1A Biological molecules Flashcards
Name 4 carbon-based molecules
Carbohydrates
Lipids
Proteins
Nucleic acid
What is the role of a Carbohydrate?
- Respiratory substrate from which cells release the energy required to carry out functions
- Have structural roles
What is a Lipid?
Major component in plasma membranes
Make up certain hormones + act as respiratory substrates
What is the role of a Protein?
Main role as enzymes
They are chemical messengers
Important components of the blood, i.e. antibodies
What is the role of a Nucleic Acid?
Carry genetic info that determines the structure of proteins (DNA)
Other roles in the synthesis of proteins/DNA (RNA)
What are the 3 ways molecules tend to bond?
Hydrogen bonds
Covalent bonds
Ionic bonds
What is a monomer?
Individual sub-unit
Form polymers
What is a polymer
A chain of repeating sub-units (monomers)
The process to form these is called polymerisation
What are the monomers of a polymer usually based of?
Carbon
What is the sub-unit of a polysaccharide?
A monosaccharide
How can polymers be formed?
Condensation reactions (dehydration synthesis)
Each time a new sub unit is attached, a molecule of water is released
i.e. the formation of a polypeptide from amino acids is a condensation reaction
How can polymers be broken down?
Hydrolysis reaction
Water molecules are used to break bonds between sub-units
i.e. polypeptides can be hydrolyzed into amino acids
What is metabolism?
All the chemical processes that take place in a living organism
Why are many molecules based on carbon?
They have 4 available bonds therefore they can form large structures
What is the difference between alpha glucose and beta glucose?
The right hand OH and H molecule flip on the beta glucose
What are monosaccharides?
Sweet tasting, soluble substances with the general formula (CH2O)n
Give 3 examples of a monosaccharide
Glucose, Galactose and Fructose
What is glucose like?
It is a 6-carbon (hexose) sugar and has the formula C6H12O6
What are reducing sugars?
All monosaccharides and some disaccharides
A sugar that can donate electrons to (or reduce) another chemical
What is reduction?
A reaction involving the gain of hydrogen or electrons
What is the test for reducing sugars called?
The Benedict’s test
Describe the test for reducing sugars.
- Add 2cm^3 of of the food sample (if the sample is not already in liquid form, fist grind it up in water)
- Add an equal volume of Benedict’s reagent
- Heat the mixture in a gently boiling water bath
- If a reducing sugar is present, the solution turns orange brown
Which order do the colours of the end solution in a reducing sugars test go in?
- Blue –> none present
- Green –> traces
- Yellow –> low
- Orange –> moderate
- Red –> high
Why is carbon the main element in molecules?
It can bond to form large stable structures
What are the 6 functional groups?
- Carboxyl
- Amino
- Methyl
- Carbonyl
- Phosphate
- Hydroxyl
What are polymers and how are they made?
They are long chains of monomers
Made via dehydration synthesis/condensation reaction
How are polymers broken down?
Via hydrolysis
What are the 4 key molecules?
DNA, Proteins (amino acids), Lipids and Carbohydrates
__1__ of elements join to make ____2____
molecules are called ____3____
1- Atoms
2- Molecules
3- Compound
What are enzymes made of?
Proteins
What is the function of carbohydrates?
- -> used by cells as respiratory substrates
- -> structural components in plasma membranes + cell walls
What is the function of lipids?
- -> bilayer of plasma membranes
- -> certain hormones
- -> respiratory substrates
What is the function of proteins?
- -> many cell structures
- -> enzymes
- -> chemical messengers
What is the function of nucleic acid?
–> carry genetic code
Most carbohydrates are ……
polymers
What is the definition of a polymer?
Large complex molecules composed of long chains of monomers
What is the definition of a monomer?
Basic molecular units
What are monomers that make up carbohydrates called?
A monosaccharide
What are the two types of glucose?
alpha glucose and beta glucose
What is the difference between the two types of glucose?
The OH and H molecule on the end of a beta glucose flips (is the opposite to alpha glucose)
Name 3 monosaccharides
- Galactose
- Glucose
- Fructose
Name 3 disaccharides
- Maltose
- Sucrose
- Lactose
Name 3 polysaccharides
- Cellulose
- Glycogen
- Starch
Explain how a disaccharide is formed?
- Monosaccharides are joined in a condensation reaction
- A water molecule is released in the process
- New bond is formed; called a glycosidic bond
- This form a disaccharide
How is maltose formed?
A condensation reaction of 2 x alpha-glucose
How is sucrose formed?
A condensation reaction of a glucose and a fructose
How is lactose formed?
A condensation reaction of a glucose and a galactose
How is cellulose formed?
A chain of beta-glucose
How is glycogen formed?
A chain of alpha-glucose molecules
How is starch formed?
A chain of alpha-glucose molecules
What is an isomer?
alpha-glucose and beta-glucose are different isomers of glucose
How would you break a glycosidic bond?
By adding water
What is hydrolysis?
Breaking of bonds using water
- The opposite to a condensation reaction
- Hydro = water
- Lysis = breaking things
What are monosaccharides like?
- sweet tasting
- soluble
- General formula: (CH2O)n –> where n is any no. 3-7
What are the names of the 3-7 monosaccharides?
3- Triose 4- Tetrose 5- Pentose 6- Hexose 7- Heptose
What do all carbohydrates contain?
- Carbon, oxygen and hydrogen
What are all carbohydrates made of?
Fructose
What are pentoses?
5 carbon monosaccharides
ex. ribose and deoxyribose
What are hexoses?
6 carbon monosaccharides
ex. glucose, fructose and galactose
What is the structure of starch?
Made of chains of alpha-glucose monosaccharides, linked by glycosidic bonds that are formed via condensation reactions
Branched & unbranched version
What is the biological function of starch?
- Main role is (long term) energy storage ie for winter months
- Starch is never found in animal cells, instead glycogen is, which serves a similar role
How does the structure of starch aid its function of energy storage?
- it is insoluble
- it is compact
- when hydrolysed it forms alpha-glucose
- Branched form has many ends
Why does being insoluble help starch?
- Doesn’t affect water potential –> water is not drawn into the cell via osmosis
- It is lage (also insoluble) it does not diffuse out of cells
Why is being compact useful for starch?
so a lot can be stored in a small space (spiral design so it can coil)
Why does starch forming alpha-glucose help its function?
alpha-glucose is both easily transported and readily used in respiration
Why does the branched form of starch help its function?
it has many ends which means they can be acted on by enzymes simultaneously meaning that glucose monomers are released very rapidly
What is the structure of glycogen?
- It has a similar structure to starch (chains of alpha-glucose monosaccharides) but has shorter chains
- More highly branched than starch
What is the biological function of glycogen?
- Stored as small granules mainly in muscles and the liver
- The role of glycogen is to be stored as energy for when needed
How is the structure of glycogen specific to its function?
- insoluble
- compact
- more highly branched than starch
How does glycogen being insoluble help its function?
- therefore does not tend to draw water into the cell via osmosis
- being insoluble it does not diffuse out of cells
How does glycogen being compact help its function?
A lot can be stored in a small space
How does glycogen being highly branched help its function?
- It is more highly branched than starch so it has more ends that can be acted on simultaneously
- Therefore is more rapidly broken down to form glucose monomers, which are used in respiration
What is the structure of cellulose?
- made of monomers of beta-glucose rather than alpha glucose
- cellulose has straight, unbranched chains. They run parallel to one another, allowing hydrogen bonds to adjacent chains
- overall noi. makes cellulose very strong
What are the biological functions of cellulose?
- cellulose provides rigidity to plant cells
- cellulose prevents the cell from bursting as water enters it via osmosis
- it does this by exerting an inward pressure
Why is cellulose in long, straight unbranched chains?
it is made of beta-glucose
Why is cellulose very strong?
- the molecular chains run parallel to each other
- they are cross linked by hydrogen bonds add collective strength
How does cellulose have extra strength?
It has molecules that are grouped to form microfibrils, in turn these are grouped to form fibres - this provides more strength
What is glycogen?
Storage molecule for animal and bacteria cells
What is starch?
storage molecule for plant cells (only found in plant cells)
What is chitin?
another example of a complex carbohydrate which is found it your hair and nails
What are the two categories sugars can be categorised into?
- reducing
- non-reducing
Which type of sugar reacts with Benedict’s solution?
reducing
What is the method for testing reducing sugars?
- add an excess of Benedict’s solution (a blue solution)
- heat in a water bath, that has been boiled
- if the test is positive, ie there are sugars present, a coloured precipitate will form
- there is a scale of results blue-green-yellow-orange-red
What is the first stage in testing for sugars?
Add an excess of Benedict’s solution (a blue solution)
What is the second stage in testing for sugars?
heat in a water bath, that has been boiled
What is the third stage in testing for sugars?
if the test is positive, ie there are sugars present, a coloured precipitate will form
What is the fourth stage in testing for sugars?
there is a scale of results blue-green-yellow-orange-red
What forms between the enzyme and substrate at the active site?
Enzyme-substrate complex
What are lipids composed of?
Carbon, Hydrogen and Oxygen
What is the proportion of oxygen to carbon and hydrogen compared to carbohydrates in lipids?
The proportion is lower
Are lipids soluble?
Lipids are insoluble
When are lipids soluble?
When in organic substances e.g. alcohol and acetone
What are the functions of lipids?
- energy storage
- waterproofing
- insulation
- physical protection
What temp are fats solid at?
10-20 degrees
What temp are oils liquid at?
10-20 degrees
What are triglycerides made of?
3 fatty acid tails and a glycerol molecule
What is released when a triglyceride is formed?
3H2O
What sort of bonds are in triglycerides?
ester
What are the types of fatty acid?
- saturated
- monounsaturated - one double bond
- polyunsaturated - many double bonds
Are fats usually saturated or unsaturated?
saturated
Are oils usually saturated or unsaturated?
unsaturated
What do triglycerides have a high ratio of?
energy storing carbon-hydrogen bonds –> when broken, lots of energy is produced
Triglycerides have a high/low mass to energy ratio
low
Are triglycerides insoluble?
Yes, they are large and insoluble molecules therefore water will not be drawn into the cell
Why do triglycerides release water when oxidised?
Because they have a high ratio of hydrogen to oxygen
What is the difference between a triglyceride and a phospholipid?
One fatty acid is replaced with a phosphate molecule
Are the fatty acid tails hydrophilic or hydrophobic?
hydrophobic
Is the phosphate molecule hydrophilic or hydrophobic?
hydrophilic
In aqueous conditions what can phospholipids form and why?
- Bilayers
- They have a phosphate head (hydrophilic) which is drawn towards water and 2 (hydrophobic) fatty acid tails which try and get away from water, forming bilayers
What is the test for lipids?
The emulsion test
What is the structure of a phospholipid bilayer named?
Fluid mosaic model - as they can flow around each other
What are the several parts that make up amino acids?
- central alpha carbon –> everything branches off of this
- one branch is a hydrogen atom
- one branch is an amino group (NH2)
- opposite branch is a carboxyl group
- 4th branch is an R-variable group
Why do composts designed for younger plants have more N that P or K (in relation to NPK in horticulture)?
Proteins are used for growth + repair - nitrogen is needed for the proteins due to the amino group
How many types of naturally occurring amino acids are there?
20
Which part of the proteins structure determines the properties of the amino acid?
The R-variable group
What do a series of amino acids join to form?
A polypeptide
What is the joining of polymers to monomers called?
polymerisation
When amino acids join what is formed?
a peptide group
What are the 4 levels of structure a protein can have?
- Primary
- Secondary
- Tertiary
- Quaternary
What is the primary structure of a protein?
The sequence of amino acids in a polypeptide chain
What does the primary structure of proteins determine?
The ultimate shape and functionality of the chain
What is the secondary structure of a protein?
The hydrogen bonds forming between the positively charged hydrogen of the -NH groups and O^- of the C=O group
Are hydrogen bonds weak or strong?
Relatively weak
What does the secondary structure of a protein create?
- An alpha helix or a beta pleated sheet
- They hydrogen bonds are strong enough to twist the polypeptide chain into a 3D shape
What is the tertiary structure of a protein determined by?
- The amino acid order
What are the bonds involved in the tertiary structure of proteins?
- Disulfide
- Ionic
- Hydrogen
What does the tertiary structure of proteins involve?
- It is a result of further twisting of the secondary structure
- It plays a significant role in determining the behaviour of the protein
What is the quaternary structure of a protein?
- Multiple polypeptides bonded together
- Only for large proteins i.e. haemoglobin
- The haem group of the haemoglobin is not a protein
What bonds hold together each level of the protein structure?
- primary
- secondary
- tertiary
- quaternary
Primary - peptide bonds
Secondary - hydrogen bonds
Tertiary - hydrogen, ionic + disulfide bonds
Quaternary - hydrogen, ionic + disulfide bonds
What are the 3 conditions needed for a reaction?
- Must collide with sufficient energy
- Free energy of the products must be less than that of the substrates
- Activation energy requirements must be met
What role do amino acids have in the structure of enzymes?
They form the specific 3D shape
How do enzymes break down molecules?
- The active site forms a small depression in the larger molecule
- Enzymes then hold the substrate in a condition which breaks the bonds easily
What is the optimal temp for most enzymes?
37 degrees - body temp
Which structure of proteins determines the functionality and how?
- Tertiary
- It is the folded structure which is the 3D structure –> forming the active site shape
What is the test for lipids?
The emulsion test
State the emulsion test
1) take a dry + grease free tube
2) To 2cm^3 of sample, add 5cm^3 of ethanol
3) Shake the tube to dissolve any lipid in the sample
4) Add 5cm^3 of water + shake gently
5) A white emulsion indicates the presence of a lipid
6) As a control repeat the procedures using water instead of the sample; this should remain clear
What are the two main types of proteins?
- FIbrous
- Globular
What are Fibrous proteins like?
Have structural functions, collagen is found in tendons that join muscle to bone
What are Globular proteins for?
Form metabolic function
Which type of proteins have a quaternary structure?
Both
What is the primary structure of collagen?
A polypeptide chain
What is the secondary structure of collagen?
Tightly coiled
Why does collagen have a high concentration of glycine?
(glycine is an amino acid) it helps it to pack close together
What is the tertiary structure of collagen?
Also a helix shape
What is the quaternary structure of collagen?
It is 3 double coiled polypeptide chains wound together
What is haemoglobin like?
- Also has a quaternary structure
- Made of alpha and beta glucose chains
Give an example of a globular protein?
- Enzymes
- Haemoglobin
What is an example of a fibrous protein?
- Collagen
What are the 4 factors affecting enzyme activity?
- temperature
- pH
- enzyme conc.
- substrate conc.
Why does temperature affect the rate of enzyme activity?
More energy = more collisions between substrates + the active site of the enzymes
What happens when an enzyme denatures from the temperature being too high?
- the bonds in the tertiary structure breaks
- due to vibrations in particles
- This unfolds the 3D structure of the enzyme
What happens at the optimum temp for enzymes?
The maximum rate of reaction
What pH do most human enzymes work best around?
pH7
Give an example of an enzyme that doesn’t work at a pH7
Pepsin, works at pH2
How does an enzyme denature due to the wrong pH?
If the pH drops below/goes above optimum, the H+ and OH- ions interfere with the ionic and hydrogen bonds in the tertiary structure
This changes its shape
For chemical reactions to occur naturally, what 3 conditions must be met?
- Reactants must collide with sufficient energy (to alter the arrangements of their atoms)
- The free energy of the products must be less than that of the substrates
- Must be sufficient activation energy
Many proteins are __1__ (___2___ proteins)
- enzymes
2. globular
What are the 3 things that determine a protein’s primary structure?
- which amino acids are present
- how many of these amino acids
- what order of amino acids
Name the structural carbohydrate found in animals and fungi
Chitin
What does RNA stand for
ribonucleic acid
What is the difference between DNA and RNA?
Uracil replaces Thymine in RNA
RNA is much shorter than DNA
Pentose sugar in DNA is deoxyribose, pentose sugar in RNA is ribose
What is the traditional model for enzymes fitting?
Lock and key model
What is the modern model for enzymes fitting?
Induced fit
What allows the enzyme to shape to the substrate?
The flexibility in the polypeptide chains`
How do enzymes make bonds?
Holds substrate molecules close enough to overcome repulsion between molecules
How do enzymes break bonds?
Enzyme puts strain of substrate, reducing the amount of energy needed to break the molecule
How can you measure the rate of reaction?
- Change in substrate/time
- Change in product/time
- grams/moles/litres
How do you calculate the rate of reaction?
- Draw a tangent to the line
- Chiny/chinx
Can enzymes be inhibited?
Yes
What can inhibit an enzyme?
“inhibitor molecules”
What are the 2 types of enzyme inhibition?
- Competitive inhibition
- Non-competitive inhibition
How is the enzyme inhibited in competitive enzyme inhibition?
- An enzyme other than the enzyme’s specific substrate is complementary to the active site
What happens in competitive inhibition?
- If the competitive molecule forms a complex with the enzyme’s active site, then the active site is occupied
- Usual substrate cannot form the intended enzyme-substrate complex
How is the enzyme inhibited in non-competitive enzyme inhibition?
The non-competitive molecule attaches to the enzyme (not at the active site) and distorts the shape of the active site
It is no longer complementary
What is the decrease in rate of reaction in a enzyme reaction due to?
- The conc. of substrate as it is all used up
- Enzymes cannot work any harder if there is a lower conc. of substrate than conc. of enzymes
Why doesn’t enzyme conc. decrease during a reaction?
They aren’t used up
Is the Benedict’s test quantitative or semi-quatative?
Semi-quantitative as you don’t get an exact result (For example a pH probe you would get a quantitative result)
