A2 (Part 1) - Cell Streucture Flashcards
(31 cards)
What are the three core principles of the Cell Theory?
- All living organisms are composed of cells.
- The cell is the basic unit of life.
- Cells come from preexisting cells.
What is inductive reasoning in biology?
Inductive reasoning involves using specific observations to form a general conclusion.
What is deductive reasoning in biology?
Deductive reasoning uses a general premise to form a specific conclusion.
What is a scientific theory in biology?
A scientific theory is a well-substantiated explanation of the natural world, based on a body of facts that have been repeatedly confirmed.
What is a microscope and why is it used?
A microscope is a device that produces magnified images of objects too small to be seen directly by the eye.
How do you calculate total magnification on a light microscope?
Total magnification = magnifying power of ocular lens × magnifying power of objective lens.
E.g., 10x ocular × 4x objective = 40x magnification.
What is the function of coarse and fine adjustment knobs on a microscope?
The coarse adjustment moves the stage up and down for rough focusing, while the fine adjustment allows precise focusing.
What are the steps for using a light microscope?
- Place slide on stage.
- Rotate to the lowest power objective.
- Use coarse focus to bring stage up (while viewing from the side).
- Look through eyepiece, adjust light and diaphragm.
- Use fine focus to sharpen the image.
- Switch to higher objective only after focusing.
How do you prepare a wet mount slide?
- Place the specimen on the slide.
- Use pipette to add a drop of water.
- Lower coverslip at an angle to avoid air bubbles.
- If needed, blot excess water with paper towel.
What are stains and their purpose
Stains are chemicals that bind to specific structures, making them visible under a microscope.
What does iodine stain and how?
Iodine stains starch brown/blue-black and shows glycogen as red.
What does methylene blue stain and how?
Methylene blue binds to acidic parts of the cell and is useful for identifying DNA and cell nuclei.
What does Gram stain distinguish?
Gram stain divides bacteria into:
• Gram-positive: stain purple (thick cell wall).
• Gram-negative: stain pink/red (thin cell wall).
How can you calculate microscope field of view (FOV)?
Method 1: Use a transparent ruler under low power.
Method 2: Multiply the diameter of low power by magnification ratio of LP/HP objectives.
How do you estimate the size of a specimen under a microscope?
Method 1: Estimate the fraction of the field the specimen occupies, multiply by FOV diameter.
Method 2: Estimate how many specimens fit across the FOV and divide FOV by count.
How do you calculate actual size from a microscope image?
Actual size = Image size ÷ Magnification.
What are the conversions between units in microscopy?
Millimetre mm —> micrometre um —> nano metre nm —> picomerte pm
X1000 all
What is resolution in microscopy?
Resolution is the ability to distinguish two close points as separate.
Compare compound light vs electron microscopes.
Light microscope:
• Max magnification ~1500x
• Low resolution
• Can observe live cells
• Colour images
• Movement visible
• Quick prep
Electron microscope:
• Magnification up to 200,000x
• High resolution (0.001 µm)
• Cells must be dead
• No colour (black & white)
• No movement seen
• Expensive & slow prep.
What structures are common to all living cells?
Plasma membrane, cytoplasm, DNA, and ribosomes.
What is the structure and function of the plasma membrane?
It’s a phospholipid bilayer acting as a selective barrier, controlling what enters and exits the cell.
What is the role of cytoplasm?
Cytoplasm supports metabolism and hosts biochemical reactions.
What is the role of DNA in cells?
DNA is the genetic material that contains instructions for making proteins and controls cell activity.
What do ribosomes do in a cell?
Ribosomes synthesize polypeptides (proteins) by translating RNA.
