Biological Molecules Flashcards
Condensation reaction
A reaction that occurs when 2 molecules are joined together with the removal of water
What is a hydrogen bond?
Weat interaction that can ocurr whenevt molecules contn a slightly negative charged atom bonded to a slightly positively charged hydrogen atom
How many covalent bonds does carbon have?
4
How many covalent bonds does hydrogen have?
1
How many covalent bonds does oxygen have?
2
How many covalent bonds does nitrogen have?
3
A double bond counts as … bonds
2
Hydrolysis
2 molecules can be split apart with the addition of water
How do most condensation reactions occur?
When 2 -OH grous react together. The reaction involves the breaking and formation of a covalent bond
The units which are joined together in condesation and hydrolysis reations are called:
Monomers
When 2 monomers join together what is formed?
Dimer
What happens when lots of molecules join together?
A polymer is formed
What do carbohydrates contain?
Carbon, hydrogen, oxygen
What do proteins contain?
Carbon, hydrogen, oxygen, nitrogen (some have sulfur)
What do lipids contain?
Carbon, hydrogen, oxygen
What do nucleic acids contain?
Carbon, hydrogen, oxygen, nitrogen and phosphorus
What is the monomer of carbonhydrates?
Monosaccharides (e.g. glucos)
What is the monomer of protein?
Amino acids
What is the monomer of nucleic acids?
Nucleotides
What is the polymer of carbonhydrates?
polysaccharides (e.g. starch)
What is the polymer of protein?
polypeptides and protiens
What is the polymer of nucleic acid?
DNA and RNA
Which is weaker a hydrogen bond ora convalent bond?
A hydrogen bond
Why do biological molecules have many hydrogen bonds?
BEcause it can help to stabalise the structure
How are glycosidic bonds formed?
It is a bond formed between 2 monosaccharides by a hydrolysis reaction (carbohydrates)
In a carbohydrate what is every carbon bonded to?
For every carbon atom, there are 2 hydrogen atoms and 1 oxygen
Functions of carbohydrates:
They act as a source o energy - glucos
They sotre energy - starch
As structural unitis -cellulous in plants and chitin in insects
Some are also part of other molecules - nuleic acids, glycoprotien
What are the 3 main carbohydrate groups?
Monosaccharides
disacarides
polysaccharides
Give information on monosaccharides
- Simplest carbohydrate
- Important as a source of energy because of the large number of carbon-hydrogen bonds
- They ar sugars (therefore they are sweet, soluble in water and insoluble in non-polar solvents
- They can exist as straight chains or as rings or cyclic forms
- Backbone of single-bonded carbon atoms with 1 double-bonded to an oxygen atom to form a carboxyl group
Give information about monosaccharides hexose sugars (like glucose)
They are the monomers of more complex carbohydrates and they are bonded together to form disaccharides or polysaccharides
In solution what form do triose and tetrose sugars take?
straight charns
In solution what form do pentos and hextos sugar take?
Rings or cyclic form
As both straight chains or ring/cyclic forms glucos can exista as a different ….
isomers
What are isomers?
they are molecules with the same formula but whose atoms are arranged differently in space)
What are the isomers in straight chains?
The -H and the -OH can be reversed
What are the isomers in a ring shaped molecule?
The ring is formed when the oxygen attached to the carbon, bonds to carbon-1. Becuase the -OH and the -H on carbon can be above or below the plane of the ring when the ring forms, there are 2 isomers: alpha glucose and beta glucose.
This small difference is very important when glucose molecules polymerize into starch or cellulose
Describe a disaccharide
It is sweat and soluble
What are the most common disaccharide?
Maltos (reducing sugar), sucrose (non-reducing sugar) and lactose (reducing sugar)
All monosaccharides are….
Reducing sugars
How are disaccharides made?
When 2 monosaccharides join together: alpha glucos + alpha glucos = maltose alpha glucos + fructose = sucrose beta galactose + alpha glucose = lactose beta glucose + beta glucose = celobiose
When the monosaccharides join a condensation reaction occurs to form a glycosidic bond. 2 hydroxyl groups line up next to each other, H2O removed leaves oxygen atom to link the 2 monosaccharide units
What is the role in the body and the type of sugar of alpha glucose?
Energy source, component of starch and glycogen, which act as energy stores.
Hexose
What is the role in the body and the type of sugar of beta glucose?
Energy source. Component of cellulose which provides structural support in plant cell walls
Hexose
What is the role in the body and the type of sugar of ribose?
Component of ribonucleic acid (RNA), ATP and NAP
Pentose
What is the role in the body and the type of sugar of deoxyribose?
Components of deoxyribonucleic acid (DNA)
Pentose
What are polysaccharides?
They are polymers of monosaccharides.
If they are made of 1 kind of monosaccharide its called homopolysaccharide (e.g. glucose)
If they are made of more types of monosaccharide its called heteropolysaccharide (e.g. hyaluronic acid)
What is glucose?
It is a source of energy, as it is a reactant in respiration
What is ATP?
It is the energy currency in cells
What happens if you join many glucose molecules together?
Polysaccharides, which is an energy source
Plant energy source: starch
human energy store: glycogen
Why does glycogen and starch form good stores of monosaccharides?
- Both compact, therefore, it doesn’t take up much room
- Polysaccharides hold glucose in hains, easily be “snipped off” by hydrolysis for respiration
- Some are branched some aren’t. Branched chains tend to be more compct, but also offer the chance for lots of glucose molecules to be snipped off by hydrolysis at the same time when lots of energy is required quickly
- Polysaccharides are less soluble in water then monosaccharides (so not to reduce water potential). Due tot their size and then any region which could form H-bonds with water are hidden within the molecule
What are the unbranched polysaccharides called?
Amulose.
What si teh enzyme amylase responsible for?
Enzyme amylase is responsible for hydrolysis 1-4 glycosidase
What are the branched polysaccharides called?
Amylopectin
Glycogen
What is teh enzyme glucosidase is responsible for?
For the hydrolysis 1-6 glycosidic linkages
Give information about cellulose
It is found in plant cell walls
It is a tough, insoluble, fibrous substance
It is a homopolysaccharide of beta glucose molecules, bonded together through condensation reactions to form glycosidic bonds
Describe the structure of cellulose
Staight chains which lie side by side. This difference in structure is a direct resu;t of bonding:
- Hydrogen and hydroxyl groups on carbon-1 are inverted in beta glucose. This means that every other beta glucose moleclue in the chain is rotated by 180 degrees - prevents chain from spiralling.
- H-bonding between the rotated beta glucose molecules in each chain - strength and stops from spiraling
- H-bonding between the rotated beta glucose in difference chains gives the whole structure additional strength. The hydroxyl goups on carbon-2 sticks our, so H-bonds can be formed between the chains
What bonds can you find inside water molecules?
Hydrogen bonds which makes, it all difficult for the water molecules to escape to become a gas. Even with hydrogen bonds water has quite a low viscosity (flow easily)
As water is a liquid at room temperature, what can it do?
Provide habitats for living things in rivers, lakes, and seas.
Form a major component of the tissues in living organisms.
Provide a reaction medium for chemical reactions.
Provides an effective transport medium e.g. in blood and vascular tissue.
Give information about the density of water.
It has unusual density changes
Like most substances, water become denser as it cools due to a reduction in the kinetic energy of the molecules bringing them closer together
However, below around 4oC, as water begins to freeze, the hydrogen bonds hold the water into a crystalline form
This makes the molecules spread out
The ice the, therefore, less dense than the liquid water, causing it to float
This provides an insulating layer, preventing the water below from freezing so that aquatic animals can survive without freezing and keep mobile
Currents and nutrients can also still circulate
It also provides a habitat for organisms to live on
It has a fairly high density, which enables it to provide good flotation to support aquatic organisms
Give information about the water as solvent
It is an especially good solvent
The polar nature of water molecules means that any other molecule that is polar or charged will be able to bind to it and dissolve eg. Na+, K+, Cl-
This allows chemical reactions to occur in solution and chemicals to be transported easily eg. uptake of nitrates from the soil by plant roots to build proteins
Oxygen can also dissolve in it for aquatic organisms to respire aerobically
Give information about the cohesion and surface tension
This cohesion causes water to form in drops
It also creates surface tension on top of a body of water, which can provide a platform for organisms to live and move eg. pondskaters
It is also responsible for the movement of water by mass flow in the transpiration stream
Give information about the water’s high specific heat capacity
It is thermally stable
Due to the large number of hydrogen bonds in the network of molecules, the movement of the molecules is restricted
Therefore, to raise the kinetic energy of the molecules and break their bonds to give an increase in temperature, relatively large amounts of energy are required (4.2J/g/oC)
This is a large specific heat capacity
This keeps the temperature of large bodies of water, like lakes and seas, thermally stable for aquatic organisms to live in
It also means that aquatic organisms need to spend less energy on temperature control
It means that the evaporation of water can remove large amounts of heat energy from any surface that it evaporates from.
Give information about the water’s high latent heat of vapourisation
This is a high latent heat of vaporisation and therefore makes evaporation an efficient cooling mechanisms eg. sweating for cooling in mammals
It keeps cells at relatively constant temperatures to keep enzyme-controlled reactions occurring at constant rates
Describe the advantages of waters’ transparency
It is transparent, which allows light to penetrate it for photosynthesis to occur underwater
