lecture 3 - What are cells made of? Flashcards
what are some examples of macromolecules?
carbohydrates
lipids
proteins
nucleic acids
what are macromolecules?
- components of cells are contained in many types of food, and are polymers and monomers
- knowledge of these macromolecules not only informs you about cellular structure, but can also help inform your dietary choices
describe the synthesis of polymers
monomers form larger molecules called polymers through polymerisation: linking monomers together via dehydration reactions (know diagram)
describe the breakdown of polymers
polymers can be shortened b removing monomers from either end using a hydrolysis reaction:
- bond between residues 4 and 5 is cleaved in the presence of water: a hydrolysis reaction
what are carbohydrates?
Carbohydrates:
>serve as fuel and building material
> include both sugars and their polymers
> examples: mono-; di- and polysaccharides
what are monosaccharides?
- are the simplest sugars
- can be used for fuel
- can be converted into other organic molecules
- can be combined into polymers
- may be linear OR form rings when dissolved in water
what are Disaccharides?
- two monomers joined with a glycosidic bond
- maltose and cellobiose
what are polysaccharides?
polymers of glucose monomers
what is starch?
> starch
- a polymer of glucose monomers: major storage form of glucose in plants
- has (1-4) and a few (1-6) linkages (branching)
we can digest this, as the glucose monomers are in alpha-configuration.
what is glycogen?
> glycogen
- consists of glucose monomers: the major storage form of glucose in animals
- has (1-4) and frequent (1-6) linkages (branching)
- we can break this down to release glucose monomers (alpha configuration)
what is cellulose?
- is a major component of the tough walls that enclose plant cells
- note the group distribtion, linearity and packing potential
- 100 billion tonnes made annually
- mammals cannot digest this as glucose is in the beta configuration
what is the glycemic index and how does it work?
- a way of measuring how quickly your blood-glucose level rises after eating carbohydrate containing foods.
- the quicker the food is digested, the faster your blood glucose level rises –> higher GI
what is low GI?
- low GI foods usually contain unrefined carbs that are difficult to break down quickly
- low GI foods satisfy cravings for longer periods of time and have been linked to lowered risk of diabetes
what are glycoproteins?
- combination of proteins and carbohydrates
- usually found on cell surfaces
- combinations of carbohydrate units and protein chains can often be used as a unique identifier of types of cells
why are glycoproteins on the cell surface important?
- bacteria and viruses have unique cell-surface glycoproteins that are recognised by our immune system to ward off infection
- glycoproteins also present on cell surfaces of eukaryotic cells and can be used to differentiate between cell types.
what is chitin?
- is found in the exoskeleton of arthropods and the cell walls of fungi
- highly resistant to enzymatic digestion
- can be used as surgical thread
what are lipids?
a diverse group of hydrophobic molecules
- are found in cellular membrane structures, storage compounds etc.
what are lipids constructed from?
- two types of smaller molecules, a single glycerol and usually three fatty acid chains
- vary in length and number and locations of double bonds they contain
what are saturated fatty acids?
- have the maximum number of hydrogen atoms possible
- have no double bonds
what are unsaturated fatty acids?
have one or more double bonds
what are phospholipids?
- have only two fatty acids
- have a phosphocholine group (a phosphate derivative) instead of a third fatty acid
- consists of a hydrophilic ‘head’ and hydrophobic ‘tails’
- result in a bilayer arrangement found in cell membranes
what are proteins?
- meat, dairy, nuts and seeds, are all foods that are rich in protein
- a protein consists of one or more polypeptides (polymers of amino acids)
what are amino acids?
- are organic molecules possessing both carboxyl and amino groups
- differ in their properties due to differing side chains called R groups
- linked by peptide bonds. the peptide bond is very different from the glycosidic bond.
what are two examples where protein structure affects its function?
Collagen
- key component of cartilage, bone and skin tissue
- durable triple helix shape allows it to form strong and flexible fibres
Glutamate receptor
- binds to the neurotransmitter glutamate to relay signals within brain cells.
- top of Y shape ‘receives’ glutamate, bottom of Y embeds into cell surface.
what are the four levels of protein structure?
1) primary structure - amino acid sequence
2) secondary structure - alpha - helix
3) tertiary structure - alpha subunit
4) quaternary structure - multiple alpha subunits
what are enzymes?
- enzymes are a specific type of protein
- enzymes bind to substrates very specifically to catalyse a reaction.
- this specificity is determines by protein structure
what are the two enzyme models?
lock and key
induced fit
what are the properties of enzymes?
- enzymes are catalysts
- are catalytically active proteins
enzymes speed up metabolic reactions by lowering energy barriers (activation energy)
what are two examples of enzymes?
Phenylalanine hydroxylase - converts amino acid 'phe -->tyr' alcohol dehydrogenase - breaks down alcohol found in stomach lining and liver
