3.1.2 Enzymes and Digestion Flashcards
(89 cards)
1
Q
What are the three types of disaccharide?
A
- Maltose
- Sucrose
- Lactose
2
Q
What is sucrose made of?
A
Glucose and Fructose
3
Q
What is Lactose made of?
A
Glucose and Galactose
4
Q
What is a condensation reaction?
A
A reaction which results in a product and a water molecule for each bond made
5
Q
What is a glycosidic bond?
A
A bond between sugars caused by a condensation reaction ( with structure C-O-C )
6
Q
What is Hydrolysis?
A
The opposite of a condensation reaction. Where a polysaccharide is broken down and the water molecule that was created in condensation joins back in
7
Q
How to perform the Benedicts Test, or test or reducing sugars.
A
Add Benedicts reagent to a sample of sugar and heat. If it is a positive result, a brick red precipitate forms.
8
Q
How do you perform a Benedicts test on non-reducing sugars?
A
- Add Benedicts reagent and heat. Get negative result.
- Add dilute HCL to separate sample to hydrolyse
- Neutralise by adding Sodium Hydrogen Carbonate
- Repeat Benedicts test and get positive result
9
Q
How do you test for starch?
A
Add 2 drops of iodine/potassium iodide to 2 cubic centimetres of test solution. If blue/black, starch is present.
10
Q
What is maltose made of?
A
Glucose and glucose
11
Q
What enzyme breaks down starch?
A
Amylase
12
Q
What is starch broken down into?
A
Maltose
13
Q
What is maltose broken down by?
A
Maltase
14
Q
Where is the only place lactose can be found?
A
Mammalian milk
15
Q
Where is Sucrose commonly found?
A
In the phloem vessels of plants
16
Q
What type of polysaccharide do alpha glucose monomers bond to create?
A
Starch
17
Q
What type of polysaccharide do beta glucose monomers bond to create?
A
Cellulose
18
Q
What are the three types of monosaccharide?
A
- Glucose
- Fructose
- Galactose
19
Q
What 5 elements are amino acids made of?
A
Carbon, Nitrogen, Hydrogen, Oxygen and Sulfur (Only in Cytosine)
20
Q
What is the structure of an amino acid?
A
A central carbon atom, with the following attached
- a hydrogen atom
- a basic amino group (usually NH2)
- a carboxy-acid group (usually COOH)
- and a variable R group
21
Q
What is the central atom in an amino acid called?
A
Alpha carbon
22
Q
How many different amino acids are there?
A
20
23
Q
What are amino acids joined together by?
A
Peptide bonds
24
Q
What is on the ends of a poly peptide chain?
A
A free amino (NH2) on the N-Terminus and a free carboxyl on the C-Terminus
25
What is the sequence of amino acids in a polypeptide chain dependant on?
The sequences of the bases in DNA
26
What is Buffer Solution?
A solution of amino acids resistant to change in pH. If excess of H+, they will affiliate with the nitrogen in the amino acids. If excess of OH-, the H from the C-OH group will disassociate and join the OH- to form H2O
27
What is primary amino acid structure?
The sequence, order and number of the amino acids in the polypeptide chain.
28
What is the secondary structure of an amino acid?
The most basic level of protein folding. Two most common types are Alpha-helix with parallel hydrogen bonds and Beta-pleated with antiparallel
29
What is tertiary structure?
Compact globular structure of a folded up polypeptide chain, held together by bonds between R groups of amino acids.
30
What are the possible types of bonds in tertiary structure?
- Weak hydrogen bonds
- Ionic Bonds
- Sulphur Bridges/disulphide bonds/Covalent S-S bonds.
(Hydrophobic Interaction) - Inward Protein Folding
(Hydrophilic Interaction) - Outward Protein Folding
31
What is Quaternary Structure?
The arrangement of different polypeptide chains with each other
32
What roles do globular proteins usually have?
Enzymes, Membrane proteins, receptors, storage proteins, etc.
33
What role do fibrous proteins usually have?
Structural roles like collagen, keratin and actin.
34
What is denaturing?
When temp or pH changes enough to cause the hydrogen bonds to break making the protein lose its 3D structure.
35
What is the test for proteins?
Buret test. Add equal volume of sodium hydroxide to aqueous protein sample. Add aqueous copper sulfate. If protein is present, solution will turn purple/lilac (and gloopy denatured protein collects at the bottom)
36
What are the five stages of digestion?
1. Ingestion
2. Digestion
3. Absorption
4. Assimilation
5. Egestion
37
What is ingestion?
Taking food into the body
38
What is digestion?
Breaking down food by mechanical and chemical means
39
What is absorption?
Taking up soluble digestion products into the body's cells
40
What is assimilation?
Using the absorbed materials of digestion
41
What is Egestion?
Eliminating the undigested materials.
42
What is alimentary canal?
The digestive tract/gut; long tube extending from mouth to anus.
43
Explain the role of the mouth in digestion
The teeth and tongue break up food to increase the surface area of the 'bolus'. Saliva also contains lysozyme which kills bacteria.
44
Explain the role of Oesophagus in digestion
Connects the mouth to the rest of the gut by transporting the bolus through secretion of mucus and peristalsis.
45
What is peristalsis?
Wave like contractions that move down the Oesophagus
46
What is the role of the stomach in digestion?
An expandable bag where food is liquified and mixes with gastric juice for up to a few hours
47
What releases the liquified food into the small intestine
Sphincter
48
What does gastric juice contain?
- Hydrochloric Acid to kill bacteria
- Mucus to protect epithelium from the Acid
- Protease Enzymes
49
What is the role of the Small Intestine in digestion?
The place where almost all digestion takes places due to secretions from the pancreas and the liver.
50
What does pancreatic juice contain and where is it secreted?
Amylase, Protease and Lipase. It is secreted into the duodenum through the pancreatic duct
51
What is Bile?
A substance secreted by the liver which contains bile salts that emulsify lipids, thus increasing the surface area and aiding lipid digestion. It also contains alkali sodium hydrogen carbonate to neutralise the stomach acid.
52
What is the rest of the small intestine called after the duodenum?
The ileum.
53
What are the key features of the ileum that assist absorption?
- Large Surface Area filled with Villi and MicroVilli
- Short Diffusion path
- steep concentration gradient between ileum and lumen due to blood flow.
54
What is the role of the large intestine?
Absorption of water to form semi solid faeces
55
What are the two stages starch is digested in?
Digested to maltose with amylase, and then glucose with Maltase.
56
Where is amylase secreted from?
The salivary amylase from the salivary gland to the mouth and pancreatic amylase from the pancreas to the duodenum
57
What is lactose broken down by?
Lactase
58
Why are some people lactose intolerant?
They don't produce the lactase enzyme.
59
What is water potential?
Water concentration for is osmosis
60
How does lactose intolerance cause flatulance?
Sugars remain in the gut and ferments to produce methane and CO2
61
How does lactose intolerance cause diarrhoea?
The presence of sugars in the gut lowers the water potential. This stops the water in the faeces from being able to be removed, and in fact causes more water to diffuse out of the colon cells and into the lumen.
62
What are enzymes?
Biological Catalysts
63
Where does the reaction take place in an enzyme?
Active Site
64
What is the name of the molecule that binds to the enzyme in the reaction?
Substrate
65
What is the term for what is formed when the substrate binds to the active site of an enzyme?
An enzyme-substrate complex
66
What are the two models to describe the action of the active sites of enzymes?
- The lock and key model
| - The Induced Fit model
67
Explain the Lock and Key model of active sites
The active site is complementary to the shape of the substrate molecule and, like a lock and key, they fit together perfectly
68
Explain the induced fit model of active sites
- Active site not complementary
- changes shape to fit the substrate
- which distorts the substrate molecule, making it more likely to change to the product
- this is because the change in shape puts strain on bonds in the substrate so more likely to change into product
- can also make active site optimum pH, charge and water concentration to facilitate the reaction
69
What are coenzymes?
Non-protein molecules that help active sites to bind to substrates. They are derived from dietary vitamins which is why vitamins are important
70
How do enzymes increase the rate of reaction?
They create an alternative pathway for the reaction to occur
71
What is the alternative pathway that enzymes create for a reaction?
E + S ES EP E + P
72
What do enzymes do in terms of energy to increase the rate of reaction?
They lower the Activation energy
73
What is Activation energy?
Minimum required energy for a reaction to take place
74
Factors that affect the rate of enzyme reactions
- Temperature
- pH
- Enzyme Concentration
- Substrate concentration
- Inhibitors
75
Why does increasing temperature up to a certain point increase the rate of reaction in enzymes?
Because the enzymes and substrates have more kinetic energy so they collide more often and more of the substrate have passed the reduced activation energy threshold
76
What is the temperature at which mammalian body enzymes denature?
About 40 degrees
77
What is denaturing?
When the weak hydrogen bonds holding together the secondary tertiary and quaternary structures in an enzyme break, so an enzyme loses structure and its active site loses shape
78
Why does pH affect the rate of enzyme reactions?
pH affects the charge of the R groups at the active site and change its shape to be better or worse suited to fit a substrate
79
Why does enzyme concentration affect the rate of enzyme reactions?
As enzyme concentration increases the rate of reaction increases linearly because there are more enzymes to catalyse the reaction
80
How does substrate concentration increase the rate of reaction?
There are more substrate molecules to collide with enzymes, but at higher concentrations enzymes will be saturated with substrate so increasing substrate concentration after that does not help
81
What are the two types of inhibitor to the rate of enzyme reaction?
Competitive and non-Competitive inhibitor
82
What is a competitive inhibitor?
A molecule with a similar structure to the substrate that competes with the substrate to bind with the active site, which reduces the overall number of enzymes which will bind with a substrate rather than an inhibitor
83
What is a non-competitive inhibitor?
A molecule which binds to a different part of the enzyme than the active site and changes the shape of the active site so the substrate no longer fits, reducing the number of active enzymes
84
How doe Cholera cause Diarrhoea?
Cholera bacterium adheres to the epithelium and and secretes CT into the cell. In the cell, CT activates a chloride ion channel in the membrane, so ions diffuse from cells into the lumen, which lowers the water potential of the gut. This causes water to be lost from cells into the gut by osmosis, which produces diarrhoea.
85
How is Cholera treated?
Through Oral Rehydration Therapy (ORT)
86
How does ORT work?
The solution, made of glucose and salt (NaCl) binds to the sodium glucose co transporter in the membrane of the epithelium. This carries the solution into the cell, lowering the water potential and causing water to diffuse into the cells by osmosis.
87
Why can salt just not be used for ORT?
The molecules will only be transported if both glucose and sodium are present.
88
What is Oral Rehydration Solution made of?
Equimolar concentrations of glucose and salt
89
Describe the induced fit model of enzyme action
Active site is not complementary but flexible. Changes in the enzyme allow the substrate to fit to form and E-S complex
