Water (A1.1) + Nucleic Acids (A1.2) + Carbs and Lipids (B1.1) + Proteins (B1.2) Flashcards
Define a hydrogen bond
force when a slightly positive hydrogen atom in one polar molecule is attracted to slightly negative atom of another polar molecule
Buoyancy as a physical property of water (2)
buoyancy = force exerted upward by fluid which counteracts gravity
density of object < density of liquid = buoyancy force > gravity = object will float
Why does ice float on water (2)
ice is less dense as water
pattern of hydrogen bonding of ice is less dense
Viscosity as a physical property of water
pure water has low viscosity - hydrogen bonds are weak so not as much internal friction
Define cohesion
ability of water molecules to stick together
Cohesion of water for water transport in plants (5)
water is sucked upwards in continuous columns
column of water under tension from both ends
tension from roots due to attraction between soil + water
tension from leaves as water lost by evaporation + attraction between water and leaf cell walls
water moves upwards because force in leaves > force in roots
Explain surface tension of water (2)
cohesion between water molecules > attraction between water and floating object
object must break hydrogen bonds to break the surface of water
Define adhesion for water (2)
hydrogen bonds forming between water + surface of solid composed of polar molecules
allows water to stick to other objects
Define capillary action
the ability of a liquid to flow through a narrow tube without external forces
Why water is a good solvent (5)
polar nature of water molecule forms shells around both charged + polar molecules
prevents molecules from clumping together so they remain in solution
water’s partially negative oxygen pole attracted to positive ions
water’s partially positive hydrogen pole attracted to negative ions
both dissolve
Define hydrophilic
substances chemically attracted to water
Examples of hydrophilic substances (2)
glucose
positive or negative ions (e.g sodium + chloride ions)
Define hydrophobic (3)
substances not attracted to water
more attracted to other hydrophobic substances
insoluble in water
Examples of hydrophobic substances (2)
non-polar molecules (not positive or negative)
lipids
Metabolism in water solvent property (2)
solutes can move + interact
allows for substrates to touch the active sites of enzymes
Thermal conductivity as a property of water
high thermal conductivity = good at absorbing/transferring heat
Define thermal conductivity
the rate at which heat passes through a material
Define viscosity (3)
how easily a fluid is able to flow
more viscosity –> more friction + resistance to flow
due to internal friction when on part of a fluid moves faster relative to another part
Applications of water’s thermal conductivity
high water content in blood –> can carry heat from parts of body to parts that need more heat or parts that dissipate heat
Define specific heat capacity
energy required to raise the temperature of 1g of material by 1 C
Specific heat capacity as a characteristic of water (2)
increase in temperature must have hydrogen bonds broken with energy
must lose an equal amount of energy to cool down
Applications of specific heat capacity of water (2)
aquatic habitats are more thermally stable
helps mammals maintain constant body temperatures
Why water is able to be retained on earth (2)
distance between sun and earth = temperatures are not high enough to vaporize water
strong gravity = oceans is held to surface, gases kept within atmosphere
Define the Goldilocks Zone (2)
habitable zone around a star
location depends on size of star, amount of energy it emits, size of planet
Parts of nucleotides (3)
pentose sugar with 5 carbon atoms
phosphate group : acidic and negatively charged part of nucleic acids
base that contains nitrogen - has either 1 or 2 rings of atoms in its structure
Phosphate group nucleotide diagram
O-
|
O- – P – O –
||
O
Deoxyribose sugar nucleotide diagram
– CH2
| O
CH CH – N
CH CH
| |
OH OH
How are nucleotides linked together
covalent bonds formed between phosphate of one nucleotide and the pentose sugar of another
What is the DNA and RNA backbone made of
chain between sugar and phosphate
Bases in DNA (4)
Adenine (A)
Cytosine (C)
Guanine (G)
Thymine (T)
Bases in RNA (4)
Adenine (A)
Cytosine (C)
Guanine (G)
Uracil (U)
Links between bases of DNA (2)
Adenine forms hydrogen bonds with thymine
guanine forms hydrogen bonds with cytosine
Strands of DNA nucleotides in relation to each other (2)
(anti)parallel - parallel but run in opposite directions
one strand ends with phosphate group other ends with deoxyribose (pentose sugar)
Differences between DNA and RNA (3)
DNA is double-stranded, RNA is single-stranded
RNA has uracil instead of thymine in DNA
pentose sugar of DNA is deoxyribose, pentose sugar of RNA is ribose
How do RNA nucleotide join together
condensation reaction - molecules combine while losing water
What happens in semi-conservative replication of DNA (3)
2 strands of double helix separate - hydrogen bonds break
free nucleotides pair with exposed complementary bases
changes 1 DNA molecule into 2 identical ones
Number of possible combinations of DNA bases (2)
4^n
where n is the number of bases
Define gene expression (2)
process which genetic code in DNA translated into protein
allows DNA to code for proteins
Define codons in genes (2)
groups of 3 bases
64 possible codons
Functions of codons in genes (3)
most codons specify a particular amino acid
one codon signals that protein synthesis should start
3 codon signal that protein synthesis should stop
Define transcription in genes
process where one DNA strand is used as template to produce RNA
How is a gene expressed (3)
copying base sequence - copy made using RNA
adenine in RNA pairs with uracil instead of thymine
synthesiszing a protein - base sequence of RNA translated into amino acid sequence of protein
Define translation in DNA
process where transcribed RNA is translated by ribosomes to produce proteins
Define a purine (3)
Adenine
Guanine
have 2 carbon rings
Number of hydrogen bonds between adenine + thymine
2 hydrogen bonds
Number of hydrogen bonds between guanine + cytosine
3 hydrogen bonds
Describe the 5’ to 3’ directionality of DNA (3)
5 and 3 = 5th + 3rd carbon on pentose
phosphate binds at 5’ and 3’
one strand will start with 5’ and end with 3’, other strand will start with 3’ and end with 5’
Define a pyrimidine (4)
Thymine
Cytosine
Uracil
has one ring
Directionality of DNA in DNA replication (2)
nucleotides added to the 3’ end of polymer
5’ phosphate of free nucleotide links to 3’ end of growing polymer
Directionality of DNA in DNA transcription (2)
nucleotides added to 3’ end of polymer
5’ phosphate of free nucleotide links to 3’ end of growing polymer
Directionality of DNA in DNA translation (3)
ribosome reads RNA sequence
ribosome that carries out translation moves along RNA to 3’ end
5’ to 3’ directionality
Why purines are complementary with pyrimidines (3)
purine to purine bond length will be too long
pyrimidine to pyrimidine bond length will be too short
complementary base pairing stabilises DNA shape
Appearance of nucleosome (2)
length of DNA wrapped twice around cores of 8 histone molecules (2 copies of 4 different histones)
additional histone molecule (H1) reinforces binding of DNA to nucleosome core
How are chromosomes formed from nucleosomes (3)
nucleosomes joined together by linker DNA
nucleosomes stacked onto each other
stacks form chromosomes
Purpose of the Hershey-Chase experiment
proving that DNA made up genetic material instead of protein
Materials used in the Hershey-Chase experiment (3)
virus - T2 bacteriophage
bacteriophage inner DNA coated in radioactive phosphorous
bacteriophage outer protein coated in radioactive sulfur
Hershey-Chase experiment results (3)
bacteriophages with radioactive phosphorous infected non-radioactive bacteria, all infected cells became radioactive
next-generation of bacteriophages produced from infected bacteria were all radioactive
bacteriophages coated in radioactive sulfur + virus coats separated = no radioactivity inside infected cell
Describe Hershey-Chase experiment (5)
bacteriophage added to bacteria
blender separates bacteriophage capsid from DNA in bacteria
centrifuge separates bacteriophage from virus to allow investigator to detect radiation location
Phosphorous - virus capsid in liquid is not radioactive, bacteria are
Sulfur - viruse capsid in liquid are radioactive, bacteria are not
Chargaff’s experiment (3)
extracted DNA from cells + mixed them with acid
acid breaks bonds between pentose sugar + base
bases separated using paper chromatography + concentration of bases measured
Chargaff’s results (2)
concentration/amount of adenine equal/similar to thymine
concentration/amount of cytosine equal/similar to guanine
Importance of Chargaff’s experiment (3)
hinted at complementary base pairing
helped watson and crick build their double helix model
dispelled tetranucleotide hypothesis
Tetranucleotide hypothesis (2)
DNA contains repeating sequence of 4 bases (4 nucleotides occur in equal amounts)
DNA was single-stranded
Define macromolecules
molecules composed of a large number of atoms
Main classes of macromolecules in living organisms (3)
polysaccharides
polypeptides
nucleic acids
Define a disaccharide
2 monosaccharides linked together
Features of carbon bonds (3)
covalent
carbon can bond to 4 atoms
single carbon bonds allow atoms to rotate
Shape which chains of carbon atoms can form (2)
rings
zig zag shape
Condensation Polymerisation (3)
two molecules join together
one molecule loses a hydroxyl group (-OH), another loses a hydrogen atom (-H)
causes formation of water
Describe a glycosidic bond
oxygen atom shared between 2 glucose molecules
Define hydrolysis (2)
chemical reaction where water is used to break covalent bond between monomers
-OH will attach to one monosaccharide, -H will attach to other
Number of carbon atoms for pentose (2)
5
e.g ribose
Number of carbon atoms for hexose (2)
6
e.g glucose, fructose
Isomers of glucose (2)
alpha-glucose
beta-glucose
Orientation of alpha-glucose (2)
hydroxyl group (OH) is orientated downward
e.g glycogen + starch
Orientation of beta-glucose (2)
hydroxyl group (OH) is orientated upward
e.g cellulose
Properties of glucose (3)
glucose is soluble + small –> easily transported
glucose is chemically stable
yields energy when oxidised
Why glucose is soluble (4)
soluble because it is polar
contains (-OH) molecules which are polar
oxygen atoms are partially negative
so carbon-hydrogen (C-H) atoms are partially positive
Applications of glucose being soluble (2)
polar so able to dissolve in water
dissolves in plasma - can be transported in blood, OH groups bond with water in plasma
Why is glucose chemically stable (2)
ring structure - atoms are bonded to minimise strain + allows for strong covalent bonds
hydroxyl groups - forms bonds with water molecules (stable in aqueous solution) + prevents glucose from undergoing reactions
Application of property of glucose being chemically stable (2)
improves structural role of cellulose in plants
helpful in starch and glycogen for storage
Oxidisation as a property of glucose (3)
addition of oxygen to a molecule
loss of hydrogen atom
loss of electrons to another atom/ion
Application of glucose property of being easily oxidised (2)
oxygen important reactant for cellular respiration
broken down by losing electrons to oxygen to form CO2 and H2O
Name 2 types of starch (2)
amylose
amylopectin
Describe amylose (2)
polysaccharide made of glucose monomers linked through alpha-1,4 -glycosidic bonds
helical shaped chain
Describe amylopectin (2)
polysaccharide made up of glucose monomers linked through alpha-1,4-glycosidic bonds with ocassional 1,6-glycosidic bonds
branched shaped chain
Amylopectin property (3)
branch shape allows amylopectin to be more packed together - allows for more efficient storage of glucose
adding + removing glucose is quicker since branch shape has more ends
major component of starch
Starch properties (2)
compact in structure due to branching and coiling - efficient storage for small space
insoluble due to large size - can store lots of glucose, ensures that water is not drawn in
Describe maltose
disaccharide formed from 2 alpha-glucose molecules joined by a glycosidic bond
Describe sucrose
alpha-glucose molecule and fructose molecule joined by a glycosidic bond
Describe lactose (2)
glucose + galactose molecule
joined by glycosidic bond
Describe the structure of glycogen (2)
linear glucose chains linked through alpha 1,4 glycosidic bonds and 1,6 glycosidic bonds
forms compact coiled structure
Features of glycogen (2)
insoluble due to large molecular size - does not affect osmotic concentration of cells
branched structure - can be easily hydrolysed to produce glucose
Cellulose characteristics (3)
structural sugar in plants
strong - hydrogen bonds between chains create lattice structure
1,4 glycosidic bond
Cellulose structure (4)
straight chain of beta-molecules
B-glucose is inverted so that -OH groups are together
hydrogen bonds form between chains (polarity between O in glycosidic bond + H in glucose)
microfibrils form - bundles of cellulose chains
Define glycoproteins
proteins that have one or more carbohydrates attached to them
Function of glycoproteins (4)
Cell-cell recognition
act as receptors on surface of cells
can act as ligands
structural support of cells + tissue
Role of glycoproteins in cell to cell recognition (2)
acts as markers on the surface of cells so they can be identified
e.g immune cells attack foreign cells with different glycoproteins
Role of glycoproteins as receptors (3)
act as receptors on cell surfaces
receive signals from other cells or molecules
e.g insulin binds to glycoproteins on surface of body cells
Role of glycoproteins as ligands
ligands - molecules that bind to receptors to initiate a biological response
Glycoprotein role in ABO blood groups (2)
red blood cells have glycoproteins : oligosaccharides called O, A, B
blood with glycoprotein A/B will be rejected by a person who does not produce it
What blood type does not cause rejection problems and why (2)
O
has same structure as A and B but with one monosaccharide less
Features of lipids (3)
hydrophobic + insoluble in water - non-polar
dissolve in non-polar solvents - non-polar solvents have similar polarity to lipids
contains carbon, hydrogen, oxygen
Name of solid lipids at room temperature
fats
Name of liquid lipids at room temperature
oils
Define a tryglyceride (4)
non-polar macromolecule + most common type of lipid
formed from one molecule of glycerol + 3 fatty acids
glycerol stays the same but there are different fatty acids
fatty acids = carboxyl groups (COOH) with a hydrocarbon tail
Name of bond formed between glycerol and fatty acid
ester bond
Define a phospholipid
glycerol molecule with a phosphate group and 2 fatty acids
phosphate head is hydrophilic when fatty acids are hydrophobic
Define saturated fatty acids (3)
straight shape due to no double bonds between carbon atoms
carbon atom in hydrocarbon bonds to 4 atoms
fatty acids can pack together, forming solid at room temp.
Define unsaturated fatty acids (3)
hydrocarbons have one or more double bonds
causes bends in shape
liquid at room temp. - bends make it difficult for molecules to pack together
Types of unsaturated fatty acids (2)
monounsaturated
polyunsaturated
Define monounsaturated fatty acids (3)
have one double bond in hydrocarbon chain
causes a bend in the chain
liquid state at room temp. - bends make it difficult for molecules to pack together
Define polyunsaturated fatty acids (3)
have 2 or more double bonds in hydrocarbon chain
causes multiple bends in chain
liquid state at room-temp - bends make it more difficult for molecules to pack together
Unsaturated fatty acids vs saturated fatty acids (melting point)
U have lower melting points than S - more double bonds = lower melting point
Why doe unsaturated fatty acids have lower melting points (2)
double bonds disrupt packing of fatty acid molecules
makes them easier to break apart
Terms used to describe different arrangement of unsaturated fatty acids (2)
cis
trans
Define cis unsaturated fatty acids (2)
hydrogen atoms attached to carbon atoms around double bond are on same side
creates bend
Define trans unsaturated fatty acids (2)
hydrogen atoms attached to carbon atoms around double bond are on different sides
linear shape + less flexible than cis
Trans fats vs cis fats (2)
cis occurs in nature, trans produced artificially
cis has lower melting points than trans
Tryglycerides function/characteristics (4)
energy storage - chemically stable so energy not lost
used as insulators to retain heat
liquid at body temperature - can act as shock absorbers
release twice as much energy per gram in respiration than carbs
Define a phospholipid bilayer (4)
double layer of phospholipids
phospholipid bilayers can form when phospholipids are placed in water
hydrophobic fatty acids will orient towards each other
hydrophilic phosphate + glycerol will orient towards water
Features of steroids (4)
lipids
hydrophobic - as they are mainly hydrocarbons
have 4 carbon rings
able to pass through phospholipid bilayer
Functions of steroids (2)
provide phospholipid bilayer with stability + flexibility
role in signalling
Describe the structure of an amino acid (5)
amino group NH2 (basic)
carboxyl group COOH (acidic)
hydrogen atom
central alpha carbon atom
side chains called R groups
Features of the R-group in amino acids (2)
R-groups vary + make amino acids different from each other
affects the way the amino acid bonds with another amino acid
Define a dipeptide
2 amino acids linked by a condensation reaction
How do amino acids link with one another (2)
carboxyl group reacts with amino group
condensation reaction - bond formed between C and N + H2O produced as by-product
Name of bond between amino acids
peptide bond (type of covalent bond)
Number of different amino acids
20
Define essential amino acids (2)
amino acids which the body cannot produced + must be obtained from diet
9/20
Define non-essential amino acids (2)
amino acids which can be produced by the body
11/20
Number of possible amino acid sequences for a polypeptide (3)
20^n
20 possible amino acids to be linked
n = number of amino acids
Importance of an amino acid order
gives the protein its function
Why does temperature cause protein denaturation (2)
high temperatures can break weak hydrogen bonds holding proteins together
protein will unfold + lose its function
Why does pH cause protein denaturation (3)
high pH = excess H+ can make it difficult to form hydrogen bonds + affecting electronegativity
low pH = lack of H+ reduce number of hydrogen bonds
denaturation = will alter protein shape
Number of codons to code for an amino acid
64
Different types of R-groups (3)
charged R-groups which form ionic bonds
R-groups with sulphur atoms that form disulphide bridges
hydrophilic + hydrophobic - some are polar or charged
Describe the primary structure of proteins (3)
sequence of amino acids
peptide bonds between carboxyl + amine group
determines shape of protein - sequence determines how polypeptide chain will fold
Describe the secondary structure of proteins (2)
the folding patterns that occur within the polypeptide chain
hydrogen bonds between O and H atoms on adjacent amino acids form structure
Name 2 types of secondary structure (2)
alpha helix
beta pleated sheet
Features of alpha-helix secondary structure (2)
polypeptide chain forms helical shape
hydrogen bond forms between amine hydrogen of one amino acid + carboxyl oxygen of another 4 residues away
Features of beta-pleated sheet secondary structure (2)
hydrogen bonds form between polypeptide chains parallel to each other
form pleated sheet shape due to tetrahedral bond angles
Define the tertiary structure of proteins (2)
folding of the polypeptide chain into a 3-dimensional structure
stabilized by interactions between R-groups of amino acids
Describe tertiary structure hydrogen bonds between R-groups
hydrogen bonds form between slightly positive hydrogen and slightly negative O or N
Describe tertiary structure ionic bonds between R-groups (4)
ionic bonds between positive + negatively charged R-groups
R-group binding with hydrogen ion = positively charged
R-group losing a hydrogen ion = negatively charged
ionic bonds are more sensitive to pH due to involvement of H+
Describe tertiary structure disulphide bonds between R-groups (3)
disulphide bond between amino acids with sulphur atoms
e.g cysteine and methionine
strongest covalent bonds
Describe tertiary structure hydrophobic interactions between R-groups (3)
water forms hydrogen bonds between polar/hydrophilic amino acids
non-polar amino acids will clump in hydrophobic clusters in the interior of the protein
to minimise contact with surround ing water molecules
Effect of R-group hydrophilic polarity on tertiary structure (2)
R-groups will orient outwards towards water
soluble in water = can allow them to carry out functions in aqueous solution
Effect of R-group hydrophobic polarity on tertiary structure (2)
R-groups reside in protein interior
stabilises protein - maximises hydrophobic interactions within centre + hydrogen bonding between amino acids on surface + water
Define quaternary structure proteins
arrangement of 2 or more polypeptide chains to form a protein
Define non-conjugated proteins (2)
proteins with only polypeptide subunits
e.g collagen + insulin
Define conjugated proteins (2)
proteins with polypeptide subunits + non-protein (prosthetic group
e.g haemoglobin containing haem to bind to oxygen
What happens after a polypeptide chain is synthesised (2)
protein folding - adopts specific 3D shape which corresponds to its function
influenced by sequence of amino acids, hydrogen + ionic bonding, hydrophobic interactions
Name the types of quaternary structure proteins (2)
Globular
Fibrous
Define globular proteins (4)
spherical shaped proteins with irregular folds
soluble in water
play roles as enzymes, transporters, regulators
e.g insulin, haemoglobin, enzymes
Features of insulin as a globular protein (4)
has 2 polypeptide chains - alpha and beta
held in 3D shape by hydrogen bonds, hydrophobic interactions, disulphide bonds
has hydrophilic exterior - allows insulin to react with water + other hydrophilic molecules in blood, able to travel through blood + bind to its receptors
has hydrophobic interior - stabilises globular shape, allows insulin to bind to receptor
Function of insulin (2)
regulates amount of glucose in bloodstream in response to high glucose levels
binds to receptors on cells - allows glucose to enter cells to be used or stored
Define a fibrous protein (3)
elongated polypeptides - polypetide chains linked together into narrow fibres with hydrogen bonds between them
insoluble in water
designed for strength + stability
Collagen as a fibrous protein (2)
3 polypeptide chains twisted together in a triple helix shape
held together by hydrogen bonds
Collagen function
provides structural support to tissues + maintains their shape
