SB1. Key Concepts - Microscopes and Enzymes

Question 1

SB1a - How do you calculate Actual Size?

Answer 1

Image Size / Magnification

Question 2

SB1a - How do you calculate total magnification in a light microscope?

Answer 2

Objective Lens x Eyepiece Lens

Question 3

SB1a - List 3 differences between Light and Electron Microscopes

Answer 3

• Electron microscopes produce a much higher resolution image due to the shorter wavelength of electrons
• Light Microscopes can show a true colour whereas electron microscopes will show a black and white image since electrons don’t have a colour spectrum
• Light microscopes can use a live specimen whereas electron microscopes have to use dead specimens due to electrons having to pass through a vacuum

Question 4

SB1a - Draw SI Units Table

Answer 4

Question 5

SB1a - What 2 things determine how good a microscope is at showing small details?

Answer 5

• Magnification: How much it can zoom in
• Resolution: The smallest distance between two distinctly different points

Question 6

SB1a - What has the development of the electron microscope allowed us to do?

Answer 6

It has allowed us to see sub-cellular structures as they have a much more powerful resolution and magnifcation

Question 7

SB1b CP - How do you use use a microscope?

Answer 7

• Put a thin sample of tissue (e.g. onion epidermis) onto a microscope slide
• Add a few drops of a suitable stain/dye (e.g. iodine), so that the sample can be seen
• Place a coverslip on top of the tissue and place the slide onto the microscope stage.
• Use the objective lens with the lowest magnification, and focus on the sample.
• Increase the magnification and refocus to see different features of the cell.
• If you record the image you see, note down the magnification it was taken at

Option 2: You microhope you’re doing it right

Question 8

SB1e - What are enzymes and what are they made up of made up of?

Answer 8

• Enzymes are biological catalysts that speed up reactions.
• They break down proteins/substances called substrates.
• Enzymes are made up of amino acids and they are proteins.
• They are needed to speed up reactions we cannot live without

Question 9

SB1e - What are the three main nutrient based enzymes? Where are they found and what do they do?

Answer 9

• Amylase: Found in saliva. breaks down starch into Sugar
• Protease: Found in the stomach, breaks down proteins into amino acids
• Lipase: Found in the stomach and pancreas, breaks down lipids into fatty acids and glycerol

Question 10

SB1e - What is a polymer?

Answer 10

• A polymer is a chain of single substances called monomers.
• The formation of a polymer is called synthesis.
• Enzymes often break down polymers into monomers

Question 11

SB1f CP - What tests are used to identify main components in food?

• Starch
• Proteins
• Lipids
• Sugars

Answer 11

• Starch: Iodine will go from yellow to blue-black
• Proteins: Biruet’s solution will go from blue to purple
• Lipids: Add ethanol and shake - a white emulsion-fatty layer should form if it is present
• Sugars: Benedict’s solution while heating which will turn anywhere from green to yellow to red, indicating how much sugar is present This is a semi-quantitative test. It mostly gives non-measurable values

Question 12

SB1f- How can we use a calorimeter?

Answer 12

• Burn a known mass of the food under a boiling tube filled with a known volume of water.
• Calculate the change in temperature of the water.

Question 13

SB1g - How do enzymes work?

Answer 13

• Each type of enzyme is in a shape that is specific to their substrate.
• They can be re-used as long as they don’t become denatured
• The idea that an enzyme bonds with a specific substrate is the lock-and-key mechanism

Question 14

SB1g - What is the function of the active site of an enzyme?

Answer 14

The active site is unique to an enzyme so each enzyme can only work on specific substrates and is where the substrate must be for anything to take place

Question 15

SB1g - What is the lock and key model?

Answer 15

• The lock and key model is a model of how enzymes work - it compares enzyme action to a lock and key because of how the substrate and active site fit together
• When the substrate binds to the active site, it forms the Enzyme-Substrate complex.
• After the enzyme catalyses the reaction, the products are released because they no longer fits tightly into the active site
• The enzyme is free to be used again

Question 16

SB1g- How are enzymes denatured?

Answer 16

• Changes in pH and temperature can affect the shape of an enzymes active site.
• When the active site can no longer accept any substrates, it is said to have become denatured.