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science > Unit 6: The Model of Cells > Flashcards

Unit 6: The Model of Cells Flashcards

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Biology 101 flashcards
1
Q

What are the parts of a light microscope? (12)

A 
Eyepiece
Arm
Stage
Coarse Adjustment knob
Fine Adjustment knob
Base
Body tube
Nosepiece
Power
Stage clips
Iris Diaphragm/Condenser
Light Source
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2
Q

Eyepiece

A

Contains the lens to view the specimen.

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3
Q

Arm

A

Attaches eyepiece and body tube to the base.

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4
Q

Stage

A

Platform on which specimen is placed.

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5
Q

Coarse Adjustment

A

Moves the stage up/down for a clearer image or to obtain a focused image.

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6
Q

Fine Adjustment

A

Focuses specimen for a sharper image or to obtain a focused image.

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7
Q

Base

A

To support the microscope.

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8
Q

Body Tube

A

Contains the 10x optical lens.

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9
Q

Nosepiece

A

Contains the 4x, 10x and 40x objective lenses.

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10
Q

Power

A

Magnifies the specimen.

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11
Q

Stage Clips

A

Holds the specimen in place.

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12
Q

Iris Diaphragm/Condenser

A

Controls amount of light that passes through the specimen.

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13
Q

Light Source

A

Transmits light through specimen.

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14
Q

Handling a light microscope

A

• When lifting the microscope, hold it upright with both hands. Use one hand to hold the arm and the other hand to support the base.

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15
Q

Steps to using a light microscope (11 steps, , 5 (‘) impt ones)

A
  1. Connect your light microscope to an outlet.
    Switch on the microscope.
  2. Before placing the specimen on the stage, or when taking out the specimen from the stage, use coarse adjustment knob to adjust the stage to the lowest position.

3’. Begin viewing the specimen with the objective lens of the lowest power first. Rotate the revolving nosepiece to the lowest power objective lens (4x).

4’. Place the glass slide gently on the microscope stage, adjusting the slide to bring the area of study into the way of the light source.

5’. Look into the eyepiece. Adjust the iris diaphragm to control amount of light falling onto the specimen. The diaphragm is the rotating disc located under the stage that has varying holes for different light intensities—rotate it until you achieve the maximum.

6’. While still looking into the microscope, turn the coarse adjustment knob to focus. Do this until you can see your specimen clearly. Stop turning the knob when the resolution is the sharpest.

  1. Use the side knob to move the stage up or down, and left or right and adjust to bring the area of study into your field of view.
  2. Rotate nosepiece to change to a higher magnification objective lens (10x) to view specimen.

9’. While still looking into the microscope, turn the fine adjustment knob to focus. Do this until you can see your specimen clearly. Stop turning the knob when the resolution is the sharpest.

  1. Examine the specimen carefully. If needed, you may need to observe it at 40x magnification. You may be required to produce a labelled drawing of the specimen.
  2. Repeat the magnification process. If you need more magnification, you can repeat the process again with the next one or two magnifications. Remember to focus each objective lens before moving on to the next objective lens.
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16
Q

Tips and things to note when using a light microscope:

1 impt point

A
  • Do not touch the lens glass with your finger. You will leave the lens smudged and hard to see through.
  • Do not skip objective lenses when increasing your magnification.
  • Gently place the coverslip over stained specimens to avoid forming air bubbles.
  • Do not turn the coarse adjustment knob too quickly as this may cause the objective lens to crack the specimen slide.
  • Adjust the diaphragm gradually to prevent excessive amounts of light from entering your eyes.
  • Handle the coverslip with care as it is thin and can cause cuts when broken.
  • Start with the objective lens that has the lowest magnification.
  • A coverslip should be placed over a fresh specimen to prevent the staining solution (iodine) from getting onto the objective lens because stains on the objective lens will result in blurred images.
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17
Q

Magnification

How to calculate magnification?

A
  • The objective lens magnifies the object / specimen by the factor marked on the selected lens.
  • The lowest power (4x) gives the smallest image. The next highest (10x) power gives a large image, and the highest power (40x) gives the largest image.
  • Calculating total magnification of the image you are viewing is easy. Usually, the power of the individual objective or ocular lens are inscribed on their surface.
  • Simply multiply the power of the objective lens (usually either 4x, 10x or 40x) with the power of the ocular lens (eyepiece-usually 10x).
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18
Q

Division of Labour (3 points)

A
  • Since a unicellular organism is only one cell, this cell has the parts to carry out all the job of the organism such as respiration, digestion, reproduction, growth and repair.
  • In a multicellular organism, different cells carry out different specialized functions.
  • Division of labour is the dividing of work in an organism among different cells. It also occurs at the organelle, organ and system levels.
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19
Q

Advantages of Division of Labour (3 points)

A
  • The multicellular organism can perform more tasks than a unicellular organism.
  • It increases efficiency. For example, red blood cells carry oxygen around the body and do not have to be involved in other tasks.
  • The cells live longer.
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20
Q

How are cells organised to form organisms? (3 points)

A
  • Multicellular organisms have cells that come in all shapes and sizes. (e.g. in the human body, there are about 200 different types of cells.)
  • Each type of cell has a specific function. Cells that have specific functions are called specialised cells. (e.g. guard cells in leaves, and nerve cells and fat cells in animals.)
  • A group of similar cells work together to form a tissue.
  • Different tissues combine to form an organ.
  • Several organs work together to make up an organ system.
  • Various organ systems work together to make up an organism.
  • Organelles → Cells → Tissues → Organs → Organ systems → Organism
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21
Q

What are organelles?

A

organelles – organized and
specialized structures within the cell that
each have a specific function.

22
Q

What are Cells? (3 points)

A
  • Living things or organisms are built from cells.
  • Cells are the basic units of an organism. They are also the smallest parts of an organism that are alive.
  • Some organisms are made of a single cell and are known as unicellular (e.g. bacteria, yeast), while others are made of many cells known as multicellular organisms (e.g. onion).
23
Q

What is a cell made of?

A
  • Cells consist of protoplasm (living matter).
  • The protoplasm consists of nucleus, cytoplasm and the cell surface membrane.
  • Cells contain organelles – organized and specialized structures within the cell that each have a specific function.
  • All cells share some common organelles.
  • Models help us understand or explain things, especially what we cannot see.
  • Models are always simpler than the actual objects and do not include everything. (limitations of models!)
  • Models can help us visualize in 3D.
24
Q

Parts of a typical animal cell?

A

Nucleus
Cytoplasm
Cell surface membrane
Vacuoles

25
Q

Parts of a typical plant cell?

A 
Nucleus
Cytoplasm
Cell surface membrane
Large central vacuole
Cellulose cell wall
Chloroplast
26
Q

Nucleus (3 pts)

A

• Largest organelle in the cell

  • Contains genetic material (DNA) in chromosomes
  • Controls all activities of the cell (including cell reproduction, division, growth, repair of worn-out parts and others)
27
Q

Cytoplasm (4 pts)

A

• Contains water, enzymes and many other substances
* Site where chemical reactions occur in the cell
• Cytosol is the fluid portion of the cytoplasm.
• (cytosol + organelles = cytoplasm)

28
Q

Cell Surface Membrane (4 pts)

A
  • Controls movement of substances in and out of the cell
  • Extremely thin structure
  • It is selectively permeable, hence allows some
  • substances to pass through but not others
29
Q

Vacuole (2 main pts)

A

• Small vesicles containing temporary storage
• of food, air and water.
* To temporarily store food, air, water and waste products.
• They are filled with air, liquid or food particles found in the cytoplasm.
• They also store waste products so that the rest of the cell is not contaminated. Eventually, these waste products are sent out of the cell.
* Animal cells have many small temporary vacuoles while plant cells have a single large central vacuole

30
Q

Large Central Vacuole (2 pts, 1 main pt)

A
  • Contains cell sap which keeps the cell firm
    • Cell sap consists of water, sugars, salts and other
    • dissolved substances.
31
Q

Cellulose Cell Wall (3 pts, 1 main pt)

A

• Made of cellulose (a type of sugar)
* Supports the cell and gives it a regular shape
• Fully permeable hence allows all substances to pass through

32
Q

Chloroplast (2 pts)

A
  • Contains the green pigment chlorophyll and is the site for photosynthesis
  • Chlorophyll absorbs light energy from the Sun and converts it to chemical energy in the synthesis of glucose during photosynthesis.
33
Q

Cell organisation in plants? (3 pts)

A

• 2 main organ systems, the shoot system (above ground) and the root system (in
• the soil).
• 3 main organs – leaf, stem and root. Some plants have flowers too.
• 3 main types of tissues – ground tissue, dermal tissue and vascular tissue
- E.g. Stem is an organ while food and water-carrying tubes are tissues.

34
Q

Red blood cell (5 pts)

A

Red blood cells are found in the blood of humans and play a role in the transport of oxygen.

Contains haemoglobin (a red pigment)

Does not contain a nucleus

Biconcave shape

Elastic

35
Q

Contains haemoglobin (a red pigment) (RBC)

A

Haemoglobin combines with oxygen easily and this helps absorb oxygen quickly and transport around the body

36
Q

Does not contain a nucleus (RBC)

A

To contain more haemoglobin for transport of more oxygen

37
Q

Biconcave shape (RBC)

A

This shape increases surface area to volume ratio of the cell, increasing rate of diffusion of oxygen in and out of the cell

38
Q

Elastic (RBC)

A

to change shape and easily squeeze through blood capillaries (which can be smaller than diameter of red blood cell)

39
Q

Xylem Tissue ( 3pts)

A

Xylem vessels are found in plants. They transport water and mineral salts up the plant and provide mechanical support to the plant.

Dead cells with long hollow tubes, without cross walls and does not have protoplasm (typical parts of a cell)

Xylem vessel wall is deposited with lignin

40
Q

Dead cells with long hollow tubes, without cross walls and does not have protoplasm (typical parts of a cell) (XT)

A

To allow the transport of water upwards quickly and without resistance

41
Q

Xylem vessel wall is deposited with lignin (XT)

A

To provide mechanical support to the plant and prevent collapse of xylem vessels

42
Q

Root Hair Cell (2 pts)

A

Root hair cells are found in the root of the plant to absorb water and mineral salts from the soil.

Has a long and narrow extension

43
Q

Has a long and narrow extension (Root Hair Cell)

A

This increases the surface area to volume ratio for the root cell to absorb water and mineral salts at a faster rate.

44
Q

Guard Cells (2 pts)

A

Guard cells are found in the leaves of the plant. They facilitate gaseous exchange.

Guard cells are two bean-shaped cells that surround a pore known as stoma

45
Q

Guard cells are two bean-shaped cells that surround a pore known as stoma (Guard Cells)

A

They facilitate gaseous exchange in and out of the leaves by regulating the opening and closing of the stoma.

46
Q

Transverse Section (T.S.)

A

cross section; horizontally cut

47
Q

Longitudinal Section (L.S.)

A

vertical section

48
Q

Whole Mount (W.M.)

A

Typically used for entire specimen

49
Q

Smear (S.M.)

A

literally smear (?)

50
Q

Magnification formula:

A

Length of Drawing ÷ Length of Specimen

note:
For drawings of specimen seen using the microscope, the magnification stated is the total power of magnification used to observe and draw the specimen. Calculation is not required.

51
Q

Correct way to draw a cell:

A
  • Large drawing; 1/2 to ¾ of space given
  • Drawn using pencil
  • Shape is accurate; no shading
  • Label lines cut across as little as possible and does not intersect
  • Clean smooth lines are drawn
  • No broken / overlapping lines
  • Cell wall drawn to correct proportions, and thickness is consistent
  • Nucleus should be labelled from the nearest side
  • Format of title: “(High power) drawing of an ( ) ( .M/S.) (X )”
  • Labels written next to label lines
  • Label lines are drawn with ruler and horizontal line with no arrowheads

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