2- Cells Flashcards
(117 cards)
1
Q
What are plasmids
A
Small loops of DNA,
Separate from main circular DNA molecule
Contsin genes that can be passed between prokaryotes
2
Q
What is the purpose of a capsule (slime capsule)
A
Protect bacteria from drying out
and attack by cells of immune system of host
3
Q
Describe the structure of function of the flagellum
A
Long tail-like structure
rotates
enables prokaryote to move
4
Q
Describe the structure of a virus
A
Nucleic acid core, genomes can be DNA/RNA, and single/double stranded
Capsid- protein coat
some have envelope outer layer, formed from membrane phospholipids of cell they were made in
5
Q
How are genes “switched off”
A
Wraps more tightly around histones
6
Q
What is the structure of the cytoplasm
A
Organelles suspended in gel-like cytosol
70% water
Contains proteins, sugar, ions, fatty acids
7
Q
What is the structure of mitochondria
A
Oval/rod shaped, 1-10 micrometers length (just visble with light microscope)
Double membraned, inner layer folds to cristae
Mitochondrial matrix
Own 70s ribosomes and DNA - small circular
8
Q
Where are ribosomes formed
A
Nucleolus
9
Q
WHere can ribosomes be found
A
Free in the cytoplasm
Part of rough endoplasmic reticulum
10
Q
What is the strucure of eukaryotic ribosomes
A
equal parts rRNA and proteins
Small (40s) subunit
Large (60s) subunit
80s
not surrounded by membrane
11
Q
what is the strutcure of prokaryotic ribosomes
A
small subunit- 30s
large subunit - 50s
70s
equal parts rRNA and proteins
12
Q
What is the structure of the endoplasmic reticulum
A
continous folds of membrane from nuclear envelope
Rough- covered in ribosomes
13
Q
What si the function of the rough ER
A
process proteins made by ribosomes
14
Q
What is the function of the smooth ER
A
involved in production, processing and storage
of lipids, carbohydrates and steroids
15
Q
What is the structure of the Golgi apparatus
A
Flattened sacs of membrane
similar to smooth ER
16
Q
What is the function of the golgi apparatus
A
Modifies proteins and lipids,
before packaging them into golgi vesicles
vesicles then transport to desired location
17
Q
What is the structure of the vesicles produced by the golgi
A
Membrane bound sac (for transport and storage)
Vesicle surface->Bilayer->internal water
18
Q
What is a lyosomes
A
Specialist vesicle containing hydrolytic enzymes, which break down biomoleculus, e.g. waste materials e.g. worn-out organelles
used by immune system cells and in apoptosis
Transport proteins ->membrane->enzymes
19
Q
What is a chromatin
A
sections of linear DNA tightly wound around histone protein
The material from which chromosomes are made
20
Q
What is the structure of the nuclear envelope
A
Double membrane, with number of nuclear pores (3000ish)
Extends into ER
Seperates nucleus from cytoplasm
21
Q
What is the function of nuclear pores
A
Allows mRNA and ribosomes to travel out of nucleus
Allows enzymes and signaling molecules to travel in
22
Q
What is the fucntion of the nucleolus
A
Manufactures ribosomal RNA
where ribosomes are assembled
23
Q
What is the structure of centrioles
A
Hollow fibres made of microtubules
2 centrioles at right angles = centrosome
24
Q
What is the structure of microtubules
A
about 25nm diameter
made of alpha and beta tubulin, combined to for dimers, which join into protofilaments
13 protofilaments in cylinder make microtubule with hollow core
25
Name and desrcibe two things that microtubules form
Cillia - hair like projections allow movement of substances over cell surface
Flagella- longer microtubules, contracts to provide cell movement
26
Give the structure and function of the phospholipid bilayer in the cell surface membrane
Hydrophillic phosphate heads face into and out of cells
Hydrophobic hydrocarbon tails in middle
allow lipid soluble substances in and out
Prevent water soluble substances entering/leaving
Semi flexible
Self-sealing
27
Give the structure and function of proteins in the cell surface membrane
Structural support, intercellular joinings
Channels for transporting water soluble substances across membrane
Active transport- carrier protins
Receptors- aid in identification, for e.g. hormones
Stick together
28
Give the structure and function of cholesterol in the cell surface membrane
Organic alcohol
V hydrophobic - prevents leakage of water and dissolved ions
Pull together fatty acid tails of phospholipids, reducing flexibility, thus lateral movement of phospholipids
makes membranes less fluid at high temps
29
Give the structure and function of Glycolipids in the cell surface membrane
Carbohydrate covalently bonded to lipid
extend into water environemnt out of cell
Receptors for spec chemicals
help maintain membrane stability
help attach to one another forming tissues
30
Give the structure and function of Glycoproteins in the cell surface membrane
Carbohydrate chains attached to external proteins on outside of cell
receptors for chemicals, e.g. hormones, neurotransmitters
Recognition sites - lymphocytes can tell dif between host and foreign
31
What is the structure and fucntion of the cell wall
Freely permeable to most substances
formed outside cell membrane
Offer structural support
Polysaccharide
Plants: cellulose
Most bacteria: peptidoglycan
Fungi: chitin
32
what are plasmodesmata
Narrow threads of cytoplasm surrounded by cell membrane
conncect cytoplasm of neighbouring plant cells
33
What is the structure of chloroplasts
Double membrane envelope - each membrane is phospholipid bilayer
SPace enclosed contains thylakoids, which stack to form granum, which are interconnected by lamellae
Stroma - fluid filled matrix
34
What is the structure of thylakoids
Fluid filled disc-like membrane sacs
contain pigments, enzymes, and electronc arriers
membrane bound
35
What is the purpose of grana
Increase surface area,
increase number of LDRs that can occur
36
What is the structure of the stroma
Contains starch grains, which store sugars formed durong photosynthesis, as starch, inside the grains
COntains loop of DNA, which codes for some chloroplast proteins
Contains 70s ribosomes
37
What is the structure and fucntion of the large permanent vacuole
COntains cell sap, and central vacuole
Surrounded by tonoplast, a selectively permeable membrane
38
What is the equation for magnification
image / actual
39
What is meant by the term magification
How many times bigger the image is than the real object
40
What is meant by the term resolution
Ability to distinguish between two objects close together
41
What can't be observed with a light microscope and why
Ribosomes
ER
Lyosomes
Resolution is limited, can't distinguish between two objects closer than half a wavelngth apart (200nm)
42
What are the two types of electron microscope
Scanning electron microscope
Transmission electron microscope
43
How do transmission elctron microscopes work
Use electromagnets to focus a beam of electrons, which is transmitted through the beam - broad static beame
Denser parts absorb more elctrons, appear darker
44
WHat are the pros and cons of TEM
High resolution images, can see internal structures within cells (organelles)
Need v thin specimen
Can't observe living, as vacuum inside, and all water removed
Lengthy treatment to prepare sample, can introduce artefacts
Not colour image
45
How does a scanning electron microscope work
Scan small beam of electrons across specimen
Beam bounces off surface, electrons are detected and a 3D image shwoing surface is formed
46
WHat are the pros and cons of SEM
used on thick/3D specimens
External 3d structure of specimens observed
Lower resolution than TEM
can't observe live specimens
Don't produce colour images
47
Describe and name the process used to break up cells
Homogenisation
sample of tissue placed in
ice cold- reduce activity of enzymes that break down organelles
Isotonic - same WP, prevent water moving into clles via osmosis, causing bursting or damage
Buffer- prevent organelle proteins denaturing
Homogensier breaks plasma membrane, releasing organelles into a solution - homogenate
Homogenate filtred through gause, removing debris, leaving filtrate
48
What is the process tat seperates cell organelles, and describe
Ultracentrifugation
Filrate placed in tube, then into centrifuge
Which separates materials by spinning
At low speed, largest heaviest organelles settle at bottom (nuclei), forming thick sediment - pellet
Solution left: supernatant, drained off, placed in another tube and process repeated at increasing speeds
49
What is the order of mass in ultracentrifugation
Nuclei>chloroplasts>mitochondria>
lysosomes>ER>ribosomes
50
What is the purpose of mitosis
Growht and repair to damaged tissue
Cells constantly dying and need to be replaced by genetically identical cells
Unicellular zygotes can grow itno multicellular organisms
51
What is the order of the cell cycle
Interphase
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
52
What happens in interphase
G1: Gap 1
Cell grows, prepares to divide,
makes RNA, Enzymes, other proteins required for growth
S: Synthesis
DNA synthesis happens/DNA replicated
G2: Gap 2
Cell grows some more
DNA checked, erros usually repaired
Tubulin protein produced for microtubules for mitotic spindle
More ATP produced
53
What happens in prophase
Nuclear envelope breaks down into small vesicles- can't be seen with light microscope
nucleolus breaks down, chromomes floating in cytoplasm
Chromosomes condenser- supercoil, shorter and fatter, consist of 2 identical sister chromatides joined at centromere, can be seen under light microscope
2 centromers move to op poles
Spindle fibres begin emerging from centrosome
54
How can prophase be identified from a photo under a light microscope
Visible chromosomes
Nuclear enevlope breaking down
55
What happens in Metaphase
Centrosomes reach op poles
Chromosomes line up at metaphase plate (spindle equator)
sindle fibres extende from centrosomes
56
How can metaphase be identified under light microscope
chromosomes lined up along middle of cell
57
WHat happens during Anaphase
Chromosomes break into 2 sister chromatids, separated at centromere
Spindles contract, reel chromatids to each pole, woth help from motor proteins
mitochondira gather round spindle fibres to provide ATP
58
How can anaphase be identified under a light microscope
Chromosomes moving away from middle to poles
59
What happens during telophase
Chromatids reach op poles, and begin to decondense, unravel
Spindle fibres break down
Nuclear envelopes form around chromosomes
60
How can telophase be identified under a light microscope
Chromosomes at op poles, begin to decondense
Nuclear envelope reforming
61
What happens in Cytokinesis
Cytoplasm divides, through cleavage furrow in animals (pinched) and cell plate in plates (cellulose builds up at metaphase plate)
Two genetically identical daughter cells formed
62
How can cytokinesis be identified under a light microscope
Cleavage furrow / cell plate
63
Give the equation for mitotic index
Number of cells in mitosis/ total
used to work out proportion of cells in sample undergoing mitosis
64
What is a tumour
Uncontrolled growth of mutated cells
65
Whats the term for mutated genes that cause cancer
oncogene
66
WHats the term for agents that cause cancer
Carcinogen
67
What is the difference between benign and maligant
Benign- don't spread, don't cause cancer
Malignant - spread through body causing cancer
68
How do malignant tumours spread
Cells can break off and travel through blood/lymhatic system, resulting in secondary growths - metastastisis
69
How can cancer treatments target the S phase of mitosis
Damage DNA and kill cells as this stage is dna synthesis, where if errors occur, they can lead to tumours
70
How can cancer treatments target the G1 phase of mitosis
Drugs can inhibit G1, treat cancerous cells, halt cycle and kill cells
Stage which produces new organelles & causes cell to grow.
If a gene that encodes enzyme involved in process are mutated, cell can be altered
71
How do chemotherapy drugs work
Disrupt mitosis by binding to tubulin and interfering with microtuble assembly and disassembly, which can lead to apoptosis
72
How do prokaryotic cells divide
Binary fission
73
What cell organelles/ features do prokaryotic cells not contain
Nucleus, chromosomes, membrane bound organelles, spindle fibres
74
What happens during binary fission
Single circular DNA molecule and plasmids undergo DNA replication
Parent divides into two cells
Cytoplasm roughly halved between daughters, each contain single copy circular DNA, and variable number of plasmids
75
How do viral particles replicate
Parasitic, use living cells to replicate,
use attachment proteins to bind to complementary receptor proteins on CSM
Inject DNA or RNA into host cell
Host uses its nucleic acids and ribosomes to produce new viral particles, which are eventually release, either when cell bursts, or individuals though membrane in "budding process"
76
When is the cell surface membrane less fluid
Increased proportion saturated fatty acid chains, as pack closer together, so high number of IMF between chains
Lower temp, as mols have less energy, so don't move as freely, so more closely packed
77
When is the cell surface membrane more fluid
Increased proportion of unsaturated fatty acids, chains are bent, so pack less tightly, so less IMFs
Higher temps, more energy so move more freely
78
What three factors affect cell surface membrane permeability
Temperature
Solvent concentration
pH
79
How does temperature affect cell surface membrane permeability
High temp increases fluidity, not tightly packs, vol of water inside expands, pressure on membrane, deforms proteins, so can't control ins and outs
Low temp (sub 0) increase permability, deform Channel and Carrier proteins, ice crystals can pierce CM, highly permeable
80
Whats the definition of diffusion
Net movement of particles from an area of higher concentration to an area of lower concentration, as a result of the random motion of molecules or ions, caused by natural kinetic energy of molecules / ions
Tends to equilibrium given time, where they are evenly spread
81
What factors affect the rate of simple diffusion
Surface area
Concentration gradient
Exchange surface thickness (diffusion distance)
82
How does facillitated diffusion differ from simple diffusion
Moelcules diffuse through carrier proteins/ channel proteins
83
Which molecules are facillitated diffusion for
Too large
Polar, repelled by hydrophobic part of M.
Not lipid soluble
e.g. glucose & amino acids - large, polar
84
What are channel proteins
Water filled pores that allow polar compounds to diffuse, avodiing nonpolar central layer of plasma membrane
Most are "gated"
85
What are Aquaporins
Channel proteins that allow water to pass through membrane
86
how do carrier proteins work
Substance binds to carrier protein, causes change of shape, from being open on one side, to open on the other.
87
What factor affects specifically facilitated diffusion
Number of channel/carrier proteins available, once all in use, rate can't increase anymore, so greater number leads to greater rate possible
88
what is the definition of osmosis
The net movement of water across a partially permeable mebrane from an area of higher water potential to an area of lower water potential
89
What is the highest water potential
Pure water 0kPA
90
WHat is meant by isotonic
Equal water potentials on either side of the membrane
91
What is the isotonic point, and how is this represented on a graph
The concentration where water has not moved into or out of the plant tissue
Where the graph crosses the x axis
92
What is meant by hypertonic
Solution outside cell has higher solute concentration than inside
Solution outside is hypertonic to the inside
93
What is meant by hypotonic
Solution outside cell has lower solute concentration than inside cell
94
When a cell is fully inflated by water, it becomes rigid and firm. What word is used to describe this
Turgid
95
When water has left the cell, and the protoplast no longer exerts pressure on the cell wall, pulling away, the plant is...
plasmolysed
96
What is it called when too much water enters an animal cell and it bursts
cytolysis
97
What is active transport
Net movement of molecules or ions into or out of a cell from a region of lower concentration to a region of higher concentration using ATP and carrier proteins
98
Where does ATP bind to carrier proteins
Inside the cell
99
What happens when ATP binds to carrier proteins
Causes a conformational shape change, opening up the path for ion to move into cell, then Pi is released
100
What is co-transport
Coupled movement of substance across a cell member via a carrier protein
101
What transport mechanism moves glucose and amino acids into epithelial cells in the ileum
Co-transport, with 2 molecules of sodium
102
WHat are 4 adaptions of the ileum that help absorb glucose
Large SA- microvilli
Short diffusion distance - capillaries, 1 cell thick
High density of carrier proteins
Maintain conc grad- constant blood supply and continuous digestion of carbohydrates in gut
103
What is the path of sodium, in assisatnce with transporting glucose and amino acids into epithelial cells lining the ileum
3 Na+ are actively transported from epithelial cells into the blood stream by a sodium potassium pump, in exchange for 2 K+ ions
This maintains a lower Na+ conc inside the epithelial cells compared to gut, so the Na+ can diffuse into the epithelial cells, via cotransport proteins, with amino acids or glucose
104
What are 5 non-specific immune responses
Skin
Mucus membrane
Saliva
Tears - contain lysozyme enzyme, destroys bacteria
Inflamation - infected area heats and swells
105
Which type of lymphocytes are involved in cell-mediated immune responses
T-Lymphocytes
106
Which type of lymphocytes are involved in humoural immune responses
B-Lymphocytes
107
What are antigens
Macromolecules
Usually proteins e.g. glycoproteins, that allow cells to be recognised
PArt of CSM of all cells
Specific
108
Which type of cell produces antibodies
B lymphocytes
109
What happens when b-lymphocyte antibodies are complementary to the pathogen
Stimulated to divide and build up its numbers, through clonal selevction
110
How do lymphocytes recognise self cells in foetuses
In foetus, L. constantly colliding with other cells.
Infections are rare as protected by mother and placenta, so collide almost exclusively with body' own material
Lymphocytes with receptors complementary to body's own cells will die or be supressed, so the remaining lymphocytes are only complementary to potential foreign material
111
How do lymphocytes recognise self cells in adults
B lymphocytes produced in bone marrow, so initially only ecounter self antigens.
Any that show immune response to self undergo apoptosis,
Rest differentiate to mature lymphocytes
112
Where are phagocytes produced
Bone marrow
113
In general, what do phagocytes do
Remove dead cells and invasive microorganisms, by ingesting and destroying them before they cause harm
Non specific
114
How do neutrophils work
Travel through body, leave blood by squeezing through capillary walls
Attract- to chemicals released by pathogen (attractants, e.g. histamine)
Move by chemotaxis, along conc grad
Attach- antibodies stimulate to attack, recognise antibody and attach
Engulf (endocytosis)- CSM extends around pathogen, trapping it in phagocytic vacuol (phagosome)
Digest- Lyosome fuses with phagosome membrane= phagolysosome, releasing lysozyme enzyme, hydrolyes cell walls, soluble products absorbed, neutrophils die = pus
115
WHat are the key differences between Macrophages and Neutrophils
Marcophages: live longer, are larger, move into organs (lungs, liver, spleen, kindey, lymph nodes)
Travel in blood as monocytes, develop when settle in an organ
Cut up pathogen instead of destriying, and display antigens on surface, which are then recognised by lymphocytes
116
What are the features of lymphocytes
White blood cell
Specific
large nucleus fills most of cell
SMaller than phagocytes
117
Where do T-lympahcytes mature
Thymus gland
