cards Flashcards
(123 cards)
1
Q
benedicts test for reducing sugars
A
add equal volumes of sugar sample and add benedicts reagent. heat the mixture in water bath for 5 mins. brick red precipitate will form
2
Q
what is a reducing sugar
A
a sugar that can reduce (give electrons to) another chemical
3
Q
benedicts test for non reducing sugars
A
with food sample, add an equal volume of dilute hydrochloric acid in a test tube in water bath for 5 mins. add sodium hydrogen carbonate solution. heat resulting solution with an equal volume of benedicts solution for 5 mins. turns orange brown
4
Q
what does dilute hydrochloric acid do in the benedicts test for non reducing sugars
A
it hydrolyses any disaccharide into monosaccharides, thus also forming reducing sugars
5
Q
structure of starch
A
amylopectin- branched chains of alpha glucose, 1-4 glycosidic bonds and 1-6, creating branches.
amylose- linear, unbranched chain by 1-4 glycosidic bonds, forms a coiled helical structure
6
Q
purpose the structure of amylose serves
A
makes the molecule compact so stored easily
7
Q
purpose of structure of amylopectin
A
larger SA for enzymes to work on, thus glucose molecules can be released much quicker rate
8
Q
structure of starch related to its function
A
- starch insoluble so doesnt affect wp
- large enough that it doesnt diffuse out of cells
- compact enough so that alot of it can be stored in a small space
- branched- each end can simultaneously be acted on by enzymes, so glucose is quickly released
9
Q
structure of glycogen related to its function
A
- insoluble- no effect on water potential of cell
- insoluble- so doesnt diffuse out of cells
- compact- alot of it can be stored in a small space
- very highly branched- each end can simultaneously be acted on by enzymes, so glucose is quickly released.
10
Q
why do animals need highly branched glycogen
A
because animals metabolic rate is faster than plants and so needs glucose to be released quicker.
11
Q
structure of cellulose
A
made up of straight chains of beta glucose. chains parallel to each other, so H bonds form cross-linkages. all the H bonds together strengthens the cellulose. forms microfibrils
12
Q
how the structure of triglycerides relate to their properties
A
- triglycerides have a high ratio of energy-storing carbon-hydrogen bonds to carbon atoms, so its a good source of energy.
- low mass to energy ratio, so theyre good energy storage molecules.
- large and non polar, therefore insoluble, therefore doesnt affect osmosis
- high ratio of hydrogen to oxygen atoms, so can release water when oxidised, hence provide a source of water
13
Q
roles of lipids
A
source of energy
waterproofing
insulation
protection
14
Q
structure of phospholipid and relation to properties
A
- polar, therefore will position itself to form a bilayer
- the structure allows them to form glycolipids by combining with carbohydrates within the CSM. these are important in cell recognition
15
Q
primary sequence of a protein
A
unique sequence of amino acids that make up a protein or polypeptide chain
16
Q
secondary sequence of protein
A
way in which the primary structure of a polypeptide chain folds e.g. alpha helix or beta pleated sheets. shape is help by H bonds
17
Q
tertiary sequence of protein
A
overall 3D structure of protein, held together by H bonds and iconic bonds and disulfide bridges
18
Q
quaternary sequence of protein
A
if a protein is made up of several polypeptide chains that are linked in various ways, the way they are arranged is called the quaternary structure
19
Q
test for proteins
A
add equal volumes of sample and sodium hydroxide to a test tube. add a few drops of dilute copper II sulfate and mix. if purple solution if protein is present. peptide bonds broken
20
Q
what are fiberous proteins made up of
A
made of long molecules arranged to form fibres. several helices may be wound around each other to form very strong fibres
21
Q
what are globular proteins made up of
A
made of chains folded into a compact structure. one of the most important classes are the enzymes. although, these folds are less regular than in a helix, they are highly specific and particular protein will always be folded in the same way.
22
Q
what is Hb made of
A
two alpha polypeptide chains
two beta polypeptide chains
an inorganic haem group Fe2+
23
Q
collagen structure
A
three polypeptide chains wound around each other
each of the three chains is a coil itself.
hydrogen bonds form between these coils
collagen molecules form further chains with other collagen molecules and form covalent cross links with each other, which are staggered along the molecules to further increase stability. collagen molecules wrapped around each other form collagen fibrils which themselves form collagen fibres
24
Q
functions of collagen
A
form structure of bones
makes up cartilage and connective tissue
prevents blood that is being pumped at high pressure from bursting the walls of arteries
25
what type of bond forms between the phosphate group and deoxyribose sugar in DNA
phosphodiester bond
26
how is DNA adapted to carrying out its function
the H bonds can easily be separated during DNA replication and protein synthesis
extremely large, thus carries alot of genetic information
base pairing allows DNA to replicate and transfer info as mRNA
27
semi conservative replication
-DNA helicase unwinds separates the two strands of DNA into single strands by breaking the H bonds between the bases
-this therefore forms 2 base templates
-free complimentary nucleotides align with the bases according to complimentary base pairing
-they are joined via condensation reaction with DNA polymerase
-new DNA molecule is formed.
28
what is meant by resolution
minimum distance apart that two objects can be in order for them to appear as separate items
29
why is sample placed in cold isotonic buffered solution
cold- reduce enzyme activity that may break down organelles
isotonic- same water potential as tissue, preventing organelles shrinking or bursting due to osmotic loss or gain
buffered- so the pH doesnt fluctuate, so that nothing alters the organelle structures or affects enzyme functioning.
30
electron microscope advantages
electron beam has a short wavelength and the microscope can therefore have high resolution. the negatively charged beam can be focused using electromagnets
31
disadvantages of electron microscope
whole system is a vacuum, so living specimens cant be studies
complex staining process the image may contain artefacts
32
function of SER
synthesises, stores and transports lipids and carbohydrates
33
function of RER
provides a large SA to synthesise proteins and glycoproteins
provides a transport pathway for materials throughout the cell
34
function of golgi apparatus
add carbs to proteins to form glycoproteins
produce secretory enzymes
secrete carbohydrates
transport, modify and store lipids
form lysosomes
35
describe binary fission
circular DNA molecule replicates and both copies attach to the cell membrane
plasmids also replicate
cell membrane grows
between 2 DNA molecules, dividing the cytoplasm into 2. a new cell wall forms between the two DNA molecules. two daughter cells are produced, each with a single copy of circular DNA and a variable number of plasmids
36
how do viruses replicate
they attach to their host cell with their attachment proteins
nucleic acids are injected into a host cell.
the genetic info contains instructions for the host cells metabolic processes to start producing the viral components, which are assembled into new viruses
37
cell mediated immunity
1. phagocytes ingest pathogens
2. the phagocyte places antigens from pathogen on its cell surface membrane, so it becomes an antigen presenting cell
3. receptors of T helper cells have complimentary fit to those antigens.
4. this attachment activates T cells to divide rapidly by mitosis and form a clone of genetically identical cells
5. the cloned T cells develop into memory cells, stimulate phagocytosis, stimulate B cells to divide and secret their antibody and activates cytoxic T cells
38
humoral immunity
1. the surface antigen of a pathogen is taken up by B cell
2. the B cell processes it and presents the antigen on its surface
3. T helper cells attach to the processed antigens, thus activating the B cell
4. B cells divide by mitosis to produce a clone of plasma cells
5. these secrete the specific antibody that can bind to the pathogens antigen
6. the antigens destroy the pathogen
7. some B cells develop into memory cells
39
what is passive immunity
produced by the introduction of antibodies into individuals from an outside source. immunity is acquired immediately. no contact with pathogens needed
short term immunity- antibodies arent replaced when broken down, memory cells not formed
40
what is active immunity
produced by stimulating the production of antibodies by the individuals own immune system
contact with pathogens needed
immunity takes time to develop
41
natural active immunity
results from an individual becoming infected with a disease under normal circumstances
long term
body produces its own antibodies
42
artificial active immunity
inducing an immune response in an individual without them suffering the symptoms of the disease e.g. vaccinations memory cells produced
43
features of a successful vaccination programme
1. vaccine must be economically available in sufficient quantities
2. must have few side effects
3. available means of producing, storing and transporting the vaccine
4. must be possible to produce herd immunity.
44
why can vaccinations not be effective
1. immunity may not be induced in people with defective immune systems
2. individuals may develop disease after the vaccination but before their immunity levels are high enough to prevent it
3. pathogen may mutate frequently, so vaccines cant prevent them from harming people
4. certain pathogens conceal themselves from the bodys immune system e.g. by hiding within cells
5. individuals may object to vaccinations due to religious, ethical or medical reasons
45
what are antibodies made up of
4 polypeptide chains
-2 are heavy chains
-2 are light chains
variable (binding) region
46
how does HIV replicate
HIV attaches most commonly to T-helper cells the protein capsid fuses with the CSM
the RNA and enzymes of HIV enter T-helper cell
reverse transcriptase converts the viruses RNA to DNA
the new DNA enters
nucleus is inserted into T helper cells DNA
HIV DNA in nucleus creates mRNA using the cells enzymes, which contains the instructions for making new viral proteins.
the viral proteins are assembled into new HIV.
47
features of specialised gas exchange surfaces
- a large surface area to volume ratio
- very thin therefore short diffusion pathway
- selectively permeable
- a transport system
48
how do insects carry out gas exchange
1. insects contract their muscles, squeezing the trachea, enabling mass movement
2. a diffusion gradient is established
3. the ends of the tracheoles are in contact with individual cells, contain a small amount of fluid in which the gases are dissolved. the fluid is drawn into the muscle tissue during exercise. this increases SA of air in contact with the cells. gases diffuse in through the spiracles down the tracheae and tracheoles
49
counter current exchange principle
- the blood and water flow in opposite directions
- blood is loaded with O2 meets water, which already has maximum O2
- blood with little O2 meets with water with O2 removed
- so diffusion concentration gradient established and maintained across the entire width of the gill lamellae
- so, 80% of O2 in water absorbed into fish blood
50
how does the structure of a plant leaf link to gas exchange
- all cells are close to stomata, and therefore surface, therefore a short diffusion pathway
-inter- connecting air spaces in the mesophyll so that gases can readily contact mesophyll cells
51
how do insects limit water loss
- small surface area to volume ratio
- waterproof coverings
- spiracles which can close
52
how do xerophytes limit water loss
- thick waxy cuticle
- rolled up leaves: traps water vapour
- hairy leaves: traps moist air
- stomata sunken in pits- traps moist air
- reduced SA-VOL ratio
by trapping air, water potential gradient is reduced
53
process of inspiration
external intercostals contract
internal intercostals relax
ribs move up and outwards, increasing thorax volume
diaphragm contracts
further increasing thorax volume
air pressure in lungs becomes lower than atmospheric pressure, so air is forced in
54
process of expiration
internal intercostal muscles contract
external intercostals relax
ribs move in and downwards
diaphragm relaxes, decreasing thorax volume
air pressure in lungs becomes greater than atmospheric pressure, so air is forced out
55
what is the vena cava connected to
right atrium
56
what is the aorta connected to
left ventricle
57
what is the pulmonary artery connected to
right ventricle
58
what is the pulmonary vein connected to
left atrium
59
how is tissue fluid formed
high hydrostatic pressure at arterial end due to contractions of ventricles
this causes tissue fluid to be forced out of the blood plasma
this is ultrafiltration
60
process of lipid digestion
in small intestine, bile salts combine with fat droplets and break them down smaller (emulsification)
lipase enzymes from pancreas hydrolyse lipids into fatty acids, glycerol and monoglycerides
short chain fatty acids: diffuse directly into blood via epithelial cell
longer chain fatty acids: combine with bile salts to form micelles, which break down into fatty acids and monoglycerides which diffuse into epithelial cells
once there, they recombine into triglycerides which can form chylomicrons
61
artery structure
thick muscle layer so that they can dilate and contract to smooth blood flow
thick elastic layer so artery can stretch and recoil with systole and diastole, smoothing blood flow.
overall thickness of wall is large so that it doesnt burst under pressure
62
why do arterioles have thinner elastic layer than arteries
blood pressure is lower
63
vein structure
muscle layer is thinner because they carry blood away from tissues, and so have less need to dilate.
elastic layer is thinner because of lower blood pressure, which doesnt need recoil.
overall thickness of wall is thinner due to low blood pressure
valves at regular intervals to ensure theres no backflow of blood
64
why do veins have thinner walls than arteries
thinner walls because blood is at lower pressure and so less stretch and recoil with each contraction of ventricles
65
capillary structure
one cell thick endothelium
allows rapid diffusion
numerous, highly branched, so provides a larger surface area
narrow lumen and diameter
spaces in lining to allow tissue fluid to form
66
how does water travel through plants
the water particles have higher water potential than the root hair cell, and so they enter the cell by osmosis down a water potential gradient.
the water potential gradient of the root hair cell is now higher than the cortex cell, and so water enters the cortex cell by osmosis
67
symplast pathway
water enters the root hair cell by osmosis, and travels from the cytoplasm of one cell to another by plasmodesmata
68
apoplast pathway
water enters the root by entering the spaces in cell walls
water moves up xylem due to H bonding in water
water travels until it reaches the casparian strip, where the water needs to travel via symplast pathway
69
cohesion tension theory
water is drawn from cell to cell by osmosis
it moves across the root cortex to keep a constant column of water
this created a tension on the column of water in the xylem
water shows cohesion due to its H bonding. this makes the column very strong
so, water is pulled up the xylem to replace water lost by evaporation
water moves between the cells of a leaf along the wpg
70
role of companion cells
they unload/load organic solutes into the sieve tubes
71
transfer of sucrose into sieve elements
sucrose is manufactured from photosynthesising cells
it diffuses by facilitated diffusion from photosynthesising cells to companion cells, down a concentration gradient. H+ actively transported into the spaces between cell walls
H+ diffuses into sieve tube elements
sucrose molecules also transported with them, through co transport
72
what is a source cell
cells that photosynthesise and make sugars
73
what is a sink cell
cells that use organic solutes
74
mass flow hypothesis
1. sugars build up at source, lowering water potential of source cells
2. water therefore enters cells by osmosis
3. sugars are then actively transported into sieve tubs by transfer cells
4. this lowers water potential in sieve tube, so water enters by osmosis
5. this causes high pressure potential at source
at sink, sugars are unloaded by companion cells
6. this raises water potential
75
investigate mass flow using aphids
1. cut across their mouth parts
the mouthparts act as a sampling tube that they collect the phloem contents
2. if the phloem is punctured with a hollow tube then the sap oozes out, showing that there is a high pressure inside the phloem
3. if the xylem is punctured then air is sucked in, showing that there is low pressure inside the xylem
76
investigating mass flow using radioactive tracers
a plant is supplied with 14C, which becomes incorporated into organic substances in the plant. the plant is then frozen in liquid nitrogen to kill and fix it quickly, and placed onto photographic film in the dark. the resulting autoradiograph shows the location of compounds containing 14C. this shows that organic compounds are transported downwards from the leaf to the roots
77
genome definition
complete set of genes in a cell
78
proteome definition
full range of proteins that a cell is able to produce
79
process of transcription
DNA unwinds and separates
template strands form due to exposed bases
free RNA nucleotides align with template strand through complimentary base pairing
RNA polymerase bonds the nucleotides together, forming a molecule of mRNA complimentary to the DNA
mRNA leaves nucleus via nuclear pore
splicing occurs- introns removed
80
process of translation
mRNA associates with a ribosome in the cytoplasm
tRNA molecules with complimentary anticodons align with the first 2 mRNA codons
peptide bond forms between amino acid molecules
tRNA that bound to the first codon is free to leave the ribosome
the ribosome moves along the mRNA by one codon and now a new tRNA with a complimentary anticodon enters the ribosome
this continues until the ribosome reaches a stop codon
81
2 mechanisms that mean meiosis will result in genetic variation
independent segregation
82
what happens during independent segregation
during meiosis 1
each chromosome aligns with its homologous partner at the equator of the cell
the combination of maternal/paternal chromosomes aligns randomly
one chromosome of each pair goes to daughter cell by chance
83
what happens during crossing over
when the chromosomes align, the chromatids of each pair become twisted around one another
tension is build and portions of chromatids are broken off, which rejoin with the chromatid of the homologous partner so, new genetic combinations of maternal and paternal alleles are produced.
84
what is ATP made of
adenine
ribose
3 phosphates
85
how does ATP store energy
has 3 phosphates, the bonds between these are unstable and so have a low activation energy, hence easily broke. when they break (hydrolyse) they release energy
86
what does ATP synthase catalyse
the formation of ATP from ADP + Pi
87
in what scenarios is ATP reformed
during photosynthesis, in chlorophyll containing plants
during respiration
substrate level phosphorylation
88
why is ATP a good immediate energy source in a cell
the instability of the phosphate bonds.
each ATP molecule releases less energy than glucose molecule, and so is smaller and more manageable
the hydrolysis of ATP to ADP is a single reaction that releases immediate energy
89
what energy requiring processes need ATP
metabolic processes
movement
active transport
activation of molecules
90
which has longer wavelength- light or beam of electrons
light
91
how does a TEM work
it has an electron gun which produces a beam of electrons
this is focused onto a specimen by condenser electromagnets
the beam passes through the specimen
some parts of the specimen absorb the electrons and appear dark
an image is produced
92
why cant the TEM produce high resolution images
there can be difficulties preparing the specimen, which can limit resolution
a higher energy electron beam may destroy the specimen
93
how does a SEM work
it directs an electron beam onto a specimen surface rather than penetrating it
the beam is passed back and forth across a specimen in a regular pattern, depending on its contours
a computer is used to build up a 3D image
94
how to calibrate an eyepiece graticule
use a stage micrometer and align it with the eyepiece graticule
then, calculate the length of each subdivision
95
define ecology
the study of the inter-relationships between organisms and their environment, including biotic and abiotic factors
96
define ecosystem
dynamic systems made up of a community and all the non-living factors of its environment. it includes all the living organisms that interact with one another and also with the physical and non-physical factors present
97
biotic
living- e.g. plants animals bacteria
98
abiotic
non living- e.g. light, temperature, humidity, water
99
define population
a group of individuals that occupy the same habitat at the same time and are potentially able to interbreed
100
define community
all the populations of different species living and interacting in a particular place at the same time
101
define habitat
a place where an organism normally lives
102
define ecological niche
position occupied by an organism in a particular ecosystem, dependent upon the resources it uses. the more resources that are taken into account then the more carefully defined the organisms niche will be, the organism will become more specialised
103
INTERspecific competition
occurs when individuals of DIFFERENT species compete for resources such as food, light and water etc
104
INTRAspecific competition
occurs when individuals of the SAME species compete for resources such as food light water etc
105
explain predation
one organism is consumed by another. predators eat their prey, reducing prey population
with fewer prey left, there is greater competition between predators for food
some cant get the food and die, reducing predator population
prey population therefore increases so the predator population also increases.
106
two ways pathogens can cause disease
release toxins
damage cell tissue
107
a vaccine can be used to produce immunity- describe how memory cells are important in this process
important because when individual is in contact with virus again, antibodies can be produced at a faster rate in a secondary immune response, and so the pathogen can be destroyed faster.
108
describe how CO2 in the air outside a leaf reaches mesophyll cells inside the leaf
-enters via stomata
-if guard cells are open
-diffuses down a CG through air spaces in spongy mesophyll
109
there are large no. of mitochondria in the epithelial cell. explain how these organelles help the cell to absorb the products of digestion
-mitochondria provides ATP
-needed for active transport of substances into the cell
110
RBCs are biconcave discs. explain one advantage of a biconcave disc over a spherical cell of the same volume in transporting oxygen
-large SA
-for diffusion
111
describe how oxygen in the air in the alveoli enters the blood in capillaries
-diffuses across alveoli epithelium
112
attaching lactase to the beads is more efficient use of lactase than adding the lactase directly to cows milk. suggest three reasons why it is more efficient to attach lactase to the beads
-lactase bead can be reused
-continuous process
-lactase not present in milk
113
what is a vaccine
-injection containing small concentration of dead/inactive pathogens to create an immune response by stimulating production of antibodies/ memory cells
114
where is amylase produced
salivary glands, pancreas, small intestine
115
where is maltase produced
epithelium of small intestine
116
where is lactose produced
pancreas, small intestine
117
where are proteases produced
stomach, pancreas, small intestine
118
describe the involvement of RER in producing chylomicrons
RER synthesises proteins in the ribosomes, which are needed to form chylomicrons
119
suggest how chylomicrons leave the epithelial cell
by exocytosis because theyre too large to leave by other methods
120
difference between species richness and diversity index
Species richness measures only number of (different) species / does not measure number of individuals.
121
directional selection
selection favours individuals in one direction from the mean of the population
e.g. when environment changes, those with advantageous allele outside of the mean will be more likely to survive and breed
122
stabilising selection
if environmental conditions are the same, those with alleles closer to the mean are favoured, they are more likely to survive and reproduce e.g. birth, weight
123
courtship behaviour results in reproductive success by...
-allowing recognition of own species
-identifying those of capable breeding
-forming a pair bond
