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| Question | Answer |
|---|---|
| What is the basic building block of organisms? | the cell |
| Where do unicellular organisms exchange materials with their environment? | through the cell membrane |
| What does it mean to say that a cell has differentiated? | the cell has specialised to do a specific tasks |
| What is a tissue? | a collection of cells of the same type collected and working together so muscle cells united and working together are muscle tissue |
| Name and describe three tissues. | • muscular tissue contracts to bring about movement • glandular tissue contains secretory cells that produce enzymes and hormones • epithelial tissue covers surfaces like the outside of organs |
| What is an organ? | several tissues combined to form a unit that performs a specific function |
| Name three organs. | heart, pancreas, stomach |
| Name four tissues found in the heart? | connective, muscle, epithelial, and nerve tissue |
| What is the function of the stomach? | it is involved in the digestion of food |
| What tissues are in the stomach? | • muscular tissue to mix the food and digestive juices • glandular tissue to produce the digestive juices • epithelial tissue covers the inside and outside of the stomach |
| What is the function of the pancreas? | it has two functions, to produce (1) hormones to control blood sugar, and (2) enzymes for digesting food |
| How many main tissues does the pancreas contain and why? | it contains two main tissues, one for each of its functions |
| What is an organ system? | a group of organs that works together to perform a task are an organ system |
| What is the relationship between cells and organisms? | similar cells combine to form tissues, tissues combine to form organs, organs combine to form organ systems, and organ systems combine to form an organism |
| Name three organ systems in the human body. | the circulatory system, the digestive system, and the gas exchange system |
| Question | Answer |
|---|---|
| What is the length of the digestive system? | between 6 metres and 9 metres |
| Why can the digestive system not absorb and use the molecules of the food you eat immediately? | because the molecules are too large and insoluble |
| What needs to happen to the molecules of the food you eat for your body to absorb and use them? | they must be broken down into small, soluble molecules |
| What is the process of breaking large food molecules into small molecules called? | digestion |
| Where does the process of digestion take place? | in the digestive system |
| List the organs of the digestive system? | mouth, gullet, stomach, liver, gall bladder, pancreas, duodenum, small intestine, large intestine, appendix, rectum, anus |
| Name the glands of the digestive system. | the pancreas and the salivary glands |
| What do the glands of the digestive system do? | they make and release digestive juices containing enzymes that break down food |
| How is food moved through the digestive system? | the digestive system is a muscular tube that squeezes food from the mouth through to the anus |
| Which are the main organs where digestion takes place? | the stomach and small intestine |
| What do digestive enzymes do? | break large, insoluble molecules down to small, soluble ones |
| How is the small intestine adapted to aid absorption of food? |
• it has a large surface area because it is covered in villi • it has a good blood supply • it has very short diffusion distances to reach the blood |
| What is the function of the small intestine? | it has two functions - (1) breaking down large, insoluble molecules to smaller, soluble molecules, and (2) absorption |
| What happens to molecules absorbed by the small intestine? | they are absorbed into the blood and transported around the body for respiration |
| How does the food move from the small to the large intestine? | the muscular walls of the small intestine squeeze the food into the large intestine |
| What happens in the large intestine? | water is absorbed from the undigested food into the blood |
| What is the material left over after the water has been reabsorbed in the large intestine? | faeces |
| What happens to faeces? | the faeces are stored then pass from the body through the rectum and anus |
| What role does the liver perform as part of the digestive system? | it produces bile |
| What is the role of bile? | bile helps with the digestion of lipids |
| Question | Answer |
|---|---|
| Name the main compounds that make up a cell. | carbohydrates, proteins, and lipids |
| What elements are contained in carbohydrates? | carbon, hydrogen and oxygen only |
| What is the main use for carbohydrates in living organisms? | they provide the fuel to supply the energy that organisms need for life |
| What are the units in carbohydrates? | sugars |
| What are small sugars called? | simple sugars |
| Name a carbohydrate that contains only one sugar unit? | glucose |
| What is the formula for glucose? | C6H12O6 |
| Name a carbohydrate that contains two sugar units? | sucrose, which is the scientific name for the sugar people put in tea and coffee |
| What is a complex carbohydrate? | a complex carbohydrate is made of long chains of simple sugar units bonded together |
| Name two complex carbohydrates. | starch and cellulose |
| Name four carbohydrate rich foods. | bread, potatoes, rice, and pasta |
| What are most carbohydrates broken down into? | glucose |
| What is the main use of glucose in animals? | cellular respiration to provide energy for metabolic reactions |
| What is the main use for cellulose in plants? | the carbohydrate cellulose is used to provide support in plants |
| What is the test for simple sugars? | they turn Benedict's solution from blue to brick red when heated |
| What is the test for starch? | starch turns yellow-red iodine solution blue-black |
| What are lipids? | solid fats and liquid oils |
| What are the elements in lipids? | carbon, hydrogen and oxygen |
| What happens when lipids are mixed with water? | lipids are insoluble in water so nothing happens |
| What are lipids used for? |
• the most efficient energy store and thus an important source of energy in the diet • used in the cell membrane and nervous system as hormones when combined with other molecules |
| What molecules are lipids made of? | three fatty acids attached to a single glycerol molecule |
| What makes lipids different? | glycerol is always the same but there are many different fatty acids leading to many different lipids |
| Name 4 lipid-rich foods? | olive oil, butter, cheese, cream |
| What makes some lipids solid and some liquid? | the different combinations of fatty acids determine whether a lipid will be solid or liquid |
| What is the test for lipids? | ethanol added to a solution results in a cloudy white layer if lipid is present |
| What are proteins used for? |
• building cells and tissues • making enzymes |
| What percentage of a human is protein? | between 15 and 16% |
| Where can proteins be found in the body? | muscle, hair, nails, enzymes |
| What elements are proteins made up of? | carbon, hydrogen, oxygen, nitrogen |
| Name 4 protein-rich foods. | meat, fish, pulses, cheese |
| What are the building blocks of proteins? | it is a long chain of small units (building blocks) called amino acids |
| How many amino acids are used in mammals? | about 20 different amino acids |
| How are different proteins produced? | by different arrangements of the 20 different amino acids |
| What is the first stage in constructing a protein? | different amino acids are connected in the order specified by the genes |
| What happens once the amino acids have been connected following the gene? | the chain is folded, coiled, and twisted to make specific 3D shapes |
| Why are proteins structured into specific 3D shapes? | to enable specific molecules to fit into the proteins |
| What factors can damage the shape of a protein? | temperature and pH |
| Why is the shape of a protein sensitive to temperature? | the bonds holding the shape of a protein are sensitive and can be easily broken |
| What term is used to describe a protein when its shape is damaged preventing it from working? | denatured |
| List the functions that proteins carry out in the body. |
• structural components of tissues such as muscles • hormones such as insulin • antibodies which destroy pathogens • enzymes which are biological catalysts |
| Describe the test for protein. | blue Biuret reagent turns purple if protein is present |
| Question | Answer |
|---|---|
| What is a catalyst? | a special chemical that speeds up reactions without changing chemically themselves |
| How often can a catalyst be used? | a catalyst can be used over and over again as it is not used up in a reaction |
| What are catalysts in living organisms called? | enzymes |
| What is the function of enzymes? | they are biological catalysts that speed up reactions in the body wihtout changing chemically themselves |
| What organic molecules are enzymes made from? | they are large protein molecules |
| How are proteins turned into enzymes? | the long chains of amino acids are folded to produce a molecule with an area that has a unique shape that fits only one specific molecule |
| What is the area of an enzyme with the unique shape called? | it is called the active site |
| What is the molecule called that the active site fits? | it is called the substrate |
| How many substrates can the active site of each enzyme fit onto? | just one, the active site is unique to fit a specific substrate |
| What happens to an enzyme if its shape changes? | it will not operate properly if the shape of the active site changes |
| Name the model the describes how enzymes work. | the lock and key model |
| Describe the lock and key method. |
• the substrate fits into the active site • the enzyme and the substrate bind together • the reaction takes place quickly • the products are released |
| Do enzymes join small molecules together to make large ones or break large molecules down in small ones? | enzymes do both |
| How do enzymes change a reaction? | they do not change a reaction, they simply make it go faster |
| What is metabolism? | the sum of all the reactions in a cell or a body |
| What three tasks can enzymes perform? |
• combine small molecules to make a large molecule • change one molecule into a different molecule • break a large molecule down into small molecules |
| Describe a reaction catalyzed by enzymes that combines smaller molecules to make a large molecule. | making lipids by combining fatty acids and glycerol |
| Describe a reaction where enzymes are used to change a molecule to another. | changing glucose to fructose |
| Describe a reaction where enzymes are used to break a large molecule into smaller molecules. | starch is broken down into glucose molecules during digestion |
| What do plants combine to make glucose? | carbon dioxide and water |
| What carbohydrates can be made from glucose? | starch, cellulose, and glycogen |
| What do plants use to make amino acids? | glucose and nitrate ions |
| What large organic molecule is made from amino acids? | proteins |
| Why does each reaction require its own specific enzyme? | because the active site is uniquely shaped to bind to only one substrate |
| Question | Answer |
|---|---|
| How does milk go off? | enzymes in bacteria break down the proteins in milk |
| Name the factors that affect the rate of chemical rections. | concentration, temperature, surface area |
| What is the temperature called where the enzyme works as fast as possible? | the optimum temperature |
| What is the average optimum temperature for enzymes in the body? | around 37 °C |
| How does an increase in temperature affect enzymes? | it increases the rate of enzyme-controlled reactions to a point, then it slows down dramatically and eventually stops |
| Why does the rate of reaction slow down as the temperature exceeds the optimum temperature? | the long amino acids chains begin to unravel changing the shape of the active site and making it difficult then unable to work |
| How do we describe the enzyme when the active site no longer fits the substrate? | it is said to be denatured |
| Will an enzyme return to acting well when the temperature is reduced to the optimum temperature? | if the active site has just begun to distort then yes, but once the enzyme has been denatured it is permanently damaged and cannot work again |
| At what temperature do most enzymes begin to denature in the human body? | at about 41 °C |
| What can happen to a person if their temperature reaches a level where the enzymes denature? | it will result in death |
| Do all enzymes operate best around 40 °C? | no, some bacteria live in water at around 80 °C so contain enzymes that work best at this temperature, and some bacteria live at 0 °C so contain enzymes that work best at this temperature |
| What is the effect of a change in pH on enzymes? | it changes the way they work, possibly even stopping them completely |
| Why does pH affect enzymes? | a change in pH affects the forces that hold the enzyme molecule together thus changing the shape of the active site |
| At what pH do enzymes work best? | different enzymes work best at different pHs |
| Why do people try to bring the temperature of a sick person down? | the enzymes in their body operate less effectively and can eventually denature leading to death |
| Question | Answer |
|---|---|
| Why can the molecules of the food we eat not be absorbed immediately? | they are too large and insoluble and need to be broken down to small, soluble molecules before they can be absorbed |
| What controls the breakdown of large food molecules? | digestive enzymes |
| What is the main difference between digestive enzymes and other enzymes in the body | most enzymes operate within the cell while digestive enzymes work outside the cell |
| Where are digestive enzymes produced? | in glands like the salivary glands and the pancreas, and the lining of the digestive system |
| What is the role of the digestive tract in the process of digestion? |
• it breaks the food into small pieces to increase surface area that can make contact with enzymes • it mixes the food and the enzymes enabling the maximum contact between the two • the muscles of the digestive system moves the food along from one area to the next with different pHs suited to different enzymes |
| What is the pH of the mouth? | it is slightly alkaline |
| What is the pH of the small intestine? | it is slightly alkaline |
| What is the pH of the stomach? | it is extremely acidic |
| What are enzymes called that break down carbohydrates? | carbohydrases |
| Name the most common carbohydrate eaten by people? | starch |
| What happens to starch in the disgestive system? | it is broken down into simple sugars in the mouth and the small intestine |
| Name the enzyme that breaks down starch | amylase |
| Where is amylase made? | in the mouth in the salivary glands and the pancreas |
| Where does the digestion of starch begin? | in the mouth where it is mixed with saliva which contains amylase produced by the salivary glands |
| What happens to the enzymes produced by the pancreas? | they flow into the small enzyme where digestion takes place - no digestion takes place in the pancreas |
| What is the name of enzymes that digest proteins? | proteases |
| Where are proteases produced? | in the stomach, pancreas, and small intestine |
| Where are proteins broken down? | in the stomach and small intestine |
| What are proteins broken down into? | amino acids |
| What are fats broken down into? | fatty acids and glycerol |
| Where are lipids broken down? | in the small intestine |
| Name the enzymes that catalyze the breakdown of lipids. | lipase |
| Where are lipases made? | in the pancreas and the small intestine |
| What happens to the food once it has been digested? | it is absorbed into the blood across the wall of the small intestine, and carried by the blood to the cells of the body |
| Question | Answer |
|---|---|
| What pH conditions does protease prefer? | the protease made in the stomach prefers acidic conditions while the protease made in the small intestine prefers alkaline conditions |
| What is the protease in the stomach called? | pepsin |
| Where does pepsin come from? | the 35 million glands in the lining of the stomach secrete pepsin |
| What pH conditions does pepsin prefer? | it prefers an acidic environment |
| What does pepsin do? | it is the enzyme in the stomach that breaks down proteins |
| What does the stomach lining produce? | pepsin, a concentrated solution of hydrochloric acid, and mucus |
| What is the role of hydrochloric acid in the stomach? |
• it creates an environment that allows pepsin to work • it kills any bacteria that make it into the stomach with food |
| How much hydrochloric acid do the glands in the stomach lining produce? | around 3 litres a day |
| What does the mucus do in the stomach? | it coats the stomach lining protecting it from being digested by the acid and the enzymes |
| What happens when someone has a stomach ulcer? | the protective mucus is damaged and the acid and enzymes of the stomach can attack the lining |
| What are pH conditions in the small intestine? | they are alkaline |
| Why are pH conditions in the small intestine alkaline? | because the digestive enzymes in the small intestine work best under alkaline conditions |
| Where are the digestive enzymes found in the small intestine produced? | in the lining of the small intestine and the pancreas |
| What is the pH of the contents of the stomach as they are released into the small intestine? | they are strongly acidic |
| How are the stomach contents made alkaline when they enter the small intestine? | bile is squirted through the bile duct onto the stomach contents as they enter the small instestine |
| Where is bile made? | in the liver |
| What does bile look like? | it is a green-yellow liquid |
| What happens to bile once it has been made? | it is stored in the gall bladder until it is needed |
| State the functions of bile |
• it neutralises the acid from the stomach • it emulsifies fats |
| What happens when bile emulsifies fat? | the large globules of fat are broken down into smaller droplets to increase the surface area for lipases to act |
| Do proteins and carbohydrates need to be emulsified? | no as they dissolve in water and this increases the surface area for enzymes to act |
| What are the consequences of gall stones? |
• they can block the bile duct stopping bile being released onto the food • they can cause extreme pain when they are large |
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