2.1.2 - BIOLOGICAL MOLECULES Flashcards
What is a monomer?
Monomers are small units which are components of larger molecules (e.g. monosaccharides, amino acids and nucleotides)
What is a polymer?
Molecules made from monomers joined together
What is a condensation reaction?
A reaction which joins monomers by chemical bonds and it involves the elimination of a water molecule
What is a hydrolysis reaction?
The opposite of condensation and it’s when water is added to break a chemical bond between two molecules
What are the properties of water?
- Liquid medium
- Important metabolite
- High specific heat capacity
- High latent heat of vaporisation
- Cohesion of molecules
- Surface tension
- Good solvent and transport medium
- Good reaction medium
- Incompressible
Describe the structure of water.
- A molecule of water is one atom of oxygen (O) joined to two atoms of hydrogen (H) by shared electrons
- Shared negative H electrons are pulled toward O atom so other side of each hydrogen atom is left with a slight positive charge
- The unshared negative electrons on the O atom give a slight negative charge
- This makes it a polar molecule — has a partial negative charge on one side and a partial positive charge on the other
- Slightly negative oxygen atoms attract slightly positive hydrogen atoms from other water molecules
- This attraction is called hydrogen bonding
What is Specific Heat Capacity?
The energy required to raise the temperature of 1 gram of a substance by 1 degree Celsius
What is Latent Heat of Evaporation?
The amount of energy required to turn 1g of liquid water into steam
How does water’s polarity benefit it?
- Makes it very cohesive: attraction between molecules of the same type (e.g. 2 water molecules)
- Makes it a good solvent: many important substance sin biological reactions are ionic (meanings they are made from one positively atom or molecule and on negatively charged atom or molecules
What molecules do carbohydrates consist of?
- Carbon
- Hydrogen
- Oxygen
What are the monomers that make up carbohydrates called?
Monosaccharides
What is glucose (in terms of structure)?
- Made up of SIX carbon atoms (HEXOSE MONOSACCHARIDE)
- Has 2 isomers
What are ribose sugars?
- Made up of FIVE carbon atoms (PENTOSE MONOSACCHARIDE)
- Found in many important biological molecules: RNA, ATP, NAD
What is glucose (in terms of function)?
- Main substrate for respiration
Name three monosaccharides.
- Glucose
- Galactose
- Fructose
Name three disaccharides.
- Maltose
- Lactose
- Sucrose
What is the word equation for Maltose?
Glucose + Glucose ⇌ Maltose
[x2 α-glucose]
What is the word equation for Lactose?
Glucose + Galactose ⇌ Lactose
[β-glucose]
What is the word equation for Sucrose?
Glucose + Fructose ⇌ Sucrose
[α-glucose]
What is a glycosidic bond?
Bonds between monosaccharides that make disaccharides or polysaccharides
Formed in condensation reactions
Name three polysaccharides.
- Cellulose
- Starch
- Glycogen
Describe the structure if Amylose
- Unbranched chain of α-glucose molecules
- Joined by 1,4 glycosidic bonds (COILED + COMPACT)
Describe the structure of Amylopectin
- Branched chain of α-glucose molecules
- Joined by 1,4 and 1,6 glycosidic bonds
Describe the characteristics of starch
- Starch stores energy in plants
- Made of polysaccharides Amylose + Amylopectin
- Insoluble in water
- α-glucose
What is the function of glycogen?
Main energy storage molecule in animals
Describe the structure of glycogen
- Formed by many α-glucose molecules
- Joined by 1,4 + 1,6 glycosidic bonds
- Large number of branches –> glucose + energy released quickly
- Large but compact –> maximises amount of energy stored
What is the function of cellulose?
Component of cell walls in plants
Describe the structure of cellulose.
- Composed of long, unbranched chains of β-glucose joined by glycosidic bonds
- Cellulose chains linked by hydrogen bonds to form strong fibres (microfibrils)
- Microfibrils mean cellulose provides structural support for cells
Describe how glycosidic bonds are formed and broken in living organisms.
- During synthesis, a hydroxyl group on one monosaccharide bonds to a hydroxyl (OH) group on the other monosaccharide, releasing a water molecule (CONDENSATION REACTION)
- A water molecule reacts with the glycosidic bond, breaking it apart (HYDROLYSIS REACTION)
What molecules do lipids consist of?
- Carbon
- Hydrogen
- Oxygen
What are lipids?
Molecules that are only soluble in organic solvents (e.g. alcohol)
What are the two types of lipids/fatty acids?
- Saturated
- Unsaturated
What is a saturated fatty acid?
- No double bonds between carbon atoms
- Saturated with hydrogen
What is an unsaturated fatty acid?
- At least one double bond between carbon atoms (causing chain to kink)
- Melt at lower temperatures than saturated fatty acids
What are triglycerides?
- Macromolecules - complex molecules with a relatively large molecular mass
- Non-polar, hydrophobic molecules
Describe the structure of a triglyceride
- One glycerol molecule + Three fatty acids
- Fatty acids have hydrophobic tail and hydrophilic head
What are phospholipids?
- A type of lipid, formed from the monomers glycerol and fatty acids
- Found in the cell membranes of all eukaryotes and prokaryotes (makes up PHOSPHOLIPID BILAYER)
^–Cell membranes control what enters and leaves a cell
Describe the structure of a phospholipid.
- One glycerol molecule + Two fatty acids + One phosphate head
^— phosphate head replaces what would’ve been another fatty acid in triglycerides - As the phosphate is polar it is soluble in water (hydrophilic)
- The fatty acid ‘tails’ are non-polar and therefore insoluble in water (hydrophobic)
amphipathic (both hydrophobic and hydrophilic parts)
How are triglycerides formed?
Ester bonds
What is an ester bond?
- Triglycerides are formed by esterification
- Ester bonds formed when a hydroxyl group from the glycerol bonds with the carboxyl group of the fatty acid
- Ester bond formation is a condensation reaction
- In forming a triglyceride, three water molecules are released
What are the functions of a triglyceride?
- Energy storage
- Insulation
- Buoyancy
- Protection
Explain buoyancy as a function of triglycerides.
The low density of fat tissue increases the ability of animals to float more easily
Explain insulation as a function of triglycerides.
- Triglycerides are part of the composition of the myelin sheath that surrounds nerve fibres
- The myelin sheath provides insulation which increases the speed of transmission of nerve impulses
- Triglycerides compose part of the adipose tissue layer below the skin which acts as insulation against heat loss (e.g. blubber of whales)
Explain protection as a function of triglycerides.
The adipose tissue in mammals contains stored triglycerides and this tissue helps protect organs from the risk of damage
What is an ion?
An atom (or group of atoms) that has an electric charge
- Cation: Positive charge
- Anion: Negative charge
What is an inorganic ion?
- An ion that doesn’t contain carbon (but there are a few exceptions)
- Important in biological processes
Name the essential cations + their chemical symbols
- Calcium - Ca²⁺
- Sodium - Na⁺
- Potassium - K⁺
- Hydrogen - H⁺
- Ammonium - NH₄⁺
What molecules do proteins consist of?
- Carbon
- Hydrogen
- Oxygen
- Nitrogen
- Sulfur
What are the monomers in proteins?
Amino acids
What are the polymers in proteins?
- Dipeptides (two amino acids join together)
- Polypeptides (more than two amino acids join together)
- Proteins are made of one or more polypeptides
Name the four levels of a protein’s structure.
- Primary Structure
- Secondary Structure
- Tertiary Structure
- Quaternary Structure
How many amino acids are found in proteins in living organisms?
There are 20 common to living organisms
What is the name of the bonds that join amino acids together?
- Peptide bonds
- This is a condensation reaction, releasing water
Explain the primary structure of a protein.
- The sequence and number of amino acids in a protein/polypeptide chain
- Different proteins have different sequences of amino acids in their primary structure
Explain the secondary structure of a protein.
- The polypeptide chain doesn’t remain straight
- Hydrogen bonds formed between nearby amino acids
- It either coils into an α helix or folds into a β-pleated sheet
Explain the tertiary structure of a protein.
- Coiled or folded chain of amino acids often further coils or folds
- More bonds form
- This is the final 3D structure for proteins made from a single polypeptide chain
Explain the quaternary structure of a protein.
- Some proteins are made from multiple polypeptide chains held together by bonds
- The quaternary structure is the way these polypeptide chains are held together (e.g. haemoglobin is made of four polypeptide chains, bonded together)
- This structure is the final 3D structure for proteins made from multiple polypeptide chains
What bonds hold together the different levels of the proteins structures?
- Primary structure: Peptide bonds
- Secondary structure: Hydrogen bonds
- Tertiary structure: Ionic bonds, Disulfide bonds, Hydrophobic and Hydrophilic interactions, Hydrogen bonds
- Quaternary structure: Determined by the tertiary structure
Describe the properties + formation of a globular protein.
- compact - water-soluble - roughly spherical
- Formed when proteins fold into their tertiary structures
^— in a way the hydrophobic R groups on the amino acids are kept away from the aqueous environment
^— hydrophilic R groups are on the outside + therefore protein is water-soluble
Describe the properties + formation of a fibrous protein
- formed from long, insoluble molecules
^— due to presence of high proportion of amino acids with hydrophobic R groups in their primary structures - Contain limited range of amino acids, usually w/ small R groups
- Amino acid sequence in the primary structure is usually quite repetitive
^— leads to very organised structures reflected in the roles fibrous proteins have - make strong, lonf molecules which are not folded into complex, 3D shapes likes globular proteins
Give THREE globular proteins
- Haemoglobin (conjugated protein)
- Insulin (hormone)
- Catalase (enzyme)
Give THREE conjugated proteins
- Collagen
- Keratin
- Elastin
What is a reducing sugar?
Can donate electrons (carboxyl group becomes oxidised), the sugars become the reducing agent
What is a non-reducing sugar?
Cannot donate electrons - cannot be oxidised
e.g. Sucrose
Describe the structure of cholesterol
Has hydrophobic and hydrophilic regions
What are the functions of cholesterol?
- Synthesised in the liver and transported via blood
- Affects fluidity and permeability in the cell membrane
- Disrupts close packing of cells membrane - increases rigidity (makes membrane less flexible)
- Barrier - prevents water soluble substances from diffusing across the membrane
- Used to produces steroid-based hormones (oestrogen, testosterone, progesterone)
Describe the structure of an amino acid
C atom bonded to:
- amine group - NH₂
- carboxylic acid group
- H atom
- R group
What is an R group?
How each amino acid differs + why amino acid properties differ (e.g. if acidic or basic, polar or no polar)
How is a peptide bond formed?
- A hydroxyl (-OH) is lost from the carboxylic group of one amino acid and a hydrogen is lost from the amine group of another amino acid
- Remaining C atom (with double bonded oxygen) from the first amino acid bonds to the nitrogen atom of the second amino acid
How is a peptide bond broken?
- Hydrolysis reaction
- Addition of water breaks the peptide bonds resulting in polypeptides being broken down to amino acids
What is a conjugated protein?
Globular proteins that contain a prosthetic group
e.g. haemoglobin which contains a prosthetic haem group
Why is water being a liquid medium useful?
- Provides habitats for aquatic organisms
- Medium for chemical reactions
- Used for transport
Why is water being an important metabolite useful?
Used in hydrolysis + condensation reactions
Why is water’s high specific heat capacity useful?
Keeps aquatic + cellular environments stable
Why is water’s high latent heat of vaporisation useful?
Evaporation has a cooling effect on organisms
Why is water’s cohesion useful?
- Water is drawn up the xylem
Why is water’s surface tension useful?
Allows pond-skaters to walk on the surface
Why is water being a good solvent + transport medium useful?
Dissolves ionic + polar molecules, allowing them to easily be transported
Why is water being good reaction medium useful?
Cytoplasm in cells is an aqueous solution where many chemical reactions happen
Why is water being incompressible useful?
Can prevent plans from wilting + act as a hydrostatic skeleton for invertebrates
Describe the importance of a globular protein’s solubility
- Important for many different functions of globular proteins
- Essential for regulating man processes necessary to life
^— e.g. chemical reactions, immunity, muscle contraction, etc
Describe the structure + function of Haemoglobin
- Conjugated protein
- Quaternary proteins made from 4 polypeptides, 2 α + 2 β subunits
^— each subunit contains a prosthetic haemorrhage group - Iron II ions present in the harm groups are each able to combine reversibly with an Oxygen molecule + transport it around the body
Describe the structure + function of Insulin
- Globular protein
- Hormone involved in the regulation of blood glucose concentration
- Hormones are transported in the bloods + therefor soluble
- Hormones must also fit into specific receptors on cell-surface membrane to have their effect + therefor have precise shapes
Describe the structure + function of Catalase
- An enzyme
- Catalase is a quaternary proteins containing 4 haem prosthetic groups
- Presesne of the iron II ions in the prosthetic groups allow catalase to interface with hydrogen peroxide + speed up its breakdown
- Hydrogen peroxide is a common byproduct of metabolism but is damaging to cells + components id allowed to accumulate
^— catalase stops this
Describe the properties + function of Keratin
- Group of fibrous preotsin present in hair, skin + nails
- large proportion of the sulfur-containing amino acid, cysteine
^— resulting in many strong disulfide bonds (bridges) forming strong, inflexible _ insoluble materials - Degree of disufide bonds determines flexibility - hair contains fewer bonds making it more flexible than nails, which contain more bonds
- Unpleasant smell produce when hair or skin is burn is due to large quantities of sulfur
Describe the properties + function of Elastin
- Fibrous protein found in elastic fibres (along w/ small protein fibres)
- Elastic fibres are present in the walls of blood vessels + in the alveoli of the lungs - give these structures flexibility to expand when needed + return to normal
- Quaternary protein made from many stretchy molecules called tropoelastin
Describe the structure + function of Collagen
- Fibrous proteins
- Connective tissue found in skin, tendons, ligaments + the nervous system
- There are a number of different forms but all are made up of 3 polypeptides wound together in a long + strong rope-like structure
^— like rope, collagen has flexibility
How does the branched structure of amylopectin affect its function?
Side branches mean enzymes can digest easily + energy release quickly
How does the COILED + COMPACT structure of amylose affect its function?
Can store a lot of energy
Name the essential anions + the
- Nitrate - NO₃⁻
- Hydrogencarbonate - HCO₃⁻
- Chloride - Cl⁻
- Phosphate - PO₄³⁻
- Hydroxide - OH⁻
Explain energy storage as a function of triglycerides
- Long hydrocarbon chains in triglycerides contain many carbon-hydrogen bonds with little oxygen (triglycerides are highly reduced)
^— when triglycerides are oxidised during cellular respiration, causes these bonds to break releasing energy used to produce ATP
Describe the properties + functions of hydrogen ions
- Proton
- Concentration in a solution determines the pH
- more H⁺ = lower pH (more acidic)
- Hydrogen bonding
Describe the properties + functions of calcium ions
- Essential for bone and enamel strucutre
- Regulate transmission of impulses from neurone to neurone
- Stimulates muscle contraction
- Helps regulate protein channels
- Necessary for formation of blood clots
Describe the properties + functions of iron ions
- cation
- Bind oxygen
^— found in haemoglobin to transport oxygen around the body - Involved in transfer of electrons during respiration + photosynthesis
Describe the properties + functions of sodium ions
- Required for transport of glucose + amino acids across cell-surface membranes
- Required for transmission of nerve impulses
Describe the properties + functions of potassium ions
- Essential for nerve transmission
- Allows reabsorption of water in teh kidneys
- Play role in guard cells opening of stomata
Describe the properties + functions of ammonium ions
- Intermediate ion that forms during the deamination of proteins in the liver + kidneys
Describe the properties + functions of nitrate ions
- Present in the soil + taken up by plants
- Provides essential source of nitrogen for protein synthesis
- Required for growth + repair in plants
Describe the properties + functions of hydrogencarbonate ions
- Work alongside hydrogen ions in the transport of carbon dioxide in the blood
Describe the properties + functions of chloride ions
- Involved in the transport of carbon dioxide in the blood
- Move in + out of red blood cels + help to maintain pH balance
Describe the properties + functions of phosphate ions
- Attaches to other molecule to form phosphate groups —> essential component of DNA, RNA + ATP
- Phosphate groups allow individual nucleotides to join up in RNA + DNA
- Found in phospholipids
Describe the properties + functions of hydroxide ions
- Role in bonding between biochemical molecules
- One oxygen atom is covalently bonded to one hydrogen atom
- Electronegative charge of oxygen allows for the formation of hydrogen bonds
