Pack 1 - Biological Molecules Flashcards
Why do some scientists believe that all life on earth originated from a common ancestor?
The cells of all living organisms contain only a few groups of carbon-based compounds that act in similar ways.
This also proves indirect evidence for evolution.
What are two uses of carbohydrates within living organisms?
Main use: Used by cells as respiratory substrates.
Secondary use: To form structural components in plasma membranes and cell walls
What are three uses of lipids within living organisms?
Bilayer of plasma membranes
Certain hormones
Respiratory substrates
What is the most common component of cells?
Water
(Hence, our search for life elsewhere in the universe involves a search for liquid water).
What is the definition of a monomer?
Monomers are the smaller units from which larger molecules are made.
What is the definition of a polymer?
Polymers are molecules made from a large number of monomers joined together.
Give three examples of a monomer
Monosaccharides
Amino acids
Nucleotides
Define condensation reaction
A condensation reaction:
Joins two molecules together (forming a chemical bond)
Involves the elimination of a water molecule.
Define hydrolysis reaction
A hydrolysis reaction:
Breaks a chemical bond between two molecules
Involves the use of a water molecule.
Name 3 common biological molecules throughout all species on Earth
Carbohydrates
Lipids
Water
What monomer makes up proteins/polypeptides?
Amino acids
What monomer makes up polysaccharides?
Monosaccharides
What monomer makes up starch?
a-glucose
What monomer makes up glycogen?
a-glucose
What monomer makes up cellulose?
b-glucose
What monomer makes up DNA?
DNA nucleotide
What monomer makes up RNA?
RNA nucleotide
Define organic (in biochemistry)
Carbon based (excluding eg. CO2)
Give an example of a condensation reaction
Alcohol + Carboxylic Acid -> Ester (+Water)
What does hydrolysis literally mean?
Hydro - Water
Lysis - Breaking
Give an example of a hydrolysis reaction
Digestion
What does carbohydrate literally mean?
Carbo - Carbon
Hydrate - Water
CH20
What does monosaccaride literally mean?
Mono - One
Saccharide - Sugar
What does mono- mean?
One
What does di- mean?
Two
What does tri- mean?
Three
What does tetra- mean?
Four
What does penta- mean?
Five
What does hexa- mean?
Six
What does hepta- mean?
Seven
What is the molecular formula of Glucose?
C6H12O2
What is the general formula of a monosaccharide?
CnH2nOn
What is the general name of a sugar?
(number) -ose
Eg. Hexose such as glucose
Name 6 monosaccharides
Glucose
Fructose
Galactose
Mannose
Ribose
Deoxyribose
What is the hydroxyl group configuration of a-glucose?
/<=>\
What is the hydroxyl group configuration of b-glucose?
/<=>/
What is the definition of an isomer?
A molecule with the same chemical formula but in a different arrangement
How does fructose differ from a-glucose?
a-glucose b-glucose
CH2OH H
<=> H <=> CH2OH
What is the main use of monosaccharides within living organisms?
Energy from respiration
What is the food test for reducing sugars?
Add Benedict’s solution to the sample
Mix and heat in a water bath
Look for a brick-red precipitate to form which indicates the presence of reducing sugar
Name 3 disaccharides
Maltose
Sucrose
Lactose
What monosaccharides does maltose consist of?
a-glucose
a-glucose
What monosaccharides does sucrose consist of?
a-glucose
fructose
What monosaccharides does lactose consist of?
a-glucose
galactose
What monosaccharide is found in maltose, sucrose and galactose?
Glucose (a)
Describe the bonds between the monosaccharides of maltose, sucrose and lactose
1,4
glycosidic
What type of bond is formed when monosaccharides join together?
Glycosidic
What are disaccharides mainly used for in living organisms?
Respiration energy
Which disaccharide is commonly found in fruit?
Sucrose
Which disaccharide is commonly found in milk?
Lactose
Define polysaccharide
Polymers
Of many glucose (monosaccharide) monomers
Joined together
In chains
Name 3 common polysaccharides
Glycogen
Starch
Cellulose
What monosaccharide is glycogen made of?
a-glucose
What monosaccharide is starch made of?
a-glucose
What monosaccharide is cellulose made of?
b-glucose
What is the role of glycogen?
Animal energy storage (glucose) (liver)
What is the role of starch?
Plant energy storage (glucose)
What is the role of cellulose?
Gives strength to plant cell walls
How does glucose within starch bond?
Mostly 1,4
Occasionally 1,6 (which forms branches)
Describe the structure of starch
Compact
Branched
Spherical
Insoluble
Why is being insoluble important for starch?
No osmotic effect/
Does not affect water potential/
Does not leave cell
Why is it important for starch to have a compact (coiled) structure?
So more energy can be stored
Why is starch coiled?
Linked 1,4 and 1,6
Why is it important that starch has branches?
So that it is readily hydrolysed
What is the test for presence of starch?
Add iodine/potassium iodide to sample
Colour change to black/blue indicates presence of starch
Describe the structure of glycogen
Compact
Very branched
Soluble
How does glucose within glycogen bond?
Linked by 1,4
Many 1,6 as well
What is the difference between starch and glycogen?
Starch is energy storage in plants
Glycogen is energy storage in animals
Why is glycogen soluble in water?
Many 1,6 bonds
Leaving exposed hydroxyl groups
Which react with water
Describe the structure of cellulose
Compact
In chains
No branches
Insoluble
Why are cellulose chains able to bond?
Hydrogen bonds
What do the OH bonds between cellulose chains create?
Hydrogen bonds
Forming cellulose fibrils
What is the name of an OH group?
Hydroxyl group
What must happen to enable the OH groups (of the monosaccharides) react to make a glycosidic bond?
Monosaccharides must get close together
How do hydrogen bonds form?
Oxygen is electronegative so
O is δ-
H is δ+
Adjacent O and H are attracted to each other
Is a hydrogen bond weak or strong?
Weak
Are many hydrogen bonds together weak or strong?
Strong
Why is cellulose polymers fully permeable?
Because there are gaps between the fibrils
What are the links between two cellulose chains called?
Crosslinks
Is the b-1,4 bond easy or difficult to break?
Difficult - resists digestion by enzymes
How do herbivores such as cows manage to digest grass?
Don’t produce cellulase
So have to grow bacteria in stomach
Called a symbiotic relationship
What cellular structure is made out of cellulose?
Plant cell walls
Give 5 features of cellulose
No branches 'Flip flop' structure H bond crosslinks Long chains Bonds difficult to break
Why does cellulose’s lack of branches link to its function?
Close together chains making it insoluble
How does cellulose’s flip flop structure relate to its function?
Makes a large molecule due to long, repeating chains
Hydrogen bonds
How are cellulose’s H bond crosslinks related to its function?
Provide strength in large numbers
How does cellulose’s long-chained structure link to its function?
Provides structural rigidity
How does cellulose’s difficult-to-break bonds link to its function?
They resist digestion
Name two groups of lipids (fats)
Triglycerides
Phospholipids
What do triglycerides consist of?
Three fatty acids
One glycerol
What bonds do lipids form?
Ester
What is the functional group called on a fatty acid?
Carboxyl (acid) group
What is the chain on a fatty acid called
C Skeleton
What is the general formula for a fatty acid C skeleton
(CH2)n(CH3)
How many water molecules are released in the formation of a triglyceride?
Three
What is the variable region of a molecule called?
R
What allows fatty acids to be different lengths?
Hydrocarbon skeleton length
Define saturated fat
A fat that has the maximum number of hydrogen atoms in them
i.e. They contain no double or triple bonds between the carbon atoms
Define unsaturated fat
A fat where not all potential hydrogen atoms are within its structure
i.e. It contains double or triple binds between its carbon atoms
What is the difference between monounsaturated and polyunsaturated fats?
Monounsaturated fats contain one double bond
Polyunsaturated fats contain more than one double bond
What is fat used for in biological organisms?
Insulation Vital organ protection Energy storage Releases water when hydrolysed Energy storage Oils waterproof skin
What is the food test for lipids?
Add ethanol
Mix/shake
Add water
White emulsion indicates presence of lipids
How do phosphates form?
When a phosphoric acid combines with a glycerol
Describe the structure of a phospholipid
Phosphate and glycerol in the head
Two fatty acid ‘tails’
Why is a phospholipid polar?
The phosphate group makes the head hydrophilic
The tails are hydrophobic
Name an important use of phospholipids
Forming (phospho)lipid bilayers
Which act as a barrier around cells
Name two differences between the properties of phospholipids and triglycerides
Triglycerides store more fats (for energy) than phospholipids
Phospholipids are polar so they are good emulsifiers
Why are phospholipids good emulsifiers?
Head is 𝛿+ (hydrophilic)
Tail is 𝛿- (hydrophobic)
Why are triglycerides good insulators?
They are poor conductors of heat and form in thick layers of fatty tissue when accumulated
Why are triglycerides good storage molecules?
Contain 3 fatty acids each
Name 5 properties of water
Polar ∴ adhesion & cohesion/surface tension
Universal solvent - for other polar molecules
High specific heat capacity
Expands when solid
High latent heat of vaporisation
What are adhesion and cohesion?
Adhesion - Water sticking to the sides of the tube it is in, forming a meniscus
Cohesion - Water ‘sticking’ to itself
Why is water adhesive and cohesive?
Adhesive - because some materials (such as glass) can be more polar than the water itself so water is attracted to the glass
Cohesive - because it is polar and the 𝛿+ H’s bond with the 𝛿- O’s
Give a practical example of adhesion and cohesion
Adhesion - capillary tubes or glass beakers
Cohesion - drinking straws or xylem
Why is water a good solvent for other polar molecules?
Water can become so heavily attracted to other molecules that it can disrupt the attractive forces within the solute
Why does water have a high specific heat capacity/latent heat of vaporisation?
The hydrogen bonds within water require a lot of heat to break
Why is water’s latent heat of vaporisation important?
Water, such as ponds, maintains an almost constant temperature providing a stable environment for fish all year round
Why is water’s high specific heat capacity important?
Animals sweat which involves transferring lots of heat into a small amount of water for it to evaporate.
What is latent heat of vaporisation?
Water takes a long time to heat meaning there is a long lag time between temperature change from air to water.
What is high specific heat capacity?
The amount of heat water can absorb or release during a state change
Why does water expand when it freezes?
The water molecules link in such a way (due to hydrogen bonding) that there are large gaps between the water molecules.
Why is water’s expansion when freezing important to marine life?
The ice floats and acts as a heat barrier, sustaining the marine life underneath
What is surface tension?
The skin that water forms in contact with air
How does surface tension occur?
The water molecules near the surface of the water bond stronger and form more closely together due to fewer water molecules to bond with
What is the constant stream of water from the roots through the stem and then out through the leaf called?
Transpiration
What tube-like transport cells of plants carry columns of water up plants from the roots to the leaves?
Xylem
Define organic chemistry
Chemistry that is carbon-based (except carbonates, oxides and dioxides)
Name two places that inorganic ions occur within organisms
Cytoplasm
Body fluids
What is another name for a hydrogen ion?
Proton
What does pH stand for?
Potenz Hydrogen
What does a low pH tell you about the number of hydrogen ions present?
There are more
What ions exist in quarternary structure of haemoglobin?
Fe2+
Describe the structure of a haemoglobin
4 Polypeptides
4 Fe2+ ions
What is the role of iron bonds in haemoglobin?
Iron bonds to oxygen to form oxyhaemoglobin
Define co transport
Two molecules passing through protein channels at the same time
How do sodium ions help the absorption of glucose and amino acids in the digestive tract?
Sodium ions are removed from the blood
This means that sodium ions from the lining of the gut are absorbed
But this time they carry glucose and amino acids with them
What is primary protein structure?
A chain of amino acids
What is secondary protein structure?
A chain of amino acids where hydrogen bonds cause the chains to become bent
What is tertiary protein structure?
Amino acids wrapped tightly together due to hydrogen, ionic and covalent bonds
What is quaternary protein structure?
When two proteins in tertiary form are bonded together
