Chapter 3- Biological molecules Flashcards
what bond is formed between amino acids?
peptide bonds
How do the interactions between the R groups of amino acids contribute to the folding of polypeptides into proteins?
-the R groups of amino acids making up a protein are able to interact with each other forming different types of bonds.
- these bonds lead to polypeptides (long chain of amino acids) folding into proteins.
what is the structure of an amino acid?
- Amine group (-NH₂) = consisting of a nitrogen atom bonded to two hydrogen atom
- Carboxyl group (-COOH)= consisting of C=O and a hydroxyl group (-OH)
- A single hydrogen atom is bonded to the central carbon
-. R Group - Central Carbon Atom
draw the structure of an amino acid
H H
| |
N— C—C=O—OH
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H R
what are the levels of protein structure?
- primary structure
- secondary structure
- tertiary structure
- quaternary structure
Describe the primary structure in the levels of protein structure.
- The primary structure of a protein refers to the sequence of amino acids in a polypeptide chain.
- The order of amino acids is determined by the genetic code (DNA sequence) and is held together by peptide bonds.
- The primary structure is important because it dictates the protein’s final shape and function.
- only bonds involved are peptide bonds
Describe the secondary structure in the levels of protein structure.
- The secondary structure refers to the folding of the polypeptide chain into structures such as alpha helices or beta-pleated sheets.
- The oxygen, hydrogen and nitrogen atoms of the amino acids interact.
- Alpha helices are coiled structures
- while beta-pleated sheets are made of parallel strands of polypeptides that are folded.
- secondary structure is the result of hydrogen bonds
Describe the tertiary structure in the levels of protein structure.
- The tertiary structure refers to the overall 3D shape of a single polypeptide chain.
- It is stabilized by a variety of bonds and interactions between the R groups (side chains) of the amino acids, including:
Hydrogen bonds
Ionic bonds
Disulphide bridges (covalent bonds between sulfur atoms)
Hydrophobic/ hydrophillic interactions ( weak interactions between polar and non-polar R groups) - The tertiary structure is critical for the protein’s function
Describe the quaternary structure in the levels of protein structure.
- refers to the arrangement of multiple polypeptide chains (subunits) into a functional protein.
- Not all proteins have quaternary structure, but those that do are composed of two or more polypeptide chains. These subunits can be identical or different.
- Quaternary structure is held together by the same types of bonds that stabilize tertiary structure (hydrogen bonds, ionic bonds, hydrophobic interactions, and disulphide bridges).
- Example: Haemoglobin, a protein made of four polypeptide chains, has a quaternary structure.
what enzymes break down peptides into amino acids, and what role does water play in this process?
- protease are enzymes that turn peptides back into amino acids.
- a water molecule is used to break the bond through hydrolysis
list features of a globular protein
- compact
- water soluble
- 3D spherical shape
- e.g. insulin
list features of a fibrous protein
- strong
- long/straight
- insoluble
- sometimes flexible
- e.g. collagen, elastin and keratin
what is a conjugated protein?
- globular proteins that contain a (non- protein) prosthetic group.
- The prosthetic group is often a metal ion, vitamin, or carbohydrate
- e.g. haemoglobin
what are proteins without prosthetic groups called?
simple proteins
what are fatty acid chains with no double bonds present called?
fatty acid chains that have no double bonds present between the carbon atoms are called saturated, because all the carbon atoms form the maximum number of bonds with hydrogen atoms
what are fatty acid chains with double bonds present called?
a fatty acid with double bonds between some of the carbon atoms is called unsaturated. the presence of double bonds cause the molecules to kink or bend and they therefore cannot pack closley together.
what are triglycerides made up of?
1 glycerol bonded (ester bond) to 3 fatty acids
what are phospholipids made up of?
2 fatty acids, 1 glycerol and 1 phosphate
Biologial roles of lipids
due to their non polar nature, lipids have many biological roles including:
- hormone production
- electrical insulation necessary for impulse transmission
- membrane formation and the creation of hydrophobic barriers
- water proofing.
also have an important role in long term storage.
what roles do lipids have in long term storage?
triglycerides in particular have an important role in long term energy storage. for example:
- thermal insulation to reduce heat loss
- cushioning to protect vital organs
- buoyancy for aquatic organisms
what are organic compounds?
- molecules that contain the chemical elements carbon (C) and hydrogen (H
- examples are: Carbohydrates, lipids, proteins and nucleic acids
what are the 3 types of carbohydrates?
monosaccharides, disaccharides and polysaccharides
what functions do carbohydrates have?
- Source of energy e.g. glucose is used for energy-release during cellular respiration
- Store of energy e.g. glycogen is stored in the muscles and liver of animals
- Structurally important e.g. cellulose in the cell walls of plants
what is adhesion?
the attraction of water molecules to the impermeable walls of xylem tissue
describe the formation of a peptide bond. (2)
through a condensation reaction between the amine group of one amino acid and a carboxyl group of another
describe ways in which the physical properties of water allow organisms to survive over a range of temperatures. (9)
- High latent heat of vaporisation- large amounts of energy required to change from a liquid to gas
- High specific heat capacity- large amounts of energy needed to change the temperature
- meaning, there is a thermally stable enviournment for aquatic organisms, and they use less energy on temperature control
- Ice is less dense than water so it floats, so the surface of ice provides a habitat for organisms. And, water beneath ice remains liquid so aquatic organisms do not freeze
- Water is a solvent for transport mediums so it is able to dilute toxic substances in the water
- Transparent- allows underwater photosynthesis
- Organisms can obtain oxygen/ carbon dioxide from water
compare the structures of glycogen and cellulose
Glycogen:
- no hydrogen bonding
- alpha glucose
- branched
- 1,4 + 1,6 glycosidic bonds
Cellulose:
- hydrogen bonding
- beta glucose
- not branched
- only 1,4 glycosidic bonds
state the properties of water
- solvent= can be used as a transport medium for solutes
-liquid= provides habitats and transport - high specific heat capacity and high latent heat of vaporisation so it is hard to change the temperature
- cohesion= water molecules are attracted to other molecules of water due to H bonding.
- density= ice is less dense than water due to H bonds. insulating water (only surface gets frozen) and providing habitats for organisms.
- polar= has areas of positive and negative charge
what are carbohydrates made up of?
- carbon
- hydrogen
- oxygen
what is the bond between glucose molecules called?
glycosidic bond through a condensation reaction.
define isomer
same chemical formula but different atom arrangement.
for example alpha glucose and beta glucose.
functions of triglycerides
- insulation
- buyoncy
- energy source
- energy store
- protection
what bond holds glycerol and fatty acids together
in a condensation reaction, ester bonds hold glycerol and fatty acids together.
how many H bonds are between the complementary bases?
A + T= 2
C + G= 3
why is a high SHC of water advantageous for living organisms?
- Provides stable habitats in aquatic environments.
-Is able to maintain a constant temperature as water temp does no fluctuate a lot.
This is important in maintaining temperatures that are optimal for enzyme activity
why is a high LHV of water advantageous for living organisms?
large amount of thermal energy must be absorbed to break the H bonds and evaporate
This is an advantage for living organisms as only a little bit of water is needed to lose a great amount of heat.
This provides a cooling effect for living organisms, e.g. evaporation of water in sweat on the skin
what are the covalent bonds found in carbohydrates, proteins, lipids and nucleic acids?
carbohydrate= glycosidic bond
proteins= peptide bond
lipids= ester bond
nucleic acids= phosphodiester bond
functions of carbohydrates
- source of energy= glucose
- store of energy= glycogen
- structural= cellulose in walls of plants
functions of lipids
- an essential components of biological membranes
- source of energy that can be respired
- store of energy= lipids are stored in fats of mammals
- insulating layer= thermal insulation in skins of mammals
functions of proteins
- growth and repair of cells
- structurally important= e.g. in muscles, keratin and collagen in skin
- can act as carrier molecules e.g. cell membrane
function of nucleic acids
- carrying the genetic code in all living organisms
- essential in the control of cellular processes e.g. protein synthesis
how to detect non reducing sugars?
first reducing sugars must be hydrolysed to break the disaccharide into two monosaccharides before a Benedict’s reagent is added to detect a colour change. e.g. sucrose
describe how these R groups interact to determine the tertiary structure of a protein
- disulphide brides
- H bonds
- hydrophobic R groups on the inside, shielded from water
- hydrophillic R groups on the outside, in contact with water
- ionic bonds between oppositley charged R groups
- some R groups attract/ repel
give 3 differences between the structure of glycogen and collagen. (3)
glycogen is branched, collagen is linear.
glycogen is a carbohydrate, collagen is a protein.
glycogen contains C, H, O. collagen contains C, H, O, N.
Describe the structure and function of cellulose.
Cellulose is straight chain molecule with many hydrogen bonds between individual chains. They produce fibers which are strong and insoluble and used in cell walls
what do biosensors do?
biosensor use biological components to determine the presence and concentration of molecules such as glucose.
what will happen when reducing sugars react with the copper ions in Benedicts reagent?
This results in the addition of electrons to the blue Cu2+ ions, reducing them to brick red Cu+ ions. when a reducing sugar is mixed with benedicts reagent an warmed, a brick red precipitate is formed.
explain why an iodine test is used in experiments to show that plants require light for photosynthesis (3).
In an iodine test a purple/black colour indicates the presence of starch (1). Starch is a product of
photosynthesis (1). The test shows that starch is produced when light is available to the plant, but not
when the plant is kept in the dark (1).
describe why oils are liquid and facts are solid at room temp (4)
Oils are (usually) unsaturated (1); unsaturated fatty acids contain double bond(s) (1); molecules
cannot pack closely (1); fats are usually saturated so fatty acids have no double bonds (1).
state the colour you would see if the sample contained amino acids instead of proteins
there would be no colour change from blue to purple (solution will remain blue), as there are no peptide bonds present so the test is negative
compare and contrast the role of R group interactions in the formation of tertiary and quaternary structures of proteins (6).
- R groups on amino acids interact
- tertiary structure- interactions within a protein molecules
- quaternary structure- interactions between protein molecules
- hold molecules together
- both involve the same interactions i.e. hydrogen bonds, ionic bonds, disulphide bond and hydrophobic/hydrophilic interactions
what do phosphodiester bonds form between?
the phosphate of one nucleotide and the hydroxyl group (OH) attached to the carbon of the deoxyribose sugar in an adjacent nucleotide.
what is the main function of nucleotides?
they are building blocks of nucleic acids (RNA and DNA), consists of a sugar molecule, phosphate and base (A, T, C, G)
what are 3 differences in the structures of amylose and cellulose
amylose is coiled, cellulose is not coiled.
amylose has 1,4 alpha glycosidic bonds, cellulose has 1,4 beta glycosidic bonds.
amylose is a globular protein, cellulose is a fibrous protein.
amylose has H bonds within molecule, cellulose has H bonds between adjacent molecules.
