B3 Flashcards
Organisation and the digestive system
What is a tissue ?
group of cells with similar functions working together to fulfill a purpose
[] muscular tissue contract to stimulate movement
[] glandular tissue made of secretory cells secrete hormones etc.
What is an organ ?
group of tissues with their own specific functions working together to perform a specific function
What is an organ system ?
groups of organs working together to perform a specific function; many different organ systems make up larger multicellular beings
Name the order of organisation in larger multicellular organisms
cells -> tissues -> organs -> organ systems -> organism
Why is digestion of food in the human body important ?
- food consumed has many nutrients
- nutrients within food are in large insoluble molecules that your body cannot diffuse in/out of cells, meaning they can’t be used
- digestion breaks the large insoluble molecules into smaller, soluble molecules which are more useful in the body
Name all the organs in the digestive system and their respective roles in digestion
- mouth
[] teeth, tongue + salivary glands
[] teeth = mechanical breakdown of food, making faster and easier to chemically process via increasing surface area - also mixes saliva with food
[] saliva = beginning of chemical breakdown (contains amylase enzymes which begin to break down starch in foods) - oesophagus
- stomach
[] pepsin (protease enzyme) in the stomach begins to break down proteins
[] muscle tissues churn the food, mixing acid and enzymes with it to faster break it down as well as provide some mechanical break down
[] hydrochloric acid kills most pathogens and starts to break down large insoluble molecules - liver
[] produces bile - gall bladder
[] stores bile - duodenum
[] squirts bile onto processed food leaving the stomach and entering the small intestine
[] aids in break down of lipids (cannot be otherwise started due to lipids being entirely insoluble) - small intestine
[] nutrients from the food are absorbed into the bloodstream
[] more enzymes mixed with the food to break it down as much as possible - large intestine
[] excess water is reabsorbed into the blood so as not to waste it in excretion of faeces - rectum
[] stores faeces - anus
How is the stomach adapted to its function ?
- contains glandular tissues which secrete enzymes like pepsin
- epithelial tissues which cover the inside and outside of the organ
[] have mucous cells in the top layer which secrete mucus to protect the tissue from the hydrochloric acid - muscular tissues to churn food in the stomach
- high conc. acid to break down large insoluble molecules better and kill ingested pathogens
How is the small intestine adapted to its function ?
- walls are only 1 cell thick
[] short diffusion distance makes absorption of nutrients into the bloodstream more efficient - walls covered in villi and microvilli to increase surface area and thus rate of diffusion as much as possible
- good blood supply surrounding small intestine
[] maintains concentration gradient that keeps diffusion efficient
[] quickly transports nutrients absorbed from broken down food into the bloodstream and around the body to where it is needed
What are complex carbohydrates ?
large molecules comprised of monosaccharide (simple sugar) units joined together as a polymer, like cellulose and starch
What are simple sugars ?
carbohydrates with only one sugar unit, like glucose
What are lipids ?
- fats and oils
[] most efficient energy store in the body - ALL lipids are insoluble in water
- made up of one glycerol unit and three fatty acids
[] these fatty acids can vary in what they are, and determine whether the lipid is solid fat or liquid oil
What are proteins (and their functions) ?
- otherwise known as polypeptides
- long chains of amino acids folded over each other
[] bonds that join the amino acids are very sensitive to temperature and pH
[] if the ideal temperature/pH range of the protein is exceeded, will denature (unravel) and thus stop working - act as hormones, enzymes, antibodies, aid in the contraction of muscle tissue etc.
Describe how to test for the presence of starch in foods
- place small sample of crushed food in dimple tray
- drop iodine solution over the sample
- if there is a colour change from orange-brown to blue-black, starch is present
Describe how to test for the presence of protein in foods
- place small sample of crushed food in boiling tube (or grind food with distilled water and filter out suspended food particles (the sample))
- put biuret’s reagent over the sample
- if changes colour from blue to purple, protein is present
Describe how to test for the presence of simple sugars in foods
- place small sample of crushed food in boiling tube (or grind food with distilled water and filter out suspended food particles (the sample))
- put Benedict’s reagent in the boiling tube
- heat boiling tube in a water bath (leave for five minutes
- colour changes:
[] blue to brick red = sugar present
[] blue to orange = some sugar present
Describe how to test for the presence of lipids in foods
- place small sample of crushed food in boiling tube (or grind food with distilled water and filter out suspended food particles (the sample))
- pour ethanol over the sample
- shake tube
[] change from clear to cloudy white shows presence of lipids
What is an enzyme ?
- protein
- biological catalyst (speeds up rate of reaction WITHOUT BEING USED UP)
- control metabolism (rate of chemical reactions) in the body
Describe the “lock and key” way in which enzymes work to break down, convert or build up molecules
- shape of enzyme’s active site (where the reaction takes place) is specific to the shape of (a) certain molecule(s) (called the substrate)
- substrate fits perfectly into active site and binds to it
- reaction takes place and substrate is split or joined
- substrate released from the active site, and enzyme can be used again
How does temperature affect enzyme action ?
too high = denatured
too low = ineffective (particles don’t have enough energy to collide and thus substrate and enzyme don’t meet)
just right = most efficient enzyme action and reactions ca be catalysed to be very quick
How does pH affect enzyme action ?
- change in pH affects the forces holding the amino acids in the protein together and so changes the shape of the molecule
[] can no longer act as a catalyst, as active site is no longer specific to the substrate
Where in the digestive system is amylase produced ?
- salivary glands
- pancreas
- small intestine
Where in the digestive system is protease produced ?
- stomach (pepsin)
- pancreas
- small intestine
Where in the digestive system is lipase produced ?
- pancreas
- small intestine
Describe the method for a practical investigating the effect of pH on the efficiency of amylase in catalysing the breakdown of complex carbohydrates
- gather equipment
[] two dimple trays
[] iodine solution + dropping pipette
[] starch solution
[] amylase solution
[] 5 buffer solutions of different pHs (4.0, 5.0, 6.0, 7.0, 8.0)
[] kettle/boiled hot water
[] beaker
[] 3 boiling tubes
[] thermometers - fill 3 boiling tubes with equal amounts of starch solution, amylase solution and the first buffer solution (pH 4)
- in a beaker, fill part-way with room temperature/cold water, then use hot boiled water to bring temperature of the water up to 35 degrees celsius (measure with thermometer)
- place the three boiling tubes in the beaker with a thermometer in each
[] leave for around 5 minutes so that all are of the same temperature - prepare two dimple trays so that they have iodine already in each divot
- combine the solutions
[] put buffer in amylase FIRST and then put starch in the buffer and amylase tube (the second that you put the starch in, start a stopwatch) - every 10 seconds, use the pipette to drop some of the mixture into the iodine and see if it tests positive for starch (colour change from orange/brown to blue/black)
[] take a “zero” reading at the very beginning of starting the stopwatch to prove that the starch is in fact present
[] repeat until there is no positive test for starch - count the number of divots which have a positive starch test and multiply by 10 to get the full time it took for the amylase to fully digest the starch
[] record this - repeat all steps 4 more times for the remaining 4 buffer solution pHs
- plot results to demonstrate at which pH the optimum pH of amylase is (at this pH, time taken to digest starch will be the lowest, or conversely the rate of reaction will be the highest)
Describe the roles of bile made in the liver in the digestive system
- neutralises acid and provides alkaline conditions for small intestine enzymes to work in
[] bile duct squirts bile (alkaline) on the acidic food mixture coming from the stomach
[] enzymes in the small intestine have an alkaline optimum pH - providing these conditions makes digestion more efficient - emulsifies fats
[] enzymes need large surface area of substrate to work effectively
[] fats are insoluble in water and so are not made smaller by the chemical and physical processes during digestion
[] bile splits up larger fat globules up into smaller globules with higher surface areas, allowing lipase enzymes to properly break them down
