B3 Organisation and the digestive system AQA

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What is a cell?
Cells are the building blocks of organisms and are specialised to perform particular jobs
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How is differentiation involved in the development of multicellular organisms?
As a multicellular organism develops, its cells differentiate to form different specialised cells in order to function properly and to perform every job
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What is a tissue?
A tissue is a group of cells with similar structure and function
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Name three types of animal tissues.
Muscular, glandular, epithelial
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What is the function of muscular tissue?
It can contract to bring about movement
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What is the function of glandular tissue?
To produce substances such as enzymes or hormones
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What is the function of epithelial tissue?
To cover some parts of the body
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What are organs?
Organs are made up of tissues working together to fulfil a purpose
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How are organs adapted to be efficient exchange surfaces?
They have: large surface areas, short diffusion paths, rich blood supplies, and mechanisms for ventilating surfaces or for moving materials
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Which types of tissues is the stomach made up of?
Muscular, glandular, epithelial
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What is the function of the muscular tissue in the stomach?
To churn the stomach contents
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What is the function of the glandular tissue in the stomach?
To produce digestive juices
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What is the function of the epithelial tissue in the stomach?
To cover the outside and inside of the stomach
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Which types of tissues is the pancreas made up of?
Two different types of glandular tissues
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What is the function of each of the types of glandular tissues in the pancreas?
One to produce hormones that control blood sugar, the other to produce some of the digestive enzymes
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What are organ systems?
Organ systems make up multicellular organisms and are made up of several organs that work together in a system to perform one particular function
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What is the organisation of a multicellular organism?
cells -> tissues -> organs -> organ systems -> organisms
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What is the function of the digestive system?
The digestive system is responsible for changing the food you eat from insoluble molecules to soluble molecules and then absorbing them into the blood
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Name the organs of the digestive system.
Mouth, oesophagus, stomach, liver, pancreas, gall bladder, bile duct, duodenum, small intestine, large intestine, rectum and anus
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What is the function of the glands (such as the pancreas and salivary glands) in the digestive system?
To produce digestive juices containing enzymes
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What is the function of the stomach in the digestive system?
The stomach is where digestion occurs
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What is the function of the liver in the digestive system?
To produce bile
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What is the function of the small intestine in the digestive system?
The small intestine is where both digestion and the absorption of soluble food molecules occur
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What is the function of the large intestine in the digestive system?
The large intestine is where water is absorbed from the undigested food, producing faeces
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What are villi?
Small finger-like projections on the inside of the small intestine adapted to absorb soluble food molecules efficiently
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How are the villi adapted to absorb soluble food efficiently?
They have: a very large surface area to absorb soluble food molecules by diffusion and active transport; a thin wall to provide a short diffusion path; a good blood supply to carry the food molecules away to maintain a concentration gradient
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What is the structure of a carbohydrate molecule?
All carbohydrates are made up of units of sugar
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What is a simple sugar?
A carbohydrate made up of one or two units of sugar
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Name two types of simple sugars and their structures.
Glucose, which has one unit of sugar, and sucrose, which has two units of sugar linked together
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What is a complex carbohydrate?
A carbohydrate made up of a long chain of simple sugar units that are bonded together
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Name two types of complex carbohydrates.
Starch and cellulose
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What is the structure of a lipid molecule?
It is made up of three molecules of fatty acids linked to a molecule of glycerol
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What is the structure of a protein molecule?
Proteins are made of long chains of amino acids which are folded to form a specific shape
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Why are proteins folded to form a specific shape?
So that other molecules can fit into these specific shapes - each protein has a specific function
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What happens to a protein molecule if it is heated?
Its shape will change and it will become denatured
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Name some of the possible functions of a protein.
They could be: a structural component of a tissue, a hormone, an antibody, an enzyme
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What are the food tests for carbohydrates?
Iodine test for starch, Benedict's test for sugars
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What is the food test for protein?
Biuret test
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What is the food test for lipids?
Ethanol test
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Explain the iodine test for starch.
The initially yellow-red iodine solution turns blue-black if starch is present
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Explain the Benedict's test for sugars.
Initially blue Benedict's solution turns brick red on heating if a sugar such as glucose is present
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Explain the Biuret test for protein.
Initially blue Biuret reagent turns purple if protein is present
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Explain the ethanol test for lipids.
Ethanol added to a solution gives a cloudy white layer if a lipid is present - during this experiment eye protection must be worn because ethanol is highly flammable and harmful
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What results would you expect if you tested some egg white with iodine solution?
The iodine solution would remain yellow-red
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What results would you expect if you tested some egg white with Benedict's solution?
The Benedict's solution would remain blue
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What results would you expect if you tested some egg white with Biuret solution?
The Biuret reagent would turn purple
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What are enzymes?
Enzymes are large proteins that control chemical reactions in cells and are biological catalysts (which means that they speed up reactions).
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What is an enzyme's active site?
It is where a substrate molecule can fit into it for reactions - only certain substrates can fit into certain enzymes' active sites so the shape of the enzyme is vital for its function
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What happens to the substrate after fitting into the active site?
It may be either joined to another molecule or broken down into smaller molecules
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Explain the 'lock and key' theory and the cycle in which the enzymes catalyse substrate molecules in digestion.
The lock and key theory is a simple model showing the shape of a substrate fitting into an enzymes active site, like a key fits into a lock, and then it splits into products which leave the active site - then the enzyme is ready to use again
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What jobs do enzymes have?
To build large molecules from many small ones such as building starch from glucose molecules; convert one molecule into another, like changing a type of sugar into another; break down large molecules into smaller ones (the role of digestive enzymes)
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What is metabolism?
The sum of all the reactions that take place in a cell or in the whole body
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What will the results be when investigating the effect of manganese(IV) oxide (a chemical catalyst) and liver (containing catalase enzyme) on the breakdown of hydrogen peroxide?
The catalase enzyme is the better catalyst, because it will produce a larger volume of oxygen quicker and reach the highest point of oxygen production first
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What does it mean if an enzyme is denatured?
The active site of the enzyme has changed shape, most often permanently, due to the conditions it has to work in, and so the enzyme cannot work properly
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What is the effect of temperature of enzyme action?
Like most other reactions, enzyme-catalysed reactions take place faster when it is warmer, up to a certain point, at which the rate will begin to decrease, and if the temperature gets too high, the enzyme becomes denatured
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Why does the temperature affect enzyme action in this way?
At higher temperatures the molecules move around quicker and so collide with each other more often, and with more energy, but if the temperature is too high, the enzyme begins to lose its shape and so the rate decreases, until it becomes denatured
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At which point is the optimum temperature for enzyme action?
Around 37°C (about human body temperature)
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What is the effect of pH on enzyme action?
Each enzyme works best at a particular pH - at the optimum pH the active site has the best shape so the enzyme works most efficiently, but if the pH is too acidic or alkaline, it will become denatured as the shape of the active site changes
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What is the effect on a protein molecule if the pH is not right?
The folded shape of the protein molecule that forms an enzyme is held together by forces; a change in pH affects these forces, which in turn changes the shape of the active site
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Fill in the gaps: The food you eat contains _____, _________ molecules which must be digested into _______, _______ molecules that can be absorbed into the _____.
large, insoluble, smaller, soluble, blood
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What are the roles of the digestive system?
To break down the food into smaller pieces to increase the surface area for enzymes to work on, mix the food with digestive juices that contain enzymes, and absorb the small, soluble food molecules into the blood in the small intestine
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How is the digestive system adapted to digest food?
It has muscles that work to push the food along and each area has different levels of pH, for example the mouth and the small intestine are alkaline and the stomach is acidic
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How are enzymes produced and how do they get into the digestive system?
They are produced by specialised cells in glands and the small intestine's lining and unlike most enzymes which stay inside the cells, pass out of the glands into the cavity of the digestive system, then come into contact with the food to digest it
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What is amylase?
An enzyme that catalyses the digestion of starch into sugars
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Where in the digestive system do amylase enzymes work?
The mouth and the small intestine
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Where in the body is amylase produced?
The salivary glands, the pancreas and the small intestine
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What are proteases?
Enzymes that catalyse the digestion of proteins into amino acids
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Where in the digestive system do protease enzymes work?
The stomach and the small intetine
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Where in the body are proteases produced?
The stomach, the pancreas and the small intestine
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What is lipase?
An enzyme that catalyses the digestion of lipids into fatty acids and glycerol
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Where in the digestive system do lipase enzymes work?
The small intestine
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Where in the body is lipase produced?
The pancreas and the small intestine
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What is pepsin?
Pepsin is a type of protease that works in the stomach
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What is trypsin?
Trypsin is a type of protease which works in the small intestine
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What are the optimum pH conditions for the amylase, protease and lipase enzymes in the small intestine?
Slightly alkaline
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What are the optimum pH conditions for the protease enzymes in the stomach?
Very acidic
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How does the body ensure that the conditions in the stomach are acidic?
Glands in the stomach wall produce hydrochloric acid to create very acidic conditions
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What is bile?
It is produced to neutralise and increase the pH of very acidic food leaving the stomach, to make the conditions in the small intestine slightly alkaline, and to emulsify fats to increase their surface area for lipase enzymes to act upon
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What does it mean to emulsify fats?
To break large drops of fats into smaller droplets
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In which parts of the body is bile produced, stored, and released?
Produced in the liver, stored in the gall bladder, released into the small intestine
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Card 2

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How is differentiation involved in the development of multicellular organisms?

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As a multicellular organism develops, its cells differentiate to form different specialised cells in order to function properly and to perform every job

Card 3

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What is a tissue?

Back

Preview of the front of card 3

Card 4

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Name three types of animal tissues.

Back

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Card 5

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