth phase before division
90
interphase active phase
Preparation for division (won't be able to see the chromosomes)
91
prophase 2
chromosomes condense
nuclear membrane dissolves
centrosomes move to opposite poles (so perpendicular to before)
92
metaphase 2
spindle fibres attach to chromatids at centromere aligning at equator of cell
93
anaphase 2
spindle fibres contract separating sister chromatids
| chromosomes move to opposite poles
94
telophase 2
chromosomes decondense
nuclear membrane reforms
cytokinesis occurs to form 4 haploid daughter cells
95
prophase 1
chromosomes condense
nuclear membrane dissolved
homologous chromosomes form bivalents (crossing over occurs here)
96
metaphase 1
spindle fibres connect to bivalents at centromere
| bivalents align along middle of cell in homologous pairs
97
anaphase 1
spindle fibres contract splitting bivalents
| homologous chromosomes move to opposite poles of cell
98
telophase 1
chromosomes decondense
nuclear membrane reform
cytokinesis occurs to produce 2 haploid daughter cells
