chapter 3 - biological molecules

what is a monomer?

smaller units that combine to make a large molecule (polymer)

what’s a polymer?

large molecule made up of many repeating units of monomers joined together by chemical bonds

what’s a condensation reaction?

removal of water to form a chemical bond between two molecules

what’s a hydrolysis reaction?

addition of water to break a chemical bond between two molecules

what’s an ion?

an atom with an electric charge

what’s an inorganic ion?

an ion that doesn’t contain carbon

what’s a cation?

an ion with a positive charge

what’s an anion?

an ion with a negative charge

what are the four types of molecules which cells of all living organisms primarily consist of?

carbohydrates, lipids, proteins and nucleic acids

what term describes carbohydrates, lipids, proteins and nucleic acids?

they are organic - meaning they contain carbon

what elements make up carbohydrates?

carbon, hydrogen and oxygen

what elements make up lipids?

carbon, hydrogen and oxygen

what elements make up proteins?

carbon, hydrogen, oxygen and nitrogen

what elements make up nucleic acids?

carbon, hydrogen, oxygen and phosphorus

what are most carbohydrates proteins and nucleic acids made of?

monomers

what is polymerisation?

process by which monomers join together to form polymers

monomer of carbohydrates

monosaccharides

monomer of proteins

amino acids

monomer of nucleic acids

nucleotides

polymer of carbohydrates

polysaccharides

polymer of proteins

polypeptides

polymer of nucleic acids

polynucleotides

what is the role of calcium ions?

nerve impulse transmission, muscle contraction and cofactor for enzymes

what is the role of sodium ions?

generating nerve impulses, muscle contraction, co-transport of glucose and amino acids

role of potassium ions?

generating nerve impulses, muscle contraction, regulating fluid balance

role of hydrogen ions?

determines the pH of solutions, used in photosynthesis reactions

role of ammonium ions?

source of nitrogen for plants

role of iron ions?

bind to oxygen within haemoglobin

role of chloride ions?

maintains blood pH in gas exchange, cofactor for amylase enzyme

role of phosphate ions?

component of nucleotides and phosholipids, bonds store energy in ATP

role of hydroxide ions?

determines the pH of solutions

role of nitrate ions?

source of nitrogen

role of hydrogen carbonate ions?

maintains blood pH

what is the structure of a molecule of water?

one oxygen atom joined to two hydrogen atoms held together by 2 covalent bonds

what term is used to describe how water has both positive and negative poles?

it’s dipolar

what is a hydrogen bond?

the force of attraction between the partially positive hydrogen and the partially negative oxygen

what happens to water molecules due to hydrogen bonding?

they stick together

what are the roles of water? x6

solvent, temperature control, cooling mechanism, habitat, metabolite, transport

what happens to ionic compounds as they are added to water?

they’re split apart and each ion is surrounded by water molecules so the compound dissolves

why is water being a solvent useful?

most biological reactions occur in solution and dissolved substances can be transported around the body

why is water resistant to rapid changes in temperature?

it has a high specific heat capacity

why does water having a high specific heat capacity make it useful?

allows the body to remain at a fairly stable temperature

what is meant by high latent heat of vaporisation and why does water have this property?

a lot of energy is needed to evaporate 1g of water due to hydrogen bonding between water molecules

why is it useful to water having a high latent heat of vaporisation?

organisms can use evaporation of water as a method of cooling without losing too much water

why is water a good habitat?

has a high specific heat capacity and high latent heat of vaporisation so it doesn’t change temperature or evaporate easily, providing a stable environment for many organisms to live in

why is ice less dense than water?

in ice water molecules are held further apart

why does ice floating form a useful property?

it creates an insulating layer at the surface of ponds and lakes, so water below this layer doesn’t freeze, allowing organisms within the water to move and survive

what reactions is water used in?

hydrolysis, condensation and photosynthesis

what is cohesion?

the tendency of water molecules to stick together via hydrogen bonds

what is adhesion?

tendency of water molecules to stick to other materials

what does strong cohesion and adhesion help water do?

flow through organisms and carry substances along with it

what happens when water molecules meet air?

create high surface tension

what are carbohydrates?

biological molecules that contain the elements carbon, hydrogen and oxygen

functions of carbohydrates

energy supply for cells, energy storage, structural components, cellular recognition, building blocks for biological molecules

how many subunits does a monosaccharide have?

one subunit (monomer)

how many subunits does a disaccharide have

two subunits (dimer)

how many subunits does a polysaccharide have?

many

examples of monosaccharides?

glucose, fructose and galactose

examples of disaccharides?

maltose, sucrose, lactose

examples of polymers?

glycogen, starch, cellulose

main function of monosaccharides?

energy source

main function of disaccharides?

transport form

main function of polysaccharides?

storage form

what are monosaccharides?

simplest form of carbohydrates known as simple sugars

how are monosaccharides classified?

according to the number of carbon atoms in each molecule

formula of glucose?

C6H12O6

what term is given to how glucose can be arranged in 2 different ways?

isomers

where is the hydroxyl group on carbon 1 in alpha glucose?

below the ring

where is the hydroxyl group on carbon 1 in beta glucose?

above the ring

properties of glucose

primary energy source in animals and plants, soluble, its bonds store lots of energy

why is glucose soluble and why is this useful?

the hydroxyl bonds can form hydrogen bonds with water so it can be transported around organisms

what happens to the energy stored in bonds of glucose when they are broken?

the energy is released

how are disaccharides formed?

when two monosaccharides join together in condensation reactions

where is maltose found?

in grains and cereals

where is sucrose found?

used as a transport sugar in plants

where can lactose be found?

main carbohydrate in milk

what are the monosaccharides which form maltose?

glucose and glucose

what are the monosaccharides which form sucrose?

glucose and fructose

what are the monosaccharides which form lactose?

glucose and galactose

what bond is formed when a disaccharide is formed?

glycosidic bond

how does a condensation reaction occur in monosaccharides?

hydroxyl group of one MS reacts with a hydroxyl group of another MS, forming a glycosidic bond and water molecule is released

how does a hydrolysis reaction occur in a disaccharide?

water molecule added to DS, breaking glycosidic bond to release the 2 MS

what is a polysaccharide?

complex carbohydrates made up of many monosaccharides joined by glycosidic bonds

what is starch used for in plants?

store excess glucose

when is starch hydrolysed?

when plants require energy

what two polymer chains make up starch?

amylose and amylopectin

what monomers make up starch, amylose and amylopectin?

alpha glucose

what is the structure of amylose

long, unbranched chain of alpha glucose joined by 1-4 glycosidic bonds

how does the angle of the glycosodic bonds in amylose impact the structure?

cause the chain to coil into a helix forming a compact structure

structure of amylopectin

long, branched chain of alpha glucose joined by both 1-4 and 1-6 glycosidic bonds

what allows enzymes to hydrolyse alpha glucose monomers easily in amylopectin?

its side branches

what does it mean that starch is insoluble?

doesn’t affect water potential so water doesn’t enter cells by osmosis

why is it important that starch is large

cannot diffuse out of cells

what happens to starch due to it having lots of side branches?

enzymes can hydrolyse the glycosidic bonds easily to rapidly release glucose

why is the feature that starch is coiled important?

makes it compact so a lot of glucose can be stored in a small space

what happens to the alpha glucose monomers released in hydrolysis reactions?

readily used in respiration

what is role of glycogen?

used by animals to store excess glucose

when is glycogen hydrolysed back into glucose?

when animals require energy

structure of glycogen

many alpha glucose monomers joined via 1-4 and 1-6 glycosidic bonds to form highly branched chains

features of glycogen

insoluble, compact, more highly branched than starch, large, hydrolysis releases alpha glucose