carbs & lipids Flashcards
(47 cards)
what is a monomer ?
a monomer is a smaller / repeating) unit / molecule from which larger molecules / polymers are made
a starch molecule has a spiral shape. Explain why this shape is important to its function in cells.
compact/occupies small space/tightly packed
the structure of cellulose is related to its role in plant cell walls. Explain how. (3)
long, straight, unbranched chains of Beta glucose
(joined by) many WEAK hydrogen bonds
form microfibrils / macrofibrils
provide rigidity/strength/support
give one feature of starch and explain how this feature enables it to act as a storage
substance
helical / spiral So compact / tightly packed / can fit (lots) into a small space
insoluble So no osmotic effect / does not leave cell / does not affect water potential
large molecule / long chain (So) does not leave cell / contains large number of glucose units
branched chains (So) rapid hydrolysis to remove glucose for respiration
hydrogen bonds are important in cellulose molecules, explain why
holds chains/cellulose molecules together/forms cross links between chains/cellulose molecules/forms microfibrils
providing strength/rigidity (to cellulose/cell wall)
weak Hydrogen bonds provide strength in large numbers
describe how lactose is formed and where in the cell it would be attached to a polypeptide to form a glycoprotein
glucose and galactose
joined by condensation
joined by glycosidic bond
added to polypeptide in Golgi
describe how the student would show that reducing sugars were present in a solution
- add Benedict’s;
- heat to 95°C;
- red/range/yellow/green precipitate (shows reducing sugar present);
describe how you would test a sample of food for the presence of starch.
- (mix / shake sample) with ethanol, then water and shake
- cloudy White / milky (emulsion)
omega-3 fatty acids are unsaturated
what is an unsaturated fatty acid?
double bond(s)
(bonds) between carbon atoms within the hydrocarbon chain
describe how an ester bond is formed in a phospholipid molecule
- condensation (reaction) OR loss of water
- between of glycerol and fatty acid
some seeds contain lipids
describe how you could use the emulsion test to show that a seed contains lipids (3)
- crush/grind
- with ethanol/ alcohol, to dissolve the lipid
- then add water then shake
- forms a white emulsion / goes white
what are the differences between a triglyceride and a phospholipid ?
- fatty acid removed
- replaced with a phosphate group
compare and contrast the structure and properties of triglycerides and phospholipids
both contain ester bonds
both contain glycerol
fatty acids on both may be saturated or unsaturated
both are insoluble in water
both contain C, H and O but phospholipids are also contain P
triglyceride has three fatty acids and phospholipids have two fatty acids plus phosphate group
triglycerides are hydrophobic/non-polar and phospholipids have hydrophilic and hydrophobic region
phospholipids form monolayer/micelle/bilayer but triglycerides don’t.
describe the biochemical tests you would use to confirm the presence of lipid, non-reducing sugar and amylase in a sample
lipid
1. add ethanol/alcohol then add water and shake/mix OR Add ethanol/alcohol and shake/mix then pour into/add water
2. white/milky emulsion OR emulsion test turns white/milky
non-reducing sugar
3. do Benedict’s test and stays blue/negative
4. boil with acid then neutralise with alkali
5. heat with Benedict’s and becomes red/orange (precipitate)
amylase
6. add biuret (reagent) and becomes purple/violet/mauve/lilac
7. add starch, (leave for a time), test for reducing sugar/absence of starch
A student carried out the Benedict’s test
suggest a method, other than using a colorimeter, that this student could use to measure the quantity of reducing sugar in a solution
- filter and dry (the precipitate)
- find mass/weight
What is a polymer? (1)
Polymers are large molecules made from joining 3 or more similar monomers together
What is a condensation reaction? (1)
removal of one water molecule which forms a bond
SPEC - joins two molecules together with the formation of a chemical bond and involves the elimination of a molecule of water.
What is a hydrolysis reaction? (1)
addition of one water molecule to break a bond
SPEC - breaks a chemical bond between two molecules and involves the use of a water molecule.
Give 2 examples of monomers (2)
Alpha/Beta glucose
Nucleotides
Amino acids
Give 2 examples of polymers (2)
Nucleic Acids
Cellulose
Starch
Protein
Name the bond formed between two monosaccharides within a condensation reaction (1)
Glycosidic bond
Draw the structure of alpha glucose (1)
Draw the structure of beta glucose (1)
https://www.aqa.org.uk/subjects/science/as-and-a-level/biology-7401-7402/subject-content/biological-molecules/carbohydrates
Which monosaccharides form maltose and which enzyme is used to hydrolyse maltose? (2)
Alpha Glucose and Alpha
Glucose
Enzyme - Maltase
Which monosaccharides form lactose and which enzyme is used to hydrolyse lactose? (2)
Alpha Glucose and Galactose
Enzyme - Lactase
