B2 - Principles Of Organisation And Digestion Flashcards
What is a tissue?
A tissue is an aggregation of cells with a similar structure and function
What is an organ?
An organ is an aggregation of tissues working together to perform a particular function
What is an organ system?
An aggregation of organs, which work together to form functioning organisms
What is a cell?
The basic building block of all living organisms
Why does food need to be digested?
To break down large, insoluble biological molecules into small, soluble ones by enzymes so that they can be absorbed in the bloodstream
What are the function of digestive enzymes?
Digestive enzymes convert food into small, soluble molecules that can be absorbed into the bloodstream
What digestive enzyme breaks down carbohydrates?
Carbohydrases.
Amylase is a carbohydrase which breaks down starch into maltose
What digestive enzyme breaks down protein?
Proteases
Example: Pepsin
What digestive enzyme breaks down lipids (fats)?
Lipases
What are the products of digestion used for?
The products of digestion are used to build new carbohydrates, lipids and proteins.
Some glucose is utilised in cellular respiration
Where is bile made, stored and released?
Bile is made in the liver, stored in the gall bladder and released into the small intestine
What is the function of bile?
Bile catalyses the digestion of lipids by converting large lipid droplets into smaller ones.
It is not an enzyme
Explain how bile increases the rate of lipid breakdown by lipase
Bile emulsifies lipids to form small droplets. This increases the S.A for enzymes to act on. Bile also is alkaline to neutralise HCI from the stomach (enzymes in the small intestine have a more alkaline pH than those in the stomach) so that the enzymes do not denature. These both increase the rate of lipid breakdown by lipase to form fatty acids and glycerol
(i) What is the qualitative reagent test for
carbohydrates/sugars? What is its positive result?
(ii) What are the different types of carbohydrate that can be tested for?
(i) Benedict’s solution.
Positive result: Blue -> Green/yellow/brick-red precipitate, depending on concentration
(ii) Glucose using Benedict’s and starch using iodine
How is the small intestine adapted for absorption?
Long in length at around 5m. This increases the surface area for absorption of the products of digestion
Interior is covered with villi. Microvilli on the surface increase the surface area further
Rich blood supply in vili. This allows for the bloodstream to remove the products of digestion, increasing the concentration gradient
Villi have a thin membrane. This ensures a short diffusion pathway
High yield of mitochondria in intestine lining cells to release energy for any molecules that cannot be absorbed into the bloodstream by diffusion and require active transport
What do carbohydrases break down carbohydrates into?
Simple sugars
What do proteases break down proteins into?
Individual amino acids, which are then absorbed into the bloodstream
What do lipases break down lipids into?
Glycerol and fatty acids. This makes the pH more acidic
What is the qualitative reagent test for starch? What is its positive result?
Iodine solution
Positive result: Orange -> blue/black
Where is amylase, a carbohydrase that breaks down starch into sugar (maltose), produced? [SgPSm]
Where does it work?
Produced in:
Salivary glands
Pancreas
Small intestine
Works in:
Mouth
Small intestine
Where is protease produced? [SPSm]
Where does it work?
Produced in:
Stomach
Pancreas
Small intestine
Works in:
Stomach
Small Intestine
Where is lipase produced? [SP]
Where does it work?
Produced in:
Pancreas and small intestine
Works in:
Small intestine
What is the function of the stomach?
Produces HCI to kill bacteria and to provide the optimum pH for the protease enzyme to function
What is the function of the small intestine?
The site where soluble molecules are absorbed into the blood by cellular transport
What is the function of the liver?
Releases bile into the small intestine to emulsify fat and neutralise stomach acid
What is the function of the large intestine?
Absorbs water from undigested food to produce faeces. This passes out of the body through the rectum and anus
Without bile to neutralise acid in the stomach, the enzymes would become ______
Denatured
Amino acids are used to build proteins such as _______ and ________
Enzymes and antibodies
Fatty acids and glycerol can be used to build new ____________ and ____________
Cell membranes and hormones
Some glucose released from carbohydrate breakdown is used in ______ to release energy to fuel all the activities of the cell
Respiration
What is the function of muscular, glandular and epithelial tissue?
Muscular tissue - moves the stomach walls to churn food
Glandular tissue - makes digestive juices
Epithelial tissues - covers the outside and inside of the stomach
What is the digestive system?
Several organs working together to digest and absorb food
What are enzymes?
Enzymes are biological catalysts that are 3D, large (tertiary) proteins made up of a chain of amino acids
Enzymes catalyse specific reactions in living organisms due to the ____ of their ________
Shape
Active site
What is the lock and key theory model of enzyme action?
The substrate is perfectly complementary to the active site. This forms an enzyme-substrate complex and products
What factors affect enzyme action?
Temperature
pH
What is a catalyst?
A substance which increases the rate of reaction without getting used up
Describe the process of human digestion
Mouth -> mechanically churns food. Salivary glands produce salivary amalyse to digest insoluble food molecules. This passes through the oesophagus into the stomach
Stomach -> pummels food with muscular walls, produces pepsin and HCI. Churning action turns food into fluid, increasing S.A for enzymes
Small intestine -> Bile released into the small intestine, which increases the rate of fat breakdown. All digestive enzymes break down large, insoluble molecules into small, soluble ones to be absorbed in the bloodstream through diffusion or active transport
Wastage —> Fluid goes to large intestine. Excess water absorbed into the bloodstream. Faeces stores in rectum before leaving through anus
Describe a method to prepare food samples
Break food using pestle and mortar
Add distilled water
Stir and filter to remove insoluble bits of food
Describe a method to test for sugars
Transfer 5cm³ of food sample to a test tube
Prepare a water bath at 75 degrees Celsius
Add 10 drops of Benedict’s solution
Place each test tube in water bath for five minutes
If green —> small concentration of sugar
If yellow —> moderate concentration
If Red —> highest concentration
Describe a method to test for starch
Transfer 5cm³ of food sample to a test tube
Add 3 drops of iodine solution
Positive result is blue-black
Describe a method to test for proteins
Transfer 2cm³ of food sample to a test tube
Add 2cm³ of Biuret solution
Positive result is purple from blue
Describe a method to test lipids (write both methods)
Transfer 5cm³ of food sample to a test tube
Use a pipette to add three drops of Sudan III
If a red layer forms, lipids are present
Suggest how damage to the mucus lining of the stomach might result in a stomach ulcer forming
Bacteria not killed by HCI so damage the mucus lining
So acid damage tissues
Explain how temperate affects how enzymes function
Explain how enzymes break down substrates
Substrate fits into active site of the enzyme
Shape of active site is specific to the enzyme and forms an enzyme-substrate complex
Bonds within substrate are broken
Enzyme is not used up !
Give one industrial use of carbohydrase, isomerase and protease
Carbohydrase -> converts starch info sugars
Isomerase -> converts glucose syrup to fructose syrup
Protease -> pre-digests proteins in baby food
Describe a method to investigate the effect of pH on the rate of reaction of amylase enzyme.
- Set up a water bath or electric heater at 25-35 degrees
- Place 3 drops of iodine solution into each well of a spotting tile
- Using a syringe, place a 2cm³ solution of amylase, starch and pH 5 buffer solution into three different boiling tubes
- Place all three boiling tubes into the water bath and wait 5 minutes for them to equilibrate
- Mix the boiling tubes and start a timer
- Every 30 seconds, place a drop from the boiling tube into the well
- Continue step 6 until the well remains orange. At this point, the starch has been fully digested. Record this time
- Repeat the investigation using different pH buffer solutions such as 7 and 12
- Repeat for each pH three times, remove anomalies and calculate a mean rate of reaction
- Calculate the rate of reaction using: Reaction = 1000/time
What is the IV, DV and CV for investigating the effect of pH on the rate of reaction of amylase enzyme?
How can the investigation be improved?
IV- pH
DV-
CV- Temperature
Suggest an explanation as to why the rate of reaction is slow at certain pH levels
High and low pH values may cause bonds holding enzymes’ structure together to break
Explain how the cells of the pancreas are specialised to produce enzymes
- Pancreatic cells have many ribosomes. This is the site of protein synthesis
- Many mitochondria to release energy for protein synthesis
Read questions in exams TWICE for every subject
Describe the structure of the heart
Muscular walls to provide a strong heartbeat
The muscular wall of the left ventricle is thicker, because blood needs to be pumped all around the body
Four chambers that separate oxygenated blood from the deoxygenated blood
Valves to make sure the backflow of blood does not occur
Coronary arteries cover the heart to provide its own oxygenated blood supply
Where is carbohydrase produced?
A person has a tumour blocking the tube leading from the gall bladder to the small intestine
ExplaIn why this person would have difficulty digesting fat (5)
- No bile reaches the small intestine
- So less emulsification fat
- So smaller surface area for lipase to break down fat
- pH of small intestine is not neutralised/alkaline
- So lipase is not at its optimum pH to break down fat
