biological molecules - carbohydrates, lipids and proteins

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  • Created by: Amelia
  • Created on: 17-04-17 18:48
what are carbohydrates?
carbohydrates are polymers made from the monomers monosaccharides. They contain the elements C, H and O
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What is glucose?
a hexose sugar (a monosaccharide with 6 carbon atoms in each molecule).
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Name the two types of glucose, and say how they differ from each other.
alpha-glucose and beta-glucose. they are isomers, so have the same molecula formula, but a different arragement of atoms.
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What is a condensation reaction?
a condensation reaction is when two molecules form a new chemical bond and in doing so release a water molecule. monosaccharides are joined together using condentation reactions.
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name the bond formed when monosaccharides join
a glycosidic bond
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What are the products when monosaccarides undergo a condensation reaction?
a disaccharide is formed along with a molecule of water.
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name the disaccharide formed from the condensation reaction between glucose and fructose
sucrose is formed
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name the disaccharide formed from a condensation reaction between glucose and galactose
lactose is formed
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what is a hydrolysis reaction?
a hydrolysis reaction breaks the chemical bond between monomers in a polymer using a water molecule.
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how can sugars be classified?
sugars can be classified as reducing or non-reducing
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what is a reducing sugar?
all monosaccharides and some disaccharides are reducing sugars
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What test can be used to find out if a sugar is reducing or non-reducing?
The Benedicts test for sugars
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How can you use the Benedicts test for sugars to find the concentration of reducing sugar?
1. Add Benedicts reagent to a sample 2. heat in a water bath that has been brought to the boil 3.A positive test forms a coloured precipitate, ranging from blue to brick red.
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what does the colour of precipitate in a positive test show about the sugar?
the higher the concentration of reducing sugar, the further the colour change goes.
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How can the Benedicts test for sugars be used to find a non-reducing sugar?
1. Add dilute HCl to sample, breaking non-reducing sugars down into monosaccharides 2.Heat in a water bath that has been brought to the boil. 3.neutralise with NaHCO3 and carry out test as for reducing sugars. +ve result = coloured precipitate
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what will the result of the bendicts test be is there is no sugar in the samlpe?
the solution will stay blue (the colour of the benedicts reagent)
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what is a polysaccharide?
a polysaccharide is formed when more than two monosaccharides are joined together by condensation reactions.
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what is starch?
starch is the main energy storage material in plants. It is made from two polysaccharides of alpha-glucose - amylose and amylopectin.
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what is amylose?
A long, unbranched chain of a-glucose. it has a coiled structure, making it compact and really good for storage.
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what is amylopectin?
A long, branched chain of a-glucose. its side branches allow enzymes to break down the molecule easily, so glucose can be released quickly.
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How do you test for starch?
use the iodine test - add iodine dissolved in potassium iodine solution to the sample. if starch is present the sample will turn a dark blue-black colour.
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What is glycogen?
glycogen is the main energy storage material in animals. It is a polysaccharide of a-glucose
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How is glycogen adapted to its function?
it has lots of side branches, meaning that stored glucose can be released quickly. it is also a very compact molecule, making it good for storage.
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What is cellulose?
cellulose is the major component of cell walls in plants. It is made of long, unbranched chains of beta-glucose.
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How is cellulose adapted to its funtion?
b-glucose molecules form straight cellulose chains which are linked together by hydrogen bonds to from strong microfibrils, providing structural support for cells.
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what is a triglyceride?
A type of lipid made up of one glycerol molecule and three fatty acids.
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What is a fatty acid?
fatty acids have a COOH group and a variable 'R' group which acts as the hydrocarbon tail. The hydrocarbon tail is hydrophobic.
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How are triglycerides formed?
Triglycerides are formed by condensation reactions between a glycerol molecule and three fatty acids.
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What type of bond is formed between the fatty acids and glycerol molecule?
an ester bond.
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What are the two types of fatty acid?
saturated (no C-C double bonds) and unsaturated ( at least one C-C double bond)
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what is a phospholipid?
Similar to triglycerides, but one fatty acid is replaced by a phosphate group. They are found in cell membranes. The phosphate group is hydrophilic, but fatty acids are hydrophobic.
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how are triglycerides adapted to their function?
Hydrocarbon tails of the fatty acids contain lots of energy, twice as much as carbohydrates. They are also insoluble, so dont affect the water potential of the cell.
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How are phospholipids adapted for their function?
They form a double layer with their hydrophilic heads facing out and their hydrophobc tails facing in, making it so water-soluble substances can't easily pass through.
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How does the emulsion test for lipids work?
1. Shake the test substance with ethanol so that it dissolves, then pour the solution into water. 2. Any lipid will show up as a milky emultion, the more lipid, the more noticeable the emulsion.
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What is a protein?
A protein is a long chain of amino acids.
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What is the general structure of an amino acids?
A carboxyl group (-COOH), an amino group (-NH2) and an R group.
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What is a polypeptide?
A polypeptide is formed when more than two amino acids are joined together by condensation reactions.
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What is the name of the bonds formed between amino acids?
Peptide bonds
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What are the four structural levels of proteins?
Primary structure, secondary structure, tertiary structure and quarternary structure
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What is the primary structure of a protein?
the sequence of amino acids in the polypeptide chain
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what is the secondary structure of a protein?
Hydrogen bonds form between the amino acids in the chain, making it automatically coil into an alpha-helix or fold into a beta pleated sheet.
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What is the tertiary structure of a protein?
polypeptide chain coiled or folded further. More hydrogen bonds and ionic bonds form between different parts of the chain. Disulfide bridges form between cysteine molecules. It is the final 3D structure for proteins made from one polypeptide chain.
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what is the quarternary structure of a protein?
This is the final 3D structure for proteins made from more than one polypeptide chain. These different chains are held together by bonds. examples of proteins with quarternary structure include haemoglobin, insulin and collogen.
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How are enzymes specialised for their function?
enzymes are usually spherical due to tight folding of polypeptide chains. They are also soluble.
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How are antibodies specialised?
Antibodies are involved in immune response. they are made up of 2 light (short) and 2 heavy (long) polypeptide chains bonded together. they also have variable regions where their amino acid sequence varies greatly.
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How are transport proteins specialised?
Channel proteins contain hydrophobic and hydrophilic amino acids, causing them to fold up and form a channel. this allows them to transport molecules and ions across membranes.
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How are structural proteins (such as keratin and collagen) specialised?
structural proteins are physically strong. they have long polypeptide chains lying parallel to each other with cross-links between them.
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What test is used for proteins?
The biuret test
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what method is used in the biuret test for proteins?
1. Add sodium hydroxide solution to make your test solution alkaline. 2. Add copper(II) sulfate solution. 3. if protein is present solution turns purple, if not it will stay blue.
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Other cards in this set

Card 2

Front

What is glucose?

Back

a hexose sugar (a monosaccharide with 6 carbon atoms in each molecule).

Card 3

Front

Name the two types of glucose, and say how they differ from each other.

Back

Preview of the front of card 3

Card 4

Front

What is a condensation reaction?

Back

Preview of the front of card 4

Card 5

Front

name the bond formed when monosaccharides join

Back

Preview of the front of card 5
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