biological molecules flashcards

define monomers

define monomers

single repeating units from which polymers are made up of

define polymers

large, complex molecules composed of long chains of monomers joined together (in a condensation reaction)

what are three examples of monomers

amino acids, nucleotides, monosaccharides

what are three examples of polymers

protein, DNA, starch

what is a condensation reaction

the formation of larger biological molecules (polymers) from smaller molecules (monomers). in each reaction, a water molecule is produced and a bond is formed.

what does the condensation of amino acids produce

proteins

what does the condensation of two monosaccharides produce

a disaccharide

what does the condensation of many monosaccharides produce

polysaccharides

what does the condensation of fatty acids + monoglycerides produce

lipids

what is a hydrolysis reaction

the breakdown of large biological molecules into smaller molecules due to bonds being broken by the addition of water molecules

why are polymers hydrolysed

monomers can easily diffuse into cells or be transported using protein channels, whereas polymers can’t

what does the hydrolysis of a protein produce

amino acids

what does the hydrolysis of a carbohydrate produce

disaccharides + monosaccharides

what does the hydrolysis of lipids produce

fatty acids + monoglycerides

what’s a disaccharide

two monosaccharides joined together by a glycosidic bond

what’s a monosaccharide

a simple sugar (e.g. glucose), composed of one monomer

what’s a polysaccharide

many monosaccharides joined together by glycosidic bonds

what’s a covalent bond

a chemical bond in which two atoms share a pair of electrons (one from each atom)

what’s a hydrogen bond

a chemical bond formed between the positive charge on a hydrogen atom + the negative charge on another atom of an adjacent molecule

define isomer

molecules with the same molecular formula as each other, but a different arrangement of atoms (e.g. alpha glucose and beta glucose)

what atoms are carbohydrates made up of

carbon, hydrogen + oxygen

name three disaccharides

maltose, sucrose + lactose

what monosaccharides is maltose made up of

glucose + glucose

what monosaccharides is sucrose made up of

glucose + fructose

what two monosaccharides is lactose made up of

glucose + galactose

what’s the chemical formula of glucose

C6H12O6

name three monosaccharides

glucose, galactose and fructose

what type of sugar is glucose

a hexose sugar

how many carbon atoms does each glucose molecule have

6

what are three examples of polysaccharides

starch, glycogen + cellulose

what is the test for reducing sugars

add Benedict’s reagent + heat in a water bath (positive result= blue to brick red)

which sugars are reducing sugars

• all monosaccharides:

  • glucose

  • galactose

  • fructose

• some disaccharides:

  • lactose

  • maltose

what colour change will there be for a positive result for testing for reducing sugars

blue to brick red

what is the test for non-reducing sugars

• boil in dilute hydrochloric acid

• neutralise by adding sodium hydrogen carbonate

• add Benedict’s reagent

• positive result= blue to brick red

name a non-reducing sugar

sucrose

what does adding hydrochloric acid to a non-reducing sugar do

a hydrolysis reaction occurs, breaking the glycosidic bond + producing glucose + fructose (two reducing sugars)

name three examples of polysaccharides

starch, cellulose + glycogen

what monosaccharide is starch made from

alpha glucose

what is the function of starch

it’s the main energy storage material in plants (it’s broken down into glucose by plants when they need more energy)

where is starch stored in plants

seeds

what are the features of starch

• insoluble in water so doesn’t affect cells water potential

• helical + compact so lots can be stored in a small space

• has branched chains which can be easily hydrolysed to quickly release glucose for respiration

what is the test for starch

add iodine solution (positive result= colour change from orange to blue/black)

what monosaccharide is glycogen made from

alpha glucose

what is the function of glycogen

main energy store material in humans/ animals

what are the features of glycogen

• highly branched so can be rapidly hydrolysed to release glucose for respiration (glycogenolysis)

• compact so lots can be stored in a small space

what monosaccharide is cellulose made from

beta glucose

what is the function of cellulose

major component of cell walls in plants

what are the features of cellulose

• long unbranched chains

• cellulose chains linked together by hydrogen bonds to form microfibrils, which provide structural support

what methods can be used to measure the concentration of reducing sugars

• filter, dry + weigh precipitate

• test light absorbance using a colorimeter

what atoms are lipids made of

carbon, hydrogen + oxygen

what are the two main groups of lipids

triglycerides + phospholipids

what are triglycerides made of

three fatty acids and one glycerol molecule joined together in a condensation reaction

what type of bonds are formed between the glycerol molecule + fatty acids in a triglyceride

ester bonds

how many molecules of water is released per triglyceride formed

three because one water molecule is released per ester bond

what are the fatty acid tails made of

hydrocarbons

are the fatty acid hydrocarbon tails in triglycerides hydrophobic or hydrophylic

hydrophobic

why are lipids insoluble in water

the fatty acid hydrocarbon tails are hydrophobic (they repel water molecules)

what varies in fatty acids

the hydrocarbon (R group)

what are the two kinds of fatty acid

saturated + unsaturated

what are saturated fatty acids

a fatty acid with no double bonds between the carbon atoms in the hydrocarbon chain of the fatty acid

what are unsaturated fatty acids

a fatty acid with at least one double carbon to carbon bond in the hydrocarbon chain of the fatty acid

what’s the function of triglycerides

chemical energy is stored in the fatty acid hydrocarbon tails, so lots of energy is released when triglycerides are broken down

do carbohydrates or lipids have more energy

lipids have twice the amount of energy per gram as carbohydrates

how do lipid droplets form

the insoluble triglycerides crowd together as droplets because the hydrophobic fatty acid tails face inwards

define hydrophilic

water loving

define hydrophobic

water hating

what are phospholipids made of

• 1 glycerol molecule

• 2 fatty acids

• 1 phosphate group

what’s the difference between triglycerides and phospholipids

one of the three hydrophobic fatty acid tails in a triglyceride is replaced by a hydrophilic phosphate group in a phospholipid

is the phosphate group in a phospholipid hydrophobic or hydrophilic

hydrophilic

are the fatty acid tails in a phospholipid hydrophobic or hydrophilic

hydrophobic

which part of a phospholipid is hydrophobic + which part is hydrophilic

the tail is hydrophobic + the head is hydrophilic, so tails face inwards + heads face outwards

what is the test for lipids

emulsion test:

• shake with ethanol

• add water

• positive= white, milky emulsion

what’s the function of triglycerides

energy storage molecules

what’s the function of phospholipids

they make up the bilayer of cell membranes (which control what enters + leaves the cell)

how does the structure of triglycerides relate to their function

• long hydrocarbon tails of fatty acids contain lots of chemical energy + this is released when they’re broken down (lipids contain twice amount of energy per gram as carbohydrates because of tails)

• insoluble, so don’t affect a cells water potential. triglycerides clump together as insoluble droplets because fatty acid tails are hydrophobic (tails face inwards + glycerol heads face outwards)

how does the structure of phospholipids relate to their function

• hydrophilic heads + hydrophobic tails, so they form a double layer with heads facing outwards on either side

• centre of the bilayer is hydrophobic, so water soluble substances can’t easily pass through it

what are dipeptides

two amino acids joined together by a peptide bond in a condensation reaction

what are polypeptides

many amino acids joined together by peptide bonds in a condensation reaction

what is the structure of amino acids

central carbon atom with 4 groups of atoms bonded to it:

• amine group (NH2)

• carboxyl group (COOH)

• hydrogen group (H)

• R group

how many different types of amino acids are there

20

what bonds form between amino acids

peptide bonds

how is a protein formed

• condensation reaction

• peptide bond forms between the carboxyl group of one amino acid + the amine group of a second amino acid

• a water molecule per bond is released as a by product

what are the functions of proteins

• enzymes

• antibodies

• transport proteins (e.g. channel proteins which transport molecules that are too large to diffuse freely or molecules that carry a large charge)

• structural proteins (e.g. collagen and keratin)

what is the test for proteins

add Biuret solution (positive result= colour change from blue to purple)

what colour change is observed for a positive Biuret test for proteins

blue to purple

define primary structure of proteins

sequence of amino acids in the polypeptide chain

what is the primary structure of a protein determined by

the gene encoding the protein

what is the importance of a proteins primary structure

• a change in the nucleotide sequence of the gene’s coding region may lead to a different amino acid being added to the polypeptide chain

• a change in the amino acids in a protein could change the protein’s structure and function

define secondary structure of proteins

the way in which the polypeptide chain coils into a helix (alpha helix) or folds into pleats (beta pleated sheet)

what are the two most common secondary structures of proteins

alpha helix or beta pleated sheet

what makes a polypeptide coil or fold

hydrogen bonds which form between amino acids in the polypeptide chain

what makes the secondary structure of proteins stable

individual weak hydrogen bonds between amino acids are weak, but there are many bonds throughout the molecule

define tertiary structure of proteins

when the secondary structure is coiled or folded further to form 3D shapes

what holds together the tertiary structure of a protein

• ionic bonds (attractions between negative + positive charges on different parts of the molecule)

• hydrogen bonds (between amino acids)

• disulfide bridges (form when two molecules of amino acid cysteine come close together)

define quaternary structure of proteins

when many different polypeptide chains are held together by bonds to form a complex quaternary structure

how do you know if a protein has a quaternary structure

it consists of more than one polypeptide chain

what is the structure of haemoglobin

four polypeptide chains + four prosthetic haem groups

what are enzymes

proteins which catalyse reactions (biological catalysts)

what is a catalyst

an substance which speeds up a chemical reaction without being used up itself

how do enzymes speed up chemical reactions

they lower the activation energies of chemical reactions by binding to the reactant molecules (substrate) + allowing the chemical bond-breaking + bond-forming process to happen more easily