Biological Molecules Flashcards
Which carbohydrate is insoluble? And why?
Polysaccharide because it is too large
Which carbohydrates taste sweet and are edible?
Monosaccharides and disaccharides
Name a monosaccharide.
Glucose
What is the formula of glucose?
C6H12O6
What are the only elements in monosaccharides?
Carbon, hydrogen and oxygen.
Monosaccharide + monosaccharide = ?
Disaccharide
Glucose + glucose = ?
Maltose
Glucose + fructose = ?
Sucrose
How are polysaccharides formed?
Formed when sugar monomers join together in a condensation reaction.
Why is the general formula for polysaccharide less for those of monosaccharides?
Because H2O has been lost in a condensation reaction
Examples of polysaccharides?
Glycogen (animals)
Starch (plants)
Why do humans use glycogen instead of starch?
Because it is more highly branched so provides more energy
What is beta glucose used for?
Cell walls
Why is glycogen stored in muscle cells?
Because these muscles constantly require energy to contract
Why is glycogen stored in liver cells?
To store glycogen to keep blood glucose levels constant, and to be broken down or built up depending on blood glucose levels.
Where are membranes found?
Around organelles and outside cells
What are the roles of membranes?
To
- separate cells from external environment
- separate organelle contents from cytoplasm
- cell recognition and signalling
- holding components of metabolic pathways in place
- regulate transport of materials into / out of cells
Which of the organelles have membranes around them? And how many?
- golgi (1)
- ER (1)
- lysosomes (1)
- mitochondria (2)
- nucleus (2)
- chloroplasts (2)
What makes ATP so great?
- ATP releases energy as it breaks it down
- can move around easily in a cell but doesn’t leave cell
- releases energy quickly - one step reaction
- releases energy in small amounts which meets the needs of cellular reactions
Which carbohydrate groups are soluble?
Disaccharides and monosaccharides
Why do organisms require nutrients?
- to synthesise molecules for growth
- to respire to to provide energy for metabolism
Joining monomers together is called…
Polymerisation
What are molecules with the same molecular formula but different structural formulae called?
Isomers
What are the uses of fats?
- storage of energy
- protection of vital organisms (eg kidneys)
- insulating the body
- to prevent evaporation in plants and animals
- as a buoyancy
- as a water source (respiration of lipids)
- as a component of cell membrane
How is a triglyceride formed?
In a condensation reaction between glycerol and three fatty acids.
What are the two isomers of glucose?
Alpha and beta glucose
When monosaccharides join together, what kind of reaction takes place and what bond is formed?
A condensation reaction takes place, so a water molecule is formed.
The bond formed is a glycosidic bond.
Examples of monomers?
Monosaccharides, amino acids and nucleotides
What is a single monomer called?
Monosaccharide
What is a pair of monosaccharides called?
Disaccharide
Monosaccharides can be combined in large numbers to form…
Polysaccharides
Glucose is a ______ sugar and has the formula ________
Hexose
C6H12O6
What is reduction?
A chemical reaction involving the gain of electrons or hydrogen
What is a reducing sugar?
A sugar that can donate electrons to another chemical.
What happens in an anabolic reaction?
Smaller molecules build larger ones
What happens in catabolic reactions?
Large molecules are broken down into smaller ones.
Why do organisms require nutrients?
- to synthesise molecules for growth
- to respire to provide energy for metabolism
Which nutrients are required?
Carbohydrates, proteins, lipids, nucleic acid, vitamins, minerals, water.
Joining monomers is called…
Polymerisation.
What elements are present in proteins?
Carbon, hydrogen, oxygen, nitrogen and som have sulphur
What elements are present in nucleic acids?
Carbon, hydrogen, oxygen, nitrogen, P
What is the general name of glucose and fructose?
Hexose
What’s the general name of ribose?
Pentose
How many carbons does ribose have?
- (Ribose is a pentose and is a 5 carbon sugar)
If there is only one formula for hexoses, how is there more than one hexose?
Because they have different arrangements of atoms.
What is an isomer?
They have the same molecular formula but a different structural formula.
Functions of glucose?
- animals transport carbohydrates as glucose
- a polar molecule that dissolves in water
- acts as a monomer
- contains -OH groups so can participate in condensation reactions
- to form disaccharides and polysaccharides
Function of alpha glucose?
It is the major respiratory substrate (contains bonds that can be broken in respiration to release energy).
Enzymes can only bind a monomer with a…
Complementary shape
How are disaccharides formed?
In a condensation reaction between 2 monosaccharides
What is the general formula of disaccharides?
C12H22O11
Examples of disaccharides?
Maltose
Sucrose
Lactose
How are polysaccharides joined?
When 2 sugar monomers join together in a condensation reaction.
What is the general formula of a polysaccharide?
(C6 H10 O5)n
Examples of polysaccharides?
Glycogen (animals)
Starch and cellulose (plants)
Starch is a mix of…
80% amylopectin and 20% amylose
Where is starch found?
As starch grains in chloroplasts or amyloplasts
Glycogen is the ______ _______ _____________ found in _______ cells
Energy
Storage
Polysaccharide
Animal
Where is glycogen found?
Found as granules in cytoplasm (in particular muscle and liver cells)
Why is glycogen a good storage molecule?
Because it is…
- compact
- insoluble in water
- rapidly broken down (because it’s so highly branched)
Why is glucose stored in muscle cells?
Glucose is used in respiration to produce ATP for muscle contraction.
Why is glycogen stored in liver cells?
Glucose is used to maintain blood glucose levels
What is cellulose?
A polymer of beta glucose and forms linear, unbranched chains
What forms a basis for a plant cell wall?
Fibres
Are fibres weak or strong?
They have a high tensile strength.
What are fibres made from?
Bundles of microfibrils
How are microfibrils formed?
From hydrogen bonds formed between adjacent cellulose molecules
Lipids are…
A diverse group of non polar molecules
In water, are lipids soluble or insoluble?
Insoluble
In organic solutions, are lipids soluble or insoluble?
Lipids are soluble in SOME organic solvents (eg ethanol)
How do you test for lipids?
In the emulsion test
In the test for lipids, what is the result if a lipid is present?
A white emulsion forms.
Because lipids are non polar, so dissolve in ethanol. They com rout of the solution when added to water and are dispersed as small droplets (emulsion) that scatter light so appears cloudy.
What is the result of the emulsion test for lipids of there is no lipid present?
The solution will remain colourless
Because it can dissolve in water.
How are triglycerides formed?
Formed in a condensation reaction between glycerol and 3 fatty acids.
What is the general formula of fatty acids?
R-COOH
What kind of bonds do saturated fatty acids contain?
Single bonds between C atoms
What kind of bonds do unsaturated fatty acids contain?
One or more double bond
How many double bonds do monounsaturated fats have?
One
How many double bonds do polyunsaturated fats have?
More than one
How does the fatty acid being mainly saturated affect the properties of the triglyceride?
- molecules pack closer together
- more hydrophobic interactions between molecules
- solid at room temperature
How does the fatty acid being mainly unsaturated affect the properties of a triglyceride?
- molecules cannot pack together as closely
- fewer hydrophobic reactions between molecules
- liquid at room temperature
How are phospholipids formed?
In a condensation reaction between glycerol, two fatty acids and phosphoric acid.
How do phospholipids form a bilayer?
The hydrophilic heads interact with water, and the hydrophobic tails interact with each other to exclude water
Uses of triglycerides?
- source of metabolic water when respire aerobically
- contain lots of H atoms (so can combine with O to form water)
- thermal insulation
- blubber provides buoyancy (since it’s less dense than water)
- shock absorber to protect vital organs
Describe the function of cellulose.
Monomer used = beta glucose
Found in = plants
Type of bond = beta 1,4 glycosidic
Structural shape = linear (unbranched chain)
Function = structural
Significance = insoluble, fully permeable to dissolve substances, hydrogen bonds between cellulose strands gives strength
What do we mean by water is a polar molecule?
Oxygen acquires small negative charge
Hydrogen acquires small positive charge
How many hydrogen bonds can a water molecule form?
4
Properties of water include:
Polar solvent Cohesion Liquid at room temperature Thermal stability Unusual density Reactant Transparent
Uses of water?
- chemical reactions take place in water
- substances are transported in water
- used for support (in plants / organisms that live in water)
- reactant in photosynthesis / hydrolysis
- provides a stable habitat for aquatic organisms
What is ice?
After molecules that form a lattice held together by hydrogen bonds
What temperature is water at its densest?
4*C
What does temperature in water density with temperature cause?
Convection currents that circulate nutrients
What does water’s high specific heat capacity mean?
It needs a relatively large amount of energy to change the temperature, so water temperature remains stable.
Why is cohesion important in water?
Because it creates surface tension that can support small animals on the surface of the water
Benefits of water’s transparent state
Aquatic predators can hunt
How does water’s density benefit living things?
When water freezes to form ice it becomes less dense. This therefore floats on the surface of water and insulates the water beneath the surface from further heat loss, allowing aquatic life to continue.
How does water’s high specific heat capacity benefit living organisms?
It requires a large amount of energy to increase temperature, so maintains optimum temperature for enzymes.
How does cohesion of water support living organisms?
It creates surface tension which can support small organisms on the surface of water (eg pond skaters).
Also allows continuous columns of water, which is important for transport of water in xylem vessels.
Explain why water is thermally stable.
A lot of energy is required to break the hydrogen bonds between water molecules and raise the temperature of water / change water from liquid to gas.
Explain cohesion of water.
Water molecules form hydrogen bonds with each other and tend to stick together
Why is water transparent?
Because of its small particle size
How is water a solvent?
Water is a polar molecule and will dissolve dissolve other polar or charged molecules and ions surrounding and separating them.
How does water’s density benefit living things?
When water freezes to form ice it becomes less dense. This therefore floats on the surface of water and insulates the water beneath the surface from further heat loss, allowing aquatic life to continue.
How does water’s high specific heat capacity benefit living organisms?
It requires a large amount of energy to increase temperature, so maintains optimum temperature for enzymes.
How does cohesion of water support living organisms?
It creates surface tension which can support small organisms on the surface of water (eg pond skaters).
Also allows continuous columns of water, which is important for transport of water in xylem vessels.
Explain why water is thermally stable.
A lot of energy is required to break the hydrogen bonds between water molecules and raise the temperature of water / change water from liquid to gas.
Explain cohesion of water.
Water molecules form hydrogen bonds with each other and tend to stick together
Why is water transparent?
Because of its small particle size
How is water a solvent?
Water is a polar molecule and will dissolve dissolve other polar or charged molecules and ions surrounding and separating them.
Carbohydrates are molecules composed of…
Carbon, hydrogen and oxygen
What are the three main types of carbohydrates?
Monosaccharide, disaccharide and polysaccharide
Give 2 examples of monosaccharides.
Glucose and ribose.
Gove 2 examples of disaccharides.
Sucrose and maltose.
Give 3 examples of polysaccharides.
Starch, glycogen and cellulose.
What happens when two monosaccharides join together?
A glycosidic bond is formed and water is released in a condensation reaction.
What type of molecules are disaccharides?
Sweet and soluble carbohydrate molecules.
How is a condensation reaction brought about in the formation of a disaccharide?
By an enzyme.
What kind of bond is a glycosidic bond?
A covalent bond
What does the word ‘hydrolysis’ mean?
Splitting up with water
What are hydrolysis reactions used for?
To break down large polymers during the digestive process.
What are polypeptides? How are they joined together?
Long chains of amino acids. These are joined together by peptide bonds.
What are proteins composed of?
1 or more polypeptide linked together.
Describes the uses in lipids.
- energy store
- metabolic water
- thermal insulation
- buoyancy
- shock protection.
Explain lipids as an energy store.
Insoluble in water. Contain many C-H bonds that can be broken to release energy.
Explain lipids as metabolic water.
Aerobically repaired fats release water. Camel’s hump is made of fat for this reason.
Explain fats as thermal insulation.
Deposited under skin to provide insulation (eg blubber in whales).
Explain water as buoyancy.
Fat is less dense than water. Therefore can provide buoyancy for whales etc
Explain lipids as shock protection.
Fat is deposited around major organs (eg lungs, heart) to absorb shock.
What is the full name of ATP?
Adenosine triphosphate.
How does ATP change to ADP?
ATP loses a phosphate group by hydrolysis and become ADP.
Why does ATP break down into ADP?
Because when it does this, energy is released as the bond is broken - and this can be used for other purposes (eg active transport, moving vesicles, constructing large polymer molecules).
Can ADP change back into ATP?
Yes - they are constantly recycled in your body.
How is ADP recycled back into ATP?
By adding a phosphate molecule to the ADP
What is the importance of ATP?
- releases energy in small, manageable amounts (appropriate for uses of the cell).
- made quickly and easily (one step reaction).
- soluble (can move around easily in the cell without leaving).
What is the highest water potential?
Pure water, 0kPa
Define osmosis (3 marks)
Water travels by osmosis from an areas of high water potential to an area of low later potential, down the water potential gradient.
Regarding osmosis, benefits of a plant structure?
The plant has a cell wall which prevents it from bursting, unlike an animal cell.
What is the highest water potential?
Pure water, 0kPa
Define osmosis (3 marks)
Water travels by osmosis from an areas of high water potential to an area of low later potential, down the water potential gradient.
What does ATP stand for?
Adenine triphosphate
What is ATP made from?
- nucleotide base: adenine
- ribose sugar
- 3 phosphate groups
What happens when energy is needed in a cell?
ATP is broken down into ADP and Pi in a hydrolysis reaction, when a phosphate bond is broken by ATP hydrolase and energy is subsequently released.
This reaction is catalysed by ATP hydrolase (an enzyme).
The spare phosphate group is often transferred to other molecules to make them more reactive so that they are the activation energy to take part in another reaction. (Aka phosphorylation).
When energy is needed in a cell, ATP is converted into ADP. What happens to the spare phosphate group?
The phosphate group is often transferred to other molecules to make them more reactive so that they have the activation energy to take part in another reaction.
This transfer is called phosphorylation.
What is phosphorylation?
When the spare phosphate group from the conversion of ATP to ADP is transferred to other molecules to make them more reactive so that they have the activation energy to take part in another reaction.
Just as quickly as ATP is used up in cells…
It is resynthesised by condensing (condensation reaction) together molecules of ADP and Pi using ATP synthase. This requires energy by respiration and photosynthesis.
What is ADP made from?
- adenine
- two phosphate groups
- ribose
How are cellulose and starch similar?
They are both polysaccharides and made of glucose.
Starch and cellulose are both made of glucose. So how are they different?
The monomer in cellulose is b-glucose. In starch, it’s a-glucose.
In cellulose, the b-glucose monomers are joined together in chains by condensation forming hydrogen bonds.
In starch, glycosidic bonds are formed.
Why do cells eg muscle fibres have large mitochondria?
Because ATP cannot be stored so has to be continuously made within the mitochondria for cells that need it.
Cells e.g. muscle fibres require energy for movement and active transport respectively so they posed large mitochondria.
Where is glycogen found?
In animals and bacteria, but never in plant cells.
How is glucose different to starch?
It has shifted chains and is more highly branched
In what way is glucose adapted to its function as a storage molecule?
- it’s insoluble (therefore doesn’t draw water into cells by osmosis).
- being insoluble, doesn’t diffuse out of cells.
- compact, so a lot can be stored in a small space.
- highly branched; so has more ends that can be acted on simultaneously by enzymes. Therefore more rapidly broken down to form glucose monomers, which are used in respiration.
Glucose is highly branched. Why is this good for its function?
As it’s more highly branched, it is more rapidly broken down to form glucose monomers, which are used in respiration. This is important in animals which have a high metabolic rate and therefore respiratory rate than plants because they’re more active.
Difference between a and b glucose?
H is on top in Aglucose, OH is on top in Bglucose.
Amylase is a type of starch. Outline this.
- monomoer is a-glucose
- found in plants
- 1,4 glycosidic bond
- helix structural shape
- storage molecule
- easily hydrolysed into glucose for respiration
- insoluble (so osmotically inactive)
- too large to cross membranes
Amylopectin is a type of starch. Outline this.
- monomer used is alpha glucose
- found in plants
- 1,4 and 1,6 glycosidic bonds
- branched (due to 1,6 glycosidic bonds)
- storage molecules
- insoluble (so osmotically inactive)
- easily hydrolysed to make glucose for respiration
- too large to x membranes.
Glycogen is a polysaccharide. Outline this.
- monomer used is alpha glucose
- found in animals
- 1,4 and 1,6 glycosidic bonds
- branches (due to 1,6 bonds)
- storage molecule
- insoluble (osmotically inactive)
- easily hydrolysed to release glucose
- too large to x membranes
Cellulose is a polysaccharide. Outline this.
- monomer used is beta glucose
- found in plants
- 1,4 glycosidic bonds
- unbranched chains
- structural molecules
- insoluble
- fully permeable to dissolved substances
- hydrogen bonds between cellulose strands gives it strength
Differs ebetween phospholipid and triglyceride?
Phospholipids have a phosphate group and only two fatty acid tails.
How are triglycerides formed?
Condensation reaction between a fatty acid and glycerol molecule. Forms an ester bond. This process happens twice more to form triglyceride.
What are tri-glycerides used for?
Energy storage molecules
Why are tri-glyclycerides good storage molecules?
- the long hydrocarbon tails of fatty acids contain a lot of chemical energy (released when they’re broken down).
- they’re insoluble, so don’t affect WP.
