Chapter 1 - Biological Molecules Flashcards
What are biological molecules?
Particular groups of chemicals that are made up and used by living organisms
What is covalent bonding?
When atoms share one or more pairs of electrons in their outermost shell
What is ionic bonding?
The electrostatic force of attraction between two or more oppositely charged ions
What is hydrogen bonding?
Weak electrostatic bond caused when the negative region of one polarised molecule is attracted to the positively charged region of another
What is a polar molecule?
A molecule with an uneven distribution of charge
What are monomers?
Small, basic molecular unit that builds polymers
What are polymers?
Molecule made up of large numbers of monomer sub-units joined together
What is polymerisation?
Process of making polymers by joining monomers together
Give examples of industrial made polymers
Polythene and polyester
Give examples of naturally occurring polymers
Polysaccharides, polypeptides and polynucleotides
What is a condensation reaction?
A reaction that releases a molecule of water when it links molecules together.
What is a hydrolysis reaction?
A reaction that hydrolyses the chemical bond between monomers by the addition of water
What does the term metabolism mean?
All the chemical processes/reactions that take place in a living organism
Define mole
The amount of a substance that contains as many particles as there are atoms
What is a molar solution?
A solution that contains one mole of solute in each litre of solution
What is an ion?
A charged atom that has received or lost an electron
What is an isotope?
Atoms of the same element that have a different number of neutrons which results in a difference in mass
What three elements are carbohydrates made from?
Carbon, hydrogen and oxygen
What are the monomers that make up carbohydrates called?
Monosaccharides
What are monosaccharides and give examples
Simple sugars i.e. glucose, galactose and fructose
What are the isomers of glucose?
Alpha glucose and beta glucose
What are disaccharides?
Pairs of monosaccharides joined together by a glycosidic bond in a condensation reaction
Give examples of disaccharides
Maltose (glucose+glucose)
Lactose (glucose+galactose)
Sucrose (glucose+fructose)
What are polysaccharides?
Large molecules formed from combining many monosaccharides together by glycosidic bonds formed in a condensation reaction
Give examples of some polysaccharides
Starch, cellulose and glycogen
What is a reducing sugar?
A sugar that can donate electrons to (or reduce) another chemical
How do you test for reducing sugars?
Benedict’s Test
- Add equal amounts of sample and Benedict’s reagent, mix gently and heat for 5 mins
- Positive reaction=red precipitate formed of copper oxide
How is the test for reducing sugars semi-quantitative?
Has variation in the colour of the precipitate formed depending on how much reducing sugar is present
- Blue = none
- Green = very low
- Yellow = low
- Orange = medium
- Red = high
How do you test for non reducing sugars?
- Do the Benedict’s test and get a negative reaction
- Add equal volumes of food sample and dilute hydrochloric acid
- Heat for 5 mins (acid hydrolyses any disaccharides)
- Slowly add sodium hydrogen carbonate solution and check pH with pH paper to ensure solution is alkaline
- Re-test with Benedict’s reagent and heat for 5 mins
- Orange-brown precipitate formed when a non-reducing sugar is present
Where is starch located in organisms?
Found only in plants in the form of small grains and large amounts are found in the seeds and storage organs
What is the role of starch?
It’s main role is energy storage as plants store excess glucose as starch
How is starch produced?
Chains of alpha glucose monomers joined together by glycosidic bonds formed in a condensation reaction
Starch is a mixture of…
2 polysaccharides of alpha-glucose: amylose and amylopectin
Describe the structure of amylose
Long, unbranched chain of alpha-glucose that is wound into a tight coil
Describe the structure of amylopectin
Long, branched chain of alpha-glucose monomers
Describe how the structure of starch relates to its function
- Insoluble - doesn’t affect water potential
- Large - does not diffuse out of cells
- Compact (when coiled) - lots of energy stored in small spaces
- Amylopectin branches - provide more area for enzymes to act on and break down the glycosidic bonds easily so glucose is released rapidly
Alpha glucose molecules are formed by what type of glycosidic bonds?
1,4 and 1,6 glycosidic bonds
Where is glycogen located in organisms?
Found in animals and bacteria and is stored as small granules in the liver and muscles
Describe glycogen’s structure
Shorter and more highly branched polysaccharide chains of alpha-glucose
Describe how glycogen’s structure relates to its function
- Insoluble - does not affect water potential or diffuse out of the cell
- Compact - lots stored in small spaces
- Lots of branches and shorter chains - more area for enzymes to act on so stored glucose can be released very quickly, important for animals with high metabolic and respiratory rates
Describe the test for starch
Add iodine solution to a sample and if it reacts with starch it produces a blue-black colouration from yellow
Describe the structure of cellulose
Long, straight, unbranched chains of beta-glucose that run parallel to each other that allows hydrogen bonds to form cross-linkages between chains which results in the formation of microfibrils that group together in parallel to make fibres
What is the purpose of cellulose?
Provides rigidity and support to plant cells as it is a major component in the cell wall
How does cellulose prevent the cell from bursting as water enters the cell by osmosis?
Experts an inwards pressure that stops any influx of water so it makes the plant cell turgid
Why is it important that stems and leaves are in a turgid state?
To provide maximum surface area for photosynthesis
