IGCSE Biology Section B/2 parts c and e

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What are three factors affecting the movement of substances?
1) Surface area to volume ratio 2) Temperature 3) Concentration gradient
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What elements are carbohydrates made from?
Carbon , hydrogen and oxygen.
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Describe and name examples of monosaccharides, disaccharides and Polysaccharides
1) simple sugar, a single unit such as glucose and fructose 2)two monosaccharide groups linked together e.g Maltose = Glucose + Glucose 3)many simple (monosaccharides) sugars together in a long chain e.g starch/cellulose
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What do carbohyrdates provide to our body?
Energy
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Describe the structure of a lipid, the elements and molecules found in it
E shape of 1 glycerol to 3 fatty acids. Carbon, oxygen and hydrogen.
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What is fat needed for?
Fats provide energy and are an energy store. They also provide insulation to the body to maintain its temperature.
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Describe the structure of a protein, and the elements and molecules found in it
Long polymer of amino acids. Carbon, oxygen, hydrogen and NITROGEN.
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What is protein needed for? What can a lack of it lead to?
it is needed for growth and repair o tissues. Enzymes and fhormones are example of proteins. Also protein can be used as energy in there is no other alternative. A lack of protein can lead to kwashiorkor, a disease where fluid collects in the tissue
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How would you test for glucose?
Add benedict's solution to the substance in a test tube which is resting in a water bath. If there is glucose, a coloured precipitate will form. The higher the concentration of glucose, the more the colour will change. Highest= red
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How would you test for starch?
Add iodine solution to the sample. If there is starch, it will turn from brown to dark black/blue.If there is no starch, it will remain brown.
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How would you test for protein?
sodium hydroxide and copper sulfate. It turns purple
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Why are vitmains A, C and D needed?
Vitamin A is found in liver. improve vision, healthy hair. Vitamin C is found in foods such as oranges. It prevents scurvy. Vitamin D is found in eggs. aid the absorption of calcium. Vitamin D can also be produced when skin is exposed to sunlight.
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Why are calcium and iron needed?
Calcium is found in milk and cheese and is needed to make bones and teeth. Iron is found in red meat and is needed to make haemoglobin for healthy blood.
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Why do we need water?
Water can be obtained through food and drink and is essential for most bodily functions. An intake of water is vital to replenish the water your body loses from sweating and breathing.
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Why do we need fibre?
Fibre can be found in foods such as wholemeal bread and vegetables. It aids the movement of foods though the gut, in order to keep the gut regulating well.
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What 3 things affect the level of energy you require
Age- children grow and are more active so need more. Pregnacy- Women need energy for the embryo also. Activity level- exercise requires energy.
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describe an experiment to calculate the energy in food
weigh small amount of food ,skewer on needle. Add 25 cm cubed of water to a test tube, held by clamp. thermometer into water record temperature before. ignite food, hold under tube. re-ignite until it will not relight. Record temperature of water.
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How can this experiment be improved?
by insulating the test tube so that some heat is retained in the heated water, and energy does not escape into the surroundings. This will give a more accurate reading.
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How do you calculate the energy in food (in joules)?
Mass of water (g) x Temperature change (celsius) x 4.2
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What is starch broken down into, and by what enzyme?
Starch can be broken down from the polysaccharide to the disaccharide of maltose by amylase
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What is maltose broken down into, and by what enzyme?
maltose can be broken down into glucose (monosaccharide) by maltase
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What are proteins broken down into, and by what enzyme?
Protease breaks down proteins into amino acids.
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What are fats broken down into, and by which enzyme?
Lipases convert lipids into glycerol and fatty acids.
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What two purposes does bile have and why?
Stored in the gall-bladder and released into the duodenum. It neutralises the stomach conditions, and emulsifies the fats into droplets so there is a bigger surface area of the lipid for the enzyme to work on. digestion is thus faster.
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What is ingestion?
Putting food or the substance into your mouth.
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What is digestion?
Digestion is the break down of large, insoluble molecules. There are mechanical (teeth) and chemical (enzymes) ways to digest the food.
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What is absorption?
Absorption is the process of moving the soluble molecules through the walls of the intestines into the blood. Water is mainly absorbed in the large intestine.
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What is assimilation?
Is the process of moving the absorbed molecules into body cells. The molecules then become part of the cell, for example amino acids makinds cellular proteins.
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What is egestion?
Not everything can be digested, so this forms faeces which are disposed of through the ****, since they have no use to the body. This process is egestion.
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What aids digestion in the mouth?
Salivary glands in the mouth produce amylase to break down the food. Mechanical work by the teeth also breaks up large pieces of food.
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What aids digestion in the stomach?
The walls secrete HCl which kills bacteria and provides optimum pH for pepsin (protease) which is produced in the stomach.
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What do the liver and pancreas do?
The pancreas produces lipase, amylase and trypsin (a protease,) which are released into the duodenum, along with bile from the gall bladder which emulsifies the fats, and neutalises the pH.
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What do the illeum and colon do?
illeum aborbs the digested molecules, through the villi, and most of the water. This is diffused into the blood stream. Then the colon absorbs the remaining water that the illeum has left, the remaining waste forms faeces, stored in the rectum.
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Name two adaptations of the illeum to aid abosption
) It is very long in length, so there is time to abosrb all the molecules before it reaches the end 2) The walls of the small intestine are covered in tiny projections called villi which increase the surface area, also because there are millions
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Name two more adaptations of the illeum/villi to aid absorption
MICRO VILLI, which increases the surface area further, allowing molecules to be absorbed into the blood easily. good supply of blood which steepens the concentration gradient, since there is a low concentration of the molecules in the blood.
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Name another adaptation of the villus
They have a single layer of surface cells to help absorb the molecules more quickly, as it makes the diffusion distance smaller.
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How does peristalsis work?
When the circular muscles contract, the longitudinal muscles relax, making the gut narrower. When the longitudinal contracts and the circular muscles relax, the gut becomes wider. This pushes the food along
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Card 2

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What elements are carbohydrates made from?

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Carbon , hydrogen and oxygen.

Card 3

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Describe and name examples of monosaccharides, disaccharides and Polysaccharides

Back

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Card 4

Front

What do carbohyrdates provide to our body?

Back

Preview of the front of card 4

Card 5

Front

Describe the structure of a lipid, the elements and molecules found in it

Back

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