1.3: Biological Molecules Flashcards
what Elements are carbohydrates made from?
Carbon, Hydrogen and Oxygen
What is the general formula for carbohydrates?
Cx(H20)y
what are Polymers?
Monomers joined together in a polymerisation reaction
what are monomers of carbohydrates called
Monosaccharides
Two Monosaccharides joined together form..
Disaccharides
Many Monosaccharides joined together are called…
Polysaccharides
Monosaccharides general formula
(CH20)n
N could be from 3 - 7
Characteristics of Monosaccharides
- Sweet tasting
- Highly soluble in water
Glucose (Monosaccharides) formula
C6H12O6 (Hexose sugar)
What are isomers?
One of two or more compounds that have the same chemical formula but different arrangements of the atoms. Same chemical formula but different ring structures
What are the isomers glucose forms?
Alpha glucose
Beta Glucose
What are the 2 main roles of monosaccharides?
- Source of energy during respiration (due to C-H bonds releasing lots of energy when broken)
- Important building blocks for larger molecules E.G. glucose is used to make starch
What reaction forms disaccharides?
Condensation Reactions
What bond and other properties are formed in a condensation reaction?
- Glycosidic bond
- Water
Rules for drawing condensation reactions
- always circle the groups
- always show that water is released
- always circle & label the bond that is formed
What is the opposite reaction to a condensation reaction?
Hydrolisis
What are polysaccharides?
Polysaccharides are polymers made of many monosaccharides joined together by glycosidic bonds (condensation reactions)
Properties of polysaccharides
- Not sugar/sweet tasting
- soluble in water
Starch
- where is it found?
- what are the monomers?
- plants ONLY
- Alpha glucose
Glycogen
- where is it found?
- what are the monomers?
- Animals & fungi
- alpha glucose
Cellulose
- where is it found?
- what are the monomers?
- Plants ONLY
- Beta Glucose
why do organisms use polysaccharides as an energy store instead of glucose?
- glucose is soluble in water
- accumulation of glucose in the cell would lower the water potential of the cell
What is the main role of starch?
Energy store - stored as granules in chloroplasts, seeds and storage organs (e.g. potatoes)
what is starch made up of? (with percentages)
Amylose (20%)
Amylopectin (80%)
Amylose
-number of alpha - glucose units per molecule
- branched vs unbranched
- type of glycosidic bond
- colour with iodine solution
1) 200-5000
2) unbranched
3) 1,4
4) Deep blue
What is the purpose of turns in the amylose structure?
6 glucose turns per unit, which allows molecules to be compact (therefore it takes up less space)
Amylopectin
-number of alpha - glucose units per molecule
- branched vs unbranched
- type of glycosidic bond
- colour with iodine solution
1) 5000 -100000
2) branched
3) 1,4 bonds along chain
1,6 between branches
4) stains red/purple
What is the main role of glycogen?
Energy store, stores as granules in the muscle and liver.
(branched structure with 1,4 bonds between monomers and 1,6 between branches)
shorter chains and more branches
What is the role of cellulose in plants?
To provide structural support
What is Cellulose made of?
Beta- glucose monomers joined by glycosidic bonds.
What is the difference in OH groups on carbon 1 between alpha and beta glucose?
Alpha glucose - OH is below
Beta glucose - OH is above
cellulose structure
- Monomers need to be rotated 180 degrees to be joined to next one
- Forms straight unbranched chains, they run parallel
- cross linked parallel chains using hydrogen bonds
- weak but together bonds cause the cellulose to be extremely strong
What are microfibrils?
60-70 tightly cross-linked cellulose molecules
How are microfibrils linked together?
Using hydrogen bonds which form cellulose fibrils
Where is cellulose found?
In the plants cell wall, makes upto 20-40% of the plant cell wall
cellulose functions for cell wall
- cellulose fibres run in different directions which provides rigidity
- Cell wall is fully permeable and it has high tensile strength, which prevents cell from bursting when water enters by osmosis
What are proteins made of?
Monomers called amino acids which make up more than 50% of the dry mass cells
What are the functions of protein?
- cell membrane components
- enzymes which control cellular reactions
- haemoglobin (o2 transport)
- keratin, protein which strengthens hair and nails
- immune response
- collagen, protein, strengthens bones and arteries
How many types of amino acids are there?
Essential / non-essential
20 types of amino acids
8 essential (must be present in diet)
12 non-essential, can make on own
same general structure
How do amino acids vary?
chemical elements found in the R group
How are dipeptides formed? What is the bond formed?
Two amino acids joined together by condensation reaction.
Peptide bond is formed
What is protein folding?
Where polypeptide chains are folded in a series of stages so that they can carry out specific functions and have a correct 3D shape
How are polypeptides formed?
Amino acids linked together by peptide bonds
How many polypeptide chains form collagen?
3
What is the primary structure in protein folding?
The order and sequence of the amino acids in the polypeptides chain.
Ultimately responsible for the final shape due to changing the amino acids in the sequence can change the function
Protein folding - secondary structure
What does it mean?
When the polypeptide chain starts to fold to become more compact.
What shape does a polypeptide chain form?
An alpha helix or a beta pleated sheet. Held together by hydrogen bonds.
Alpha Helix structure (protein folding)
Hydrogen bonds form between amino acids 4 residues apart.
Form part of the carboxylic group of one amino acid and part of the amine group another 4 spaces away
Beta Pleated sheet structure (protein folding)
Folded into a flat structure with amino acid chains running alongside each other and held together by hydrogen bonds
What is the tertiary structure (protein folding)
How the secondary structure present in the polypeptide chain fold together to produce a precise 3D shape
How is the tertiary structure shape held together (4 bonds)
- Hydrogen bonds
- Ionic bonds
- Disulphide bonds
- Hydrophobic bonds
How can hydrogen bonds form in amino acids?
- Can occur between polar R groups of different amino acids
- Forms between part of the carboxylic group of one AA and part of the anime group of another
How can hydrogen bonds be broken?
By high temperature or PH changes
When do ionic bonds occur?
Between oppositely charged R groups of different AA
How are ionic bonds broken?
By PH changes
What are R groups (amino acids)
another atom or group of atoms bonded to the central atom
When do Disulphide bonds occur?
Between R groups of different cysteine AA
How are disulphide bonds broken?
By reducing agents
How do hydrophobic interactions occur?
Between non polar of hydrophobic R groups of different amino acids so that they try to come close together away from water
What is the quaternary Structure? (polypeptide bonds)
Is the association of two or more polypeptide chains. The associated chains are held together by 4 types of bonds. (hydrogen, ionic. disulphide, hydrophobic.)
What does hydrophobic mean?
doesn’t like water, this means they will concentrate themselves into the centre of the protein
What does hydrophilic mean?
Likes water, so will more likely be on the outside of the protein
What is an example of a reducing sugar?
Glucose
What reagent is used to test for reducing sugar?
Benedict’s reagent
What is the method used to test for reducing sugars?
- Add a few drops of Benedict’s reagent
- Put the test tube in a water bath and heat 80-90c for 10 minutes
What is a positive result of the reducing sugars test?
Brick red/orange
What is a negative result of the reducing sugars test?
Blue
What solution is used to test for starch?
iodine solution
What is the method for testing for starch?
- Add 5cm cubed of iodine solution to the substance
- watch to see whether the result is positive or negative
What is the positive result for starch?
blue/black colour
What is a negative result for starch?
Brown/orange
What reagent is used for non-reducing sugars?
Benedict’s reagent
What is an example of a non-reducing sugar?
Sucrose
What is the method to test for non-reducing sugars?
- Test for reducing sugars originally, if the test obtains a negative result then get a fresh sample.
- using the fresh sample add hydrochloric acid to break the glycosidic bonds.
- Then neutralise the sample with sodium hydrogen carbonate solution
- Add the Benedict’s reagent to the sample and place into a water bath, heating @ 90 degrees for 10 minutes
What is a positive result for non-reducing sugars?
brick red/orange
what is the negative result for non-reducing sugars?
Blue
What reagent is used to test for proteins?
Buiret reagent
What must you NOT do with the method of the protein food test?
Heat the buret reagent
What is the method used to test for proteins?
Add biuret reagent containing sodium hydroxide and copper sulphate to the sample
What is a positive result of the proteins test?
Lilac/purple colour
What is a negative result of the proteins test?
Blue colour
What is the emulsion test for?
Lipids
What is used to test for lipids?
Absolute Ethanol
What is the method used for the lipids test?
Add absolute ethanol to the sample and then shake. Pour the top part of the liquid into water and shake again. You should then see a positive or negative result
What is a positive result of lipids?
A white cloudy emulsion/ milky white emulsion
What is a negative result of lipids?
It would be colourless or transparent
What is an example of a globular protein with a quaternary structure?
Haemoglobin
What is a haemoglobin molecule made of?
Four polypeptide chains - two alpha chains and two beta chains held together by hydrogen bonds. Contains a haem group also
What is a haem group and what is it usually called?
a group containing a Fe2+ ion (iron)
called a prosthetic group as its part of a protein made from amino acids.
What can one molecule of oxygen do with the haem group?
Bind reversibly with the iron in the haem group
How much can each molecule of haemoglobin carry?
4 molecules of oxygen (O2)
In haemoglobin folding what do the hydrophilic r groups do in the amino acids?
arrange themselves outside of the haemoglobin molecule, making it soluble
In haemoglobin folding what do the hydrophobic r groups do in the amino acids?
arrange themselves on the inside of the haemoglobin molecule which helps to maintain the shape of the molecule
Is haemoglobin unstable or stable?
unstable, not fully rigid due to needing flexibility
What is an example of a fibrous protein in a quaternary structure?
Collagen
What is each collagen molecule made of?
3 helical polypeptide chains arranged in a triple helix held together by hydrogen bonds.
Why is the collagen molecule closely packed?
because every 3rd amino acid in the polypeptide chain is glycine which is the smallest amino acid (just contains hydrogen)
Where is collagen found?
Tendons, skin and connective tissue
What bonds can collagen molecules form with each other?
covalent bonds with parallel collagen molecules
What do the covalent bonds form?
collagen fibrils
What do the covalent bonds cross links do?
They are staggered which increases tensile strength of the fibril
What are lipids?
Lipids are a diverse group of chemicals.
What are the most common types of lipids?
triglycerides - found in fats and oils
What is triglycerides made from?
1 glycerol molecule and 3 fatty acids joined together in a condensation reaction and linked by ester bonds
What are ester bonds?
forms when a hydroxyl (-OH) group from the glycerol bonds with the carboxyl (-COOH) group of the fatty acid
What are the features of the hydrocarbon fatty acid tail?
- hydrophobic
- Insoluble in water
What is the difference between saturated and unsaturated fatty acid?
saturated: have hydrocarbon chains connected by single bonds only.
unsaturated: have one or more double bonds
What does the bond between neighbouring carbon atoms do to the structure?
Leads to a kink in the hydrocarbon chain
Increases the fluidity of the lipid formed (oils have more C=C that fats
As it reduces the intramolecular forces so fatty acids cant pack as closely together
what is the difference between monounsaturated and polyunsaturated fatty acid?
Monounsaturated: one c=c double bond in the hydrocarbon chain
polyunsaturated: more than one c=c double bond in the hydrocarbon chain
What are the roles of triglycerides?
- source of energy for the body
- used to make water / metabolise water
- insulator
- bouyancy
What are phospholipids?
a special type of lipid found in a cell membranes.
What is the difference between lipids and phospholipids?
One of the fatty acid tails is replaced by a phosphate group.
What are the features of the phospholipid structure?
head of the phospholipid is hydrophilic (water loving) and the tail is hydrophobic (water hating).
What are the roles of phospholipids?
- major components of cell membranes as they form a bilayer when in water
- responsible for the partially permeable nature of cell membranes and allow lipid soluble substances to enter and leave the cell and prevent water soluble substances from entering and leaving the cell.
What are the 3 regions of cholesterol?
- hydrocarbon tail
- ring structure
- hydroxyl group
What is the hydroxyl group in cholesterol characteristics?
polar which makes this part of the molecule soluble in water (hydrophilic)
What is the ring structure and hydrocarbon chain in cholesterol characteristics?
This part is non-polar and makes this part of the molecule insoluble in water (hydrophobic) but it is fat soluble.
What is the definition of a fat soluble and water soluble region in the same molecule?
Amphipathic molecule
What is the role of cholesterol?
- regulates membrane fluidity in cell membranes
- makes membranes less fluid at high temps and more fluid at low temps
- reduce side to side movement of phospholipids.
- increases the mechanism stability of the cell
- prevents leakage of water and dissolved ions from the cell.
Are fatty acids alkali or acid?
acid, so lowers the PH
