As/A level Bio : Chapter two - Water, carbohydrates, and lipids Flashcards
Chemical properties of water?
Water is bonded by covalent bonding
Water is polar (o = negative, h = positive)
Forms hydrogen bonds between molecules
Thermal properties of water (3.5)?
Water has a high specific heat capacity and it is liquid from 0 - 100 degrees so it provides the perfect habitat for living things.
When cooled the individual molecules lose kinetic energy, slowing down, and the hydrogen bonds do not break so water forms a more rigid structure - ice.
Ice is less dense so it floats on water creating an insulating layer, and keeping the temperature below is at constant.
Water as a solvent?
Water is polar so it acts as a solvent with any other polar molecules
carbon-containing molecules dissolve by forming hydrogen bonds with the water hydroxyl groups
How does water’s ability to act as a solvent help living organisms?
As water can dissolve polar molecules and ions, water can act as a transport medium, transporting the necessary molecules easily around living organisms.
Water also allows chemical reactions to take place within the cell and allow molecules to be dissolved in the cytosol
How do water’s cohesive and adhesive properties help living organisms?
As water form hydrogen bonds that pull towards each other water is cohesive (cohesion) This creates water tension that some organisms use to ‘skate’ over the top.
As water also has adhesive properties water can stick to surfaces. due to this, water can move up narrow tubes - in the xylem or vascular tissues of plants.
Why is water’s polarity useful?
Non-polar substances cannot be dissolved in water. This is an important property of the phospholipid bilayer.
Why does carbon make a good building block?
Because it can form up to 4 covalent bonds (electron pairs) These bonds are stable and strong enough to make larger molecules.
What is a monomer?
A single small molecule that many combine with other monomers to build up larger molecules called polymers
What is a dimer?
A molecule formed of two monomers joined together by a condensation reaction
What is a polymer?
A large molecule build from many similar monomers joined together by covalent bonds to form a chain or branched chain
What type of bonding do carbohydrates use?
Glycosidic bonds
What reaction produces or breaks glycosidic bonds?
A condensation reaction produces glycosidic bonds while a hydrolysis reaction breaks them.
What is a condensation reaction?
A chemical reaction where two molecules are joined together with by releasing a water molecule (a hydrogen from one and an OH from the other) to form a covalent bond and a larger molecule.
What is a hydrolysis reaction?
A chemical reaction where a covalent bond between a larger molecule is broken by the addition of a water molecule (an H goes to one and an OH to the other), ending in two smaller molecules.
How are polymers stabilized
Polymers are often large molecules and tend to be stabilized by many hydrogen bonds.
What is the function of carbohydrates?
Carbohydrates are an energy source for organisms though some carbohydrates are important structurally in plants e.g cellulose
What is the specific formula for carbohydrates?
(Cx(H20)y)
What are monossacharides?
Monosaccharides are the simplest carbohydrates formed from a singular sugar molecule
Properties of monosaccharides?
- they are a single molecule
- are sweet to taste
- soluble in water
- no glycosidic bonds
- exist and a single ring or straight chain
- their role is to release energy or act as monomers
