carbs and lipids Flashcards
biological molecules
what are the 5 biological molecules?
- carbohydrates
- lipids
- proteins
- DNA/RNA
- water
what are monomers?
individual units that makes up a polymer
what are polymers?
many repeating units of monomers
what are some examples of monomers?
- nucleotide
- monosaccharide e.g. glucose
- amino acids
what is the definition of a condensation reaction?
when 2 molecules join together to form a chemical bond which releases a water molecule
what is the definition of a hydrolysis reaction?
2 molecules separated to break a chemical bond using a water molecule
what are some examples of a polymer?
- polynucleotide (DNA/RNA)
- polysaccharide e.g. starch
- polypeptide (protein)
why are lipids not polymers?
because its not made from many repeating units of monomers, therefore it cant be a polymer
what is the chemical formula of the molecule that is produced by a condensation reaction?
C12H22O11
-not C12H24O12, it is initially when the 2 molecules joins together
but releasing one H2O
molecule (2 hydrogens and 1 oxygen) reduces the number of hydrogen and oxygen atoms.
what are monosaccharides? include examples
monomers from which larger carbohydrates are made.
e.g. glucose (alpha + beta), galactose, fructose
What is the name of this structure ?
alpha glucose
What is the name of this structure ?
Beta glucose
What structure is this ?
Galactose
describe the difference between the structure of alpha and beta glucose.
- they are isomers : same molecular formula but differently arranged atoms.
- OH group is below carbon 1 in alpha glucose but above carbon 1 in beta glucose
how are disaccharides formed ?
when two monosaccharides joins together via condensation reaction to form a glycosidic bond
what does 2 alpha glucose form?
maltose
what does glucose and fructose form?
sucrose
what does glucose and galactose make?
lactose
what is the structure of maltose?
What are polysaccharides and include some examples
Many monosaccharides joined together via condensation reaction to form glycosidic bonds.
E.g. starch, glycogen + cellulose
describe the function and structure of starch
- energy store in plant cells in the formation of grains
- polysaccharide of a-glucose
- some has 1,4-glycosidic bonds so is unbranched (amylose)
-some has 1,4 and 1,6- glycosidic bonds so is branched (amylopectin)
describe the function and structure of glycogen
- energy store in animal cells (cytoplasm) in the form on granules
-polysaccharides of many a-glucose joined via condensation reaction in the form of glycosidic bonds
-1,4 and many more 1,6 glycosidic bonds compared to starch - branched
describe the function and structure of cellulose
- provides strength and structural support to plant/algal cell walls
- polysaccharide of many b-glucose molecules joined via condensation reaction to form b-1,4 glycosidic bonds
- 1,4 bonds are straight and unbranched chains
-chains linked in parallel by hydrogen bonds, forming microfibrils
explain how the structures of starch relate to their functions
- large: cant diffuse out of cell
- insoluble: osmotically inactive
-helical : compact energy store ( helix shape due to the force of attraction between the positive and negative)
-branched: rapidly release a-glucose when needed
explain how the structures of glycogen relate to their functions
- large: cant diffuse out of cell
- insoluble: osmotically inactive
-helical : compact energy store
-branched: rapidly release a-glucose when needed - branched : compact/ fit more molecules in small area + more ends for faster hydrolysis which releases glucose for respiration to make ATP for energy release
explain how the structure of cellulose relates to its function
-every other b-glucose is inverted in a long, straight, unbranched chain
-parallel bonds can form hydrogen bonds (crosslinks) to form microfibrils (adds strength) which joins to form strong fibres - provides strength to plant cells
what are the reducing sugars?
- the monosaccharides : a/b glucose, galactose + fructose.
- the disaccharides: maltose + lactose.
(sucrose is the only non reducing sugar)
how does reduction happen?
-reduction is the gain of electrons (OIL RIG).
- oxidation is the loss of electrons
- a reducing sugar is able to lose an electron (oxidation) and give it to another compound
- we test reducing sugars by giving them something to reduce - benedict reagent
how does the solution of benedict turn from blue to red in the form of a chemical reaction?
simple term: the benedict solution is blue but when it gains an electron it turns red
what is the test for reducing sugars?
- add benedict solution (blue) to sample
- heat in a boiling water bath
- positive results : green/yellow/orange/red precipitate - increasing quantity of sugar
- results are SEMI- QUANTITATIVE
what is the test for non reducing sugars?
- get a negative benedict’s test - stays blue
- boil with HCL to hydrolyse into reducing sugars in a water bath. (normally with water but will require a lot more energy)
- cool and neutralise HCL with alkali using NaOH ( sodium hydroxide)
- add benedict reagent
- heat in a boiling water bath
- positive results: green/yellow/orange/red precipitate
describe the biochemical test for starch
- add iodine dissolved in potassium iodine (orange/brown) and shake/stir
- positive results: blue-black
suggest some methods to measure the quantity of sugar in a solution
- carry out Benedict’s test as above, then filter and dry precipitate
- find mass/weight
- colorimeter
diagram of how a colorimeter works
how to identify unknown glucose concentration?
- make sugar solutions of known concentrations ( e.g. dilution series)
- heat a set volume of each sample with a set volume of Benedict’s solution for the same time
- use a colorimeter to measure absorbance of light of each known concentration.
- plot calibration curve - concentration on X-axis and absorbance on y-axis then draw a line of best fit
- repeat Benedict’s test with unknown sample and measure absorbance
- read off graph to identify concentration of unknown solution
NOTE: using “amounts” is too vague to get the mark. must use “volume” instead
how does starch and glycogen act as energy stores?
they are made of a-glucose which is the substrate for respiration in cells. this produce ATP for energy release
TRUE OR FALSE
cellulose is strong because of hydrogen bonds
FALSE - hydrogen bonds are weak individually but strong in high numbers. (you need to specify there are many hydrogen bonds)
what are lipids used for?
- energy store
- insulation ( thermal, electrical - myelin sheaths cover nerves)
- water proofing ( waxy cuticle)
- protection (lipids covers heart + kidneys)
what are the 2 types of lipids?
- triglycerides
- phospholipids
describe the structure of a fatty acid (RCOOH)
- variable R-group - hydrocarbon chain ( could be saturated or unsaturated)
- COOH = carboxyl group
What structure is this?
Glycerol
Describe the difference between saturated and unsaturated fatty acids
- saturated - no C=C double bonds in hydrocarbon chain- all carbons fully saturated with hydrogen
- unsaturated - one or more C=C double bond in hydrocarbon chain (creating a bend/ kink)
Describe how triglycerides form
- 1glycerol molecule and 3 fatty acids
- 3 condensation reactions removing 3 water molecules
- forming 3 ester bonds
What is the general structure of triglycerides?
- consists of fats (solid at room temp) and oils (liquid at room temp)
- never bonds together
explain how the properties of triglycerides are related to their structure
- hydrophobic/ non-polar fatty acids- insoluble in water (clump together as droplets, tails inwards) : osmotically inactive so no effect on water potential of cell - waterproofing
-low mass to energy ratio : don’t have to carry heavy energy store - high ratio of H atoms to O atoms : water can be released during breakdown
- high ratio of energy storing of C-H bonds to carbon atoms in hydrocarbon chain: energy dense molecule - used in respiration to release more energy than the same mass of carbohydrates
what is the general structure of a phospholipid?
- the fatty acid tails are non-polar: electrons are evenly spread. the tails are hydrophobic
- the phosphate head is polar: delta positive and delta negative regions. This is an uneven distribution of electrons. The head is hydrophilic
What is the chemical structure of a phospholipid?
Diagram of what a phospholipid look like in water
- two layers : phospholipid bilayer
- a molecule with polar and non polar regions is called “AMPHIDATHIC”. This property is essential to form a phospholipid bilayer
describe the difference between the structure of triglycerides and phospholipids
one fatty acids of a triglyceride is substituted by a phosphate- containing group
NOTE: phosphate groups NOT phosphorus
describe how the properties of phospholipids relate to their structure
form a bilayer in cell membrane, allowing diffusion of lipid- soluble (non-polar) or very small substances and restricting movement of water-soluble (polar) or larger substances
explain how the structures of phospholipids relate to its function
- phosphate head are hydrophilic : attracted to water so point to water (aqueous environment) either side of membrane
- fatty acid tails are hydrophobic: repelled by water so point away from water/ to interior of membrane
- glycolipids can form: allows for cell recognition - protein/ carbs
Describe the test for lipids
- Add ethanol, shake (to dissolve lipids), then add water
- Positive result = milky white emulsion
