Chapter 1: Carbohydrates/Lipids Flashcards
What is the theory of evolution?
the theory that all organisms on Earth are descended from one COMMON ancestor and that they have changed over time
How can biochemistry be used as evidence for the theory of evolution?
this is because all animals share same biochemistry, no matter how diverse they are, so it proved that animals and plants have a common ancestor.
What are the definitions of monomers and polymers?
monomer- a small, basic molecular unit
polymer- a large chain made up of small repeating units
What is an isomer?
molecules with the same formula but are arranged in different ways
What is the general formula of a monosaccharide?
(CH₂O)ₙ
How are biological polymers formed?
by condensation reactions, which forms a chemical bond between monomers
releases a water molecule
How are biological polymers broken down?
by hydrolysis reactions
breaks the chemical bond between monomers
uses a water molecule
What are the monomers of carbohydrates?
monosaccharides
What are the two types of glucose?
alpha glucose
beta glucose
(need to be able to draw their structures!!!!)
Glucose is a _____ sugar?
hexose- a monosaccharide with six carbon atoms in each molecule
What type of bond is formed between two monosaccharides?
glycosidic bonds
1-4 is because the bond is formed between the first and the fourth carbon atom of the glucose mol.
How are the disaccharides maltose, sucrose and lactose produced?
(α) glucose + glucose == maltose (found in wheat)
(α) glucose + fructose == sucrose (1-2 glycosidic bond)
(β) glucose + galactose == lactose (1-4 glycosidic bond)
What are the two classifications of sugars?
reducing and non-reducing
this is dependent on their ability to donate electrons when in a copper sulfate solution (present in Benedict’s solution)
(ketone and aldehyde ability to donate electrons)
How to test for reducing sugars?
add Benedict’s solution to sample
HEAT it in a water bath
if positive, solution goes from blue to green/yellow/orange/brick-red (red being the most concentrated) (a red PRECIPITATE will be observed)
How to test for non-reducing sugars?
heat sample with dilute HCl
neutralise sol. with sodium hydrogencarbonate
then heat with Benedict’s reagent to the sample
if positive, colour change from blue to green/yellow/orange/brick-red
What is the test for starch (polysaccharide)?
add a few drops of iodine in potassium iodide solution to the sample
if starch present, solution will turn blue/black
Why do you add HCl in test for non-reducing sugar?
to allow ACID HYDROLYSIS to occur
breaks down bonds using acid
What are three properties of fructose?
its a simple sugar (monosaccharide)
- very soluble
- found in fruits
- sweeter than glucose
What are three properties of galactose?
- not as soluble as glucose
- has a role in the production of glycolipids and glycoprotein
What are two examples of pentose sugars?
ribose and deoxyribose
What is the function of starch and what two components make up starch?
it is used as an energy storage molecule in plants
- amylopectin
- amylose
What is amylose?
- it is a long ,UNbranched chain of alpha - glucose mol.
- coiled, helical structure
- compact (so it can store more mol. in the same place)
- joined by several alpha 1-4 glycosidic bonds
What is amylopectin?
- long, branched chain of alpha - glucose
- many branches means enzymes can reach glycosidic bonds quicker- so gl. can be released quicker
- has 1-4 (for chains) and 1-6 (for branches) alpha glycosidic bonds
- 1-6 bonds allow branches to be formed
How does starch affect water potential in cells?
it does not affect water potential because it is insoluble, makes it good for storage
What is cellulose used for?
it is used in plants for structural support
it is very strong and prevents cells from bursting
makes up the cell wall as it has great TENSILE stength
What is the structure of cellulose?
its a long, unbranched chain of BETA glucose mol.
forms 1-4 glycosidic bonds by every other monomer rotating 180°
the chains are linked by HYDROGEN bonds which then forms strong fibres-microfibrils, forms a MATRIX
What things make cellulose strong?
- hydrogen bonds that join the chains
- every other monomer is rotated
- microfibril fibres are very strong
What is glycogen used for?
energy store of glucose in animals
What is the structure of glycogen?
- it is made of alpha glucose mol.
- forms 1-6 glycosidic bonds
- very branched structure, so stored glucose can be released quicker because enzymes can act on glycosidic bonds easier
- its also a compact mol. so good for storage
Where is glycogen stored?
it is stored as small granules in the liver and muscles
How can you compare glycogen to starch?
density, solubility & rate of breakdown
-glycogen is less dense
-glycogen is also more soluble
-it is broken down quicker than starch
this proves that animals have higher metabolic requirements
Why is starch a good storage mol.?
- it is unbranched and coiled so compact, can fit more in smaller space
- insoluble
- large mol. so it can fit many glucose molecules into a smaller space
- amylopectin is highly branched so enzymes can have quicker access to the bonds, release the glucose faster
Why is it important to have two differing forms of glucose?
more biochemical advantages
greater diversity for chemical reactions as each isomer has its own advantages in reactions
e.g- alpha-gl, is better with storage
beta-gl. is better for structural support
What are two similarities between structure of starch and cellulose?
- both contain glycosidic bonds
- both are polysaccharides
- both have 1-4 links
What functional groups are inverted in cellulose?
the hydroxyl and hydrogen groups on every other monomer is inverted
What sugars are reducing sugars?
ALL monosaccharides and some disaccharides (e.g- maltose, lactose)
What is an example of a non-reducing sugar?
sucrose
What are two structural differences between glycogen and starch?
- starch is made up of amylose and amylopectin, but glycogen is just alpha-glucose
- glycogen is more highly branched
- *(optional)-glycogen has more terminal ends than starch
Describe how you could separate a mixture of monosaccharides in solution?
paper chromatography
a spot of sol. on chrom. paper and paper is suspended in a solvent
larger mol. move slower up the paper, travel less distance
sep. out into different spots
What is a serial dilution?
when you create a set of solutions that decrease in concentration by the same factor each time
What are the roles of lipids (5)?
- plasma membranes
- energy storage
- insulation
- protects delicate organs
- waterproofing- waxy cuticles -conserve water
What are triglycerides made of?
one glycerol molecule
3 fatty acids
What is the formula for glycerol?
C₃H₈O₃
What is the structure of a fatty acid?
long chain hydrocarbons
- contain a carboxylic group (COOH- double C=O bond)
- a varied hydrocarbon tail
What are the two types of fatty acids?
saturated- all single C-C bonds in the fatty acid chain
unsaturated- one or more C=C bonds in the fatty acid chain
mono-unsaturated (one C=C bond)
poly-unsaturated (two or more C=C bond)
What state are unsaturated fatty acids in?
liquid because of the double bond, they have a kink in their structure which means that they can’t be packed closely together (NOT A STRAIGHT chain)
saturated fatty acids have straight chains so all the mol. can pack closely together
How many types of fatty acids are there?
around 70 and they affect the triglyceride’s properties
How are triglycerides formed?
by condensation reactions, the fatty acids join to the glycerol and form an ESTER bond
the reaction happens between the carboxyl (fatty acids) and hydroxide (glycerol) groups
What is the structure of a phospholipid?
- 1 glycerol
- 2 fatty acids
- 1 phosphate group
What is a property of the fatty acid chains and the phosphate group?
fatty acid= non-polar: hydrophobic
phosphate group= polar: hydrophilic
What is the function of a phospholipid?
found in the cell membrane
makes up the phospholipid bi-layer membrane
What type of molecule is a phospholipid?
amphipathic (have a hydrophobic and hydrophilic part)
What are the properties of a triglyceride that help it carry out its function?
- function: energy storage molecule
- large fatty acid chain- many bonds that release energy when broken down/ high energy
- insoluble in water so it does no affect water potential
What are the properties of phospholipids that aid their function?
the centre of the layer is hydrophobic so water soluble substances can’t easily pass through it- the membrane acts as a barrier to those substances
What is the test for lipids?
emulsion test
- shake the sample with some ethanol
- then add some water to solution
- any lipid will show up as a milky emulsion
- the more lipid there is the more noticable the milky colour will be
What does hydrophobic mean?
repels water or does not mix with water
What substance (not an enzyme) is used to break down lipids?
water
water is needed in the reaction of hydrolysis
What does emulsion mean?
a milky suspension of tiny droplets
How should a sample be prepared for the emulsion test and why should it be prepared like this?
grind and crush sample into a powder to allow the lipids to be exposed to ethanol during shaking
Why do phospholipids assemble in a bilayer?
because the hydrocarbon tails are hydrophobic (non-polar) so they arrange toe-to-toe to minimise contact with water
How is glucose stored within the cell?
α-glucose mol. undergo a condensation reaction
1-4 glycosidic bonds to form chains
1-6 glycosidic bonds to form branches
condensation rxn. releases water molecules
and glycogen is formed
(When a question asks ‘how’ its asking for the PROCESS)
What is the formula for maltose?
C₁₂H₂₂O₁₁
What bond does a lactose molecule have ?
1-4 glycosidic bond
What bond does a sucrose molecule have?
1-2 glycosidic bond
What is the ideal temperature for an enzyme to work?
37℃
Why is glycogen a good storage molecule? (4)
- highly branched-so enzymes can reach glycosidic bonds faster and release glucose faster
- insoluble so it doesn’t affect water potential
- easily synthesised and broken down so it can respond rapidly to hormones (insulin and glucagon)
- compact structure- can fit more into a small storage granule
How are branched molecules advantageous for energy storage molecules?
- allows enzymes to reach glycosidic bonds faster and release glucose faster when needed
- allows for even more folding which gives it even more compactness
What is the feature that allows cellulose to form long chains?
in every other monomer, it is inverted
this is because in beta glucose, the -OH and -H are inverted
What is the product of incomplete digestion of cellulose?
methane
What is one similarity and a difference between glucose and fructose?
similarity: both are hexose sugars
difference: glucose has a six-atom ring
pentose has a 5-atom ring
What two ways can glycosidic bonds be broken?
enzyme hydrolysis
acid hydrolysis- boil the solution in a test tube with the acid
Why are storage molecules such as starch advantageous compared to glucose?
- insoluble so does not affect water potential
- highly folded so its a compact structure
- can easily be broken down
What is an unsaturated fatty acid?
- a long hydrocarbon chain
- one or more C=C double bonds in the chain
- it has a terminal COOH- group
What groups of lipids are present in nuts?
phospholipids and triglycerides
What does the R mean in COOHR-?
R means the hydrocarbon chain
Why is a white emulsion formed in the emulsion test?
because a triglycerides have non-polar fatty chains
therefore, it is hydrophobic
forms micelles in water
How is a phospholipid bilayer formed?
phospholipids have a polar (hydrophilic) head -phosphate group
phosphate groups can form hydrogen bonds with the water
fatty acids hidden from the water
to form a bilayer
Why can some substances not pass the phospholipid membrane?
hydrophilic
polar
substance is too large
What effects do double bonds have on intermolecular forces?
they disrupt intermolecular forces
How can you measure the quantity of glucose after a benedict’s test?
use a colorimeter
or filter out the precipitate and weigh it
Give two ways in which the structure of starch is different from cellulose
starch is a polymer of alpha glucose (not beta)
starch is helical but cellulose is not
starch contains 1-6 glycosidic bonds (cellulose 1-4)
Explain how cellulose is adapted for its function in plant cells?
cellulose chains are LONG and STRAIGHT, which are linked by MANY hydrogen bonds, which forms fibrils, which have high tensile strength so cellulose can support the cell wall
