2.2 Biological Molecules Flashcards
Properties of water
Medium in which all metabolic reactions take place (70%-95% of the mass of a cell is water)
Major habitat for organisms
Composed of hydrogen and oxygen, 1 oxygen atom combines with two atoms of hydrogen by covalent bonding
Water as a whole is electrically neutral but sharing of atoms is uneven
Polar molecule
Polar molecule in water
sharing of electrons is uneven and oxygen attracts electrons more strongly than hydrogen atoms resulting in a weak negatively charge region on the oxygen atom and a weak positively charged region on the hydrogen atoms, resulting is asymmetrical shape
Polar molecule
When one molecule has one end that is negatively charged and one end is positively charged
Dipole
Separation of charge due to electrons in the covalent bonds being unevenly shared
Why are Hydrogen bonds formed in water
A result of polarity of water hydrogen bonds form between positive and negatively charged regions of adjacent water molecules
Hydrogen bond strength
When there are few they are weak so they are constantly breaking and reforming
When there are a large numbers present they form a strong molecule
What properties do hydrogen bonds contribute to water
Excellent solvent
Relatively high specific heat capacity
Relatively high latent heat of vaporisation
Water is less dense when a solid
Water has high surface tension and cohesion
It’s acts as a reagent
Water as a solvent
As its a polar molecules many ions and covalently bonded polar substances (eg glucose) will dissolve in it.
What does water being a good solvent lead to
Allows chemical reactions to occur within cells (as dissolved solutes are more chemically reactive when they are free to move about)
Metabolites can be transported efficiently (except non polar molecules which are hydrophobic)
Specific heat capacity
Amount of thermal energy required to raise the temperature of 1kg of a substance by 1’c
Water specific heat capacity
4200j/kg’C
Why does water have high specific heat capacity
Due to many hydrogen bonds present in water, its takes a lot of energy to break these bonds and a lot of energy to build them, thus them temperature of water does not fluctuate greatly
What are the advantages of water’s high specific heat capacity for living organisms
Provides suitable habitats
Able to contain constant temperature as water is able to absorb a lot of heat without big temperature fluctuations which is vital in maintain temperatures that are optimal for enzyme activity
Water in blood plasma
Vital in transferring heat around the body, helping to maintain a fairly constant temperature
As blood passes through more active (warmer) regions of the body, heat energy is absorbed but the temperature remains firmly constant
Water in tissue fluid
Plays an important role in maintaining a constant body temperature
High latent heat of vaporisation
In order to change state from liquid to gas a large amount of thermal energy must be absorbed by water to break the hydrogen bonds and evaporate
How does high latent heat of vaporisation benefit animals
Only a little water is required to evaporate for the organism to lose a great amount of heat, this provides a cooling effect for living organisms, (eg transpiration from leaves or evaporation of water in sweat)
Cohesion in water
Hydrogen bonds between water molecules allow for strong cohesion between water molecules
What does cohesion between water molecules allow
Columns of water to move through xylem of plants through blood vessels in animals
Enables surface tension where a body of water meets the air, these hydrogen bonds occur between the top layer of water molecules to create a sort of film on the body of water (this allows insects such as pond skaters to float)
Adhesion is water molecules
When water is able to hydrogen bond to other molecules which enables water to move up xylem due to transpiration
Key molecules that are required to bold structures that enable organisms to function
Carbohydrates, proteins, lipids, nucleic acids, water
Monomers
Smaller units from which larger molecules are made
Polymers
Molecules made from a large number of monomers joined together in a chain
Polymerisation
Carbon compounds can form small single subunits (monomers) that bond with many repeating subunits to form large molecules (polymers)
Macromolecules
Very large molecules
Contain 1000 or more atoms so high high molecular mass
Polymers can be macromolecules however not all macromolecules are polymers as the subunits of polymers have to be repeating units
Covalent bonds
Sharing of two or more electrons between two atoms
Can be formed equally forming a non polar covalent bond
Can be formed unequally forming a polar covalent bonding
Properties of covalent bonds
Very stable as high energy required to break bonds
Multiple pairs of electrons can be shared forming double or triple bonds
Covalent bonds in monomers
When two monomers are close enough that their outer orbitals overlap which results in their electrons being shared and a covalent bond forming. If more monomers are added then polymerisation occurs and/or a macromolecule forms
Condensation reaction
Occurs when monomers combine together by covalent bonds to form polymers or macromolecules and water is removed
Hydrolysis
Breaking down a chemical bond between two molecules and involves the use of a water molecule
Hydrolysis of polymers
Covalent bonds are broken when water is added
Type of Covalent bonds in carbohydrates
Glycosidic
Type of covalent bond in proteins
Peptide
Type of covalent bond in lipids
Ester
Types of covalent bond in nucleic acids
Phosphodiester
Why are Carbon atoms key to organic compounds
Each carbon atom can form 4 covalent bonds making the compound very stable
Carbon atoms can form covalent bonds with oxygen, nitrogen and sulfur
Carbon atoms can form straight chains, branched chains or rings
What do carbohydrates, proteins, lipids and nucleic acids contain making them organic compounds
Carbon and hydrogen
Function of carbohydrates
Source of energy e.g. glucose is used for energy-release during cellular respiration
Store of energy e.g. glycogen is stored in the muscles and liver of animals
Structurally important e.g. cellulose in the cell walls of plants
3 types of carbohydrates
monosaccharides, disaccharides and polysaccharides
Monosaccharide
Single sugar monomer, all are reducing sugars
Examples of monosaccharide
Glyceraldehyde (3c), ribose (5c), glucose (6c)
Function of monosaccharide
Source of energy in respiration, building blocks for polymers
Disaccharide
A sugar formed two monosaccharides joined by a glycosidic bond in a condensation reaction
Examples of disaccharides
Maltose-(glucose+glucose)
Sucrose-(glucose+fructose)
Lactose-(glucose+galactose)
Function of disaccharide
Sugar fund in germinating seeds (maltose)
Mammal milk sugar (lactose)
Sugar stored in sugar cane (sucrose)
What makes up maltose
Glucose+glucose
What makes up sucrose
Glucose+fructose
What makes up lactose
Glucose+galactose
Polysaccharide
A polymer formed by many monosaccharides joined by glycosidic bonds in a condensation reaction
Examples of polysaccharide
Cellulose (glucose)
Starch (glucose in the form of amylose and amylopectin)
Glycogen (glucose)
What makes up cellulose
Glucose
What makes up starch
Glucose in the form of amylose and amylopectin
What makes up glycogen
Glucose
Function of polysaccharides
Energy storage- (plants-starch, animals-glycogen)
Structural- cellulose cell wall
Types of lipids
triglycerides (fats and oils), phospholipids, waxes, and steroids (such as cholesterol)
Functions of lipids
Source of energy
Store of energy
Insulating layer
Lipids as a source of energy
Source of energy that can be respired (lipids have a high energy yield)
Lipids as a store of energy
lipids are stored in animals as fats in adipose tissue and in plants as lipid droplets
Lipids as an insulating layer
thermal insulation under the skin of mammals and electrical insulation around nerve cells
Eg of carbohydrate as source of energy
glucose is used for energy-release during cellular respiration
Carbohydrates as store of energy
glycogen is stored in the muscles and liver of animals
Eg of carbohydrates being structurally important
cellulose in the cell walls of plants
Functions of proteins
Required for cell growth
Structurally important
Can act as carrier molecules in cell membrane
Eg of proteins being structurally important
in muscles, collagen and elastin in the skin, collagen in bone and keratin in hair
Eg of nucleic acids
DNA and rna
Function of nucleic acids (dna and rna)
Carrying the genetic code in all living organisms
Nucleic acids are essential in the control of all cellular processes including protein synthesis
Reducing sugars
Can donate electrons and the sugars become the reducing agent
Examples of reducing sugars
glucose, fructose and galactose
Non-reducing sugars
cannot donate electrons, therefore they cannot be oxidised
Example of non reducing sugar
Sucrose
Glucose molecular formula
C6H12O6
Why is glucose so important
The main function of glucose is as an energy source
It is the main substrate used in respiration, releasing energy for the production of ATP
Glucose is soluble and so can be transported in water
Penrose sugars
Sugars that contain five carbon molecules
Learn how to draw alpha and beta glucose
Type?
What Penrose sugar makes up rna and dna
Ribose-rna
Deoxyribose-dna
What does a glycosidic bond result in
one water molecule being removed, thus glycosidic bonds are formed by condensation
Example of Penrose and heroes monosaccharide
Pentose-ribose
Hexose-glucose
Difference between heroes and Penrose monosaccharide
Pentose- five carbon atoms
Hexose- six carbon atoms
How is a glycosidic bond formed
A condensation reaction between two monosaccharides forming disaccharides and polysaccharides
How are glycosidic bonds broken down
Water is added in hydrolysis, disaccharides and polysaccharides are broken dow in hydrolysis reaction
What happens when you heart sucrose
When sucrose is heated with hydrochloric acid this provides the water that hydrolyses the glycosidic bond resulting in two monosaccharides that will produce a positive Benedict’s test
What result does sucrose give in Benedict test when not heated
Sucrose is a non-reducing sugar which gives a negative result
Condensation reaction
two molecules join together via the formation of a new chemical bond (glycosidic bond), with a molecule of water being released in the process
How to calculate chemical formula of disaccharide
you add all the carbons, hydrogens and oxygens in both monomers then subtract 2x H and 1x O (for the water molecule lost)
Examples of disaccharides
Maltose, sucrose and lactose
All three of the common examples above have the formula C12H22O11
Maltose
The sugar formed in the production and breakdown of starch
Sucrose
The main sugar produced in plants
Lactose
A sugar found only in milk
Monosaccharide components of maltose
Glucose + glucose
Monosaccharide components of sucrose
Glucose + fructose
Monosaccharide components of lactose
Glucose + galactose
What are Starch, glycogen and cellulose
Polysaccharides
What are polysaccharides
macromolecules (polymers) that are formed by many monosaccharides joined by glycosidic bonds in a condensation reaction to form chains
These chains may be:
Branched or unbranched
Folded (making the molecule compact which is ideal for storage eg. starch and glycogen)
Straight (making the molecules suitable to construct cellular structures e.g. cellulose) or coiled
What two polysaccharides construct starch
Amylose
Amylopectin
Amylose in starch
(10 - 30% of starch)
Unbranched helix-shaped chain with 1,4 glycosidic bonds between α-glucose molecules
The helix shape enables it to be more compact and thus it is more resistant to digestion
Amylopectin in starch
(70 - 90% of starch)
1,4 glycosidic bonds between α-glucose molecules but also 1,6 glycosidic bonds form between glucose molecules creating a branched molecule
What makes up glycogen
It is made up of α-glucose molecules
There are 1,4 glycosidic bonds between α-glucose molecules and also 1,6 glycosidic bonds between glucose molecules creating a branched molecule
Glycogen has a similar structure to amylopectin but it has more branches
Monomer in amylose, amylopectin and glycogen
Glucose for all of them
Branched feature in amylose, amylopectin and glycogen
Amylose- no
Amylopectin- yes (every 20 monomers)
Glycogen-yes (every 10 monomers)
Do amylose, amylopectin and glycogen have a helix (coiled) shape
Amylose- yes
Amylopectin- no
Glycogen- no
Glycosidic bonds present in amylose, amylopectin and glycogen
Amylose- 1,4
Amylopectin- 1,4 and 1,6
Glycogen- 1,4 and 1,6
Cellulose
polysaccharide found in plants
It consists of long chains of β-glucose joined together by 1,4 glycosidic bonds
Why is cellulose strong
β-glucose is an isomer of α-glucose, so in order to form the 1,4 glycosidic bonds consecutive β-glucose molecules must be rotated 180° to each other
Due to the inversion of the β-glucose molecules, many hydrogen bonds form between the long chains giving cellulose its strength
Why are starch and glycogen storage polysaccharides
they are:
Compact
So large quantities can be stored
Insoluble
So they will have no osmotic effect, unlike glucose which would lower the water potential of a cell causing water to move into cells
What is starch stored as in plants
It is stored as granules in plastids such as amyloplasts and chloroplasts
Plastids
Plastids are membrane-bound organelles that can be found in plant cells. They have a specialised function eg. amyloplasts store starch grains
Why does starch take longer to digest than glucose
Due to the many monomers in a starch molecule
How can amylopectin in starch help the plant
has branches that result in many terminal glucose molecules that can be easily hydrolysed for use during cellular respiration or added for storage
Glycogen
the storage polysaccharide of animals and fungi, it is highly branched and not coiled
Glycogen in liver and muscles cells
have a high concentration of glycogen, present as visible granules, as the cellular respiration rate is high in these cells (due to animals being mobile)
Benefits of glycogen being more branched than amylopectin
Makes it more compact which animals store more
Branching in glycogen
The branching enables more free ends where glucose molecules can either be added or removed allowing for condensation and hydrolysis reactions to occur more rapidly – thus the storage or release of glucose can suit the demands of the cell
Cellulose
main structural component of cell walls due to its strength which is a result of the many hydrogen bonds found between the parallel chains of microfibrils
What does the high tensile strength of cellulose allow
it to be stretched without breaking which makes it possible for cell walls to withstand turgor pressure
How does cellulose increase strength of the cell walls
The cellulose fibres and other molecules (eg. lignin) found in the cell wall forms a matrix