2.1.2 - Biological Molecules Flashcards
What kind of molecule is water?
Water is polar covalently bonded within molecule.
What does water being polar mean?
The unequal sharing of the electrons results in a slightly positively and slightly negative side of the molecule.
What are water molecules held together by?
Why?
Hydrogen bonds
Because of the attraction between the + and - poles.
What is cohesion?
The tendency of water molecules to stick together.
(3) What are the consequences of cohesion?
- High melting and boiling point.
- High specific heat capacity.
- High latent heat of vaporisation.
What is the significance of a high boiling point?
It means water is a liquid at Earth surface temperatures.
(2) What is the significance of a high specific heat capacity?
- Aquatic habitats remain at fairly stable temperatures, cooling/warming slowly.
- Bodies of living organisms are also temperature stable and they have to lose/absorb a lot of energy to become cooler/warmer.
What is the significance of a high latent heat of vaporisation?
Evaporation of water can be harnessed as a very effective cooling system.
What is dissolution?
When water molecules can easily move between ions or other polar molecules and separate them.
What is dissolution?
When water molecules can easily move between ions or other polar molecules and separate them.
What does hydrophilic mean?
Substances that are polar and often water-soluble.
What does hydrophobic mean?
Substances that repel water, causing droplets to form. They are often non-polar.
What is an example of a hydrophobic substance?
Lipids lack polar bonds. Polar covalently bonded water molecules act to exclude non-polar molecules which cause the fats to clump together.
(3) Why is the hydrophobic nature of fats advantageous?
It makes fats useful storage units as:
* They stay together in one compact unit.
* Can’t react.
* Have no osmotic effect on the cell.
At what temperature does water reach its maximum density?
4°C
What does this mean?
When ponds and lakes cool they first freeze at the top meaning aquatic organisms can stay alive beneath the ice as it provides an insulating layer, reducing further cooling.
What is the viscosity of water like?
Low
(2) What is this important for?
- Movement of aquatic organisms.
- Mass flow systems like the blood system.
What elements do carbohydrates contain?
C, H, O
What elements do lipids contain?
C, H
What elements to proteins contain?
C, H, O, N, S
What elements do nucleic acids contain?
C, H, O, N, P
What % of organic matter in a cell is carbohydrates?
10%
(4) What are the functions of carbohydrates?
- Energy source
- Energy store
- Structure
- Can form parts of molecules
What is the general formula for carbohydrates?
Cn(H2O)n
What are the simplest carbohydrates?
monosaccharides
(3) What are the properties of monosaccharides?
- Polar and soluble in water
- Sweet tasting
- Form crystals
How are monosaccharides grouped and give examples (3)?
by their carbon number (e.g triose / pentose / hexose)
What are diasaccharides?
2 sugars
How are polysaccharides made?
By linking many monosaccharides.
What is sucrose made up of?
glucose + fructose
What is lactose made up of?
glucose + galactose
How are diasaccharides formed?
A glycosidic bond is formed between a hydroxyl group on one monosaccharide molecule and a hydroxyl group on another.
What does a 1-4 glycosidic bond mean?
The two monosaccharides are joined at carbon atoms 1 and 4.
Why is the formation of a glycosidic bond a condensation reaction?
Water is produced.
What are the forward and backward reactions for the formation of disaccharides?
Forward - Condensation
Backward - Hydrolysis
What observations characterise the presence of sugars?
colour change from blue when Benedict’s solution is added.
Why does a colour change take place?
Blue copper (II) ions from copper (II) sulfate in Benedict’s solution are reduced to red copped (I) ions by the aldehyde groups in the reducing sugar.
Why is a precipitate formed?
The red copper (I) oxide is insoluble in water and precipitated out of solution.
What are reducing sugars?
A sugar that serves as a reducing agent due to its free aldehyde or ketone functional groups in its molecular structure.
How are reducing sugars formed?
The hydrolysis of disaccharides form monosaccharides which have the aldehyde functional group.
