Biological Molecules !

how is water formed ?

a slightly negative oxygen bonds to 2 slightly positive hydrogens

what kind of molecule is water ?

a polar molecule

what bond forms between 2 water molecules ?

a hydrogen bond

what are the properties of hydrogen bonds ?

they are easily made + broken

why can photosynthesis occur underwater ?

light can pass through water as it is transparent 

why is ice useful for a habitat?

ice is less dense than water so ice floats + insulates water underneath 

why can water climb the xylem walls through capillary action?

water is adhesive, so it sticks to other polar molecules

why is water a good habitat?

it has a high specific heat capacity so it requires a lot of heat to change water’s temperature

why is water a good transport medium?

because it is a solvent so ions and other polar molecules dissolve in it

why can water climb the xylem walls as a body of water?

because water is cohesive so water molecules stick together

what is a monomer?

small molecules that build up to make larger molecules

what is a condensation reaction?

joining monomers together, creating water as a side product

what is a hydrolysis reaction?

breaking down a polymer, utilising water

what polymer does amino acids make?

proteins

what polymer does glucose make?

starch, glycogen and cellulose

what polymer do nucleotides make?

nuclear acids (DNA or RNA)

what do carbohydrates contain?

carbon, hydrogen and oxygen

what do carbohydrates do in organisms?

act as an energy source (respiration), an energy store (starch/glycogen) and a structure (cellulose)

what do 2 alpha glucoses make?

maltose

what do 3x alpha-glucoses make?

starch/glycogen

what do fructose and alpha-glucose make?

sucrose

what do alpha-glucose and galactose make?

lactose

what do 3x beta-glucoses make?

cellulose

what is a saccharide?

a sugar/carbohydrate

what is ribose used for?

to make nucleotides (which make up nuclear acids)

what is a pentose?

A monosaccharide with 5 carbon atoms.

what is glucose?

an energy source

how is glucose useful as an energy source?

• soluble → can easily be transported

• small molecule → can diffuse across cell surface membrane

• can bind to enzymes → readily respired to release energy

how is glucose turned into a storage molecule (starch/glycogen)?

its polymerised through condensation reactions

what is a feature of polysaccharides ?

they’re insoluble (can’t dissolve in water)

what is a starch a storage molecule for?

plant cells

where is starch found?

in chloroplasts

what is starch made of?

amylose and amylopectin

what are features of amylose?

• makes up 80% of starch

• only made of 1,4 glycosidic bonds

• straight chain that coils into a helix

why is amylose efficient?

it is compact so more energy can be stored

what are features of amylopectin?

• makes up 20% of starch

• made of 1,6 and 1,4 glycosidic bonds

• is branched

why is amylopectin efficient?

• branched so more hydrolysis reactions can happen at once so more energy is released at once

what is glycogen a storage molecule for?

animal cells

what is the structure of glycogen ?

• branched like amylopectin

• has 93% (1,4) glycosidic bonds (meaning it has more branches)

why does glycogen have more branches than starch?

as glucose needs to be released faster in animal cells, for movement

what are properties of cellulose?

• 1,4 glycosidic bonds

• high mechanical strength

what is the structure of cellulose?

• straight unbranched chain (linked by hydrogen bonds) to form cellulose microfibrils

what are kind of molecule are lipids?

non-polar

why are lipids useful?

thermal/electrical insulation, protecting vital organs, makes up membranes, waterproofing (waxy cuticle on plants)

what are fats?

solid at room temperature (has more saturated fatty acids)

what are oils?

liquid at room temperature + (has more unsaturated fatty acids)

what does it mean for a fatty acid to be saturated?

has no double carbon bonds

why are triglycerides a good energy store ?

• compact → more energy stored

• insoluble in water → no effect on cell water potential

• generates 2x as much energy as carbohydrates (at the same mass)

what are triglycerides ?

lipids

why are triglycerides insoluble in water?

• long hydrocarbon chains that are non-polar.

• This means they cannot form hydrogen bonds

what are phosphate groups?

polar molecules ( making them hydrophilic)

what makes up cell membranes?

phospholipid bilayers

what part of the phospholipid bilayer is hydrophilic?

the top part (the phosphate group) as it is polar like water

what makes the phospholipid a selectively permeable membrane ?

only polar molecules can pass through

what are the roles of proteins ?

structure (keratin & collagen), storage, growth/repair, enzymes, protection (antibodies), hormones

what bond is formed between 2 amino acids?

peptide bonds

what bond is formed between glycerol and fatty acids or phosphate groups?

ester bonds

what are polypeptides?

long chains of amino acids held together by peptide bonds

where are polypeptides made?

ribosomes

what is primary structure of a polypeptide ?

the specific sequence of amino acids that form the protein

what is secondary structure of a polypeptide?

coiling/folding of the polypeptide due to the formation of hydrogen bonds

what is tertiary structure of a polypeptide?

3D shape of the protein molecule

what 2 types of secondary structure is there ?

alpha helixes and beta pleated sheets

how is the tertiary structure (the 3D shape) held together?

1. Disulphide bonds (strongest) 

2. Ionic bonds

3. Hydrogen bonds

4. Hydrophilic/phobic interactions (weakest)

what is quaternary structure ?

3D arrangement of MULTPLE polypeptide chains in a protein

what are globular proteins ?

spherical proteins that are soluble in water 

examples of globular proteins ?

insulin, enzymes and haemoglobin

why are globular proteins soluble in water ?

because polar amino acids are on the outside of the polypeptide chain

what are fibrous proteins ?

fibre shaped proteins that are insoluble in water

examples of fibrous proteins ?

elastin, keratin + collagen

why are fibrous proteins insoluble in water ?

because nonpolar amino acids are on the outside of the polypeptide chain