1a. BIOLOGICAL MOLECULES Flashcards
Define polarity
An uneven distribution of electrons in a covalent bond
Describe the polarity in a water molecule
The hydrogen atoms are polar positive and the oxygen atom is polar negative
Describe how hydrogen bonds are created between water molecules
The polar positive hydrogen atoms in one molecule are attracted to the polar negative oxygen atoms in another molecule.
Recall the five properties of water that make it important for living things
High specific heat capacity
High latent heat
Metabolite
Universal solvent
Cohesive
Explain how having a high latent heat of vaporisation makes water important for organisms
It provides a cooling effect through evaporation
Explain how being a metabolite makes water important for organisms
It acts as a metabolite in condensation and hydrolysis reactions
Explain how being a universal solvent makes water important for organisms
It transports substances and allows reactions to occur
Explain how being cohesive makes water important for organisms
It supports columns of water
Explain how having a high specific heat capacity makes water important for organisms
Because water can buffer changes in temperature
Explain how water acts as a temperature buffer in cells
Water has a high specific heat capacity therefore it absorbs a lot of energy before the temperature increases
Why are biological molecules able to dissolve in aqueous solutions?
Most biological molecules are also polar
Explain how water moves as a continuous stream in transport vessels
Water is cohesive therefore the water molecules are attracted to each other
Which ion reduces pH in living organisms?
H+
Which ion is a component in Haemoglobin?
Fe2+
Which ion is involved in the co-transport of glucose and amino acids?
Na+
Which ion is a component of DNA and RNA?
PO4 3-
What is a nucleotide?
The basic building block of nucleic acids
Describe the three-part structure of a nucleotide
All nucleotides are made up of phosphate, a sugar and a nitrogenous base
Describe the structure of ATP
One ribose sugar, adenine, and three phosphtes
Which type of reaction occurs when phosphate groups are removed from ATP?
Hydrolysis
Which type of reaction occurs when phosphate groups are added to ADP?
Condensation
Why is ATP not a good long term energy store?
It is unstable over long periods of time
How ATP not being a good long term energy store overcome?
Your body uses large molecules as stores of energy, e.g. lipids and carbohydrates
Name five energy requiring processes that use ATP
Metabolic processes
Movement
Active transport
Secretion
Activation of molecules
Explain why its important that ATP only releases energy in small amounts
If large amounts of energy were released at once, it would increase the temperature of the cell and denature proteins
Describe four ways ATP is adapted for its function
It is small & dissolves in aqueous solutions
It releases energy instantaneously and in small amounts
It’s easily reformed from ADP
Pi can phosphorylate other molecules
Explain why ATP being small and dissolving in aqueous solutions helps it carry out its function
It means it’s easily transported
Explain the function of Pi phosphorylating another molecule
The Pi changes the molecule’s shape and lowers it’s activation energy
Define metabolism
The sum of all chemical reactions in the organism
Recall the two types of metabolism
Anabolic and catabolic
Define anabolic reactions
Reactions that build up smaller molecules into larger molecules, which requires energy
Give an example of anabolic reactions
Photosynthesis
Define catabolic reactions
Reactions that break down larger molecules into smaller molecules, which releases energy
Give an example of catabolic reactions
Respiration, protein synthesis
State the four most common elements in biological molecules
Carbon
Hydrogen
Oxygen
Nitrogen
State how many bonds each comment element in biological molecules makes
Carbon = 4
Hydrogen = 1
Oxygen = 2
Nitrogen = 3
Recall the five types of interactions within biological molecules
Ionic, covalent, disulphide bridges, hydrophilic/hydrophobic interactions, hydrogen bonds
Describe ionic bonding
Electrostatic attraction between a metal and a non-metal
Describe covalent bonding
The sharing of electrons between two non-metal elements
Describe disulphide bridges
Bonding between two sulphur atoms
Describe Hydrogen bonding
The polar positive hydrogen atoms in one molecule are attracted to the polar negative atoms in another molecule.
Describe hydrophilic / hydrophobic interactions
Hydrophilic groups dissolve in aqueous solutions, hydrophobic groups dissolve in organic solutions
Define a condensation reaction
Joining 2 molecules, creating a chemical bond and removing a molecule of water
Define a hydrolysis reaction
Breaking a chemical bond between 2 water molecules and involving the use of a water molecule
Recall the general formula for carbohydrates
(CH2O)n
Describe how to number the carbons within a monosaccharide
Clockwise, starting with the carbon after the oxygen in the ring
Name three hexose monasaccharides
Glucose, fructose and galactose
Name two pentose monasaccharides
Ribose and deoxyribose
Name the two structural forms of glucose
Alpha and beta
Explain the difference between alpha and beta glucose
In alpha glucose, the OH group on carbon 1 is pointing down, whereas in beta glucose, the OH group on carbon 1 is pointing up
Draw a molecule of alpha glucose
Draw a molecule of beta glucose
Name the type of bond within a di/polysaccharide
Glycosidic bond
Describe how a 1, 4 - glycosidic bond is formed between two glucose molecules
OH from one glucose and the adjacent H from another are removed as a molecule of water. A bond forms between carbon 1 and carbon 4 with an oxygen atom in between
Name the disaccharide containing two alpha glucose
Maltose
Name the disaccharide containing glucose and fructose
Sucrose
Name the disaccharide containing galactose and glucose
Lactose
Recall the formula for disaccharides
C12H22O11
Draw a molecule of maltose
Recall the three polysaccharides
Starch, glycogen and cellulose
Describe the function of starch
Storage of glucose in plants
Describe the structure of starch
A polymer of many alpha glucose monomers joined with 1,4 glycosidic bonds in a chain, with branches formed by 1,6 glycosidic bonds. It is coiled.
Describe the function of glycogen
Storage of glucose in animals
Describe the structure of glycogen
A polymer of many alpha glucose monomers, joined with 1,4 glycosidic bonds, many branches formed by 1,6 glycosidic bonds. It is coiled.
Explain why glycogen is more branched than starch
Animals move therefore they need a faster release of glucose for respiration. Many branches means more free ends, so more glucose can be removed at once for respiration
Explain why the coiled structure of starch and glycogen important for their function?
It makes them compact, this means that many glucose molecules can be stored in a small area
Why is it important for starch and glycogen to be insoluble?
So they do not affect the water potential of the cell
Why is it important for starch and glycogen to be large molecules?
So they cannot cross the cell membrane
State which monosaccharides cellulose is made from
Beta glucose
Describe the structure of one cellulose chain
Long straight chain of beta glucose with every other beta glucose is inverted. No branches.
Describe the structure of a cellulose fibre
Chains of cellulose join by many hydrogen bonds to form a microfibril, many microfibrils join with crosslinks to make a macrofibril, many macrofibrils join with crosslinks to form a fibre
Describe the function of cellulose
To strengthen cell walls in plants
Describe the properties of cellulose
Insoluble, strong, difficult to break down
Describe the importance of hydrogen bonds in cellulose
One hydrogen bond alone is weak, many hydrogen bonds together are very strong. This strengthens cell walls
Define a lipid
Any molecule that is soluble in an organic solvent (e.g. alcohol)
Name the two main types of lipid
Triglycerides and phospholipids
Recall the five uses of lipids in the body
Formation of membranes
Source of energy
Waterproofing
Insulation
Protection
Name the two types of membranes lipids are used to create
Cell surface membranes and organelle membranes
Give two examples of how lipids are used for waterproofing in organisms
A leaf’s waxy cuticle and skin oils
Give two ways lipids are used for insulation in organisms
Thermal insulation and electrical insulation around neurones
Describe how lipids are used for protection in organisms
They are stored around delicate organs
Describe the structure of a triglyceride
One glycerol and three fatty acids held together by three ester bonds
Draw a triglyceride (the tails can be any length greater than three carbons long)
Name the reaction that creates a triglyceride
Esterification (& condensation)
How many molecules of water are produced when one triglyceride is formed?
Three
Why are fatty acids called carboxylic acids?
Because they contain a COOH (carboxyl) group
Describe the structure of a phospholipid
A phosphate head and two fatty acid chains
State which part of a phospholipid is hydrophilic and hydrophobic
Head (phosphate) is hydrophilic, tails (fatty acids) are hydrophobic
Describe the structure of a phospholipid bilayer
Many phospholipids sit next to one another in a layer. There are two layers. The hydrophobic tails face towards each other, and the hydrophilic heads dissolve in the surrounding aqueous solutions.
Explain the purpose of a phospholipid bilayer
Separate two aqueous environments
Name the two types of fatty acid chain found in lipids
Saturated and unsaturated
Describe the difference in structure between saturated and unsaturated fatty acids
Saturated fatty acids have only single C-C bonds (so are straight chains), unsaturated fats have one or more double C-C bonds (are therefore kinked/bent)
What state of matter are fats and oils at room temperature?
Fats are solid at room temperature and oils are liquid at room temperature
Do fats contain saturated or unsaturated fatty acid chains?
Saturated
Do oils contain saturated or unsaturated fatty acid chains?
Unsaturated
Explain why fats are solid at room temperature
The fatty acids are saturated and are therefore straight chains. There are stronger intermolecular forces beween triglyceride molecules. Therefore more energy is required to break them.
Explain why oils are liquid at room temperature
The fatty acids are unsaturated and are therefore kinked chains. There are weaker intermolecular forces beween triglyceride molecules. Therefore less energy is required to break them.
Explain why lipids are an excellent store of energy
They contain a high number of carbon to hydrogen bonds, therefore a lot of energy is released when the bonds are broken.
Why can lipids store a lot of energy in a small space?
They have a low mass to energy ratio
Why do lipids not affect the water potential of a cell?
They are insoluble
How many naturally occurring amino acids are there?
20
Describe how amino acids give us indirect evidence for evolution
Proteins in all living organisms are made up of the same 20 amino acids
Describe the basic structure of an amino acid
Amino group (NH2), carboxyl group (COOH), R group (varies), Hydrogen
Draw the general structure of an amino acid
Describe, referring to the groups, how two amino acids bond to make a dipeptide
The amine group on one amino acid bonds to the carboxyl group on the other amino acid. OH from carboxyl group and H from the amino group are removed (to form one water molecule) then the carbon and nitrogen join to form a peptide bond.
Draw a dipeptide
Name the four levels of protein structure
Primary, secondary, tertiary, quaternary
Describe primary protein structure
The sequence of amino acids in a polypeptide chain
State the bonds in the primary protein structure
Peptide bonds
How is the sequence of amino acids in a polypeptide chain determined?
By the sequence of bases in the gene that codes for it
Describe secondary protein structure
Alpha helices joined by hydrogen bonds
Describe where hydrogen bonds form between alpha helices
Between NH+ (amine group) and CO- (carboxyl group) (NOT R GROUPS)
Describe the tertiary structure of a protein
Alpha helices are folded into a 3-D shape
State the bonds/interactions that can occur within a tertiary protein
Hydrogen bonds, disulphide bridges, ionic bonds, covalent bonds
Explain how the 3D structure of a protein is determined
The tertiary structure depends on the sequence of amino acids because this determines the type and position of the bonds between R groups.
Describe the quaternary structure of a protein
When two or more subunits (polypeptides) bond together.
State the bonds/interactions that can occur within a quaternary protein
Hydrogen bonds, disulphide bridges, ionic bonds, covalent bonds
Describe why the 3D shape of an enzyme is important to its function
The 3D shape of the active site must be complementary to the substrate
Describe why the 3D shape of a hormone is important to its function
The 3D shape of the hormone must be complimentary to the receptor.
Describe the reaction that breaks down polypeptides
One molecule of water is removed to break the peptide bond between amino acids
Name the two main groups of proteins
Fibrous (structural) and globular (functional)
Give three examples of structural proteins
Keratin, collagen, elastin
Give three examples of functional proteins
Haemoglobin, insulin, any enzyme or hormone
Why is it important for globular proteins to be soluble in water?
So they can dissolve in the blood and be transported through the body.
Describe the structure of collagen
Three polypeptide chains, wound into a rope like shape. Crosslinks between chains.
Describe the function of collagen
Provide strength and flexibility to connective tissue (e.g. tendons & ligaments)
Name the food test for reducing sugars, and state a positive result
Benedict’s solution. A positive result - brick red precipitate will form
Describe how to carry out the test for reducing sugars
Add Benedicts solution and heat.
Describe how to carry out the test for non-reducing sugars
Test using Benedict’s solution, and you’ll get a negative result. Boil the sample with acid, and neutralise with alkali. Test again with Benedict’s solution, and a brick red precipitate will form (a positive result).
Describe and explain the positive result for the test for non-reducing sugars
Non-reducing sugars are converted into reducing sugars, so Benedict’s solution turns brick red
Name the food test for proteins, and a positive result
Biuret reagent. Positive result - purple
Name the food test for lipids, and state a positive result
Emulsion test (ethanol). Positive result - a cloudy emulsion
Describe how to carry out the emulsion test
Add ethanol, then distilled water and shake.
