mock revision topic 2 Flashcards
1
Q
how does surface area affect rate of diffusion
A
- greater sa = greater number of molecules or ions that can cross it at any one moment, so the faster diffusion occur
- sa of cell can be increased by folding
2
Q
diffusion pathway across exchange surfaces
A
- this is v short
- only one layer of epithelial cells
- shorter diffusion pathway = less time taken to absorb substances
3
Q
what is ficks law of diffusion
A
- rate of diffusion is directly proportional to SA x Conc Diff / thickness of membrane
4
Q
structure of trachea and how it relates to its function
A
- tube tht allows air to travel to lungs
- contains c-shaped rings of cartilage, ensures tube remains open at all times and doesnt collapse
- c shape prevents friction with oesophagus and increases flexibility wen food is being swallowed
- layer of mucus covering lining to trap dust and pathogens, to prevent lung infection
- have cilia on lining tht wafts any mucus towards top of trachea to remove any trapped particles
5
Q
structure and function of bronchi
A
- similar structure to trachea but thinner walls and smaller diameter
- the cartilidge rings are also full circles rather than c-shaped
6
Q
structure and function of bronchioles
A
- narrow and self supporting tubes with thin walls
- gets smaller as it gets closer to alveoli, and theres many bronchioles
- have elastic fibres and smooth muscle enabling adjustment of airway size to increase or decrease airflow
7
Q
structure and function of alveoli
A
- wall is single layer of flattened and squamous epithelium
- thin and permeable for easy diffusion of gases
- large sa to volume ratio, as spherical, enables the rapid rate of gas exchange
- surrounded by extensive capillary network = good blood supply = steep conc gradient so faster rate of gas exchange and diffusion
- layer of moisture lines alveoli, enabling oxygen and carbon dioxide to dissolve in layer of moisture, so exchange happens in solution rather than with air inside alveoli
8
Q
describe the structure of a phospholipid
A
- molecule of glycerol
- a phosphate grp forming the polar phosphate head (hydrophilic)
- two fatty acid tails, making up the non polar and hydrophobic lipid tail
9
Q
what substances make up the cell membrane?
A
- the phospholipid bilayer ( two layers of phospholipids, joined and facing opposite ways)
- integral and peripheral (intrinsic and extrinsic) proteins
- cholesterol
- glycolipids and glycoproteins
10
Q
properties of the cell membrane and what the model is usually referred to as
A
- fluid mosaic model: the scattered pattern produced by components within phospholipid bilayer looks somewhat like a mosaic
- fluid as the proteins and phospholipids can move around within the bilayer by diffusion
- it is partially permeable
11
Q
what substances can pass through the cell membrane and cannot
A
- small, non-polar molecules can pass through gaps between phospholipids but large, polar molecules must pass through channel and carrier proteins
12
Q
what are intrinsic proteins
A
- integral proteins
- embedded in the membrane with their precise arrangement determined by hydrophobic and hydrophillic region
13
Q
what are extrinsic proteins
A
- periphal proteins
- found on the outer or inner surface of the membrane
14
Q
what is the function of cholesterol on membrane
A
- regulates membrane fluidity, increases mechanical strength and stability of membranes, without it, the membranes would break down and cells would burst
- increases fluidity at low temps by preventing phospholipids from packing too closely together, so stops from becoming too rigid
- at higher temp, cholesterol binds to hydrophobic tails, stabilising and causing phospholipids to pack closer together
15
Q
what is the function of glycolipids and glycoproteins
A
- act as cell markers, or antigens for cell to cell recognition
16
Q
PAG
A
17
Q
simple diffusion
A
net movement of substance from higher conc to lower conc
18
Q
how does temperature effect rate of diffusion
A
- molecules and ions have more kinetic energy at higher temp
- they move faster so results in higher rate of diffusion
19
Q
how does conc gradient affect rate of diffusion
A
- if there r more molecules on one side of a membrane than other, at any moment, more molecules will randomly move across the membrane from that side than the other
- greater diff in conc = greater diff in no of molecules passing in the two directions so faster diffusion rate
20
Q
why is facilitated diffusion used
A
- some substances cannot diffuse directly through phospholipid bilayer as its large, polar molecul like gluocse or amino acids, or theyre ions
- so they are transported across proteins
21
Q
what are channel proteins
A
- pores tht extend through one side of membrane to other side
- allow charged substances to diffuse through cell membrane
- most channel proteins are gated, so part of the channel protein on inside of the membrane can move in order to close or open the pore
22
Q
what are carrier proteins
A
- they switch between two shapes
- binding site of carrier protein is open on one side of the membrane first, and then open to other side of membrane when the carrier protein switches shape
23
Q
examples of active transport
A
- reabsorption of useful molecules and ions into blood after filteration into kidney tubules
- absorption of some products of digestion from digestive tract into blood
- loading sugar from photsynthesising cells of leaves into phloem
24
Q
molecules tht travel via endocytosis
A
- large molecules such as proteins, lipids and some carbohydrates
25
Q
process of endocytosis
A
- cell surrounds substance w section of cell surface membrane
- membrane engulfs substance and pinches off inside the cell to form temporary vacuole with injested substance contained inside
26
Q
process of exocytosis
A
- vesicles containing substance pinch off from sacs of golgi apparatus
- these vesicles move towards cell surface
- fuses with cell surface membrane and is released to outside of cell
27
Q
substances tht travel out via exocytosis
A
- hormones, some enzymes and some lipids
28
Q
what is the structure of a nucleotide
A
- sugar (ribose, or deoxyribose)
- nitrogenous base
- phosphate
29
Q
what are purines
A
- nitrogenus base structure
- adenine and guanine
- they have a double ring structure
30
Q
what are pyrimidines
A
- cytosine, thymine and uracil
- single ring structure
31
Q
what is the sugar-phosphate backbone?
A
alternating deoxyribose sugars and phosphate groups bonded together. (covalent bonds - phosphodiester bonds.)
32
Q
what does antiparallel refer to
A
- two strands in the DNA double helix, which run parallel, but opposite directions
- one strand runs 5’ to 3’ and the other runs 3’ to 5’
33
Q
similarities and diff in structure of RNA and DNA
A
- like DNA, RNA is a polynucleotide - so made of many nucleotides, linked together in a chain
- like DNA, RNA contains nitrogenous bases A, G, and C
- unlike DNA RNA never contains nitrogenous base thymine, it instead contains uracil
- unlike DNA, RNA nucleotides contain pentose sugar ribose, instead of deoxyribose
- RNA molecules are made up of only one polynucleotide strand
- they are also relatively shorter compared to DNA
34
Q
what happens during transcription
A
- DNA is transcribed and mRNA molecule is produced
35
Q
where does transcription take place
A
- nucleus of the cell
36
Q
what is RNA polymerase
A
- enzyme that joins together nucleotides to form mRNA
- also breaks apart hydrogen bonds to unzip the DNA double helix strand
37
Q
antisense vs sense strand
A
- antisense strand has the same bases as the mRNA (the template strand)
- sense strand is the coding strand
38
Q
where does translation take place
A
- cytoplasm, specifically on the ribosome
39
Q
structure and function of tRNA
A
- single stranded
- folded into specific pattern
- carries anticodons complementary to the codons on mRNA and hence DNA sense strand
- attaches to mRNA and amino acids
40
Q
what does it mean that genetic code is non-overlapping
A
- each base is only read once
- the adjacent codons dont overlap
41
Q
meaning when genetic code is said to be degenerate
A
- 4 bases, so 64 different codons (triplets) but theres only 20 amino acids that commonly occur in biological proteins, which is why the code is said to be degenerate
- multiple codons can code for same amino acids
- this nature can limit effect of mutations
42
Q
what is the nature of genetic code
A
- non overlapping
- degenerate
- universal - same triplet codes for same amino acids in all living things
43
Q
3 parts of an amino acid
A
- amino group
- r group
- carboxylic acid group
44
Q
what/how are peptide bonds formed
A
- covalent bonds
- formed via condensation reaction between two amino acids
- OH is lost from carboxylic acid grp of one amino acid and hydrogen lost from the amine grp of another amino acid
45
Q
what is primary structure of a protein
A
- linear amino acid sequence of the polypeptide chain
- determined by DNA sequence of gene coding for a protein
- it is specific for each protein, one alteration in sequence of amino acids can affect function of protein
46
Q
what is the secondary structure of a protein
A
- folding of protein chain into either alpha helix or beta pleated sheets
47
Q
why does the secondary structre of a protein occur
A
- weakly negative nitrogen and oxygen atoms interact with the weakly positive hydrogen atoms to form hydrogen bonds
- ONLY HYDROGEN BONDS
48
Q
how does the alpha helix shape happen
A
- hydrogen bonds form between every fourth peptide bond
- between oxygen of carboxyl grp and hydrogen of amine grp
49
Q
how does the beta pleated sheet shape form
A
- two parts of polypeptide chain is parallel to each other, so hydrogen bonds can form between the parallel peptide bonds
50
Q
tertiary structure
A
- further folding and attractions
- additional bonds form between the R groups to give a specific 3D shape
- hydrogen bonds between R grps
- disulphide bridges between cystein amino acids
- ionic bonds between charged R grps
- weak hydrophobic interactions between non-polar R grps
51
Q
when does quaternary structure happen
A
- in protein that consists of more than one polypeptide chain
- such as haemoglobin
- the bonds formed r same as in tertiary structure
52
Q
structure of globular protein
A
- compact
- spherical
- non polar R grps oriented towards centre of protein away from aqueous surrounding and polar towards/outside of the protein
- folding of protein due to specific R grp interactions, results in globular proteins having specific shapes
53
Q
what are conjugated proteins
A
a protein that contains a non-protein chemical grp, such as a prosthetic grp
54
Q
general functions of globular proteins
A
- orientation of R grps means theyre generally soluble, as water molecules can surround polar, hydrophilic R grps
- can be easily transported as theyre soluble
- enzymes and immunoglobulins
55
Q
describe structure and function of haemoglobin
A
- oxygen carrying pigment found in rbc
- quaternary structure as it is made of 4 polypeptide chains, held together by disulphide bonds
- has 4 haem grps which binds to oxygen
56
Q
structure of fibrous proteins
A
- long polypeptide chain strands, with cross linkages due to hydrogen bonds
- little or no tertiary structure
- limited no of amino acids with sequence usually being very repetitive
- this creates organised structures
57
Q
function of fibrous proteins
A
- have large number of hydrophobic R grps, so insoluble in water
- strong and insoluble means theyre suitable for structural roles, like keratin, elastin, collagen
58
Q
collagen structure and function
A
- three polypeptide chains, closely held together by hydrogen bonds, to form a triple helix
- in the three helices, every 3rd amino acid is glycine, whos R side chain is v small, so it can fit into very small space on inside of triple helix
- on either side, theres proline, and hydroxyproline, which have big R grps, which keep out of each others way to maintain strong fibrous structure
59
Q
what type of proteins are enzymes
A
- globular proteins
- have a very precise 3D shape to fit to their particular substrate, which comes from their folding pattern
- determined by the complex tertiary structure of the protein
60
Q
what would happen if theres a change in sequence of amino acids in the polypeptide chain to the function of an enzyme
A
- order of amino acids determines the shape of an enzyme, as amino acids have specific R grps which form different bonds in the tertiary structure
- diff amino acid sequence means tertiary structure is altered
- active site changes so substrate no longer fits active site, and no longer complimentary
- enzyme substrate complex will not be able to form, and enzyme cannot carry out its function
61
Q
describe lock and key hypothesis
A
- random movement causes enzyme and substrate to collide
- substrate enters active site
- enzyme substrate complex forms, charged grps attract, and distorts the substrait, which aids bond breakage or formation
- products r released from active site and enzyme is left unchanged, and ready to accept another substrate molecule
62
Q
describe the induced fit model
A
- its a modified model of enzyme activity
- similar to lock and key, but:
- enzyme and active site can change shape slightly as substrate enters the enzyme
- known as conformational changes. ensures ideal binding arrangement between enzyme and substrate is achieved, to maximise ability of enzyme to catalyse reaction
63
Q
why is DNA replication called semi-conservative replication
A
- in each new DNA molecule produced, one of the polynucleotide DNA strands is from the original DNA molecule being copied, and the other polynucleotide DNA strand is newly created by the cell
- DNA molecule has conserved half of the original DNA and then used this to create a new strand
64
Q
steps for DNA replication
A
- two strands of DNA unwind and split apart
- free nucleotides line up along each strand, according to complimentary base pairing rules
- DNA polymerase joins the nucleotides together as phosphodiester bonds form between each deoxyribose and adjacent phosphate grp. DNA ligase joins partly formed strands together
- hydrogen bonding links the two strands together
65
Q
different types of mutations
A
Insertion
Deletion
Substitution
Duplication
Inversion
66
Q
what is DNA polymerase
A
- its an enzyme which synthesises new DNA strands from the two template strands
67
Q
describe the meselson and stahl experiment
A
- bacteria were grown in a broth with heavy nitrogen 15 isotope (DNA contains nitrogen in its bases)
- after some time, the culture of bacteria had DNA that contained only heavy nitrogen
- a sample of DNA from the nitrogen 15 culture of bacteria was extracted and spun in a centrifuge
- this showed that the DNA containing heavy nitrogen settled near the bottom of the centrifuge tube
- the bacteria containing only nitrogen 15 was taken out of that broth and added to a broth containing only lighter nitrogen 14
- the bacteria was left for enough time so only one round of DNA replication took place, before the DNA was extracted and spun in the centrifuge
68
Q
what would have been seen in the meselson and stahl experiment if conservative replication had taken place
A
- the original template DNA molecules would only contain heavier nitrogen and would settle at bottom of the tube, whereas the new DNA molecules would only contain lighter nitrogen and settle at the top of the tube
69
Q
what would have been seen in the meselson and stahl experiment if semi-conservative replication had taken place
A
- all DNA would contain both heavy and light nitrogen, and so they would settle in the middle of the tube
70
Q
what happens when theres too much water in the mucus, healthy person
A
- detected by the epithelial cells
- carrier proteins in basal membrane pump sodium ions out the cell
- decreases sodium ion conc in cells, so theres a concentration gradient across the apical membrane
- sodium ions in mucus diffuse into the cell from the apical membrane into the epithelial cell (facilitated diffusion through the ENaC)
- raises conc of Na ions in the basal membrane = potential difference between tissue fluid and apical membrane mucus
- electrical gradient is created which causes negatively charged chloride ions to diffuse out mucus into tissue fluid
- this increases ion conc in tissue fluid = water drawn into tissue fluid from the epithelial cell by osmosis, then water conc in cell drops + solute conc increases
- this means water drawn out of mucus into the epithelial cells by osmosis
71
Q
chromosome definition
A
- long DNA molecule which contains genes tht code for several diff proteins
72
Q
what is a homologous pair of chromosomes
A
- pair of chromosomes that match in size and shape, that contain same genes at the same loci
73
Q
uses of genetic screening
A
- identifiying individuals who are carrying an allele at a gene locus for a particular disorder
- screening of embryos prior to implantation during fertility treatment
74
Q
what is chorionic villus sampling
A
- removing and testing a small sample of cells from placenta, using needle
- cells contain foetal DNA which can be analysed for genetic disorders
- carried around 11-14 weeks of pregnancy.
75
Q
what is amniocentesis
A
- removing and testing small sample of cells from from amniotic fluid
- carried out at around 15-20 weeks of pregnancy
- the fluid contains foetal cells which can be analsyed (the DNA)
- 1 percent risk of miscarriage
76
Q
A
