B2-Organisation

• What are cells?


  Cells are the basic units of structure and function in living things
• What is the process by which cells become specialised?

  Differentiation
• When does differentiation occur?

  During the development of a multicellular organism
• What do specialised cells form?

  tissues which form organs which form organ systems
• What is a tissue?

  -A tissue is a group of similar cells that work together to carry out a particular function

  -It can include more than one type of cell
• What are the examples of tissue in mammals?

  -Muscular tissue-which contracts to move whatever it is attached to

  -Glandular tissue-makes and secretes chemicals like enzymes and hormones

  -Epithelial tissue-covers come parts of the body e.g inside the gut
• What is an organ?


  A group of different tissues that work together to perform a certain function.
• What are examples


  -Muscular tissue-which moves the stomach wall to churn up the food.

  -Glanduar tissue-which makes digestive juices to digest food

  -Epithelial tissue-which covers the outside and inside of the stomach
• What is an organ system?

  A group of organs working together to perform a particular function

  The organ systems work together to make entire organisms.
• What are the differnt types of organs that make up the digestive system?

  -Glands-the pancreas and salivary glands-which produce digestive juices

  -The stomach and small intestine whch digests food

  -The liver-produces bile

  -The small intestine, which absorbs soluble food molecules

  -The large intestine-which absorbs water from undigested food,leaving faeces.
• What are chemical reactions?


  -the making and breaking of chemical bonds

  -that make you work
• What do living things have going on inside them at all times?

  -Living things have thousands of different chemical reactions going on inside them at all times.

  -These need to be carefully controlled to get the right amount of substances
• How can you make a reaction happen quickly?

  -Raising the temperature-This would speed up the useful reactions but also the unwanted ones too.

  Also a limit to how far we can rase the temperature before a living creature's cells begin to denature.
• What do living things produce?

  -Living things produce enzymes that act as biological catalysts.

  -Enzymes reduce the need for high temperature and we only have enzymes to speed up the useful chemical reactions in the body.
• What is a catalyst?


  A catalyst is a substance which increases the speed of a reaction, without being changed or used up in the reaction.
• What are enzymes?


  -Enzymes are all large proteins and all proteins are made up of chains of amino acids.

  -These chains are folded int unique shapes which enzymes need to fo their jobs.
• What do chemical reactions involve?

  Involve things either being split apart or joined together.
• What do enzymes have?

  -Every enzyme have an active site with a unique shape that fits onto the substance involved in a reaction.

  -Enzymes are also very picky-they usually only catalyse one specific reaction.

  -They have optimum temperatures they work best at

  -All enzymes have an optimum ph that they work best at.

  Often neutral ph 7 but not always
• What are the conditions for an enzyme to work?

  -For the enzymes to work-the substrate has to fit into its active site.

  -If the substrate doesnt match-the enzymes active site then the reaction wont be catalysed.
• Describe the lock and key diagram?

  -Lock and key model of enzyme action is sipler tha how enzymes actually work.

  -The active site changes shape a little as the substance binds to it to get a tighter fit-this is the induced fit model of enzyme action.
• What happens to a recation and enzyme when temperature is increased?

  1) Changing the temperature changes the rate of an enzyme-catalysed reaction.

  2) Like with any reaction, a higher temperature increases the rate at first.

  -But if it gets too hot some of the bonds holding the enzyme together break.

  - This changes the shape of the enzymes active site so the substrate doesnt fit anymore.

  -The enzyme is said to be denatured
• What happens to a reaction and enzye when the ph changes?

  -If the ph is too high or too low,the ph interferes with the bonds hokding the enzyme together.

  -This changes the shape of the active site and debatures the enzyme
• What is pepsin?


  An enzyme used to break down proteins in the stomach-it works best at ph 2 which means that it is well-suited to the acidic conditions there.
• Describe a method to investigate the effect of ph on amylase enzyme activity

  1) Put a drop of iodine solution into every well of a spotting tile

  2) Place a bunsen burner on a heat-proof mat and a tripod and gauze over the bunsen burner.

  Put a beaker of water on top of the tripod and heat the water until it is 35 degrees celcius

  Try to keep the temperature of the water constnat throughout the experiment.

  3) Use a syringe to add 1cm cubed of amylase solution and 1cm cubed of a buffer solution with a ph of 5 to a boiling tube.Using the test tube holders put the tube into the beaker of water and wait for 5 minutes.

  4) Next, use a different syringe to add 5 cm cubed of starc solution to the boiling tube.

  5) Immediately mix the contents of the boiling tube and start a stop clock.

  6) Use continuous sampling to record how long it takes for the amylase to break down all the starch.Use a dropping pipette to take a fresh smaple from the boiling tube every 30 seconds and put a drop in a well.When the iodine solution remains browny-orange starch is no longer present.

  7) Repeat the whole experiment with buffer solutions of different ph values to see how ph affects the time taken and keep any control variables the same each time.
• What does amylase too?

  The enzye amylase catalyses the breakdown of starch to maltose.
• How do we detect starch?

  Its easy to detect starch using iodine solution-if starch is present the iodine solution will chnage from browny orange to blue-black
• How do you calculate the rate of reaction?

  Rate = 1000/time or Change/time
• What are starch ,proteins and fats examples of?

  Big molecules
• What happens to the big molecules?

  -They are too big to pass through the walls of the digestive systems ,so digestive enzymes break these big molecules down into smaller ones like sugars, amino acids,glycerol and fatty acids.

  -These smaller molecules can pass easily through the walls of the digestive system,allowing them to be absorbed in the blood stream.
• Where is amylase produced?

  Salivary glands, pancreas, small intestine
• What does amylase actually do?

  -Example of a carbohydrase, it breaks down starch

  -Breaks strach into maltose or other sugars
• Where is protease made?

  Stomach ( pepsin) , pancreas, small intestine
• What does protease actually do?

  Protease breaks down proteins into amino acids
• Where is lipase made?

  Pancreas and small intestine
• What does lipase do?

  Lipase breaks down lipids into glyceol and fatty cids
• What does the body do to the products of digestion?

  -The body makes good use of the products of digestion.

  -Can be used to make new carbohydrates, proteins and lipids.

  -Some of the glucose that is made is used in respiration
• Where is bile produced?

  -Bile is produced in the liver.

  -It is stored in the gall bladder before it is released into the small intestines.
• What does hydrochloric acid do?

  Hydrochloric acid in the stomach makes the ph too acidic for enzymes in the small intestine to work properly
• What does bile do?

  Bile neutralises the the acid and makes conditions alkaline.

  The enzymes in the small intestines work bets in these conditions.
• What does bile also do?

  -Bile emulsifies fats, breaking them into tiny droplets.This gives a much bigegst surface area of fat for the enzyme lipase to work on-which makes its digestion faster.