A2.2: Cell Structure Flashcards
State the three parts of the cell theory.
- All living organisms are made of cells
- Cells are the basic units of life
- All cells arise from pre-existing cells
Compare the use of the word theory in daily language and scientific language.
Daily use:
- Theory is a guess and there is doubt
Scientific use:
- THeory has been proven true through repeated observations and experiments and there is no current doubt
Distinguish inductive from deductive reasoning.
Inductive reasoning:
- Theories developed from observations
Deductive reasoning:
- Using a general premise to form a specific conclusion
Outline the process of inductive reasoning that led to the development of the cell theory.
- 17th century, biologists examined animal and plant tissues and saw every specimen contained at least one or more cells
- Subcellular components have never been seen to perform functions of life whereas full cells have
- Cells have been observed coming from other cells but never observed spontaneous generation
Outline how deductive reasoning can be used to predict the characteristics of a newly discovered organism.
General Premises:
- All organisms are made of one or more cells
- Slime moulds are living organisms
Specific conclusion after a deduction:
- Slime moulds are made of cells
Define magnification
- How much larger an object appears compared to its real size
Given the magnification of the ocular and objective lenses, calculate the total microscope magnification.
Total magnification = Oclar x Objective
Demonstrate how to focus the microscope on a sample.
- Turn the coarse adjustment knob so that the stage moves upward and downward toward the objectives
- Turn the fine adjustment knob for perfect focus
Demonstrate how to make a temporary wet mount and stain a microscopic sample.
- Place sample on slide
- Use pipette to place drop of water on specimen
- Place edge of cover slip over the sample at an angle and carefully lower it into place; preventing air bubbles from being trapped under the cover slip
- if there is to much water, take a piece of paper towel and hold it close to one edge of the cover slip to draw out some water
Define Field of View (FOV)
Diameter of the area visible through the microscope
Describe how to measure the field of view diameter of a microscope under low power.
- Place transparent metric ruler under low power objective lens of a microscope to measure the diameter of field of view on low power magnification
Determine the relationship betw. magnification and FOV
- As magnification increases, FOV is smaller (inverse relationship)
Calculate the field of view diameter of a microscope under medium or high power.
Diameter (at LP) x Magnifictaiton (of LP objective) / Magnification (of HP objective) = Diameter (at HP)
Use a formula to calculate the magnification of a micrograph or drawing.
IAM
- Magnification = Image size / Actual size
If given the magnification of a micrograph or drawing, use a formula to calculate the actual size of a specimen.
IAM
- Actual size = Image size / Magnification
Compare quantitative and qualitative observations.
Quantitative observations:
- involve measuring or counting something and expressing the result in numerical form
Qualitative observations:
- involve describing something in non-numerical terms, such as its appearance, texture, or colour like in Drawing
State the criteria for drawing cell structures
- Title including the magnification of the microscope it is viewed under and how many cells have been drawn. The scientific name is underlined.
- Scale line
- Drawing Magnification (not lens magnification)
- Labelled with straight lines pointing to one side of the drawing
Define resolution and magnification.
Resolution:
- The smallest interval distinguishable by the microscope which then corresponds to the degree of detail visible in an image
Magnification
- How much larger an object appears compared to its real size
Compare the functionality of light and electron microscopes.
Light:
- Uses multiple lenses to blend light and magnify images
Electron:
- Uses electron beams focused by electromagnets to magnify and resolve
Compare the benefits of electron and light microscopes
Light microscope:
- easy to use
- cheaper
- can observe cells alive and dead in colour
- cell movement can be studied
- no need for high-voltage electricity
Electron microscope:
- High resolving power (resolution)
- High magnification
Compare the limitations of electron and light microscopes
Light microscopes:
- Low magnification
- Low resolving power (resolution)
Electron microscopes:
- Expensive
- Requires cells to be dead
- no movement of cells can be seen
- no colour can be seen without stain or dye
- high-voltage electric current is required
State a benefit of using fluorescent stains to visualize cell structures.
Generates particularly bright images
Outline the process of visualizing specific proteins in cells using immunofluorescence technology.
- Label cells with different fluorescently stained antibodies to bind to specific target proteins within a cell
- The protein can be tracked and located as it moves in the cell
Outline the process of producing images of cell surfaces using freeze-fracture electron microscopy.
- involves the rapid freezing of cells and then fracturing them along lines of weakness including the center of membranes
- Surfaces are then etched with a coating creating a replica of the surfaces that can be seen with an electron microscope
Outline the process of visualizing specific proteins using cryogenic electron microscopy.
- A solution with the protein is frozen and bombarded with a beam of electrons
- A computer analyses the patterns of diffraction off the sample to produce an image of the structure
Outline the function of structures that are common to all cells.
- Plasma membrane
- Cytoplasm
- DNA
- Ribosomes