Biological Molecules Flashcards
What is a polysaccharide?
A polymer from many monosaccharides, which are joined by glycosidic bonds that form in condensation reactions.
What are monosaccharides?
Sweet-tasting, soluble substances that have the general formula (CH2O) n
N - 3-7
Give examples of monosaccharides
Galactose, glucose and fructose
What is a disaccharide?
A Disaccharide is the condensation of two monosaccharides
Give examples of disaccharides
Sucrose, maltose and lactose
What is the formula for Glucose, Fructose and Galactose?
C6H12O6
What is the general formula for a disaccharide?
CnH2nOn
What makes maltose?
Joining of 2 glucoses
What makes sucrose?
Glucose and Fructose joined by an alpha 1,4 glycosidic bond
What makes lactose ?
Glucose and Galactose joined by a beta 1,4 glycosidic bond
Is sucrose reducing or non-reducing?
Non-reducing
Is maltose and lactose non-reducing or reducing?
Reducing
Where is sucrose found in living things?
Sugar cane
Where is maltose found in living things?
Germanated seeds
Where is lactose found in living things?
Milk
What is a condensation reaction?
When a molecule of water is removed
What is a hydrolysis reaction?
The addition of water that causes a breakdown
Are polysaccharides soluble or insoluble?
Insoluble as they are large molecules
What are polysaccharides suitable for?
Storage
Give examples of polysaccharides
Cellulose, starch and glycogen
What is starch?
It is a polysaccharide that’s found in small grains. It’s forms a component of food and is a major energy store in diets
What is starch made up of?
Chains of alpha glucose monosaccharides linked by glycosidic bonds that are formed by condensation reactions
What is the main role of starch?
It’s an energy store
Does starch affect water potential and why?
No it does not because it is insoluble and therefore does not draw water into the cells by osmosis.
Why is starch compact?
It has a helix shape, and so allot of it can be stored in a small space
What happens when starch is hydrolysed?
It’s forms Alpha glucose, which is easily transported and readily used in respiration
Why does starch have many ends?
So enzymes can act of the ends, and the glucose monomers can be released very rapidly.
What is the two forms of starch?
Amylose and amylopectin
Describe the synthesis of starch
Two alpha/beta glucose being arragated together through a condensation reaction
Amylose is tightly coiled, why is this feature important?
Can be a compact shape and allow more space in the cell, letting more molecules inside.
Where is glycogen found?
Animals and bacteria
What is the structure of glycogen?
Has short chains, highly branched.
What is glycogens role?
Store of energy for respiration and affects the rate of metabolism.
What is cellulose made of?
Monomers of beta glucose rather than alpha glucose
What chains do cellulose have?
They have Straight, unbranched chains. They run parallel to one another,. It allows hydrogen bonds to form cross-linkages between straight chains.
What do cellulose molecules form?
Microfibrill
What makes cellulose strong?
Individual hydrogen bonds add very little strength to a molecule: many make a huge contribution to strength
What is cellulose formed by?
Its bonded by OH (hydroxyl groups) every 2 cellulose molecules and become inverted for condensation reaction to occur
What are the characteristics of lipids?
Organic molecules, insoluble in water, soluble in organic solvents
What are the main groups of lipids?
Trygyclerides and phospholipids
What do phospholipids contribute to?
The flexibility of membranes and the transfer of lipid-soluble substances across them
Lipid is a source of energy enhance further
When oxidised, lipids provide twice the energy as the same mass of a carbohydrate and release valuable water.
Waterproofing is a role of lipids, enhance further
Lipids are insoluble so it’s useful. Insects and plants have waxy, lipid cuticles.
Insulation is a role of lipids, enhance further
Fats slow conductors of heat and when stored beneath the body surface help to retain body heat. Act as electrical insulators in the mylein sheath around nerve cells.
Protection is a role of lipid, enhance further
Fat is often stored around delicate organs, such as the kidney.
What are trygyclerides?
They have 3 fatty acids and 1 glycerol
What do fatty acids form?
An ester bond with glyercol in a condensation reaction.
What does a fatty acid contain?
Large hydrocarbon chain and a carboxylic group (COOH)
How many ester bonds are there in a trygyclerides?
3 ester bonds
Give the specific functions of proteins in living things
Acting as enzymes and hormones. Making antibodies,. Tissue regeneration. Providing nutrient transport
What differs in the 20 essential amino acids?
The side-chain group/ R group
What is the peptide bond between two amino acids?
C-N
What is a polypeptide?
A chain of many hundreds of amino acids
What is a fibrous protein?
Form long chains that are run parallel to one another, chains linked by cross-bridges and so form very stable molecules. And is insoluble in water
What is a globular protein?
Form circular chains that are irregular and wide of R groups. And is soluble in water.
Describe the primary structure of a protein and the bonds
A sequence of amino acids found in its polypeptide chains and the sequence determines it’s properties and shape. It has a covalent peptide bond
Describe the secondary structure of a protein and the bonds
The shape which polypeptide chain forms as a result of hydrogen bonding. It’s known as an alpha helix. Hydrogen bonds are formed between atoms of the polypeptide backbone.
Describe the tertiary structure of a protein and the bonds
Due to the bending and twisting of the polypeptide helix into a compact structure. It has disulfide, ionic and hydrogen bonds.
Describe the quaterny structure of a protein and the bonds
Combination of a number of different polypeptide chains and associated non-protein groups into a large, complex protein molecule, e.g Haemoglobin
Enzymes act as what?
Catalysts lowering activation energy
What is activation energy?
The minimum amount of energy required to start of a reaction
What does lowering the activation energy do?
Enzyme allow reactions to take place at lower temperatures than normal
What is a substrate?
A molecule on which the enzyme acts
What is an active site?
A specific region of the enzyme is functional.
What is an enzyme substrate complex?
Where a substrate binds to an enzymes active site held by bonds that temporarly form between certain amino acids of the active site and groups on the substrate molecule
What does the induced fit model propose?
That the active site forms as the enzyme and substrate interact
In the induced fit model, the proximity of the substrate leads to what?
A change in the enzyme that forms the functional active site.
As the active site changes shape, what does the enzyme do?
Puts a strain on the substrate molecule, distorting the bonds in the substrate which lowers the activation energy needed to break the bond
What is the lock and key model?
Where the shape of the substrate exactly fits with the active site of the enzyme
What is a limitation of lock and key model?
It’s seen be considered a rigid structure where actually it is flexible.
When measuring a enzyme catalysed reaction, the formation of the products of the reaction is changed most frequently. True or false
True
One of the changes most frequently measured in a enzyme catalysed reaction is the dissappearance of what+
The substrate
At first there is a lot of substrate but no product so it is very easy for the what?
Substrate molecules to come into contact with the empty active sites on the enzyme molecules
All enzyme active sites are filled at any given moment and the substrate is rapidly broken down into its products. What happens to the amount of substrate?
It decreases resulting in an increase in the amount of product
As the reaction proceeds, there is what left of the substrate and left of the product?
Less of the substrate and more of the prodcuct
As it becomes difficult for the substrate molecules to come in contact with the enzyme molecules, why?
There are fewer substrate molecules and also the product molecules may get in the way of substrate molecules and prevent them from reaching an active site
Why does the graphs eventually flatten out in an enzyme catalysed reaction?
All the substrate has been used up and so now new product can be produced
How do we measure the grate of a reaction?
By finding the gradient (a/b)
A rise in tempature increases what?
The kinetic energy of molecules
If there are more effective collisions, what does this result in?
More enzyme substrate complexes being formed and so rate of reaction increases.
The temperature rise also begins, why?
To cause the hyrogen and other bonds in the enzyme molecule to break
What is denaturation?
A permanent change to the enzymes active site and the enzyme does not function again.
The optimum temperature differs from enzyme to enzyme. True or false
True
Once an active site on an enzyme has acted on its substrate, it is free to do what?
Repeat the procedure on another substrate molecule
A graph of a rate of reaction against enzyme concentration will initially show a proportionate increase, why?
there are more substrate than the enzyme’s active sites can cope with
If the substrate is limiting, what does this mean if we increase enzyme concentration?
It will have no effect on rate of reaction.
If the concentration of an enzyme is fixed and substrate concentration is slowly decreased, what does this mean for the rate of reaction?
It increases in proportion to the concentration of the substrate
Why is there an increase in proportion to the concentration of a substrate when substrate concentration is slowly increased?
A low substrate concentrations, the enzyme molecules have only a limited number of substrate molecules to collide with, the active sites are not working to full capacity.
What does a competitive inhibitor do?
They bind to the active site of an enzyme
What does a non-competitive inhibitor do?
They bind to an enzyme at a position other than the active site called the allosteric site
Competitive inhibitors have a molecular shape similar to that of the substrate, what does this allow?
It allows them to occupy the active site of an enzyme to compete with the substrate for the available active site.
What happens to the competitive inhibitor if the substrate concentration is increased?
the effect of the competitive inhibitor is reduced
is the inhibitor always bound to the active site?
No, eventually a substrate takes its place
As the substrate and the non competitive inhibitor are not competing for the same site, an increase in substrate concentration does or does not decrease the effect of the inhibitor?
It does not
