S2 - Human Nutrition Flashcards
biological molecules:
-carbohydrates
-proteins
-lipids
carbohydrates:
-they are made of carbon, oxygen and hydrogen
-starch and glycogen are large, complez carbohydrates, which are made up of many smaller units joined together in a long chain
maltose (and other simple sugars) -> starch
proteins:
-proteins are made up of long chains of amino acids
-they all contain carbon, nitrogen, hydrogen and oxygen atoms
amino acids -> proteins
lipids:
-lipids (fats and oils) are built from fatty acids and glycerol
-lipids contain carbon, hydrogen and oxygen atoms
glycerol & fatty acids -> lipid
how to make a food sample:
1) get a piece of food and break it up using pestle and mortar
2) transfer the ground up food to a beaker and add some distilled water
3) give the mixture a good stir with a glass rod to dissolve some of the food
4) filter the solution using a funnel lined with filter paper to get rid of the solid bits of food
testing for glucose:
use the Benedict’s Test to test for glucose:
-if the food sample contains glucose, the solution in the test tube will change from its normal blue colour
-it will become green or yellow in low concentrations of glucose
-it will become brick-red in high concentrations of glucose
testing for starch:
use Iodine solution to test for starch:
-if the sample contains starch, the colour of the solution will change from browny-orange to black or blue-black
testing for proteins:
use the Biuret Test to test for proteins:
-if the food sample contains protein, the solution will change from blue to pink or purple
-if no protein is present, the solution will stay blue
testing for lipids:
use the Sudan III Test to test for lipids:
-if the sample contains lipids, a milky white emulsion will form
-if the sample doesn’t contain lipids, it will remain colourless
practical: investigating starch production:
1) cover half of a small leaf with foil
2) place the plant on a windowsill for 48 hours so that ligh can reach it
3) put the leaf into boiling water to kill and preserve it
4) put the leaf in a boiling tube containing hot ethanol for 10 minutes (this removes the chlorophyll pigment)
5) dip the leaf in boiling water to soften it
6) put lead in a Petri dish and cover with iodine solution
7) the covered half of the leaf will remain orange-brown, whereas the exposed half will change to blue-black (as iodine solution changes colour in the presence of starch, as photosynthesis tuned the glucose into starch for storage)
nutrition in humans:
-humans need to eat a balanced diet in order to mantain their health
-this should consist of carbohydrates, proteins, lipids, dietary fibre, vitamins, minerals and water
nutrient sources and functions:
-carbohydrates: bread, cereals, pasta, rice, potatoes
-> a high energy source
-proteins: meat, fish, eggs, pulses -> for growth and repair
-lipids: butter, oil, nutes -> a high energy source and for insulation
-dietary fibre: vegetables, bran -> to provide roughage to keep food moving through gut-defiency causes constipation
-vitamin A: carrots, green vegetables -> needed for vision, especially in the dark, and for growth
-vitamin C: citrus fruits, broccoli, peppers -> helps to absorb iron
-vitamin D: margarine, oily fish -> helps to absorb calcium
-calcium: milk -> for bone and teeth strength-defiency can cause rickets (curving of bones)
-iron: red meat -> needed for haemoglobin-defiency can cause anaemia
-water: water, juice, milk -> needed for cell reactions to take place
factors affecting energy requirements: age
-energy requirements generally increases as we approach adulthood
-energy needs of adults go down as they age
factors affecting energy requirements: activity levels
-if you are more active then you will need more energy for movement
factors affecting energy requirements: pregnancy
-energy requirements will increase in order to support growth of foetus
-energy needs also increase due to the extra mass of the baby
human alimentary canal:
-the alimentary canal is the passage food moves through once it has been eaten
human alimentary canal: mouth
-mechanical digestion: teeth break up large food piece into smaller pieces with larger surface area : volume ratio (food bolus)
-chemical digestion: amylase breaks down starch into glucose
-salivary glands produce saliva to lubricate the food bolus so it can be swallowed easily
human alimentary canal: oesophagus
-tube from mouth to the stomach
-food bolus moves down due to unidirectional wave-like contractions (peristalsis) created by circular muscles and longitudinal muscles that create a squeezing action
human alimentary canal: pancreas
-produces carbohydrase, protease and lipase enzyme
-secretes enzymes into the stomach and small intestine
human alimentary canal: small intestine
duodenum:
-the first part of the small intestine
-carbohydrases, proteases and lipases digest food here
-bile is released into the duodenum, bile is produced in the liver and stored in the gallbladder, it has 2 roles:
1) it is alkaline to neutralise the hydrochloric acid which comes from the stomach, the enzymes in the small intestine have a higher (more alkaline) optinum pH than those in the stomach
2) it breaks down large drops of fat into smaller ones (emulsifies it), the larger surface area allows lipase to chemically break down the lipids into glycerol and fatty acids faster
-peristalsis also occurs here
ileum:
-lined with villi to maximise absorption of digested soluble molecules into blood
-villi have a thin lining, a large network of capillaries and have a large surface area
human alimentary canal: large intestine
-water is absorbed here, to produce faeces
-faeces is stored in the rectum and the removed through the anus
digestive enzymes:
carbohydrates (starch):
-broken down by carbohydrases
-starch -> maltose by amylase
-maltose -> glucose by maltase
proteins:
-broken down by proteases in the stomach and small intestine
-proteins -> amino acids
lipids:
-broken down by lipases
-lipids -> glycerol + 3 fatty acids
the alimentary canal:
-mouth: salivary glands in the mouth produce amylase enzyme in the saliva + teeth break down food
-oesophagus: the muscular tube that connects the mouth and stomach
-stomach: it pummels the food with its muscular walls + produces the protease enzyme, pepsin + it produces hydrochloric acid to: kill bacteria + give the optinum pH for the protease enzyme to work
-liver: where bile is produced
-gall bladder: where bile is stored
-pancreas: produces protease, amylase + lipase enzymes, it releases these into the small intestine
-large intestine: also called the colon, where excess water is absorbed from the food
-small intestine: produces protease, amylase and lipase enzymes to complete digestion + this is also where nutrients are absorbed out of the a.c. into the body + the first part is the duodenum and the last part is the ileum
-rectum: the last part of the large intestine + where faeces are stored before they are excreted
villi in the small intestine:
-the small intestine is adapted for absorption of food
-it’s very long, so there’s time to break down and absorb all the food before it reaches the end
-big surface area for absorption, because the walls of the small intestine are covered in millions of vili
-each cell on the surface of a villus has its own microvilli-they increase the surace area even more
-villi have a single permeable layer of surface cells and a good blood supply to assist quick absorption
