All biological molecules

What are the monomers that form carbohydrates?

Monosaccharides

What’s the bond that holds monosaccharides together?

Glycosidic bonds

What are the 3 monosaccharides that we need to know?

Glucose, Galactose, Fructose

What is a disaccharide and name the 3 disaccharides that we need to know along with the monomers they’re made of.

Disaccharide = made of two monosaccharides: Maltose = glucose + glucose; Sucrose = glucose + fructose; Lactose = glucose + galactose

What are the two isomers of glucose and how are they different in structure?

Alpha and beta glucose

What sort of sugar is glucose?

Hexose sugar

What are the 3 polysaccharides formed from glucose?

Starch, glycogen, cellulose

Name features, properties, and functions of starch.

Made of α-glucose, found in plants, energy store, short/compact/branched, insoluble so doesn’t affect water potential

Name features, properties, and functions of glycogen.

Made of α-glucose, found in animals, energy store, short/compact/branched, insoluble so doesn’t affect water potential

Name features, properties, and functions of cellulose.

Made of β-glucose, found in plant cell walls, provides strength/structure, long straight chains, forms microfibrils then fibres, hydrogen bonds

What’s the test for reducing sugars?

Heat with Benedict's reagent in water bath. Positive test: Blue → green → yellow → orange → brick red. Higher concentration of reducing sugar = more colour

What’s the test for non-reducing sugars?

Hydrolyse into monosaccharides with HCl in water bath, neutralise with sodium hydrogencarbonate, then perform Benedict's test as normal

What’s the test for starch?

Iodine test: Positive = brown/orange → blue/black

What are the two types of lipids?

Triglycerides and phospholipids

Describe structure and properties of triglycerides

3 fatty acid tails attached to glycerol head with ester bond formed in condensation reaction; energy stores (hydrocarbon tails release a lot of energy when broken); insoluble in water so don’t affect water potential; bundle together as droplets

Describe structure and properties of fatty acids

Fatty acids have R group (hydrocarbon chain) and carboxyl group joined to the carbon that forms an ester bond with the glycerol; fatty acid tails are hydrophobic which makes lipids insoluble in water

What's the difference between saturated and unsaturated fatty acids and which are liquids at room temp and why?

Saturated fatty acids have single bonds; unsaturated fatty acids have double bonds causing a kink and fewer hydrogen bonds between them, so the structure is no longer straight; unsaturated fats are liquid at room temperature, saturated fats are typically solid (e.g., butter)

Describe structure and properties of phospholipids

A phosphate group and 2 fatty acid tails attached to glycerol head with ester bond in condensation reaction

What’s the test for lipids?

Emulsion test: Add ethanol and shake for a minute; Positive test = cloudy milky emulsion

What’s the monomer that makes up proteins?

Amino acids

What’s the general structure of an amino acid?

Amine group, carboxyl group, R group and hydrogen joined to central carbon

What bond holds amino acids together?

Peptide bond

What makes up a dipeptide, polypeptide and protein?

Dipeptide = 2 amino acids; Polypeptide = more than 2 amino acids; Proteins = one or more polypeptides

What’s the primary structure of a protein?

Sequence of amino acids

What’s the secondary structure of a protein?

Primary structure/chain of amino acids coiled and folded with hydrogen bonds into an alpha helix or beta sheet

What’s the tertiary structure of a protein?

3D structure; Chain of amino acids coiled or folded further; Hydrogen and ionic bonds between dipoles on molecule; Disulphide bridges between sulphur atoms; Hydrophobic interactions

What’s the quaternary structure of a protein?

Several different polypeptide chains interacting together with prosthetic group (e.g., haem group in haemoglobin)

What are enzymes and their function?

Proteins and biological catalysts that lower the activation energy

How do enzymes increase rate of reaction through lowering activation energy?

Enzyme-substrate complexes formed; In a joining reaction, they hold the two substrate close reducing repulsion so they bond more easily; In a breakdown reaction, the active site puts strain on bonds and breaks/distorts them so they break up more easily

What are the two types of enzyme inhibitors and what is their function?

Competitive: similar shape as the substrate, occupy active sites so no more enzyme-substrate complexes are formed; Non-competitive: binds to an area that’s not on the active site and alters its shape so no enzyme-substrate complexes form

What’s the effect of increasing substrate concentration when competitive and non-competitive inhibitors are involved?

Competitive inhibitor: increases rate of reaction because it’s more probable for enzyme-substrate complexes to form; Non-competitive inhibitor: little effect because the inhibitor doesn’t compete with substrates but still prevents enzyme-substrate complexes

What are the 3 factors affecting enzymes and their rate of reaction?

Temperature (optimum usually 37°C, denatures after this causing active site to change shape); pH (optimum pH 7, can denature if too acidic or alkaline); Substrate concentration

Describe induced fit model

Substrate binds to active site and enzyme-substrate complex is formed; Active site shape is slightly changed to mould around the substrate and become complementary; Substrate bonds are broken/made/distorted to lower activation energy

What is DNA and RNA?

Both are kinds of nucleic acid that carry information

What are the monomers that make up DNA and RNA?

Nucleotides

What’s the general structure of a nucleotide?

Pentose sugar connected to a phosphate group and nitrogen-containing base

What are the bonds that hold together nucleotides and what sort of reaction joins them together?

Phosphodiester bonds form between the phosphate group of one nucleotide and the pentose sugar of another nucleotide in a condensation reaction

What’s the structure of a DNA nucleotide?

Deoxyribose sugar connected to a phosphate group and nitrogen-containing base; base could be adenine, thymine, cytosine, or guanine; A-T, C-G

What’s the structure of DNA?

Double helix structure with two long polynucleotide strands wound around each other; complementary bases held together by hydrogen bonds; sugar-phosphate backbone along antiparallel strands

What’s the structure of RNA and the RNA nucleotide?

Ribose sugar connected to phosphate group and nitrogen-containing base; uracil instead of thymine; A-U, C-G; nucleotides form a single polynucleotide strand (not double) and RNA strands are much shorter than DNA polynucleotides

Why did many scientists doubt that DNA carried the genetic code?

Because of its relative simplicity

Why does DNA need to replicate?

DNA clones before cell division so new cell has full amount of DNA

Through what ‘method’ does DNA replicate?

Semi-conservative replication

Describe the process of semi-conservative replication

DNA helicase breaks hydrogen bonds between bases on two polynucleotide chains forming two single strand templates; Free-floating DNA nucleotides are attracted to their complementary exposed bases (A to T, C to G); DNA polymerase joins adjacent nucleotides in condensation reaction sealing the phosphodiester backbone and hydrogen bonds form between the bases

What are the enzymes involved in semi-conservative replication?

DNA helicase and DNA polymerase

What’s the conservative model?

Original DNA molecule remains intact and a separate copy is made from completely new nucleotides

What is the semi-conservative model?

The original DNA strand splits into two, then acts as a template for each to become full strands; therefore, two new molecules both have half of the original DNA

What’s the role of ATP?

Energy store because cells can’t get energy directly from glucose

What’s the structure of ATP?

A nucleotide derivative made up of a ribose sugar, adenine base, and 3 phosphate groups

Where is the energy stored in ATP?

In the high energy bonds between phosphate groups

How is the energy in ATP released?

By breaking the phosphate group bond in a hydrolysis reaction

What happens when ATP is broken down?

ATP becomes ADP (adenosine diphosphate) and an inorganic phosphate (Pi)

Why is energy released from ATP?

Because the bond between phosphate groups is broken

What enzyme catalyses the breakdown of ATP?

ATP hydrolase

How can ADP be resynthesised into ATP?

By a condensation reaction between ADP and inorganic phosphate

What enzyme catalyses the resynthesis of ATP?

ATP synthase

What other function does inorganic phosphate have?

It can be added to a compound (phosphorylation) to make the compound more reactive

Why is water important in reactions?

Water is included in many reactions in the body, such as hydrolysis and condensation

Why is water being a solvent a useful property?

most metabolic reactions take place in a solution

Why does water have a high specific heat capacity and why is it helpful?

Water sticks together with hydrogen bonds, so it takes more energy to break the bonds rather than heating the water molecules; this helps buffer against sudden temperature changes

Why is water’s high specific heat capacity important for organisms?

It keeps conditions stable for enzymes and cellular processes, counteracts rapid temperature changes

What is latent heat of vaporisation in water?

Hydrogen bonding gives water a high latent heat of vaporisation, meaning it requires a lot of energy to turn liquid into gas

Why is high latent heat of vaporisation useful for organisms?

It allows sweating to cool organisms down as sweat evaporates

What is cohesion in water?

Water molecules stick together because they are polar, creating cohesion

Why is cohesion important in water?

It helps water flow, e.g., in the transpiration stream in plants

What is surface tension in water?

Strong cohesion at the surface creates high surface tension, allowing small insects to walk on water and sweat to form droplets

Why is water polar?

Oxygen is more electronegative than hydrogen, so it pulls the shared electrons closer, giving oxygen a slightly negative charge and hydrogen a slightly positive charge

What is hydrogen bonding in water?

Occurs between a slightly positive hydrogen atom in one molecule and a slightly negative oxygen atom in another molecule

What are positive ions called?

Cations

What are negative ions called?

Anions

Where are iron ions found in haemoglobin?

Fe²⁺ ions are in the centre of the 4 polypeptide chains that make up haemoglobin

What part of haemoglobin binds to oxygen?

The Fe²⁺ ion binds to oxygen, temporarily becoming Fe³⁺ until oxygen is released

What determines pH in the body?

The concentration of H⁺ ions

How does more H⁺ ions affect pH?

More H⁺ ions = lower pH = more acidic

Why are hydrogen ions important?

pH affects enzymes and enzyme-controlled reactions

What is the role of sodium ions?

Na⁺ ions help co-transport glucose and amino acids

What happens when a phosphate ion is attached to a molecule?

It becomes a phosphate group

What is the role of phosphate groups in DNA and RNA?

They allow nucleotides to join together

What is the role of phosphate groups in ATP?

Bonds between phosphate groups store energy