B3: Organisation and the Digestive System Flashcards
What is a tissue?
A group of same type cells
What is an organ?
A group of tissues working together for the same function
What is an organ system?
A group of organs which work together to perform one function
What are the adaptations of muscle cells?
They have special protein fibres which can change their length (useful for contraction)
They are packed with mitochondria (provides the energy needed for contraction)
What are the 3 main nutrients in food?
Carbohydrates, Protein and Lipids
What is the purpose of the digestive system?
To break down large molecules into smaller molecules to be digested
What happens during digestion?
Large molecules are broken down using enzymes, the small molecules are now able to be absorbed into the bloodstream
Describe the process of digesting food (mouth - stomach)
The food enters the mouth, where it is chewed and broken down by enzymes in the saliva (starch is digested into smaller sugar molecules). The food then passes down the oesophagus and into the stomach, where the digestion of proteins begins (HCl assists in the process). The churning action of the stomach turns the food into a fluid (increasing the SA for enzymes to digest more efficiently).
Describe the process of digesting food (stomach - large intestine)
The churned fluid is passed to the small intestine (chemicals are released by the pancreas (protease, lipase (starts digestion of lipids) and amylase) and the liver(bile to neutralise the acid, and increase lipase efficiency). The walls of the small intestine release protease and lipase. The small food molecules produced are absorbed into the bloodstream (either by diffusion or active transport
Describe the process of digesting food (large intestine - anus)
The fluid makes its way down the large intestine, where excess water is absorbed into the bloodstream,
and the faeces is released from the body
What happens to the products of digestion?
Used to build new carbohydrates, lipids and proteins.
Glucose produced is used in respiration
Which organs release amylase?
Salivary glands
Pancreas
Small intestine
Which organs release protease?
Stomach
Pancreas
Small Intestine
Which organs release lipase?
Pancreatic fluid
Small Intestine
What is the purpose of enzymes and what is their shape?
They are biological catalysts and are large protein molecules with a groove on their surface (active site) where the substrate goes
How do enzymes catalyse reactions?
Each type of enzyme has a specific active site shape designed to fit a specific substrate. Thus, when the specific substrate enters the active site, it is broken down (if it does not fit, it is not broken down)
What happens when proteins are digested?
Long chains of amino acids, when digested, they convert back to individual amino acids, which are absorbed into the bloodstream. When absorbed by body cells, they are joined together in a different order to make human proteins
What is the structure of starch?
A chain of glucose molecules
What happens when starch is digested?
Simple sugars are produced
What is the structure of a lipid?
A molecule of glycerol which is attached to 3 molecules of fatty acids
What happens when lipids are digested?
Glycerol and fatty acids are produced
Where is bile made and stored?
Made in liver and stored in the gall bladder
What is the role of bile?
Increases the efficiency of lipid digestion - it emulsifies fatty acids and increasing their SA to increase the efficiency of lipase.
Bile is alkaline, allowing it to neutralise stomach acid, creating alkaline conditions in the small intestine (optimum for lipase)
How does temperature affect enzyme activity?
As temp increases, reaction is faster as the collisions per second between enzyme and substrate are more frequent.
At a certain temp, the optimum temp is reached, which is the maximum possible frequency of successful collisions.
Past the optimum, activity rapidly decreases to 0, this is because high temperatures denatures the active site and changes it shape, thus the substrate no longer fits
How does pH affect enzyme activity?
Every enzyme has a specific optimum pH, the active site will denature if conditions are too acidic or alkaline
What are the optimum pH s of all 3 enzymes?
Protease - acidic (in the stomach)
Lipase - alkaline (released from pancreas)
Amylase - Neutral
How is the small intestine adapted to absorb the products of digestion?
Very long - provides a large surface area for efficient digestion
Interior contains villi - increase surface area, very good blood supply to rapidly absorb the products of digestion, increasing the conc. gradient, thin membrane, short diffusion path
Villi have microvilli - increasing surface area even further
