Mod 2 Chap 3: Biological Molecules Flashcards
Define a monomer.
A small molecule that binds to other identical molecules to form a polymer.
Define a dimer.
Two monomers joined together.
Define a polymer.
A large molecule made from many small monomers.
What elements make up the biological molecules carbohydrates?
Also, what are their monomers and polymers?
Elements: C, H, and O
Monomer: Monosaccharides (e.g. Glucose)
Polymer: Polysaccharides (e.g. Starch)
What elements make up the biological molecules proteins?
Also, what are their monomers and polymers?
Elements: C, H, N, O and S.
Monomer: Amino acids
Polymer: Polypeptides
What elements make up the biological molecules Nucleic Acids?
Also, what are their monomers and polymers?
Elements: C, H, O, N and P.
Monomer: nucleotides.
Polymer: DNA.
What is covalent bonding?
A bond in which atoms share electrons with other atoms. This allows them to ‘fill’ their outer shell and results in a strong bond with the other atom.
What is a condensation reaction?
A condensation reaction occurs when two molecules are joined together with the removal of water.
What is a hydrolysis reaction?
A hydrolysis reaction occurs when two molecules are split up by the addition of water.
What elements make up the biological molecules Lipids?
Elements: C, H and O.
How does hydrogen bonding occur between water molecules?
- water = 2 H atoms, each covalently bonded w/ O atom.
- but, as O atom has greater number of protons in its nucleus, it exherts a stronger attraction for shared electrons (O atom has a greater electronegativity), it has greater pull on electrons.
- so O atom becomes slightly negative + H atoms become slightly positive
- when this happens, we say molecule is polar (e.g. Structure of water is polar).
- in structure of water: H = delta positive, O = delta negative.
- so water forms hydrogen bonds
- in water molecules, hydrogen bonds are weak + covalent bonds are strong
Describe the properties of water.
- it’s a solvent
- high specific heat capacity: large heat energy needed to increase kinetic energy
- has high latent heat of vaporization (heat energy / has an unusually high BP): is a liquid at room temp due to H bonds, takes a lot of energy to increase its temp + turn it gaseous
- when freezes it turns to ice, + actually then becomes less dense, this due to H bonds as they fix positions of polar molecules slightly further apart than average distance in liquid state, when cooled below 4 degrees
- has cohesive properties + surface tension: moves as one mass as molecules are attracted to eachother
- has adhesive properties: water molecules are attracted to other materials, e.g. When you wash hands they become wet
- it’s a reactant
- it’s a liquid at room temp
- it’s dense
Relate the properties of water to its role in living organisms / how this benefits life.
SOLVENT:
- molecules + ions can move around + react in it
- so many reactions happen in cytoplasm of cells (as is 70% water)
- molecules + ions can also be transported around living things when dissolved in water
HIGH LATENT HEAT OF VAPORISATION:
- so water can help cool living things + keep their temp stable
- e.g. mammals cooled when sweat evaporates
- e.g. plants cooled when water evaporates from mesophyll cells
COHESION AND SURFACE TENSION:
- columns of water in plant vascular tissue are pulled up xylem tissue together from roots in transpiration stream
- insects like pond-skaters can walk on water
HIGH SPECIFIC HEAT CAPACITY:
- living things need a stable temp for enzyme-controlled reactions to happen properly
- aquatic organisms need a stable environment in which to live
REACTANT:
- important for digestion + synthesis for large biological molecules
LIQUID:
- provides habitats for living things in rivers, lakes + seas
- forms major component of tissues in living organisms
- provides a reaction medium for chemical reactions
DENSITY:
- water more dense than ice, so aquatic organisms have stable environments to live in through winter
- ponds + other water bodies are insulated against extreme cold, as ice layer reduces heat loss.
What are the roles of carbohydrates?
- energy store
- energy source
- structural
- form part of other molecules
Describe the three main groups of carbohydrates.
Monosaccharides: (simple sugars)
Disaccharides: (complex sugars)
Polysaccharides: (complex carbohydrates)
How are sugars held together?
Glycosidic bonds
Describe monosaccharides (+ structure, role + how they are categorised).
- simple sugars
- energy source due to large number of C-H bonds
- soluble
- exist as single ring shape or straight chain
- no glycosidic bonds
- categorized by their number of C atoms, into:
- hexose: 6 carbons
- pentose: 5 carbons
- triose: 3 carbons
- roles in organisms: energy, transported in blood, monomers for other carbohydrates
Describe glucose as a hexose monosaccharide.
- hexose monosaccharide so has 6 carbons
- two forms of it: alpha / beta glucose
- alpha + beta glucose structures drawn differently (draw)
- alpha + beta glucose are isomers of eachother
Describe ribose as a pentose monosaccharide.
- pentose monosaccharide so has 5 carbons atoms
- is the sugar present in RNA nucleotides
Describe glucose’s molecules’ properties.
- polar
- soluble in water, due to H bonds between hydroxyl groups + water molecules
- important they are soluble as means glucose is dissolved in cytosol of cell.
Describe disaccharides (+ structure, role + examples).
- two single sugar molecules joined by a condensation reaction / covalently joined
- soluble
- have one single glycosidic bond
Examples: - sucrose (glucose + fructose)
- lactose (glucose + galactose)
- maltose (glucose + glucose)
- roles in living organisms: energy release, storage and transport in plants
Two monosaccharides will form a…
Disaccharide
Describe oligosaccharides.
- 3-10 sugar molecules joined into a chain
- not easily digested
- found in leaks, onions, garlic etc
Describe polysaccharides ( + structure, role + types).
- polymers or monosaccharides
- many molecules covalently joined
- insoluble
- have many glycosidic bonds
- long chains that may be branched / coiled
- two types of them:
- homopolysaccharides: (monomers are all the same)
- herteropolysaccharides: (more than one type of monomer)
- roles in living organisms: energy storage, structural component of cell walls
Describe the structure of the polysaccharide starch through amylose.
- a type of starch
- formed by alpha glucose molecules joined together by 1-4 glycosidic bonds
- is a polysaccharide in starch
- angle of bond means long chain of glucose twists to form a helix
- helix further stabilized by H bonds within molecule
- makes polysaccharide more compact + much less soluble than glucose molecules used to make it
Describe the structure of the polysaccharide starch through amylopectin.
- another type of starch
- formed when glycosidic bonds form in condensation reactions between carbon 1 + 6 on two glucose molecules, unlike amylose
- so, amylopectin has branched structure
- made by 1-4 glycosidic bonds between alpha glucose molecules
Describe the structure of the polysaccharide glycogen.
- equivalent energy storage molecule in animals + fungi to starch in plants
- forms more branches than amylopectin so is more compact + less space needed for it to be stored
- coiling or branching of it also makes it v compact for ideal storage
- branching also means free ends where glucose molecules can be added or removed, speeding up process of storing / releasing glucose required by cell
- key properties (as in amylopectin): insoluble, branched + compact, so ideally suited to storage roles they carry out
Describe the structure of the polysaccharide cellulose.
- straight chain molecule, formed when polysaccharides formed from glucose are unable to coil / form branches
- cellulose molecules make H bonds w/ eachother forming micro fibrils
- micro fibrils join together forming macro fibrils, which continue to produce fibres
- these fibres = strong, insoluble + used to make cell walls
- cellulose = v hard to breakdown into its monomers + forms fibre necessary for a healthy digestive system
Describe lipids.
- have large amounts of carbon + hydrogen, but low amounts of oxygen
- insoluble in water as non-polar, but water is polar
(Only polar molecules are soluble in polar solvents) - soluble in alcohol
3 most important lipids:
- triglycerides
- phospholipids
- cholesterol
Describe the lipid triglycerides (as an example of a macromolecule).
- made of fatty acids + glycerol
- 3 fatty acids per 1 glycerol
Draw the structure of glycerol.
3 C’s in middle
3 H’s coming off top of them
3 OH’s coming off bottom of them
2 H’s, one each side
(Draw)
Describe / draw the general structure of fatty acids.
- hydrocarbon chains attached to a carboxyl group (-COOH)
Carboxyl group on end: C w/ double bond to O above, and a bond to HO beneath
Hydrocarbon chains: a number of C’s in middle (any number from 2 - 22+), w/ H’s above + beneath them + one at end
How many carbons are in a: short hydrocarbon chain? Medium hydrocarbon chain? Long hydrocarbon chain? Very long hydrocarbon chain?
Short: <6
Medium: 6-12
Long: 13-21
Very long: 22+
Describe saturated fatty acids (in triglycerides).
- no C=C double bonds
- example of saturated fatty acids: palmitic acid (in animal fat)
Describe monounsaturated fatty acids (in triglycerides).
- one C=C double bond
- example of monounsaturated fatty acid: oleic acid (in olive oil)
Describe polyunsaturated fatty acids (in triglycerides).
- two or more C=C double bonds
- example of polyunsaturated fatty acid: linoleic acid (in nuts)
Describe animal lipids.
- saturated
- solid at room temp
- fats
Describe plant lipids.
- unsaturated
- liquid at room temp
- oils
- fatty acids in them contain a kink which makes them more fluid
Describe ester bonds.
- formed by condensation reactions
Draw
Describe the lipid phospholipids.
- same structure as triglycerides, except one fatty acid has been replaced by a phosphate group
- phosphate head is attached to a water soluble group e.g. Choline
- when surrounded by water, phosphate group becomes negatively charged (so polar), so now top part of molecule (phosphate + choline group) are attracted to water - HYDROPHILIC
- fatty acid tails still repelled by water - HYDROPHOBIC
- so overall, whole phospholipid is AMPHIPATHIC - part of them is hydrophilic + part is hydrophobic.
Explain how phospholipids being amphipathic determines their behaviour when exposed to water.
- they form micelles: heads face out towards water (hydrophilic), tails face in away from water (hydrophobic)
OR
- they form bi-layers: 2 rows of phospholipids, facing opposite / away from eachother, heads face outwards (hydrophilic), tails face in towards eachother (hydrophobic)
Describe the roles of the lipid triglycerides (as an example of a macromolecule) in living organisms.
- long hydrocarbon tails contain lots of chemical energy, so good for energy storage
- storage of carbon in bacteria
- thermal insulation
- buoyancy for aquatic animals
- cushioning to protect vital organs e.g. Heart
Describe the role of the lipid phospholipids (as an example of a macromolecule) in living organisms.
- found in cell membrane in all eukaryotes + prokaryotes to control what enters + leaves cell
- this poss due to hydrophilic heads + hydrophobic tails, as form a double layer (bi-layer) w/ a hydrophobic centre, so soluble substances can’t easily pass through
Describe the role of the lipid cholesterol in living organisms.
- help strengthen cell membrane by interacting w/ phospholipid bilayer in eukaryotic cells
Describe the type of lipid, sterols.
- type of lipid found in cells
- complex alcohol molecule
- based on a four carbon ring structure w/ a Hydroxyl (OH) group at one end
- have dual hydrophobic + hydrophilic characteristics like phospholipids (only hydroxyl group is hydrophilic)
- types of sterols: cholesterol
Describe cholesterol as a type of sterol, and lipid.
- manufactured in liver + intestines
- important role in formation of cell membranes
- becomes positioned between phospholipids w/ hydroxyl group at periphery end of membrane
- this adds stability to cell membranes + keeps fluidity regulated
- used to manufacture vitamin D, steroid hormones + bile
Describe proteins.
- elements present in them: C, H, O, N + sometimes S
- over 500 amino acids exist, but only 20 used to make proteins
Describe the general amino acid structure.
Draw
- amino group on left: (N bonded to one H above it, + one below)
- carboxyl group on right: (C double bonded to O above + bonded to OH below)
- C in middle bonded to R above (that varies in each amino acid), + bonded to H below
What is R in the amino acid glycine?
H
What is R in the amino acid alanine?
CH3
What is R in the amino acid cysteine?
CH3S
Describe how dipeptides are formed.
- amino acids join + are held together by peptide bonds (example of a condensation reaction)
- water produced
- result is a dipeptide
- peptide bonds can be broken by hydrolysis reactions
How can bonds in proteins such as amino acids be denatured?
High temperature:
- give molecules more kinetic energy so vibrate more, causing weak H bonds to break, breaks down tertiary structure of protein, changing 3D shape of protein so can’t perform its function
Changes in pH:
- if rises or falls too much, amount of H+ & OH- ions unbalanceds, causing ionic bonds + H bonds to break, + breaks proteins tertiary (3D) structure, changing it so cannot perform its function.
What bonds are present in the primary structure of proteins?
Peptide bonds only.
What bonds are present in the secondary structure of a protein?
Hydrogen bonds: pull amino acid chain into a coil shape (an alpha helix)
What bonds are present in the tertiary structure of a protein?
- disulfide bonds
- ionic bonds
- hydrogen bonds
- hydrophobic + hydrophilic interactions
What bonds are present in the quaternary structure of a protein?
- linking together of polypeptide chains
- interactions between diff subunits (individual proteins).
What types of proteins are there? Give examples of each type.
Globular:
- haemoglobin (a globular conjugated)
- insulin
- pepsin
Fibrous:
- collagen
- keratin
- elastin
Describe the globular protein haemoglobin.
- quaternary protein made of four polypeptides, two alpha + two beta subunits
- each subunit contains a prosthetic haem group
- iron II in haem helps it transport O2 around body
- also a conjugated protein (subdivision of globular)
Describe the globular protein insulin.
- hormone involved in regulation of blood glucose concentration
- hormone, so has precise shape to fit on receptors on cell surface membranes
- soluble as has to be transported in bloodstream.
Describe the globular protein pepsin.
- enzyme that breaks down proteins into smaller peptides
- produced in stomach + one of main digestive enzymes
- expressed as zymogen called pepsinogen
- can break peptide bonds next to aromatic amino acids
- has hydrogen bonds
- has 3 di-sulfide bridges
Describe the fibrous protein collagen.
- connective tissue found in skin, tendons, ligaments etc
- number of diff forms of collagen, all made of 3 polypeptides wound together in rope like structure (triple helix)
- flexible
- has H bonds between polypeptide chains, forming long quaternary proteins w/ staggered ends
- allows proteins to form long fibrils called tropcollagen, which cross link to produce strong fibres
Describe the fibrous protein keratin.
- present in hair, skin, nails.
- has large proportion of amino acid cysteine, which contains sulfur
- results in many strong, inflexible + insoluble materials
- degree of disulfide bonds determines flexibility
- large quantities of sulfur present, explaining unpleasant smell of burnt hair, for e.g.
Describe the fibrous protein elastin.
- found in elastic fibres present in wall of blood vessels
- gives these structures flexibility
- a quaternary protein made from stretchy molecules: tropoelastin, link to make elastin a large stable structure
- tropoelastin helps stretch + recoiling
- elastin structure stabilized by cross link in covalent bonds
