Biological Molecules Flashcards
What does the prefix MONO mean?
One
What does the prefix DI mean?
Two
What is a monomer?
A small molecule that combine to make a larger one
Whats a polymer?
A large molecule made of small repeating units (monomers)
What is the monomer found in carbohydrates?
Monosaccharides
What is the monomer found in proteins?
Amino acids
Whats the formula for glucose?
C6 H12 O6
What are disaccharides?
Double sugars
Whats an isomer?
Molecules with the same formula, but different structures like alpha and beta glucose
What is the test used for reducing sugars?
Benedict’s reagent
If reducing sugars are present, what colour will the solution turn?
Brick red
What bonds link glucose to another glucose?
Glycosidic bond
What type of reaction forms glycosidic bonds?
Condensation reactions
How are glycosidic bonds broken?
Hydrolysis- adding a water molecule
What does glucose + glucose make?
Maltose
What does glucose + galactose make?
Lactose
What does glucose + fructose make?
Sucrose
What is a reducing sugar?
When the sugar can donate an electron to another molecule
What substance do you use to test for starch?
Iodine
Whats the colour change if starch is present?
From orange to blue black
Is starch found in animals or plants?
Plants
What is starch made of?
Alpha glucose chains
What structure does starch have?
Compact
Is glycogen found in animals or plants?
Animals
What is glycogen made of?
Alpha glucose chains
What is cellulose made of?
Beta glucose
What are the roles of lipids?
Energy, waterproofing, insulation, protection
What are triglycerides?
A type of lipid with 3 fatty acid tails
What are phospholipids?
A type of lipid with 2 fatty acid tails and 1 phosphate
What are saturated fats?
Fats with a single carbon bond
What are unsaturated fats?
Fats with at least one double carbon bond
What is an enzyme?
A biological catalyst that speeds up the rate of reactions
What effect do enzymes have on the activation energy of a reaction?
They lower the activation energy needed for the reaction to occur
What are the two models of enzyme action?
Lock and key, induced fit
Describe the induced fit model of enzymes
The substrate doesn’t perfectly fit the enzyme’s active site, but as the substrate approaches, the enzyme’s active site changes.
Describe the lock and key model of enzymes.
The substrate fits perfectly into an enzyme’s active site, the same way a key fits in a lock.
What shape are enzymes?
Globular
Name some examples of monomers?
glucose, galactose,fructose, amino acid
Name some examples of polymers?
Starch, glycogen, cellulose, proteins, DNA
Describe a hydrolysis reaction?
A hydrolysis reaction is when water molecule is added to break a chemical bond
Describe a condensation reaction?
A water molecule is removed, to form a chemical bond between 2 molecules
What type of bond is formed between 2 monosaccharides?
Glycosidic bond
What are the 3 most common types of monosaccharide?
glucose, fructose and galactose
Describe the chemical test for reducing sugars?
-add 2cm of food sample and 2cm of benedict solution
-heat
-positive result will show colour change (brick red,green,yellow)
-negative result will show no colour change (blue)
Describe the test for non reducing sugars?
-first carry out benedict’s test, if negative result is shown there may be reducing sugars
-add dilute hydrochloric acid and heat in water bath
-neutralise the solution with sodium hydrocarbonate
-repeat the benedict test
- if colour changes, a non reducing sugar is present
What type of reaction is involved in forming a disaccharide from two monosaccharides?
A condensation reaction- water molecule is removed in order to form a bond between the monosaccharides
What type of reaction is involved in breaking down a disaccharide to form 2 monosaccharides?
Hydrolysis reaction- adding a water molecule to break the bond between the 2 monosaccharides
How is maltose formed from its monosaccharides?
Glucose + Glucose —> Maltose
How is sucrose formed from its monosaccharides?
Glucose + Fructose —> Sucrose
How is lactose formed from its monosaccharides?
Glucose + Galactose —> Lactose
What disaccharides are reducing sugars?
maltose and lactose
Describe the biochemical test for starch?
-add 2cm of food sample into a test tube
-add two drops of iodine to the solution
-shake or stir
-if colour changes to blue black, starch is present
Explain why starch is suitable for storage in plants?
-it is compact so lots can be stored in a small space
-it’s insoluble and doesn’t diffuse out of cells
Why is glycogen a useful energy store in animals?
It is branched out, so more ends can be acted on by enzymes as it can be broken down rapidly to form glucose monomers
Why is cellulose suited to its structural function?
there are a high number of hydrogen bonds which make a considerable contribution to strengthening cellulose
What carbohydrate stains deep blue with iodine solution?
Starch
What carbohydrate is known as animal starch?
Glycogen
What carbohydrates are found in plants?
starch, cellulose, glucose
What monosaccharide is found in starch?
alpha glucose
What are 5 roles of lipids?
-energy source
-waterproofing
-insulation
-protection
-cell membrane flexibility
Describe the biochemical test for lipids?
-add food sample to tube and add ethanol
-shake the test tube
-add distilled water and shake
-milky white emulsion shows a positive test result for lipids
What’s the difference between saturated , monounsaturated and polyunsaturated fatty acids?
Saturated fatty acids have no double carbon bonds
Monounsaturated have one double bond between carbons
Polyunsaturated have more than one double carbon bond
What bond is formed between each fatty acid and the glycerol ?
ester bond
Describe the biochemical test for proteins?
carry out biuret test, colour change (lilac) shows positive result for proteins
What’s the structure of an amino acid?
Amino group, carboxyl group,hydrogen atom, R group
How are amino acids linked to form polypeptides?
Peptide bonds, form a sequence of amino acids called polypeptides through condensation reactions
What’s the primary structure of protein?
Hundreds of amino acids join to form a polypeptide through peptide bonds
What’s the secondary structure of proteins?
the hydrogen of the amino group and oxygen of carboxyl group form weak hydrogen bonds which cause the polypeptide chain to form an alpha helix or beta pleated sheet
What is the tertiary structure of proteins?
The helix bends and twists into a compact structure by ionic,hydrogen and disulfide bonds
What’s the quaternary structure of protein?
Multiple different polypeptide chains form a complex protein molecule
What’s the difference between fibrous and globular proteins?
Globular proteins are spherical and compact whereas fibrous proteins are long and narrow
What is the structure of a phospholipid?
2 fatty acid tails, a phosphate head and a glycerol
what is the function of phosphates and how does this relate to their structure?
the main building block of cell membranes, so have a structural purpose
hydrophilic heads face the aqueous environment
What is a triglyceride?
a type of lipid made from 3 fatty acids and a glycerol unit
How does the structure of triglycerides relate to the function?
they are insoluble, so a major store of energy that won’t dissolve
What is the active site of an enzyme?
the area of an enzyme that the substrate binds to, and where the reaction is catalysed
What is an enzyme substrate complex?
When the enzyme and substrate binds together and the active site fits around the substrate
How do enzymes speed up chemical reactions?
enzymes speed up reactions by reducing the activation energy needed, they bring the substrate closer to the enzymes active site
Why can changing one amino acid in an enzyme prevent it from functioning?
changing one amino acid may change the shape of the active site, so that the substrate can no longer bind to it anymore. so the enzyme may not be able to break down the substrate
How does temperature affect enzyme reactions?
At low temperatures, the kinetic energy of the enzyme is not sufficient so the rate of reaction is low. As the temperature increase up to the optimum, so does the rate of reaction
How does pH affect the rate of reaction?
PH affects the enzymes shape as it can disrupt the bonds in the tertiary structure of an enzyme. Each enzyme has an optimum temperature they work best at.
How does enzyme concentration affect the rate of reaction?
As enzyme concentration increases, there are more active sites for substrates to bind to, however after a point there will be more enzymes than substrates, so no effect on the rate of reaction.
How does substrates concentration affect rate of reaction?
The more substrates there are, the more enzyme-substrate complexes will form so the rate of reaction is increased. However, after a point, there will be more substrates than enzymes, so the rate of reaction cannot increases any further.
What is a competitive inhibitor of enzyme action?
Something that prevents enzyme action by binding to the active site
Whats a non-competitive inhibitor of enzyme action ?
Something that binds away from the active site, but still prevents enzyme action by changing the tertiary structure.
How would you calculate rate of reaction from a graph?
The gradient of the graph shows the rate of reaction - the steeper it is the faster the reaction is. To find the mean rate of reaction, do total products/time.
