Unit 1

What is the function of Hydrogen Carbonate (HCO^3-)

Natural Buffer

Why are buffers important?

They help prevent pH changes, e.g., in the blood where the pH must be maintained so not to affect biochemical reactions

Chemical compounds are either:

* Organic (complex carbon-containing)
* Inorganic (all other simpler compounds)

Water has a _ _ between hydrogen atoms and oxygen atoms

Covalent bond

Water is a _ molecule as it carries charges

polar

Water is a dipole, what does this mean?

It has 2 areas of opposite charge

What sort of bond holds multiple water molecules together?

Hydrogen bonds

The attraction between water molecules due to hydrogen bonds makes water?

Cohesive

What are the 5 main properties of water?

* solvent
* specific heat capacity
* Latent heat of vaporisation
* density
* surface tension

Water is a good solvent due to its dipoles, this means...

It will dissolve anything with charges

What is surface tension

The strong force which causes the surface of a liquid to take up as little space possible

What is the function of Sodium? Potassium? (Na+, K+)

* determines solute concentration in cells
* Maintains electrical gradients across neurones

What is the function of calcium (Ca^2+)

* Forms and maintains bones and teeth
* Important in blood clotting and muscle contraction
* Important part of the middle lamella of plant cell walls

What is the function of magnesium (Mg^2+)

* Essential in giving chlorophyll its light-absorbing qualities
* Activates enzymes

What is the function of Iron (Fe^2+, Fe^3+)

Part of the haem group (haemoglobin)

What is the function of Nitrate (NO3-)

* Nitrogen is used to make proteins
* Nitrate is a component of amnio acids, nucleic acids and chlorophyll

What is the function of Phosphate (PO4^3-)

* Cell membranes (phospholipids)
* ATP
* proteins and Nucleic acids
* Buffer

What is a buffer

chemical or substance that controls changes in pH

Organic compounds contain what 3 atoms?

* Oxygen
* Hydrogen
* Carbon

What are the 4 main groups of organic molecules?

* carbohydrates
* lipids
* proteins
* nucleic acids

Carbohydrates range in complexity

* monosaccharides
* disaccharides
* polysaccharides

Glucose and fructose share the same molecular formula, this makes them...

Isomers

How are monosaccharides classified?

By the number of Carbons they contain

What classification do sugars glucose and fructose get?

hexose sugars

What are the 2 forms of glucose called?

Alpha and Beta

How do alpha and beta glucose differ?

The position of the hydroxide (OH)

What is an advantage of having 2 forms of glucose?

It gives a greater variety in the polysaccharides that glucose can form

How is a disaccharide formed?

Condensation reaction between 2 monosaccharides

Why are disaccharides more useful than monosaccharides?

* Easier to store
* More suitable for transport

What monosaccharides make up maltose, sucrose, lactose?

* Alpha glucose + alpha glucose
* Alpha glucose + fructose
* Alpha glucose + galactose

Name the bond formed when a disaccharide forms?

Glycosidic bond

A polysaccharide is formed when?

Many monosaccharides join via condensation reactions

What are the 2 ways alpha glucose can be bonded?

* 1-4 glycosidic bond
* 1-6 glycosidic bond

What does amylose look like?

* long
* spiraled chains
* 1-4 glycosidic bonds

What does amylopectin look like?

* Spirals with branching
* mixture of 1-4 and 1-6 glycosidic bonds

What is starch made from?

long chains of alpha glucose molecules which spiral and branch, mixture of amylose (20%) and amylopectin (80%)

Where is starch found?

Cytoplasm of most plant cells, inside chloroplasts→as starch grains

How is starch adapted for storage in plants?

* Compact - folded
* Insoluble - doesn't affect water potential
* Branched - terminal ends - readily hydrolysed
* Large - cannot diffuse through cell membrane

Glycogen is the storage of carbohydrates in...

animal and fungal cells

Where is glycogen stored (animals)?

Muscle and liver cells → as small granules

Glycogen is more branched than starch why is this useful?

there are more terminal ends available that can be hydrolysed to provide energy for respiration

What sugar molecule is cellulose made from?

Beta glucose

Where is cellulose found?

Plant cell walls

What structure does cellulose have?

Straight - unbranched due to alternate beta glucose molecules are rotated through 180

What sort of links join beta glucose molecules together?

Cross-links (hydrogen bonds)

What do these links make cellulose?

Tough and has great tensile strength due to its cross-links

Why can’t humans digest cellulose?

We do not have the enzyme cellulase, which digests cellulose

What atoms do lipids contain?

* Carbon
* Hydrogen
* Oxygen

How do lipids differ from carbohydrates?

Higher proportion of hydrogen to oxygen

What are the 2 main types of lipids?

Triglycerides, Phospholipids

What are the functions of triglycerides?

* store/supply energy
* insulation
* protection

What are the functions of phospholipids?

* composition of structures - plasma membranes
* pulmonary surfactant

How are triglycerides formed?

condensation reactions between 1 glycerol molecule and 3 fatty acid molecules

What is a saturated fat?

* No double carbon bonds
* contain the max no. of hydrogen atoms

What are unsaturated fats?

* contains double carbon bonds
* does not have the max no. of hydrogen atoms

What does mono/polyunsaturated fats mean?

* Monounsaturated → 1 double carbon bond
* Polyunsaturated → > 1 double carbon bond

What makes up a phospholipid?

* 1 glycerol molecule
* 2 fatty acid molecules
* 1 phosphate group

Why are phospholipids good for plasma membranes?

* The phosphoric acid head is polar/hydrophilic
* the fatty acid tails are non-polar/hydrophobic
* forms a bilayer

What are proteins made from?

amino acids → building blocks,each amino acid has an amino acid group (NH2) and a carboxyl group (COOH)

Proteins contain what elements?

* Carbon
* oxygen
* hydrogen
* nitrogen
* sometimes sulphur

What are the functions of proteins?

* Control chemical reactions and metabolic processes
* Formation of structures e.g. connective tissue
* Immune system
* Source of energy during starvation
* Important as buffers

What does the R group do?

* Determines how it folds - 3D shape
* Determines properties - soluble

2 amino acids join to form a...

dipeptide via a condensation reaction

What is the bond between amino acids called?

peptide bond

More amino acids joining together create?

polypeptide chains

What is a protein made from?

One or more polypeptide chains - folded, branched or cross-linked

What is primary structure?

The sequence of amino acids

What is secondary structure?

The way the amino acid chain folds to make shapes

What 2 ways can secondary structure be described?

* Alpha helix
* Beta pleated sheet

What is tertiary structure?

* Further folding to form a complex 3D shape
* R groups form bonds holding the 3D shape

What bonds are involved in tertiary structure?

* Hydrogen
* ionic
* disulphide
* hydrophobic interactions

What is quaternary structure?

2 or more polypeptide chains bonded together

What are globular proteins?

polypeptide chains folded to form spherical shape, usually soluble, complex tertiary structure, sometimes quaternary

What are fibrous proteins?

long parallel fibres of polypeptide chains cross-linked, insoluble and have structural role, secondary structure

What is a conjugated protein?

a protein with another molecule (non-protein, prosthetic group),

e.g. Glycoproteins - mucin, lipoproteins, nucleoproteins

What type of proteins are enzymes?

* Globular proteins
* Tertiary structure - hydrogen and ionic bonds create specific active site
* become denatured when H bonds break

How do prions form?

Secondary folding of proteins goes wrong

What are prions?

mis-folded proteins that are infectious and can replicate

Prions cause what sort of disease?

Neurodegenerative

Prions cause...

* impairs brain function
* changes in memory, personality and behaviour
* decline in intellectual function
* difficulty co-ordinating movements

How can proteins begin to mis-fold?

PrP can spontaneously change,mutations in DNA can code for prion protein,eating contaminated meat

What are 3 examples of prion diseases?

* Scrapie - sheep
* bovine spongy encephalopathy (BSE) - cows
* creutzfeldt-jakob disease (CJD) - Humans

Why are viruses termed 'obligate parasites'?

Can only reproduce inside a host cell,cause disease in the host cell

What is a bacteriophage?

A virus that attacks bacterial cells, they contain DNA inside a protein coat (capsid)

How does a bacteriophage infect a bacterial cell?

* Tail fibres attach to bacterial cell surface
* base plate is pinned to cell surface
* helical protein contracts to force core into bacterial cell
* This injects the viral DNA into the host cell
* DNA codes for new viral protein coats to be produced
* Replicated DNA goes inside protein coats to form new viruses
* Eventually the bacterial cell undergoes lysis and the new viruses infect other cells.

HIV is a retrovirus, what does this mean?

HIV contains RNA instead of DNA

What does HIV do once inside the helper T cell?

* Uses enzyme reverse transcriptase to make its RNA into DNA
* the HIV DNA is incorporated into the host cell DNA
* Host cell starts to make new HIVs

What does HIV do to the body?

* HIV attacks specific lymphocytes, helper T cells
* HIV takes over the T cells and damages the body's ability to fight off germs and diseases

What happens when the number of T cells falls to a very low number?

* People become more susceptible to other infections and certain types of cancer
* HIV develops into AIDS which is life-threatening and results in infections that cannot be fought and leads to death

How is HIV transmitted?

* Direct contact with blood or bodily fluids of an infected person
* During birth (mother to baby)
* During breastfeeding (mother to baby)
* Unprotected sex
* Sharing needles

How are viruses not true cells?

* Don't have cytoplasm or organelles
* inert unless they gain access to a living cell
* Cannot reproduce without a host cell

Similarities between bacteriophages and HIV

* Very small (nm) non-cellular
* Contain genetic material
* Protein coat

Differences between bacteriophages and HIV

* Shape
* Phages have tail fibres and base plate
* HIV has capsid inside phospholipid bilayer
* HIV has glycoproteins (120)
* HIV has reverse transcriptase
* Bacteriophages contain DNA, HIV has RNA

What is an enzyme?

A biological catalyst that speeds up metabolic reactions

What type of molecules are enzymes?

Globular proteins that have a precise 3D shape due to hydrogen, ionic and, disulphide bonds and hydrophobic interactions of tertiary structure

What is an active site?

the groove in an enzyme molecule to which the substrate binds

What makes enzymes specific?

the precise shape of the active site is complimentary to the substrate. The enzyme cannot catalyse other reactions

What is an anabolic reaction?

the build up of molecules

What is a catabolic reaction?

the breakdown of molecules

What is activation energy?

the amount of energy needed to initiate a reaction