Unit 1: Section 2 - The Digestive System Flashcards
Polymers are long chains of?
Monomers
Digestion is the process in which……………?
Large molecules are hydrolysed by enzymes to produce smaller molecules that can be absorbed and assimilated
Are protein and most carbohydrates polymers or monomers?
Polymers
In carbohydrates the monomers are called?
Monosaccharides
In proteins the monomers are called?
Amino acids
What elements to monosaccharides contain?
Carbon, hydrogen and oxygen
What elements do amino acids contain?
Carbon, hydrogen, oxygen and nitrogen
Which element is present only in monomers in protein?
Nitrogen
What’s the difference between absorption and assimilation?
Absorption is when molecules move from the digestive system into the blood where as assimilation is where absorbed molecules are incorporated into body tissues
What’s is assimilation?
Assimilation is where absorbed molecules are incorporated into body tissues
How does physical digestion happen in the mouth and stomach?
By the teeth in the mouth, and by the churning movement of the stomach muscles in the stomach
Why does physical digestion make digestion easier?
It breaks down food into smaller pieces giving a larger surface area for chemical digestion to take place on
What happens during chemical digestion?
Polymers are hydrolysed into smaller more soluble molecules which can be absorbed
How is the digestive process started in the mouth?
Teeth begin to break down the food (physical digestion) and the tongue is used to push food down the oesophagus
Why is saliva secreted?
Makes food easier to swallow and it contains enzymes which start chemical digestion
How is the digestive process continued in the oesophagus?
It takes food from the mouth to the stomach using peristalsis
What is peristalsis?
Wave like movements caused by contraction and relaxation of muscles, pushing food down the digestive tract
Why is mucus secreted in the oesophagus?
To lubricate the foods passage downwards
How is the digestive process continued in the stomach?
The stomach walls produce gastric juice to break down the food in the stomach (chemical digestion). Any the peristalsis of the stomach turn food into an acidic fluid called chyme
What do gastric juices contain?
Hydrochloric acid, pepsin and mucus
What are the two main parts of the small intestine?
Duodenum and ileum
The duodenum and ileum are parts of the?
Small intestine
What happens in the duodenum?
Bile and pancreatic juice neutralise the acidity of the chyme and break it down into smaller molecules
What happens in the ileum?
Small soluble molecules are absorbed through villi in the lining of the walls
What’s another name for the large intestine?
Colon
What happens in the large intestine?
Water, salts and minerals are absorbed
What final part of the digestive process happens in the rectum?
Faeces are stored in the rectum and then pass through the anus on defecation
What is the name of the glands in the digestive system?
The salivary glands and the pancreas
What do the salivary glands do?
Secrete saliva
What does saliva contain?
Mucus, mineral salts and salivary amylase
What does the pancreas release into the duodenum and why?
Pancreatic juice, to provide enzymes for digestion and to neutralise the hydrochloric acid from the stomach
Why does the acidity of the chyme have to be neutralised?
So that the digestive enzymes can work in the small intestine
What enzymes are within the pancreatic juice?
Amylase, trypsin, chymotrypsin and lipase
What does bile contain that neutralise the stomach acid?
Sodium hydrogencarbonate
What three classes can digestive enzymes be divided into?
Carbohydrases, proteases and lipases
Carbohydrases catalyse the……….?
Hydrolysis of carbohydrates
Proteases catalyse the……….?
Hydrolysis of proteins
Lipases catalyse the……….?
Hydrolysis of lipids
What enzymes is produced by the salivary glands?
Amylase
What enzymes is produced by the stomach?
Pepsin
What enzymes are produced but the pancreas?
Amylase, trypsin, chymotrypsin, carboxypeptidase and lipase
What enzymes are produced in the ileum?
Maltese, sucrase, lactase and peptidase
Where is amylase produced?
In the salivary glands and pancreas
Where is pepsin produced?
In the stomach
Where is trypsin produced?
In the pancreas
Where is carboxypeptidase produced?
In the pancreas
Where is chymotrypsin produced?
In the pancreas
Where is lipase produced?
In the pancreas
Where is maltase produced?
In the ileum
Where is sucrase produced?
In the ileum
Where is lactase produced?
In the ileum
Where is peptidase produced?
In the ileum
What are four examples of a carbohydrase?
Amylase, maltase, sucrase and lactase
What are four examples of a protease?
Pepsin, trypsin, chymotrypsin and carboxypeptidase
What is an example of a lipase?
Lipase
Amylase hydrolysis what? into?
Starch into maltose
Pepsin, trypsin and chymotrypsin hydrolyse what? Into?
Protein into peptides
Carboxypeptidase and peptidase hydrolyse what? Into?
Peptides into amino acids
Lipase hydrolyses what? Into?
Lipids into fatty acids and glycerol
Maltase hydrolyses what? Into?
Maltose into glucose
Sucrase hydrolyses what? Into?
Sucrose into glucose nod my fructose
Lactase hydrolyses what? Into?
Lactose into glucose and galactose
What is a dipeptide?
When two amino acids are joined together
What’s the difference between dipeptides and polypeptides?
Dipeptides only contain two amino acids and polypeptides contain three or more
What’s the same general structure that all amino acids have?
A carboxyl group, and an amino group attached to a carbon atom
What is the difference between different amino acids ?
The variable group
What reaction forms polypeptides from amino acids?
Condensation reactions
What molecules is released during a condensation reaction?
Water
What are the bonds between amino acids called?
Peptide bonds
What’s the opposite of a condensation reaction?
Hydrolysis
What happens during hydrolysis of polypeptide?
The peptide bond between the amino acids is broken down and a water molecules is added to form separate amino acids
What’s the difference between hydrolysis and a condensation reaction?
In condensation reactions a water molecule is formed, hydrolysis reactions use a water molecule
What are the names of the different structures of protein?
Primary, secondary, tertiary and quaternary
What is the primary structure?
A sequence of amino acids in a polypeptide chain
What is a secondary structure?
Hydrogen bonds form between amino acids in the polypeptide chain causing it to coil into an alpha helix or fold into a beta pleated sheet
What two things do polypeptide chains from in the secondary structure?
Alpha helixs and beta pleated sheets
What is the tertiary structure?
The coiled or folded chain of amino acids are coiled up and folded even further, and many more bonds form between different parts of the polypeptide chain
Do all proteins have a quaternary structure and why?
No as some are only made up of one polypeptide chain
What is the quaternary structure?
Several polypeptide chains are held together by bonds.
Name three quaternary structure proteins?
Haemoglobin, insulin and collagen
Why enzymes usually spherical in shape?
Due to the tight folding of the polypeptides
What polypeptides are antibodies made up of?
Two light polypeptide chains and two heavy polypeptide chains
Why structural proteins strong?
They consist of long polypeptide chains lying parallel to each other with cross links between them making them strong
What test can you do to identify a protein?
Biuret
What is the biuret test for proteins?
1.) add a few drops of sodium hydroxide to the solution
2.) then add some copper sulfate to the solution
3.) positive results - changes to purple
negative results - solution stays blue
When doing a biuret test for protein why do you need to add sodium hydroxide to the solution?
To make it alkaline
What causes lactose intolerance?
When you don’t have enough of the enzyme lactase you can’t break down the lactose properly, causing lactose intolerance
When you have lactose intolerance what happens to the undigested lactose?
It is fermented by bacteria in the stomach causing intestinal problem
What intestinal problems does lactose intolerance cause?
Stomach cramps, excessive flatulence and diarrhoea
How does lactose intolerance cause diarrhoea?
Having a high concentration of lactose in the intestine causes water to move out of the blood into the intestines by osmosis. Meaning your faeces are more runny
What’s another name for lipids?
Triglyceride
What bonds form between fatty acids and glycerol to form lipase?
Ester bond
What are three examples of monosaccharides?
Glucose, fructose and galactose
What type of bond forms between two monosaccharides?
Glycosidic bond
What is a disaccharide?
Two monosaccharides joined together
What’s the difference between disaccharides and polysaccharides?
Polysaccharides contain more than two monosaccharides, disaccharides only contain two
What are the two forms a glucose called?
Alpha and beta
What reaction joins together two monosaccharides?
Condensation reaction
What is a general term for monosaccharides and disaccharides?
Sugars
What two groups can sugars be classified into?
Reducing and non reducing sugars
What is the test called you can do for sugars?
Benedict’s test
What’s the test you can do to find reducing sugars and what are the results?
Add Benedict’s reagent and heat it
If it contains reducing sugars it will turn brick red, if no reducing sugars are present it will stay blue
If reducing sugars are present what do you expect to happen after the Benedict’s test?
It will turn brick red
If reducing sugars aren’t present what can you do next to see if there are any non reducing sugars?
You have to break them down into their monosaccharides by boiling it with dilute Hydrochloric acid, you then add sodium hydrogen carbonate to neutralise the solution and carry out the Benedict’s test again
What two polysaccharides are starch made up of?
Amylose and amylopectin
How is starch hydrolysed into alpha glucose molecules?
Starch is hydrolysed by amylase into maltose
Maltose is then hydrolysed by maltase into alpha glucose molecules
What test can you do to see if starch is present?
Add iodine dissolved in potassium iodide solution
If starch is present it will change to a dark blue black colour, if no starch is present it will remain a browny orange colour
What’s the definition of a catalyst?
A substance that speeds up chemical reactions without being used up or changed in the reaction itself
What are enzymes?
They are biological catalysts, catalysing metabolic reactions in your body
What’s the part of an enzymes where the substrate binds to?
Active site
What is activation energy?
The minimum amount of energy that needs to be supplied to the chemicals before the reaction will start
Do enzymes increase or decrease activation energy?
Decrease
Why can enzymes lower the temperature that some reactions can happen!
The activation energy for most reactions if given as heat, as enzymes decrease the activation energy they also decreases the temperature at which a reaction will happen
What is it called when a substrate fits into the enzymes active site?
Enzyme - substrate complex
What is the reason why enzymes substrate complexes lower the activation energy when substrate molecules are being joined together?
Being binded to the enzyme holds the two substrates closer together, reducing any repulsion meaning they can bond more easily
What is the reason why enzymes substrate complexes lower the activation energy when substrate molecules are being broken apart?
When the substrate binds to the active site it puts a statin on the bonds in it so they can be broken more easily
How many models are there for how enzymes work?
Two
What are the names of the two models for how enzymes work?
The lock and key model
The induced fit model
The enzymes and substrate have a what shape?
Complementary
What does the lock and key model show?
The active site of the enzyme and the substrate have a complementary shape and fit together perfectly, they then bind together to form an enzyme-substrate complex. After this the substrate is released as two products. Or alternatively two substrate fit into the active site together and bond and become one product
What does the induced fit model show?
The active site and substrate have a similar shape and when they bind together the active site changes shape slightly so that they are now complementary, forming an enzyme substrate complex. After this the substrate is released as two products. Or alternatively two substrate fit into the active site together and bond and become one product
Why can enzymes only catalyse one reaction?
The shape of the active site is specific to the substrate
What does the shape of the active site depend on?
The enzymes tertiary structure, which is determined by its primary structure
Name five things that affect enzyme activity
Temperature, pH, substrate concentration, competitive and non competitive inhibitors
What two ways can you measure enzyme activity?
- ) measure the amount of product produced
2. ) measure the amount of substrate left
Why does an increase in temperature increase the rate of reaction between enzymes and the substrates?
More heat means the substrate molecules have more energy and move faster, meaning they are more likely to collide with the enzymes active site, the energy of these collisions also increases more likely resulting in a reaction
What happens if you increase the temperature too high for an enzyme?
An increase in temperature makes the enzymes molecules vibrate more, these vibrations eventually cause the peptide bonds holding the enzyme in shape to break. This makes the enzyme and it’s active site change shape so it no longer fits the substrate. Denaturing it
When the enzyme changes shape and can no longer catalyse the reaction it is said to be?
Denatured
What’s the effect of a too high or too low pH on the rate of reaction between enzymes and their substrates ?
Above and below the optimum pH the H+ and OH- ions can distrust the ionic and hydrogen binds holding the enzymes tertiary structure in place, making it change shape and become denatured
What does an increase in substrate concentration do to the rate of reaction?
Increase it up until the saturation point
Why does an increase in substrate concentration cause the rate of reaction between the enzyme and substrate but only up till the saturation point?
More substrate means there will be more collisions between the substrate and active sites increasing the rate of reaction. However at saturation point all the active sites are occupied and increasing the substrate anymore won’t make any difference
What are the molecules called that can prevent enzyme activity?
Enzyme inhibitors
How do competitive inhibitors prevent enzyme activity?
They have a similar shape to the substrate molecules, and compete with the substrate molecules to bind to the active site. However no reaction takes place when they do they just block it for the substrate molecules meaning they can’t react
How much the enzyme is inhibited depends on?
The relative concentrations of the inhibitors and substrate
How do non competitive inhibitors prevent enzyme activity?
They bind to the enzyme away from the active site. Causing the active site to change shape so the substrate molecules can no longer bind it it
Will increasing the concentration of substrate make any difference to non competitive inhibitors?
No as non competitive inhibitors don’t use the active sites and they will still alter the shape of the active sites
