Module 2 Flashcards
Components and functions of cell surface membrane
- phospholipids form bilayer ( hydrophobic tails inwards, hydrophilic tails outwards )
- provides barrier to large/polar molecules and ions
- proteins from carrier or channel proteins across membrane
- for active transport / facilitated diffusion
- cholesterol molecules fit between phospholipids
- stabilises membrane structure and regulate fluidity
- glycoproteins (and glycolipids)
- receptors for cell communication
roles of membranes within cells
- form edge of organelles within a cell
- isolation of organelle contents from cytoplasm
- site for attachment of enzymes and ribosomes (RER)
- provide selective permeability to control what enters and leaves organelles
- separates areas of different concentrations to provide gradients
cell signalling- how receptors work
- release of cell signal molecules e.g. hormones by exocytosis into blood
- proteins/glycoproteins/glycolipids act as receptors (e.g for hormones/ drugs )
- receptor is specific as the shape of the receptor and hormone are complementary
- hormone binds to receptor
- binding causes change in cell and brings about a response
Role of glycoproteins
- cell signalling ( communication to work together )
- antigens for…
- cell recognition (self/ non self )
- receptors found on target cells
- for hormones/cytokines to trigger responses in cells
- cell adhesion- hold cells together in tissue ( attaches to base membrane to stabilise tissue )
- forms bonds with water molecules to stabilise membranes
- (forms glycocalyx to attract water and dissolved solutes)
- receptors on transport proteins
substances crossing membranes
small non polar molecules
-diffuse through bilayer
large substances
- use carrier proteins
- specific to certain molecules
- protein changes shape to allow molecule through
- facilitated diffusion/ active transport ( uses ATP against gradient, faster, one way)
- endo/exocytosis
- bulk transport
polar substances
- through channel proteins
- facilitated diffusion
Active transport
- carrier proteins
- low to high conc
- uses ATP
- one direction
- faster than diffusion
facilitated diffusion
- carrier/ channel proteins
- large molecules e.g. glucose
- ions/polar molecules e.g K+
- when large/polar/water soluble materials cant pass through bilayer
- no ATP
diffusion through bilyaer
small non polar molecules
compare carrier and channel proteins
CARRIER
- specific to molecule
- molecules attach to one side
- protein changes shape
- releases molecules on other side
- carries large molecules across in facilitated diffusion
- carries all molecules in active transport which requires energy
CHANNEL
- specific to molecule
- forms pore in centre of protein
- hydrophilic lining in pore
- allows charged and polar molecules across membrane in facilitated diffusion
diffusion definition
the net movement of molecules from a region of high concentration of that molecule to a region of low concentration of that molecule down a concentration gradient. passive.
facilitated diffusion definition
the net movement of molecules from a region of high concentration of that molecule to a region of low concentration of that molecule down a concentration gradient through carrier proteins (large molecules) or channel proteins (charged molecules). passive.
Active transport definition
the movement of molecules or ions across a membrane from a region of low low concentration to a region of higher concentration of that molecule, against the concentration gradient. uses ATP to drive protein pumps within the membrane
Osmosis definition
the net movement of water molecules from a region of high water potential to a region of low water potential down the water potential gradient across a partially permeable membrane. passive
stages in producing an extracellular protein
- nucleus contains gene which codes for protein
- transcription produces mRNA
- ribosomes/ RER are production site
- protein transported to Golgi
- Golgi modifies and packages protein into vesicle
- vesicles move towards the cell surface membrane
- vesicles fuse with cell surface membrane
- protein released by exocytosis
stages of exocytosis
- vesicles move towards cell surface membrane
- along microtubules
- vesicles fuse with cell surface membrane
- released by exocytosis
- movement of vesicles on microtubules and fusion with membrane requires ATP
Stages of endocytosis
- molecule binds to receptor
- causes cell surface membrane to invaginate (fold in on itself )
- requires ATP
- membrane fuses with itself
- forming a vesicle
- vesicle moves through cytoplasm to designated organelle
Roles of the cytoskeleton
- cell support and stability to maintain shape
- movement of cilia
- movement of flagellum to move cell
- changing shape of cell (exo/endocytosis)
- move organelles
- anchor organelles
- move chromosomes and mRNA
Microtubules (cytoskeleton)
- hollow tubulin cylinders 25nm
- maintain cell shape and anchor organelles
- make up 9+2 flagellum and cilia in eukaryotes
- move vesicles using microtubule motor proteins ATP
- spindle fibres move chromosomes
Intermediate filaments (cytoskeleton)
- keratin cables 10nm
- maintains cell shape and anchors organelles
Actin microfilaments (cytoskeleton)
- 2 twisted actin stands 7nm
- maintains cell shape
- causes muscle contraction
- involved in cytokinesis
- allows pseudopodia
organisation of cells in a multicellular organism
- cells differentiate
- groups of similar specialised cells work together to perform a common function to form tissues
- groups of tissues work together to form organs
- groups of organs work together to form organ systems
Cell Cycle
Interphase
- G1, S, G2
- G1- cells grow, respiration, proteins made, organelles replicated
- s- DNA replication, chromosomes become sister chromatids joined by centromere
- G2- DNA replication checked for mistakes, organelles replicated
Mitosis
- Prophase- sister chromatids condense and supercoil, nuclear envelope breaks down, centromere replicates, spindle fibres form
- Metaphase-sister chromatids line up at equator, spindle fibres attach to centromere
- Anaphase- spindle fibres shorten, pull sister chromatids apart towards opposite poles
- Telophase- chromosomes uncoil, nuclear envelope reforms
Cytokinesis
- cytoplasm cleaves down furrow to split cytoplasm
- produces 2 new genetically identical daughter cells ( and to parent )
Mitosis - prophase
- chromosomes condense and supercoil to shorten and thicken
- chromosomes consist of sister chromatids joined by centromere
- now visible under light microscope
- nuclear envelope breaks down
- centriole divides in 2, each daughter centriole goes to opposite poles of the cell
- spindle fibres (microtubules) begin to form
mitosis - metaphase
- chromosomes (sister chromatids) line up along equator
- spindle fibres attach to centromere
mitosis - anaphase
- centromere splits
- chromatids separate
- spindle fibres shorten
- pulls identical chromatids to opposite poles with centromere leading
mitosis - telophase
- chromosomes uncoil
- nuclear envelope reforms
- spindle fibres break down
mitosis vs meiosis
- mitosis produces 2 genetically identical diploid daughter cells used for growth and repair. it occurs in all body cells and involves only one division
- meiosis produces 4 genetically different haploid daughter cells and is used for producing gametes. it occurs only in the ovaries and testes and involves 2 divisions
cell division and budding in yeast cells
- nucleus divides by mitosis
- bulge in surface of cell
- nucleus moves into bulge
- bulge nips/ pinches off
- leaves uneven distribution of cytoplasm
red blood cell differentiation
- no nucleus or many organelles ( e.g. Golgi, mitochondria, ER) provides maximum space for haemoglobin to increase oxygen carrying capacity
- also makes it more flexible to fit through capillaries ( well developed cytoskeleton )
- filled with haemoglobin ( made when immature ) which binds to oxygen forming oxyhaemoglobin to transport it to aerobically respiring cells
- bioconcave disc shape to provide large surface area and SA:VOL for oxygen exchange for more efficient uptake into red blood cells
root hair cell differentiation
- hair like projection into soil provides large SA for osmosis and active mineral uptake into roots
- thin wall for short diffusion path
- many mitochondria provides energy for active transport of minerals
- many carrier proteins for active transport of minerals
- many channel proteins for uptake of water via osmosis
neutrophil ( phagocytes ) differentiation
- lots of lysosomes contain lysin enzymes to digest pathogens
- multi-lobed nucleus to fit between gaps in capillary endothelium to leave blood
- many mitochondria to move lysosomes and phagosomes through cell along microtubules
Sperm differentiation
- haploid nucleus so zygote from fertilisation is diploid
- many mitochondria so energy for flagellum movement
- long and thin for ease of movement
- enzyme in acrosome to digest egg protective coating so sperm can fertilise it
Protein structure
Primary- order of amino acids joined in a polypeptide chain. joined with peptide bonds
Secondary- coiling or folding of chain into alpha helixes or beta pleated sheet. held with H bonds
Tertiary- overall 3D shape
-H bonds
-Ionic bonds between oppositely charged R groups
-Disulphide bridges between sulphurs on different amino acids
-Hydrophobic and hydrophilic interaction - hydrophobic move inside, hydrophilic move outside
Quaternary- more than one polypeptide to make final functional version of the protein
how does DNA structure determine specific shape of proteins
- DNA codes for proteins
- DNA transcribed then translated into polypeptide chain
- 3 bases code for 1 amino acid
- sequence of bases determines sequence of amino acids- primary structure
- secondary- coiling/folding into alpha helixes or beta pleated sheets with H bonds
- tertiary- overall 3D shape
- quaternary- more than one polypeptide chain held to make final functional version
properties of collagen for function
- high tensile strength
- not elastic
- flexible
- insoluble
role of fats in organisms
- energy source
- energy store ( adipose cells store lipids )
- phospholipid bilayers
- thermal insulation
- myelin sheath of neurones for electrical insulation
- steroid hormones
- waxy cuticle of leaves - prevents drying
amylose
- carbohydrate polysaccharide
- a glucose joined with 1,4 glyosidic bonds
- coiled, unbranched, compact
- energy storage in plants
- insoluble
- stored in starch grains and reacts with iodine to turn it black
amylopectin
- carbohydrate polysaccharide
- a glucose joined with 14 glycosidic bonds. branches form 1,6 glycosidic bonds
- compact
- energy storage in plants
- insoluble
- stored in starch grains, branches are hydrolysed to release a glucose for respiration for energy.
- less branched than glycogen
glycogen
- carbohydrate polysaccharide
- a glucose joined with 1,4 glycosidic bonds. branches form 1,6 glycosidic bonds
- more compact and more branched than starch
- energy storage in animals
- insoluble
- branches hydrolysed to release a glucose for respiration for energy. more branched than glycogen, more ends for hydrolysis. more energy release
cellulose
- carbohydrate polysaccharide
- cellulose chains: b glucose with 1,4 glycosidic bonds. every other is flipped 180 in relation to last. long and unbranched
- microfibrils: chains cross link with H bonds ( cross link into macrofibrils )
- structural, in plant cell walls
- insoluble
- strong, pectin glues macrofibrils in cell wall in criss cross for increased strength. lets water through but stops cell from bursting
Haemoglobin
- globular protein
- quaternary, 4 subunits ( 2 a chains, 2 b chains ) each has haem prosthetic group
- carries oxygen in blood
- soluble
- haem group is non protein and contains Fe2+ ion
Collagen
Collagen chain: every 3rd amino acid is glycine
Collagen molecule: quaternary, £ chains tightly wound, H bonds gives strength
Collagen fibrils: collagen molecules cross linked with covalent bonds
-structural in animals ( artey walls, cartilage, tendons, connective tissue )
-insoluble
-high tensile strength, not elastic, flexible
Tryglyceride
- lipid
- 3 fatty acids joined to glycerol with ester bonds
- energy store in animals
- insoluble
- compact storage in adipose cells, can be broken down more completely than carbs so releases more energy and metabolic water
Phospholipid
- lipid
- 2 fatty acid tails ( bonded with ester bonds ) and a phosphate group head bonded to a glycerol
- phospholipid bilayer membrane
- heads soluble, tails not
- more unsaturated bonds means more fluid membrane, prevents freezing in cooler climates (non homeotherms)
cholesterol
- lipid
- 4 carbon rings
- steroid hormones, decreases fluidity in membranes
- insoluble
- deposited in blood vessel causing atherosclerosis - narrowed vessels, increased bp, risk of myocardial infarction
Compare the structures of collagen and haemoglobin
SIMILARITIES.
-both proteins made of amino acids
-held together by peptide bonds
-both tertiary structures with H, ionic, disulphide
-both have quaternary structure with more than one polypeptide chain
DIFFERENCES
-haemoglobin is globular, collagen fibrous
-haemoglobin has hydrophobic R on inside and hydrophilic R on outside, collagen does not
-haemoglobin has 4 polypeptide chains, collagen has 3
-haemoglobin has 2 different types of polypeptide chain, collagens are all the same
-haemoglobin has a wider range of amino acids, a third of collagens are glycine.
compare glycogen and collagen
- glycogen is a polysaccharide, collagen is a protein
- monomers in glycogen are alpha glucose, in collagen they are amino acids
- glycogen has glyosidic bonds between monomers, collagen has peptide bonds
- glycogen branched, collagen unbranched
- glycogen non helical, collagen is helical
- only one chain per molecule in glycogen, 3 in collagen
- no cross links in glycogen, cross links in collagen
compare glycogen and cellulose
- no H bonds In glycogen, H bonds in cellulose between chains
- glycogen polysaccharide of alpha glucose, cellulose polysaccharide of beta glucose
- glucose has 1,4 and 1,6 glycosidic bonds in glycogen but only 1,4 in cellulose
- glycogen branched, cellulose isn’t
- glycogen has no fibres, cellulose does
- all glucose molecules same orientation in glycogen, but alternate flipped 180 from last in cellulose
compare phospholipids and triglycerides
- 2 fatty acids in phospholipids, 3 in triglycerides
- 2 ester bonds in phospholipids, 3 in triglycerides
- phosphate group in phospholipids
- both have glycerol
- both have fatty acids
- both have ester bonds
- both contain CHO
why is glycogen a good storage molecule
- insoluble
- doesn’t reduce water potential of cell
- can be hydrolysed easily
- as lots of branches for enzymes to attach to
- compact
- so high energy content for mass
water
HYDROGEN BONDING
water and temperature stability
- many/stable H bonds between molecules
- lots of energy needed to break hydrogen bonds to break apart and heat molecules
- high specific heat capacity
- large amounts of energy must be removed to freeze
- liquid under normal temperatures
- slow to change temp so stays fairly constant
- lakes/oceans/large volumes provide thermally stable environment
- internal body temp changes minimised for aquatic life so close to enzyme optimum
water and ice floating
- water expands from 4 to freezing point
- ice less dense as molecules spread out
- max H bonds form, molecules in open lattice
- ice floats on water
- insulates water beneath
- large bodies of water don’t freeze completely
- organisms don’t freeze and can move and swim
- causes currents to circulate nutrients
- support for large organisms on ice (penguins or polar bears)
water as a solvent
- solvent for polar or ionic substances, ions attracted to water which cluster
- gases soluble
- reactions can take place
- water plants can obtain nutrients e.g nitrates for proteins
water as a transport medium
- transports food particles for water dwelling organisms
- transports male gametes for external fertilisation and stops them drying out
- transport medium for blood cells
- low viscosity aids movement
water as transparent
- transparent to light
- plants can photosynthesise under water
water in plants
- forms long unbroken columns of water
- in xylem for transpiration
- due to cohesion
- reactant in photosynthesis
- role in hydrolysis reactions
water and cooling
- high latent heat of vaporisation
- lots of energy needed for molecules to escape
- evaporation has cooling effect
- sweating, panting, transpiration
water as a surface
- can use as habitat
- due to high surface tension
- water boatmen, pond skaters, water lily pads
**protein test- what is it
- add biuret
- blue to lilac
**reducing sugar test (what is it)
- add benedicts reagent and heat
- blue to red precipitate ( yellow/orange/green)
non-reducing sugar test
- boil with HCl to hydrolyse and free up OH groups
- neutralise with sodium hydrogencarbonate
- add benedicts and heat
- blue to red precipitate
starch test
- add iodine
- orange to blue/black
lipid test
- add alcohol then mix with water
- white emulsion
quantitative food test for sugar- determining conc of unknown solution
- get known concentrations of reducing sugar
- heat with excess benedicts
- use same volumes of solution each time
- colour change to red
- remove precipitate to obtain filtrate
- calibrate colorimeter with distilled water
- use red colour filter
- read transmission/absorbance for each known conc filtrate
- more transmission/less absorbance = more sugar?
- draw calibration curve
- plot transmission / absorbance against sugar conc
- use reading of transmission/ absorbance of unknown to read of graph to determine concentration
structure of a DNA nucleotide
- one phosphate group
- one nitrogenous base (ATCG)
- both joined to deoxyribose pentose sugar
- with a covalent bond
structure of an RNA nucleotide
- one phosphate group
- one nitrogenous base ( AUGC)
- both joined to ribose pentose sugar
- with a covalent bond
difference between DNA and RNA
- rna has ribose instead of deoxyribose
- rna has uracil instead of thymine
- rna single stranded not double
- rna smaller
Structure of nucleotide chain
- 2 nucleotides bonded with 1 covalent bond
- between phosphate group of one and pentose sugar of other
- forming sugar phosphate backbone bonded by phosphodiester bonds
how 2 nucleotide chains bonded
- H bonds between bases
- complementary base pairing
- purine to pyrimidine
- A to T with 2 H bonds
- C to G with 3 H bonds
DNA replication
- double helix untwisted ( gyrase )
- DNA unzipped when helicase breaks H bonds between bases
- both strands act as a template for free DNA nucleotides to align and complementary base pair
- H bonds reform
- new strand synthesised in 5’ to 3’ direction by DNA polymerase
- leading continuously synthesised, lagging in fragments later joined by ligase
- activated nucleotides extra phosphates hydrolysed to provide energy to form phosphodiester bond
- molecule twists into double helix
- now 2 identical DNA molecules
why DNA replication is semi conservative
-2 identical molecules made, each with 1 strand from the original molecule (conserved strand and template) and 1 new strand
Enzyme wording
- globular proteins
- specific
- active sites
- substrate complimentary to active site
- Enzyme substrate complexes
- Lock and key/ induced fit
Why enzymes are specific
-shape of active site is complimentary to correct substrate and will form ESC, any other substrate will not
Induced fit hypothesis
- as substrate binds to active site, shape changes slightly
- active site binds tighter around substrate molecule
- oppositely charged groups on substrate and active site interact holding the substrate in place in the ESC
- shape puts strain on bonds in substrate to destabilise it so reaction occurs more easily
- product formed and is different shape to reactant so is released from the active site
Temperate and enzyme activity
UP TO AND INC OPTIMUM
-as molecules are heated they gain KE and move faster, results in more frequent collisions and greater force of collisions
-more ESCs form so higher rate and more product
ABOVE OPTIMUM
-molecules have more KE
-enzymes vibrate more, breaking weaker bonds (ionic and H)
-tertiary structure changes as enzyme unfolds
-so active site loses complimentary shape
-no ESCs form as substrate doesn’t fit
-enzymes denatures
-irreversible so reaction stops
enzyme activity and pH
NOT AT OPTIMUM
-change in pH (H+) alters distribution of charge
-so hydrogen and ionic bonds break
-enzyme loses tertiary structure
-changes shape of active site of enzyme
-substrates not attracted to AS as H+ alter charge
-substrates cant bind as not complimentary
-no ESC=no product= no reaction
-enzymes denatured at pH extremes
OPTIMUM
-H+ concentration gives tertiary structure its best shape with a most complementary active site
Increasing Enzyme concentration
SUBSTRATE IN EXCESS
-as enzyme concentration increases, rate increases
-more enzymes means more likely successful collisions means more active sites so more ESCs so more product and higher rate
SUBRTATE USED UP
-rate decreases as substrate used up as less product is formed. the substrate is limiting factor
Substrate concentration on enzyme activity
ENZYME IN EXCESS
-as substrate conc increases, rate increases
-more substrate = more frequent collisions between substrates and active sites so more ESCs form and and more product forms so higher rate
WHEN ALL ACTIVE SITES OCCUPIED
-not possible for more ESCs to form so increasing substrate conc has no effect on rate, it plateaus
-enzyme conc is limiting factor
Competitive inhibitors
- similar shape to substrate
- complementary to active site so bind and block it
- prevents ESCs forming and slows rate as no product can form
- don’t bind permanently, reversible
non-competitive inhibitors
- fit into allosteric site
- alters tertiary structure of enzyme and changes active site shape
- substrate cant fit, no ESCs, rate decreases
- binds permanently to enzymes- irreversible, enzyme becomes useless
competitive inhibitor conc on rate
- rate depends on relative concentrations of substrate/ inhibitor
- more inhibition is substrate conc low/ lower than inhibitor
- higher chance of inhibitor entering active site than substrate so less ESC and less product
- effects reduced by increasing substrate conc
non competitive inhibitor conc on rate
- increasing substrate conc has no effect on rate as they bind irreversibly, if all enzymes have inhibitor bound reaction stops
- changing conc of inhibitor will further reduce the rate, fewer ESCs so less product
- limits Vmax
