Nutrients / Biology Practicals Flashcards
Where are carbohydrates mostly found?
They are found in starchy foods, such as bread, pasta, potatoes, and fruits & vegetables.
Why do we need carbohydrates?
They are an energy source. They provide us with most of the energy we need to carry out chemical reactions and to move around.
What are lipids and where are they found?
Lipids are considered both fats and oils, and they are found particularly in oily fish, nuts and seeds, dairy products and avocados.
Why do we need lipids?
They provide energy, and often act as a longer term store of energy. They also keep us warm by insulating, and they protect our organs.
Where are proteins mostly found?
Proteins are found particularly in nuts and seeds, meat and fish, and also legumes (meaning things like lentils/beans).
Why do we need proteins?
We need proteins to grow and repair damaged tissue. They can also be used for energy, but only if we don’t have enough carbohydrates or lipids.
What is the difference between vitamins and mineral ions?
Vitamins are organic molecules, meaning that they are made by living organisms. Whereas minerals are inorganic, and are generally much simpler molecules.
Where can you find vitamin A and what is it good for?
You can find it in foods like liver or leafy vegetables.
You need it for good vision and to keep your skin and hair healthy.
Where can you find vitamin C and what is it good for?
You can get vitamin C from fruit and vegetables (particularly citrus fruit like oranges).
You need it to prevent yourself from getting scurvy.
Where can you find vitamin D and what is it good for?
Your body is able to make vitamin D itself using sunlight, but you can also get it in foods like eggs and oily fish.
Its main purpose is to help you absorb calcium.
Calcium is a mineral ion. Where can you find it and what is it good for?
You can find calcium in dairy products like milk, as well as leafy vegetables.
You need calcium for strong bones, so therefore if you don’t eat enough of it/don’t absorb it (due to a lack of vitamin D), you could get a condition like rickets, where your bones can be deformed.
Iron is a mineral ion. Where can you find it and what is it good for?
You can get iron from red meat, spinach and beans.
Iron is a really important component of haemoglobin, which helps your red blood cells transport oxygen. If you don’t get enough iron, you could develop anemia.
What is fibre and where is it found?
Fibre is a type of carbohydrate, however we normally think of it separately due to us not absorbing it into our body.
It is found in wholemeal foods like wholemeal bread and brown rice, as well as in fruits and vegetables.
What is the role of fibre?
Its role is to help food move properly through our intestines. It stops us from getting either diarrhoea or constipation.
Where do you find water?
You find water in our drinks, and also from most foods like oranges and strawberries for example.
What is the role of water?
You need water for many things, such as chemical reactions. However, the main thing is that most of our bodies is made from ~70% water. We are continuously losing water by breathing, sweating and urinating, so we are constantly having to replace all of the water we lose.
What are the steps that all food practicals have in common?
You must prepare your food sample and break it up using a mortar and pestle.
Then, you must put this crushed food into a beaker with some distilled water, and stir it with a glass rod until some of it dissolves.
Lastly, you must filter out the solution using a funnel that has been lined with filter paper to get rid of all the solid bits of food that we don’t need.
The solution that we end up with will be our sample.
Does the Benedict’s Test only test for reducing sugars or non-reducing sugars?
Reducing Sugars
What are the steps for the Benedict’s Test (test for reducing sugars)?
- You prepare your food sample and break it up using a mortar and pestle.
Then, you must put this crushed food into a beaker with some distilled water, and stir it with a glass rod until some of it dissolves.
Lastly, you must filter out the solution using a funnel that has been lined with filter paper to get rid of all the solid bits of food that we don’t need. You will then be left with a solution which is your sample. - You must transfer 5cm^3 of your sample to a test tube.
Along with this, you must prepare a water bath and set it to 75°C. - Once your water bath is ready, you can add about 10 drops of Benedict Solution to your test tube, and place it in the water bath for 5 minutes. For safety reasons, you must use a test tube holder to place it in the water bath, pointing the tube away from you.
- If no reducing sugars are present, your solution will stay blue.
If there are reducing sugars present, your solution should change to either green, yellow, or brick red, depending on the concentration.
What are the steps of the Iodine Test (testing for starch)?
- You prepare your food sample and break it up using a mortar and pestle.
Then, you must put this crushed food into a beaker with some distilled water, and stir it with a glass rod until some of it dissolves.
Lastly, you must filter out the solution using a funnel that has been lined with filter paper to get rid of all the solid bits of food that we don’t need. You will then be left with a solution which is your sample. - You take 5cm^3 of your food sample, and add a few drops of iodine solution. This will turn your solution into a browny-orange colour.
- Next, you give it a gentle shake. If a sample did contain starch, the solution will change from that browny-orange colour to a blue-black colour.
What are the steps of the Biuret Test (testing for proteins)?
- You prepare your food sample and break it up using a mortar and pestle.
Then, you must put this crushed food into a beaker with some distilled water, and stir it with a glass rod until some of it dissolves.
Lastly, you must filter out the solution using a funnel that has been lined with filter paper to get rid of all the solid bits of food that we don’t need. You will then be left with a solution which is your sample. - You add 2cm^3 of your sample to a test tube. Then, you must add another 2cm^3 of the biuret solution/POTASSIUM HYDROXIDE followed by COPPER SULFATE to your sample, turning it blue.
- Next, you give it a gentle shake. If the solution did contain protein, the solution would change from blue to pink or purple.
What are the steps of the Sudan III Test (testing for lipids)?
- You prepare your food sample and break it up using a mortar and pestle.
Then, you must put this crushed food into a beaker with some distilled water, and stir it with a glass rod until some of it dissolves.
You will then be left with a solution which is your sample. - You get 5cm^3 of your sample, noting that you do not need to filter it for this test. Then, you add 3 drops of the Sudan III Stain Solution to the test tube.
- Gently shake your test tube. If a lipid is present, it should get stained by the Sudan III solution, and as the lipid separates from the water (because it’s not soluble), you will see a bright red layer at the top of your solution.
What are the steps for the Emulsion Test (testing for lipids)?
- You prepare your food sample and break it up using a mortar and pestle.
Then, you must put this crushed food into a beaker with some distilled water, and stir it with a glass rod until some of it dissolves.
Lastly, you must filter out the solution using a funnel that has been lined with filter paper to get rid of all the solid bits of food that we don’t need. You will then be left with a solution which is your sample. - You take your food sample and add 2cm^3 of ethanol, and shake it vigorously.
- You then add an equal volume of distilled water (2cm^3), and if it goes a cloudy white colour, that means a lipid was present. If there isn’t any cloudy white colour, then there was no lipid.
