-Module 2; Biological molecules Flashcards
Structure of water
One atom of oxygen joined to two hydrogens by a covalent bond.
H’s shared electrons are pulled to the oxygen atom, causing each H to be slightly positive.
Oxygen is left slightly negative.
This makes water a polar molecule, a dipole.
What are the features of hydrogen bonding between water molecules?
The slightly negative charge on the oxygen atom is attracted to and forms a hydrogen bond with the slightly positive charge of a hydrogen on another water molecule.
We use the delta sign to show slightly negative and slightly positive.
What are the 5 main properties of water?
1- High specific heat capacity
2- Cohesive and adhesive
3- Hight latent heat of vaporisation
4- Lower density when solid
5- Good solvent
What is meant by a high specific heat capacity of water and what is the benefit of this?
SHC is the energy needed to raise the temperature of a gram of a substance by 1 degree.
H bonds between water molecules can absorb a lot of energy.
Water has a high SHC.
Important bc large fluctuations in temp are not good for aquatic organisms.
What is meant by High latent heat of vaporization and why is it important?
Lots of energy is needed to break the bonds between water molecules to change water from a liquid to a gas. This makes water an excellent coolant.
Roles of water as a coolant.
Sweat evaporates, carries heat away.
Plants transpiration, water evaporates from leaves and carries heat away.
Temperature buffer for chemical reactions in prokaryotes and eukaryotes.
Proper function of enzymes- active in a narrow temp range.
What is cohesion in water?
Cohesion is the attraction between water due to hydrogen bonding.
What are the roles of water being cohesive?
Transport
Transpiration
Blood
Phloem
Surface tension (provides habitat)
Why is surface tension formed?
Water molecules are more attracted to each other than the air.
How do hydrogen bonds behave in water related to cohesion?
They are relatively weak so break and reform constantly, however they occur in such large numbers that water remains cohesive.
What is adhesion?
The attraction between a water molecule and another polar molecule.
What are the roles of cohesion and adhesion together?
The combination of the two is capillary action, this is what allows water to move through the xylem tubes.
Why does water have a lower density when solid?
As water changes state from liquid to solid, each water molecule forms four hydrogen bonds to other water molecules, creating a hexagonal lattice structure. This makes ice less dense than liquid water and is why ice floats.
Why is water being less dense when solid than liquid important?
Ice forms a protective barrier which reduces the rate of heat loss and makes the environment more stable for aquatic organisms.
How does water dissolve substances?
Water is polar and therefore the slightly positive end of water will be attracted to negative ions and vice versa. Water molecules surround each ion and dissolve the substance.
Why is it important that water is a good solvent for living organisms?
Transport of molecules and ions in living organisms (blood/phloem)
Ions can dissolve in water in blood and are important in the regulation of pH and water balance.
Most chemical reactions take place in a solution.
What substances dissolve in water?
Ions and polar molecules.
To identify these, look for -OH and -SH groups in chemical structures.
Why is it useful to organisms that water is a liquid at room temp?
Effective transport medium, eg, blood/phloem.
Habitat for aquatic organisms.
Medium for chemical reactions.
What are the roles of carbohydrates?
Energy storage (starch)
Energy source (glucose)
Structural (cellulose)
What are the molecules in carbohydrates?
What ratio are they usually in?
Carbon, hydrogen, oxygen.
They are usually in the ratio of C:H:O is 1:2:1.
What is a single sugar unit called? What about two and more?
Monosaccharide, disaccharide, polysaccharide.
What are monomers?
They are small, basic units like monosaccharides.
What are polymers?
Polymers are large, complex, molecules composed of long chains of monomers joined together, eg cellulose, starch and proteins.
What are the structural features of glucose of a monosaccharide?
Glucose has 6 carbon atoms and is therefore a hexose monosaccharide.
Has the formula C6H12O6.
Two forms fo structural isotopes (alpha and beta)
Draw a glucose monosaccharide.
/…
What is the difference between alpha and beta glucose?
Alpha glucose the hydroxyl group at carbon 1 points down.
Opposite for beta.
What are the features of fructose?
Pentose sugar.
It is very sweet and soluble and is the most common sugar in nectar and fruit.
Fructose is sweeter than glucose which is sweeter than galactose.
What are the features of galactose?
It is not as soluble as glucose and has an important role in the production of glycolipids and glycoproteins.
What are pentose monosaccharides?
They contain 5 carbon atoms, example deoxyribose and ribose.
How are disaccharides formed between two alpha glucose?
When two alpha glucose are side by side, the two hydroxyl groups react. When this happens, bonds are broken and new bonds are formed in different places forming new molecules. The bond is formed between carbon 1 and carbon 4. This means it is a glycosidic 1-4 bond. The reaction is a condensation reaction.
What are the enzymes involved in hydrolysis?
Hydrolase enzymes.
How is alpha lactose formed?
Beta galactose and alpha glucose with a beta 1-4 glycosidic bond directed upwards.
How is beta lactose formed?
Beta galactose + beta glucose joined with a beta glycosidic bond.
How is sucrose formed?
Alpha glucose + beta fructose
What are the 3 important disaccharides to learn and what are they made up of?
Maltose is made up of two glucose.
Lactose is made up of glucose and galactose.
Sucrose is made of glucose and fructose.
Why are the 5 key features of a polysaccharide energy storage molecule?
Compact - energy dense.
Insoluble - would not affect the water potential of the cell.
Easy to add glucose to - condensation reaction
Easy to remove glucose from - hydrolysis
Metabolically inactive
How is starch formed and what is it’s use?
Glucose is produced during photosynthesis and is converted to and stored in the chloroplasts and in membrane bound starch grains of plant cells. Used as a source of energy for the plant.
What is the structure of starch?
Starch is a polysaccharide made up of many alpha glucose molecules.
There are two kinds of glycosidic bonds that can form between the glucose molecules which allows two slightly different structural units to be formed; amylose and amylopectin.
What are the features and structure of amylose?
Amylose makes up 30% of starch.
It is a long unbranched chain of a-glucose connected by 1-4 glycosidic bonds only.
It coils into a compact helix which is then held in place by hydrogen bonds.
The OH groups are arranged to the inside of coil, making amylose less soluble as these are the groups that would H-bond with water.
What are the features and structure of amylopectin?
Makes up 70% of starch.
Chains of alpha-glucose connected by 1-4 glycosidic bonds to form helical shapes.
Approx every 25 glucose, a 1-6 glycosidic bond forms by condensation, creating a branch.
Highly branched structure has multiple sites for hydrolysis allowing glucose to be removed quickly.
Where is glycogen found and what is it’s function?
It is stores in small granules, particularly in the muscles and the liver.
It is used as an energy storage molecule by animals and fungi.
What is glycogen’s structure?
It is made of alpha glucose.
Branch points every 10th residue and are 1-6 glycosidic bonds.
Why do animals use glycogen not starch?
Glycogen is coiled making it more compact for easier storage.
It is highly branched and so easier access to free ends where hydrolysis takes place, means glucose can be released quickly.
Plants are immobile and animals are active so need a lot more energy.
Why is it important that glucose is stored and not always freely available in the blood or phloem?
Glucose is soluble. Too much glucose will lower the water potential of the blood, causing water to move out of cells by osmosis.
What is the structure of cellulose?
Cellulose is made up of long, unbranched chains of B glucose.
The hydroxyl groups on carbon 1 and 4 are too far apart.
Alternate B glucose molecules must be inverted so that they are close enough to form a 1-4 glycosidic bond.
It is a straight chain molecule.
How many cellulose chains bind together to form a microfibril?
60-70.
