Chapter 3- Biological Molecules Flashcards
Name the covalent bond between two adjacent amino acids
Peptide bond
Name the type of reaction involved in breaking peptide bonds and what happens
Hydrolysis
Water added
How can you control pH?
Add buffer solution
Why is it good to repeat investigations?
- improve reliability
- allows you to calculate mean
- identify anomalous results
What are the three main lipids?
- triglycerides
- phospholipids
- cholesterols
Which elements do triglycerides and cholesterols contain?
Carbon
Hydrogen
Oxygen
Are lipids soluble or insoluble?
Insoluble
Which lipids are important in membrane structure?
- phospholipids
- cholesterol
How to do emulsion test for lipids and how positive result identified?
- mix with ethanol and water
- if positive = goes cloudy
How might the lipid content of food that comes from microorganisms differ from food that comes from animals?
- less lipids
- less saturated fat
- more saturated fat
- less cholesterol
Describe the primary level of protein structure
-sequence of amino acids joined by peptide bonds
Describe the secondary level of protein structure
- initial folding of polypeptide chain
- hydrogen bonds
Describe the tertiary level of protein structure
- ionic bonds
- Hydrogen bonds
- disulfide bonds
- hydrophobic and hydrophilic interactions
- secondary structure undergoes further folding
Describe the quaternary level of protein structure
When 2 or more polypeptides are joined together to form a protein
Describe formation of hydrogen bond between 2 water molecules and why water can form these bonds
- between electropositive H and electronegative O of adjacent water molecules
- water molecule is polar
Water is a solvent. Why is this good for the survival of organisms?
- able to dilute toxic substances
- medium for metabolic reactions
- organisms can take in minerals like tissue fluid, xylem, phloem
- internal transport medium
General structure of amino acid
COOH
H C R group
NH2
Property of collagen that makes useful component of blood vessel walls
- strong
- insoluble
Structure of collagen?
- peptide bonds between amino acids in polypeptide
- every 3rd amino acid is glycine
- glycine is a small R group thus allows closeness of polypeptide chains
- 3 polypeptide chains twisted around each other
- H bonds between polypeptide chains
- no hydrophilic R groups on outside of molecule
Ways in which structure of haemoglobin differs from that of collagen?
- contains prosthetic haem group
- globular
- hydrophilic R groups on outside of molecule
- 4 sub units which are 2 alpha and 2 beta sub units
Describe the formation of a peptide bond between 2 amino acids
- between amine group of one amino acid and carboxyl group of another
- H from amine combines with OH from carboxyl to produce water molecule in condensation reaction
Describe high latent heat of vaporisation as a property of water that allows organisms to survive over a range of temperatures
- large amount of energy needed to change from liquid to gas
- evaporation is efficient cooling mechanism
- e.g. sweating
Describe high specific heat capacity as a property of water that allows organisms to survive over a range of temperatures
- large amount of energy needed to raise temp
- stable environment for aquatic organisms
- thus organisms use less energy on temp control
- temp of organism changes slowly
- metabolic reactions carried out normally
- due to many hydrogen bonds between water molecules. Lot of energy needed to break these bonds.
Describe ice is less dense than water as a property of water that allows organisms to survive over a range of temperatures
- floats
- surface of ice provides habitat for organisms
- ice forms an insulating layer
- keeping water below ice still liquid
- thus organisms do not freeze
- and can still move
Describe surface tension as a property of water that allows organisms to survive over a range of temperatures
Habitat for insects
Describe transparency as a property of water that allows organisms to survive over a range of temperatures
-allows underwater photosynthesis
Where hydrogen bonds found in biological molecules
- between water molecules
- protein secondary structure
- protein tertiary structure
- between chains of cellulose
Roles of cholesterol?
- make vitamin D
- make bile
- stabilises membranes
- waterproofs skin
How molecular structure of cholesterol similar to molecular structure of a carbohydrate
-6 membered ring
Disease which high blood cholesterol is a risk factor
- stroke
- type 2 diabetes
- coronary heart disease
Why glycogen is a good storage molecule?
- insoluble = doesn’t affect water potential of cell
- compact= stores lot of energy
- lots of branching for enzymes to attach
- can be broken down and built up easily
Function of glucose?
- provides energy
- used for respiration
Structure of glycogen?
- made from alpha glucose
- 1,4 and 1,6- glycosidic bonds present
- branched
- all glucose units in same orientation
Primary structure of haemoglobin?
- sequence or amino acids
- amino acids joined by peptide bonds
Secondary structure of haemoglobin?
- hydrogen bonds present
- forms alpha helix and beta pleated sheets
Tertiary structure of haemoglobin?
- secondary structure undergoes further folding
- hydrogen, disulfide, ionic bonds present
- hydrophobic or hydrophilic interactions
- soluble so hydrophilic R groups on outside of molecule
Quaternary structure of haemoglobin?
- 4 sub units which are 2 alpha and 2 beta chains
- each polypeptide has 1 prosthetic haem group
- prosthetic haem group contains Fe2+ ions
Ways that the structure of haemoglobin is similar to collagen?
- more than 1 polypeptide
- have quaternary structure
- both have amino acid sequences
- both have peptide bonds
- both have hydrogen, disulfide, ionic bonds
- both have hydrophobic or hydrophilic interactions
Why is ice less dense than water?
Water molecules spread out to form lattice structure
Structure of triglyceride?
-one glycerol attached to 3 fatty acids by 3 ester bonds
Roles of lipids?
- insulation
- energy store
- used in membranes
- waterproofing
- buoyancy
What causes anaemia and what does this do?
- Lack of iron
- body unable to produce sufficient amounts of haemoglobin
What is wrong with the graph used to determine whether someone is underweight or overweight?
- does not distinguish between male and female
- doesn’t take into account bone density
- may be pregnant
Diseases associated with obesity?
- coronary heart disease
- type 2 diabetes
- cancers
- gall stones
Describe how R groups interact to determine tertiary structure of proteins
- can form disulfide bonds
- can form hydrogen bonds
- can form ionic bonds
- hydrophilic R groups on outside of molecule
- hydrophobic R groups on inside of molecule
Differences between structure of glycogen and collagen
\+carbohydrate -protein \+made of alpha glucose units -made of amino acid units \+glycosidic bonds -peptide bonds \+branched -linear
Properties of collagen
- strong
- insoluble
- flexible
- does not stretch
How the conc of a reducing sugar can be measured using colorimeter?
- using known concentrations of reducing sugar, heat with Benedicts
- ensure same vol of solution each time
- solution changes to brick red
- remove precipitate
- calibrate colorimeter using water and red filter
- record reading of transmission
- more transmission = more sugar present
- draw calibration curve plotting transmission against sugar conc
- use transmission reading of unknown and read off graph to find conc
Why is water a solvent?
-high solubility due to charged ions being attracted to and binding with water molecules
Colour of iodine solution in presence of starch?
Blue-black
Meaning of primary structure?
Sequence of amino acids
When proteins heated to high temperature, tertiary structure disrupted. Why?
- increases K. E
- h, disulfide, ionic bonds break
- hydrophobic and hydrophilic interactions break
- change in 3D shape
- protein denatures
Why enzyme is described as extracellular?
-works outside cell
Structure of amylose?
- coiled
- contains alpha glucose
- all monomers in same orientation
- no h bonds between molecules
- alpha 1,4 glycosidic bonds
Structure of cellulose?
- straight chained
- contains beta glucose
- beta 1,4 glycosidic bonds
- adjacent monomers in opposite orientation
- h bonds between molecules
Which properties of cellulose make it suitable for cell wall?
- strong
- insoluble
Bonds in triglyceride?
3 Ester bonds
Uses of carbohydrates in organisms
- provide energy
- store energy
- build macromolecules
What is a condensation reaction?
When 2 monomers become bonded together through the removal of a molecule of water
Glucose + glucose =
Maltose
Galactose + glucose =
Lactose
Glucose + fructose =
Sucrose
How is the structure of cellulose related to its function?
- beta glucose monomers arranged in straight chains
- chains joined by h bonds
- provides strength and structure
Where and how is glucose stored in humans?
Stored as glycogen in liver / muscles
Similarities between starch and glycogen?
- both msdemof alpha glucose molecules
- both contain branched chains
- compact
- insoluble
Name the polysaccharide chains in starch and how is their structure adapted to function of starch?
- amylose
- straight chain polymer
- forms helix for max compact storage
- amylopectin
- branched
- max surface area for enzyme action
How benedict’s test is carried out and what to expect if reducing sugar present?
- sample must be in solution
- Benedict’s reagent added
- test tube heated in water bath
- turned brick red if present
Carbohydrates that are reducing sugars?
- galactose
- glucose
- fructose
- maltose
- lactose
Example of non reducing sugar?
Sucrose
Uses of lipids in animals?
- storage as fat
- cell membranes
- waterproofing
- thermal insulation
Main use of triglyceride?
Energy storage molecule
Describe the structure of a triglyceride using hydrophobic and hydrophilic
- one glycerol molecule attached to 3 fatty acid chains
- glycerol head is hydrophilic- interacts with water
- fatty acid tails are hydrophobic- repel water
Example of where unsaturated fats are found?
Vegetable oil
Olive oil
Difference between saturated and unsaturated lipids?
- In the hydrocarbon tail of saturated lipids all the carbon atoms are joined by a single bond.
- in unsaturated lipids two or more of the carbon atoms are joined by a double bond
How does the presence of a double bond in a lipid affect its boiling point?
-lowers the boiling point
What is a hydrolysis reaction?
Spilling up a bond with water
Significance of R group?
- variable group
- gives each amino acid its specific characteristics
What 2 forms can secondary protein structure take?
- alpha helix
- beta pleated sheets
How test for protein works?
- sample mixed with equal volume of sodium/ potassium hydroxide
- few drops of copper sulphate added
- purple colour change in presence of protein
How glucose molecule is well suited to its function?
- soluble so easily transported around organism
- easily broken down to produce ATP and release energy
- molecules can join to produce maltose
Structural similarities between lactose and maltose?
- made up of 2 hexoses
- glycosidic bonds
