Topic 1 - Cell Biology Flashcards
(216 cards)
1
Q
State three parts of the cell theory.
A
The cell is the basic unit of life (nothing smaller is alive).
All living things are composed of cells.
Cells come from preexisting cells.
2
Q
Outline evidence that supports the cell theory.
A
Repeated observations and experiments support the cell theory.
We have never observed the cell theory not to be true.
3
Q
Compare the use of the word theory in daily language and scientific language.
A
In daily use: a theory is a guess, there is doubt.
In scientific use: a theory has been shown to be true through repeated observations and experiments. There is no current doubt. As of yet, no evidence has been collected that does not support the idea.
4
Q
Define “trend” and explain why trends are useful in scientific study.
A
A prevailing tendency, a generalization.
Trends lead to the development of predictions of what we expect to observe.
5
Q
Define “discrepancy” and explain why discrepancies are useful in scientific study.
A
An observation that does not fit the general trend; a variation from the trend.
Discrepancies from trends can lead to scientific questions. Answering those questions can lead to new discoveries and a deeper understanding of how the world works.
6
Q
List features that would be considered a “trend” related to the cell theory.
A
All living things are composed entirely of true cells.
Cells are small.
Typical cell structures (such as membrane and genetic material)
7
Q
Describe features of striated muscle fibres that make them a discrepancy from a typical cell.
A
Striated muscle fibres are large cells that have multiple nuclei (while most eukaryotic cells have one nucleus).
8
Q
Describe features of red blood cells that make them a discrepancy from a typical cell.
A
Red blood cells have no nucleus (while most eukaryotic cells have one nucleus).
9
Q
Describe features of giant algae that make them a discrepancy from a typical cell.
A
Giant algae can be a large, single celled organism with a single nucleus.
Organisms as large as giant algae would be expected to be multicellular, but they have only one cell with one nucleus.
10
Q
Describe features of aseptate fungal hyphae that make them a discrepancy from a typical cell.
A
Aseptate fungal hyphae are tube-like structures that contain no cell membranes between the many nuclei.
Aseptate hyphae are not divided up into individual cells, resulting in a continuous cytoplasm along the length of the hyphae.
11
Q
Outline the functional characteristics shared by all life, including organisms consisting of only one cell.
A
1) All life has a cellular structure (according to the cell theory, all living things are composed of cells).
2) All life exchanges energy and matter with the environment (including intake of nutrients and excretion of waste).
3) All life has metabolism (chemical reactions within the organism).
4) All life can recognize and respond to changes in environmental conditions.
5) All living things can grow and/or develop through the lifespan (increase in size, mass or number of cells within the organism)
6) All life has the capability for reproduction (production of similar cells/organisms from existing ones).
7) All life has a maintenance of homeostasis (regulating for a stable interior environment).
8) At the population level, life adapts and changes over time.
12
Q
Describe characteristics of Paramecium that enable it to perform the functions of life.
A
1) The paramecium is a single-celled eukaryotic organism;
2) The paramecium is a heterotroph, and eats smaller unicellular organisms in order to obtain energy and matter;
3) The cytoplasm contains dissolved enzymes that catalyze metabolic reactions such as digestion and synthesis of cellular structures;
4) The paramecium can control beating of cilia to move in different directions in response to changes in the environment;
5) The cell will grow until it reaches a maximum surface area to volume ratio, at which point it will divide;
6) The nucleus of the cell divides via mitosis to make another nuclei before the cell reproduces asexually (two paramecium can also fuse before dividing to carry out a form of sexual reproduction);
7) Waste products from digestion are excreted through an anal pore, an example of exchanging matter with the environment;
8) To maintain homeostasis, excess water within the cell is collected into a pair of “contractile vacuoles” which alternately swell and expel water through an opening in the cell membrane.
13
Q
Describe characteristics of Chlamydomonas, a photosynthetic unicellular organism, that enables it to perform the functions of life.
A
1) Chlamydomonas is a single-celled eukaryotic organism;
2) Chlamydomonas is an autotroph, using photosynthesis to obtain energy and matter;
3) The cytoplasm and chloroplast contain dissolved enzymes that catalyze metabolic reactions such as digestion, photosynthesis, cellular respiration and the synthesis of cellular structures;
4) A light sensitive “eyespot” allows Chlamydomonas to sense light and swim to it using its two flagella, illustrating the organism’s ability to respond to changes in the environment:
5) The cell will grow until it reaches a maximum surface area to volume ratio, at which point it will divide;
6) The nucleus of the cell divides via mitosis to make another nuclei before the cell reproduces asexually (the nuclei can also fuse and divide to carry out a form of sexual reproduction);
7) The oxygen byproduct of photosynthesis diffuses out through the cell membrane, an example of exchanging matter with the environment;
8) To maintain homeostasis, excess water within the cell is collected into a pair of “contractile vacuoles” which alternately swell and expel water through an opening in the cell membrane.
14
Q
Calculate the total microscope magnification.
A
Multiply the magnifying power of the ocular by the magnifying power of the objective lens that you are using.
15
Q
Define “magnification.”
A
How much larger an object appears compared to its real size.
16
Q
Define “field of view.”
A
The diameter of the area visible through the microscope.
17
Q
Outline how to determine the diameter of a field of view using low power magnification.
A
Place a transparent metric ruler under the low power objective of a microscope.
Focus the microscope on the scale of the ruler, and measure the diameter of the field of vision in millimeters.
18
Q
What is the formula for calculating the field of view diameter of a microscope under medium or high power?
A
If you know the diameter of the FOV at one magnification, you can determine the diameter of FOV at another magnification with the following formula:
Diameter of FOV#2 = diameter of FOV#1 x magnification#1 divided by magnification#2
19
Q
Outline how to estimate the size of a sample in the microscope field of view.
A
Estimate the fraction of the field of view that the object occupies.
Multiply the FOV diameter by that estimated fraction.
For example: the paramecium takes up about 2/3 of the FOV diameter. If I know the size of the field of view is 5 mm, I can then estimate the size of the paramecium: (2/3)*5mm = 3.3 mm
20
Q
Outline how to focus the microscope on a sample.
A
Place a slide on the stage so that it is centered under the objective lens.
Turn the revolving nosepiece so that the lowest power objective lens is “clicked” into position.
While looking at the objective lens and the stage from the side, turn the coarse focus knob so that the stage moves upward toward the objectives. Move it as far as it will go without touching the slide.
Look through the eyepiece and adjust the light source and diaphragm until you attain the maximum, comfortable level of light.
Slowly turn the coarse adjustment so that the stage moves down (away from the slide). Continue until the image comes into broad focus. Then turn the fine adjustment knob, as necessary, for perfect focus.
Move the microscope slide until the image is in the center of the field of view. Then re-adjust the light source or diaphragm in order to attain the clearest image.
Once you have attained a clear image, you should be able to change to a higher power objective lens with only minimal use of the fine focus knob. If you cannot focus on your specimen, repeat the above steps and work from objective to objective until the higher power objective lens is in place.
21
Q
Demonstrate how to draw cell structures seen with a microscope using sharp, carefully joined lines and straight edge lines for labels.
A
Drawing Materials: All drawings should be done with a sharp pencil line on white, unlined paper. Diagrams in pen are unacceptable because they cannot be corrected.
Positioning: Center drawing on the page. Do not draw in a corner. This will leave plenty of room for the addition of labels.
Size: Make a large, clear drawing; it should occupy at least half a page.
Labels: Use a ruler to draw straight, horizontal lines. The labels should form a vertical list. All labels should be printed (not cursive).
Technique: Lines are clear and not smudged. Avoid ‘feathery’ pencil lines and gaps. There are almost no erasures or stray marks on the paper. Color is used carefully to enhance the drawing. Stippling is used instead of shading.
Accuracy: Draw what is seen; not what should be there. Avoid making “idealized”drawings. Do not necessarily draw everything that is seen in the field of view. Draw only what is asked for. Show only as much as necessary for an understanding of the structure - a small section shown in detail will often suffice. It is time consuming and unnecessary, for example, to reproduce accurately the entire contents of a microscopic field. When drawing low power plans do not draw individual cells. Show only the distribution of tissues. When making high power drawings, draw only a few representative cells; indicate thickness of walls, membranes, etc.
Title: The title should state what has been drawn and what lens power it was drawn under (for example, phrased as: drawn as seen through 400X magnification). Title is informative, centered, and larger than other text. The title should always include the scientific name (which is italicized or underlined).
Scale: Include how many times larger the drawing is compared to life size and a labeled scale bar that indicates estimated size.
22
Q
Define “micrograph.”
A
A photograph taken through a microscope to show a magnified image of an item.
23
Q
State why the magnification of a drawing or micrograph is not the same as the magnification of the microscope.
A
We draw structures much larger than the size we see them when viewed under a microscope. The image produced in the microscope is often much smaller than what is shown in a drawing.
24
Q
Use a formula to calculate the magnification of a micrograph or drawing.
A
Drawing magnification indicates how many times larger the drawing is compared to life size.
Drawing magnification = drawing size / actual size
25
Given the magnification of a micrograph or drawing, use a formula to calculate the actual size of a specimen.
If you know the magnification of an image, you can determine the size of the specimen.
Actual size = drawing size / drawing magnification
26
Define and provide an example of a unicellular organism.
An organism composed of a single cell.
For example: paramecium, amoeba and chlamydomonas.
27
Define and provide an example of a multi-cellular organism.
An organism composed of multiple cells.
For example: turtle, oak tree, eagle.
28
Define "emergent property."
Characteristics and/or abilities that only arise from the interaction of the component parts of a structure.
29
Provide an example of emergent properties at different hierarchical levels of life.
Heart cell --> emergent property of life
Heart tissue --> emergent property of synchronized contractions
Heart organ --> emergent property of being able to pump blood
30
Define "tissue."
A group of cells that specialized in the same way to perform the same function.
31
Outline the benefits of cell specialization in a multi-cellular organism.
By becoming specialized, cells can be more efficient in their role. They can have particular structures and metabolisms that maximize the function of the cell for a specific purpose.
32
Define "differentiation."
The development of specialized structures and functions in cells.
33
Describe the relationship between cell differentiation and gene expression.
Differentiation in cells is due to different gene expression in different cell types.
All cells in a multi-cellular organism contain the same genes, but different cells will express different genes.
To express a gene means to "switch it on" so that the protein (or other gene product) is made.
34
Define "zygote."
The cell that results from a sperm fertilizing an egg.
35
Define "embryo."
Early stages of development after the zygote divides.
36
List two key properties of stem cells that have made them on the active areas of research in biology and medicine today.
Stem cells can divide repeatedly: useful for treatment of tissues that have been killed or damaged because they can produce large numbers of identical cells.
Stem cells are not differentiated: they have not "turned off" genes so they can still specialize to produce different cell types and a variety of different tissues.
Because of these two key properties, stem cells are used in medical research and treatment of disease.
37
Explain why stem cells are most prevalent in the early embryonic development of a multi-cellular organism.
The cells of the early embryo are the most versatile because they have differentiated the least. As the embryo develops, the cells gradually become more differentiated.
38
Contrast the characteristics of embryonic, umbilical cord and adult somatic stem cells.
Embryonic stem cells: the inner cell mass of an embryo can differentiate into any body cell (pluripotent)
Umbilical stem cells: can only differentiate into blood cells (multipotent)
Adult somatic stem cells: found in bone marrow, skin and liver, have limited differentiation ability (multipotent)
39
Define "totipotent."
A stem cell that can become any body cell (including placenta in placental mammals).
A zygote is totipotent.
40
Define "multipotent."
A stem cell that has partially differentiated but can still become multiple, related cell types.
Umbilical cord stem cells are multipotent.
41
Define "pluripotent."
A stem cell that can become any body cell.
The inner cell mass of a blastocyst is pluripotent.
42
Explain how stem cells are used in the treatment of Stargardt's disease.
Stargardt's disease is a recessive genetic disease that causes light detection cells of the retina to degenerate. Vision becomes progressively worse and eventually leads to blindness.
As a treatment, retina cells derived from embryonic stem cells are injected into the eyes. These cells attach to the retina, divide and differentiate into healthy retinal cells which improves vision.
43
Explain how stem cells are used in the treatment of leukemia.
Leukemia is a cancer that leads to the uncontrolled division of the cells that create white blood cells.
A person with leukemia is given chemotherapy, which kills the cancer cells. Then, bone marrow (containing adult stem cells) is transplanted from a donor to the person with leukemia. The stem cells establish themselves, divide and start to produce new blood cells.
44
Discuss the benefits and drawbacks in using adult stem cells.
Benefits
Can divide endlessly and can differentiate.
Can be used to repair and regenerate tissues.
Can be fully compatible with adult self-donor, so no risk of immune rejection.
Fewer ethical considerations since creation and/or destruction of embryos is not involved.
Adults can give consent for use of their stem cells.
Drawbacks
Hard to find and obtain from the body, and some tissues contain few stem cells.
Multipotent, so limited cells types can be created.
45
Discuss the benefits and drawbacks in using embryonic stem cells.
Benefits
Unlimited division and differentiation potential.
Cells won't have genetic mutations that have accumulated with age.
Drawbacks
Risk of becoming tumorous if division can't be controlled.
Creation and/or destruction of embryos is involved.
46
Discuss the benefits and drawbacks in using cord blood stem cells.
Benefits
Easy to obtain and store.
Cells are compatible with newborn from which they were acquired (no immune system rejection)
Drawbacks
Multipotent, so limited cells types can be created.
47
Explain why biological research must take ethical issues into consideration.
Biological research is a human endeavor and as such will lead to people having different opinions about what is ethical and should be permitted.
The ethics must be considered while deciding what is best for the collective societal good.
48
Outline the activities occurring in the volume and at the surface of the cell.
The cell volume is full of cytoplasm in which many metabolic reactions are occurring. The metabolic reactions require reactants (i.e. nutrients and oxygen) and may produce waste (i.e. urea and CO2).
The cell surface area is the cell membrane, through which reactants and waste enter and leave the cell.
49
Calculate the surface area, volume and SA:V ratio of a cube.
Surface area= side length^2
Volume= side length^3
SA:V ratio = [length^2 / length^3] = side length^-1
50
Explain the benefits and limitations of using cubes to model the surface area and volume of a cell.
Cubes are often used to model cell size because they can be manipulated, visualized and easily measured.
However, cells are not cubic in shape.
Cells are more difficult to manipulate and measure because of their microscopic size.
Luckily, the relationship between surface area and volume is the same in both cubes and cells.
51
Describe the relationship between cell size and the SA:V ratio of the cell.
If cell size increases, the surface area to volume ratio decreases.
This means that with larger cells, there is less surface area relative to the amount of volume.
52
Explain why cells are often limited in size by the SA:V ratio.
Larger cells (more volume) have more metabolic reactions occurring in the cytoplasm and as such require more reactants and produce more waste and heat. The exchange of nutrients, waste and heat is a function of the cell membrane (surface area).
However, since the amount of surface area (membrane) relative to the amount of volume (cytoplasm) decreases in larger cells, the cell will not have a large enough surface area (membrane) to moves reactants into and waste and heat out of the cell. Larger cells have a reduced efficiency of exchange because they have relatively less surface area compared to smaller cells.
53
List three adaptations of cells that maximize the SA: volume ratio.
1. Long extensions, such as in neurons.
2. Thin, flattened shape, such as in red blood cells.
3. Microvilli, such as in small intestine epithelial cells.
54
Explain how an improvement in apparatus allowed for greater understanding of cell structure.
Technology = machinery and equipment developed from the application of scientific knowledge.
Begets = gives rise to; brings about.
Discovery = the act of finding or learning something for the first time.
55
Define "resolution."
The smallest interval distinguishable by the microscope, which then corresponds to the degree of detail visible in an image created by the instrument.
56
Compare the functionality of light and electron microscopes.
LIGHT MICROSCOPES
Use lenses to bend light and magnify images.
Used to study dead or living cells in color.
Cell movement can be studied.
Larger field of view.
Objects can be magnified up to 2000X.
Can resolve objects 200 nm apart.
ELECTRON MICROSCOPES
Uses electron beams focused by electromagnets to magnify and resolve.
Requires cells to be killed and chemically treated before viewing.
No movement can be seen.
Without stain or dye, no color can be seen.
Smaller field of view.
Can magnify objects up to 250,000 times.
Can resolve objects that are 0.2 nm apart.
57
Outline the major differences between prokaryotic and eukaryotic cells.
Prokaryotic Cells
Smaller (about 0.2 - 2 um)
DNA in nucleoid region (no nuclear membrane)
No membrane bound organelles
Cell wall of peptidoglycan
Smaller ribosomes (70s) in cytoplasm
DNA is circular and without histone proteins
Has plasmid DNA
Asexual cell division
Eukaryotic Cells
Bigger (10-100 um)
DNA in a true nucleus
Membrane bound organelles present
Cell wall of cellulose (plants) or chitin (fungus)
Larger ribosomes (80s) in cytoplasm and on ER
//also has 70s ribosomes within mitochondria and chloroplasts//
DNA is linear with histone proteins
Do not have plasmid DNA
Asexual or sexual cell division
58
State the function of the prokaryotic cell cell membrane.
Forms the boundary of the cell, acts as a selective barrier
allowing certain materials to pass into and out of the cell, but not others.
59
State the function of the prokaryotic cell nucleoid.
Location of the genetic material for inheritance and protein coding; circular DNA not associated with histone proteins.
60
State the function of the prokaryotic cell plasmid.
Smaller, circular DNA not associated with DNA in the nucleoid. Often contains genes for antibiotic resistance.
61
State the function of the prokaryotic cell cytoplasm.
Primarily water and dissolved molecules, the location of many metabolic reactions.
62
State the function of the prokaryotic cell ribosome.
Responsible for catalyzing the formation of polypeptides during protein synthesis. Size is 70s.
63
State the function of the prokaryotic cell cell wall.
Found in most prokaryotic cells.
Provides shape and protection to the cell.
Composed of peptidoglycan.
64
State the function of the prokaryotic cell pili.
Pilus (singular)
Found in some (not all) prokaryotic cells.
Hair-like structures that help the cell attach to surfaces.
65
State the function of the prokaryotic cell capsule.
Found in some (not all) prokaryotic cells.
Helps the cell maintain moisture and adhere to surfaces. Protects the cells from other organisms.
66
State the function of the prokaryotic cell flagella.
Found in some (not all) prokaryotic cells.
Long extension used for cell locomotion.
67
Contrast the size of eukaryotic and prokaryotic ribosomes.
Prokaryotes have a smaller, 70s ribosome.
Eukaryotes have a larger, 80s ribosome. Although, the mitochondria and chloroplasts within eukaryotic cells have 70s ribosomes.
(The "s" stands for Svedberg unit, a measure of particle sedimentation rate)
68
Explain why understanding of the ultrastructure of prokaryotic cells must be based on electron micrographs.
"Ultrastructures" are small structures of/in a biological specimen that are too little to see with a light microscope.
69
Draw the ultrastructure of E.coli, including the cell wall, pili, flagella, plasma membrane, cytoplasm, 70s ribosomes, and nucleoid with naked DNA.
Cell wall drawn uniformly thick and outside the cell membrane
Capsule drawn outside the cell wall
Pili drawn as hair-like structures connected to cell wall
Flagellum drawn at one end only and longer than pili
Cell membrane represented by a continuous single line
70S ribosomes drawn as small discrete dots (not circles)
Nucleoid DNA shown as a tangled line not enclosed in membrane
Plasmid drawn as a small circular ring of DNA
Cytoplasm labeled within the cell
70
Define "asexual reproduction."
Asexual reproduction creates offspring from a single parent organism.
The offspring are genetic clones of that parent.
71
Outline the four steps of binary fission.
1. The nucleoid DNA replicates to create an exact duplicate copy.
2. The nucleoid DNAs attach to the cell membrane.
3. The cell membrane (and wall, if present) grow, causing the cell to elongate and the DNA molecules to move apart from each other.
4. The cell membrane pinches inward, creating two genetically identical cells.
72
State the meaning and advantages of eukaryotic cells being "compartmentalized."
Compartmentalization is the presence of membrane bound partitions (organelles) within the eukaryotic cell. The compartments allow for:
1. Specialization of regions within the cell for specific functions.
2. Molecules needed for a specific function to be concentrated in a region within the cell.
73
State structural differences between plant and animal cells.
Animal Cells
No cell wall
No chloroplasts
No large vacuole
Not a fixed shape
Stores carbohydrates as glycogen
Plant Cells
Cell wall
Chloroplasts
Large vacuole
Fixed shape
Stores carbohydrates as starch
74
Draw and label a diagram of the ultrastructure of a generic animal cell.
Cell membrane shown as a single continuous line
Nucleus drawn with double membrane and nuclear pores
Mitochondria with a double membrane, the inner one folded into internal projections, shown no larger than half the nucleus
Rough endoplasmic reticulum drawn as a multi-folded membrane with dots on surface
Golgi apparatus drawn as a series of enclosed sacs with evidence of vesicle formation
80S ribosomes drawn as small discrete dots (not circles) in cytoplasm and on rER
lysosome and vesicles drawn as circles with single line
75
Draw and label a diagram of the ultrastructure of a generic plant cell.
Cell wall drawn on outside perimeter with two continuous lines to indicate the thickness
Cell membrane shown as a single continuous line
Nucleus drawn with double membrane and nuclear pores
Vacuole drawn with a single continuous line
Chloroplast drawn with a double line and internal stacks of thylakoid
Mitochondria with a double membrane, the inner one folded into internal projections, shown no larger than half the nucleus
80S ribosomes drawn as small discrete dots (not circles) in the cytoplasm and on rER
76
Explain why cells with different functions will have different structures.
Cells will have different types and/or quantities of organelles depending on the primary function of the cell type.
This allows for cells to specialize for a specific task.
77
Deduce the function of the cell based on the structures present.
This is a cell from a pancreas exocrine gland.
It has a lot of rough endoplasmic reticulum, so it can be deduced that the cell secretes a protein.
There are vesicles concentrated near one edge of the cell containing the protein that will be excreted.
78
Deduce the function of the cell based on the structures present.
These are cells from an aquatic leaf.
There are many chloroplast present, so it can be deduced that the cells do photosynthesis.
79
Deduce the function of the cell based on the structures present.
This cell is from the small intestine. It is an epithelial cell of a villus.
This cell has many microvilli which increase the surface area for nutrient absorption.
There are many vesicles (dark stain) containing materials brought into the cell via endocytosis.
80
State the function of an exocrine gland cell in the pancreas.
Exocrine gland cells synthesize molecules (often proteins) for secretion from the cell into an external space.
Exocrine gland cells of the pancreas secrete enzymes that function in digestion in the small intestine.
81
Describe the function of the plasma membrane in an exocrine gland cell.
Forms the boundary of the cell, acts as a selective barrier allowing certain materials to pass into and out of the cell.
82
Describe the function of the nucleus in an exocrine gland cell.
Contains most of the genes that control the eukaryotic cell, contains the nucleolus and chromatin.
83
Describe the function of the mitochondria in an exocrine gland cell.
The location of aerobic cellular respiration used to make ATP.
84
Describe the function of the Golgi apparatus in an exocrine gland cell.
Consists of flattened membranous sacs; receives transport vesicles from the ER,
modifies proteins produced in the ER, produces secretory vesicles
85
Describe the function of the lysosomes in an exocrine gland cell.
Contains digestive enzymes that are used to break apart cellular debris and waste.
86
Describe the function of the vesicles in an exocrine gland cell.
Transport materials within the cell and out of the cell via exocytosis.
87
Describe the function of the endoplasmic reticulum in an exocrine gland cell.
Ribosomes on the ER synthesize proteins which are then moved through the ER and packaged into vesicles for transport.
88
State the function of a palisade mesophyll cell of a leaf.
Palisade mesophyll cells are found on the upper surface of a leaf and have the primary job of performing photosynthesis.
89
Describe the function of the cell wall in a palisade mesophyll cell of a leaf.
Provides structural rigidity and support.
90
Describe the function of the plasma membrane in a palisade mesophyll cell of a leaf.
Forms the boundary of the cell, acts as a selective barrier allowing certain materials to pass into and out of the cell.
91
Describe the function of the chloroplast in a palisade mesophyll cell of a leaf.
Location of photosynthesis reactions.
Produce carbohydrates using light energy, CO2 and H2O
92
Describe the function of the vacuole in a palisade mesophyll cell of a leaf.
Membrane bound sacs, larger than vesicles, stores water and dissolved nutrients and helps maintain cell turgidity.
93
Describe the function of the nucleus in a palisade mesophyll cell of a leaf.
Contains most of the genes that control the eukaryotic cell, contains the nucleolus and chromatin.
94
Describe the function of the mitochondria in a palisade mesophyll cell of a leaf.
The location of aerobic cellular respiration used to make ATP.
95
Identify the plasma membrane in a micrograph of a eukaryotic cell.
Look for a thin line around the edge of the cell.
96
Identify the ribosomes in a micrograph of a eukaryotic cell.
Tiny dark dots, can be "free" in the cytoplasm or "bound" to the rough ER.
97
Identify the nucleus in a micrograph of a eukaryotic cell.
Often stained a darker color, look for a nuclear membrane and the nucleolus.
98
Identify the rough endoplasmic reticulum in a micrograph of a eukaryotic cell.
Look for stacks of lines, often with visible little dark dots attached.
Typically closer to the nucleus than Golgi.
99
Identify the Golgi apparatus in a micrograph of a eukaryotic cell.
Look for stacks of lines, without little dark dots attached.
Typically further from the nucleus than ER.
100
Identify the lysosome in a micrograph of a eukaryotic cell.
Little sacs, often a light grey color.
Hard to distinguish from vesicles.
101
Identify the mitochondria in a micrograph of a eukaryotic cell.
Often stain dark. Circular or kidney shapes with internal wavy lines.
102
Identify the chloroplast in a micrograph of a eukaryotic cell.
Typically an oval shape with stacks visible on the inside.
If image is in color, the chloroplasts will be green.
103
Identify the vacuole in a micrograph of a eukaryotic cell.
Clear sac, typically larger in size than a vesicle or lysosome. More prevalent in plant cells than in animal cells.
104
Identify vesicles in a micrograph of a eukaryotic cell.
Little roundish sacs. Often stain dark.
Can be hard to distinguish from lysosome.
105
Identify the flagella in a micrograph of a eukaryotic cell.
Long tail-like structure emerging from the main cell body.
106
Identify the cell wall in a micrograph of a eukaryotic cell.
Rigid outermost layer of a plant cell, external to the cell membrane. Thicker than the cell membrane.
107
Draw a simplified diagram of the structure of the phospholipid, including a phosphate-glycerol head and two fatty acid tails.
Head = phosphate and glycerol
Tails = fatty acids
108
Define hydrophilic.
Polar and/or charged molecules (or regions of molecules) to which water can attract.
"Water loving."
109
Define hydrophobic.
Nonpolar molecules (or regions of molecules) to which water will not attract.
"Water fearing."
110
Define amphipathic.
A molecule that contains both hydrophilic and hydrophobic regions.
i.e. a phospholipid
111
Outline the amphipathic properties of phospholipids.
Amphipathic means there are both hydrophilic and hydrophobic regions in a single molecule. Phospholipids have a hydrophilic head region and hydrophobic tails.
112
Explain why phospholipids form bilayers in water.
There is water both outside and inside the cell. Phospholipids will arrange themselves in a bilayer so that the hydrophilic head associates with water and the hydrophobic tails face each other, away from the water.
113
State the primary function of the cell membrane.
The cell membrane is semi-permeable and controls the movement of substances into and out of the cell.
114
Contrast the structure of integral and peripheral proteins.
Peripheral proteins sit on one side of the surface of the cell membrane.
Integral proteins are embedded in the hydrophobic middle of the bilayer. Some integral proteins are "transmembrane" meaning they span both sides of the bilayer.
115
List functions of membrane bound proteins.
1. Receptor proteins receive extracellular signals.
2. Transport proteins move ions and molecules across the bilayer.
3. Enzymes catalyze reactions.
4. Adhesion proteins anchor the cell to other cells.
5. Recognition proteins identify the cell type in a multicellular organism.
116
Contrast the two types of transport proteins: pumps and channels.
Channel proteins are used for passive transport of molecules as they move across the bilayer from higher to lower concentration.
Pump proteins are used for active transport of molecules as they move across the bilayer from lower to higher concentration.
117
Identify the structure of cholesterol in molecular diagrams.
Cholesterol is a lipid that can be distinguished by its characteristic four-ring structure.
118
Describe the structural placement of cholesterol within the cell membrane.
Cholesterol fits between phospholipids in the cell membrane, with its hydroxyl (-OH) group by the heads and the hydrophobic rings by the fatty acid tails.
119
Describe the function of cholesterol molecules in the cell membrane.
Cholesterol acts as a regulator of membrane fluidity. At high temperatures if stabilizes the membrane and reduces melting. At low temperatures is prevents stiffening of the membrane.
Membrane fluidity influences how permeable the structure is to solutes.
Too fluid (higher temps) = too permeable
Too stiff (lower temps) = not permeable enough
120
Draw and label the structure of a cell membrane.
Phospholipid bilayer shown with heads facing in opposite directions
Phospholipids with labelled hydrophilic/phosphate head and hydrophobic/hydrocarbon tail
Peripheral protein, shown as globular structure at the surface of the membrane
Integral protein shown as embedded globular structure
Glycoprotein shown as embedded globular structure with protruding carbohydrate (shown as a branching, antenna-like structure)
Channel protein shown with a pore passing through it
Cholesterol shown in between adjacent phospholipids
121
Describe the observations and conclusions drawn by Davson and Danielli in discovering the structure of cell membranes.
Davson and Danielli proposed the "protein-lipid sandwich" model of the cell membrane, in which a phospholipid bilayer was embedded between two layers of proteins.
122
Describe conclusions about cell membrane structure drawn from freeze-etched electron micrograph images of the cell membrane.
Cells are rapidly frozen and then fractured. Fracture occurs along lines of weakness, including between the two layers of phospholipids.
Freeze-etched cell membranes provided evidence that the membrane was a bilayer with embedded proteins.
123
Describe conclusions about cell membrane structure drawn from cell fusion experiments.
Cell fusion experiments showed that protein molecules can move from place to place within the cell membrane; there is fluidity.
124
Describe conclusions about cell membrane structure drawn from improvements in techniques for determining the structure of membrane proteins.
Improvements in tools and techniques allows scientists to extract membrane proteins and determine their chemical and physical properties.
The membrane proteins were found to be varied in shape and size. Additionally, some proteins had hydrophobic regions.
These findings did not match the model proposed by Davson and Danielli, in which proteins were uniform in shape and hydrophilic.
125
Compare the Davson-Danielli model of membrane structure with the Singer-Nicolson model.
Singer and Nicolson proposed a membrane model that incorporated evidence about membrane proteins that did not comply with the Davson-Danielli model.
Rather than having proteins on the surface of the phospholipids, Singer-Nicolson proposed a model in which proteins were embedded within and through the membrane, called the fluid mosaic model.
126
Describe why the understanding of cell membrane structure has changed over time.
As tools and technology advance, our understanding of biological structures and functions improves.
Techniques such as freeze-fracture, cell fusion, fluorescent tagging and protein purification have enabled scientists to gain a more accurate understanding of the structure of the cell membrane.
127
Explain the purpose of developing models in science.
Models are conceptual representations used to explain and predict phenomena.
128
Describe simple diffusion.
Net movement of molecules from areas of higher concentration to areas of lower concentration, without the input of energy (passive).
129
Explain two examples of simple diffusion of molecules into and out of cells.
1. Gas exchange by diffusion in lung alveoli cells.
2. Gas exchange by diffusion through eye cornea cells.
130
Outline factors that regulate the rate of diffusion.
Concentration of the diffusing molecule
Increase concentration gradient, increase diffusion rate
Temperature
Increase temperature, increase diffusion rate
Pressure
Increase pressure, increase diffusion rate
131
Describe facilitated diffusion.
Movement of molecules from higher to lower concentration through a transport protein without the input of energy.
132
Describe one example of facilitated diffusion through a protein channel.
The CFTR protein is a channel protein that controls the flow of H2O and Cl- ions into and out of cells inside the lungs. When the CFTR protein is working correctly, as shown in Panel 1, ions freely flow in and out of the cells. However, when the CFTR protein is malfunctioning as in Panel 2, these ions cannot flow out of the cell due to a blocked channel. This causes Cystic Fibrosis, characterized by the buildup of thick mucus in the lungs.
133
Define osmosis.
The movement of water by diffusion across a membrane.
134
Predict the direction of water movement based upon differences in solute concentration.
Water moves from hypotonic solutions into hypertonic solutions.
135
Compare active transport and passive transport.
Passive Transport
Does not require energy input
Molecules move from high to low concentration, "with" the gradient.
Active Transport
Requires energy input
Molecules move from low to high concentration, "against" the gradient.
136
Explain one example of active transport of molecules into and out of cells through protein pumps.
Pumps are proteins that actively transport other molecules using ATP as an energy source.
For example, the proton pump is used in photosynthesis and respiration.
137
Describe the fluid properties of the cell membrane and vesicles.
Fluidity refers to the viscous flow of phospholipids in the cell membrane and organelles of the endomembrane system (including vesicles).
Fluidity is affected by:
-fatty acid length
-fatty acid saturation
-presence of cholesterol
138
Explain vesicle formation via endocytosis.
In endocytosis, the cell activity transports molecules into the cell by engulfing them into vesicles formed from the cell membrane.
139
Outline two examples of materials brought into the cell via endocytosis.
White blood cells can engulf bacteria when fighting infection.
Single celled organism like amoeba can engulf bacteria as a food source.
140
Explain release of materials from cells via exocytosis.
A secretory vesicle moves towards the cell membrane, fuses with the membrane and releases its contents into the extracellular space.
141
Outline two examples of materials released from a cell via exocytosis.
Secretion of neurotransmitter at synaptic terminus.
Secretion of digestive juices from exocrine glands.
142
List two reasons for vesicle movement.
Transport vesicles can move molecules between locations inside the cell (e.g. proteins from the ER to the Golgi).
Secretory vesicles can move molecules from inside the cell to outside of the cells (e.g. to secrete a protein hormone).
143
Describe how organelles of the endomembrane system function together to produce and secrete proteins (rough ER, smooth ER, Golgi and vesicles).
1. In the nucleus, transcription of DNA, creating mRNA.
2. Translation of mRNA at a ribosome on the Rough ER, creating a protein.
3. Packaging of the protein into a transport vesicle.
4. Transport of the protein inside the vesicle to the Golgi.
5. Modification of the protein within the Golgi.
6. Packaging of the protein into a secretory vesicle.
7. Secretion of the protein when the vesicle fuses with the cell membrane during exocytosis.
144
Outline how phospholipids and membrane bound proteins are synthesized and transported to the cell membrane.
Phospholipids are synthesized at the ER. The phospholipids become part of the ER membrane.
When a transport vesicle buds off the ER, the newly made phospholipid will be part of the vesicle. There may also be proteins (made at a ribosome on the ER) than embed in the vesicle.
As the vesicle moves through the cell towards the Golgi and then towards the cell membrane, the new phospholipid and protein are also transported.
When the vesicle fuses with the cell membrane, the new phospholipid and protein will become part of the cell membrane.
145
Describe the structure of the sodium-potassium pump.
The sodium-potassium pump is an integral membrane protein. It had binding sites for three sodium ions, two potassium ions and an inorganic phosphate group (which comes from ATP).
146
Outline the steps of sodium-potassium pump action.
1. Three sodium ions bind with the protein pump inside the cell.
2. The pump protein is phosphorylated by ATP and changes shape.
3. By changing shape, the three sodium ions are released out of the cell.
4. At that point, two potassium ions from outside the cell bind to the protein pump.
5. The inorganic phosphate (which came from the ATP) is released from the pump, restoring the original shape of the protein.
6. The potassium ions are then released into the cell, and the process repeats.
147
Describe the role of the sodium-potassium pump in maintaining neuronal resting potential.
The sodium-potassium pump is found in many cell (plasma) membranes. Powered by ATP, the pump moves sodium and potassium ions in opposite directions, each against its concentration gradient. In a single cycle of the pump, three sodium ions are extruded from and two potassium ions are imported into the cell. The rest of the ion movement is a net negative charge in the cell, called the resting potential.
148
Describe the structure of the potassium channel.
The potassium channel is an integral membrane protein that facilitates the diffusion of potassium ions out of the cell.
The channel has a "ball and chain" gate mechanism that will only open the channel for potassium movement when a specific cell voltage is reached.
149
Explain the specificity of the potassium channel.
Potassium channels are designed to allow the flow of potassium ions across the membrane, but to block the flow of other ions--in particular, sodium ions.
150
Describe the action of the "voltage gate" of the potassium channel.
When a neuron is firing, the voltage of the cell changes. The potassium channel will only open when the voltage of the cell has reached its peak (of about 30mv).
151
Explain what happens to cells when placed in solutions of the same osmolarity.
Isotonic solutions are solutions that have the same osmolarity. Water moves into and out of the cell equally, resulting in no NET movement of water.
152
Explain what happens to cells when placed in solutions of higher osmolarity.
Hypertonic solutions are solutions that have more solutes than the cell. Water will move out of the cell and as a result the cell will shrivel (animal) or plasmolyze (plant).
153
Explain what happens to cells when placed in solutions of lower osmolarity.
Hypotonic solutions are solutions that have fewer solutes than the cell. Water will move into the cell. Animal cells will swell and may burst. Plant cells will become turgid with a vacuole full of water and pressure on the cell wall.
154
Outline the use of normal saline in medical procedures.
Normal saline is a solution of water and salt ions that is isotonic to human blood. It is used as an eye wash, to flush wounds and intravenously to rehydrate patients. During organ transplant, while out of a body the organs are bathed in normal saline.
Because the solution is isotonic to body cells, the cells will not shrink or swell when exposed to the saline solution.
155
Define osmolarity.
The concentration of solutes in a solution.
156
Define isotonic.
The osmolarity of two solutions is the same.
157
Define hypotonic.
A solution with a lower osmolarity (fewer solutes) compared to another solution.
158
Define hypertonic.
A solution with a higher osmolarity (more solutes) compared to another solution.
159
Determine osmolarity of a sample given changes in mass when placed in solutions of various tonicities.
The osmolarity of a sample is the point at which there is no net movement between the sample and the solution in which it is placed.
Samples will gain mass when placed in a hypotonic solution (as water moves into the sample). Samples will lose mass when placed in a hypertonic solution (as water moves out of the sample). There will be zero change in mass when the sample is placed in an isotonic solution.
160
Define quantitative.
Data that is in the form of a number obtained in a count or measurement.
161
Define qualitative.
Data that is descriptive or subjective.
162
Explain the need for repeated measurements (multiple trials) in experimental design.
Multiple trials allows one to see if the results of each measurement show consistency. Consistent findings reinforce the strength of the conclusion.
163
Discuss implications of all cells being formed from preexisting cells.
Implication #1: We can trace the origin of all the cells in our body back to the first cell; the zygote produced by the fertilization of a sperm and egg.
Implication #2: The origins of all cells can be traced back through billions of years of evolution to "LUCA" the last universal common ancestor of all life on Earth.
Implication #3: There must have been a first cell that arose from non-living material.
164
Outline the four processes needed for the spontaneous origin of cells on Earth.
1. The synthesis of simple organic molecules from inorganic compounds.
2. The assembly of these organic molecules into polymers.
3. The formation of a polymer that can self replicate (enabling inheritance).
4. Packaging of molecules into membranes with an internal chemistry different from the surroundings.
165
Outline the experiments of Miller and Urey into the origin of organic compounds.
Boiled water evaporates and moves into the larger flask, where it combines with methane, ammonia and hydrogen gases in a large flask.
Sparks are fired between electrodes to simulate lightning.
A cooling condenser turns steam back into liquid water, which drips down into the trap, where organic molecules produced in the reactions also settle.
166
Define polymerization.
The process in which relatively small molecules, called monomers, combine chemically to produce a large chainlike molecule, called a polymer.
167
Define monomer.
"one part"
The single building block unit of a polymer.
168
Define polymer.
"many parts"
A large molecule composed of many monomer subunits.
169
Outline properties of RNA that would have allowed it to play a role in the origin of life.
RNA can self-replicate.
RNA can serve as a genetic code for protein synthesis between generations.
RNA can act as a catalyst, speeding up the polymerization of amino acids to form proteins.
170
Outline why fatty acids were likely the primary component of the membrane of early cells.
Fatty acids are structurally much simpler than phospholipids and may have formed more readily in a prebiotic environment.
Similar to phospholipids, fatty acids have a hydrophobic tail and hydrophilic head and can thus form the same types of structures, such as vesicles, micelles and bilayers.
171
State the endosymbiosis theory.
Theory that mitochondria and chloroplasts evolved from free living prokaryotic cells that were engulfed (but not digested) by early eukaryotic cells.
The mitochondria and chloroplasts evolved as "symbiotic" (together, both benefiting) "endobionts" (inside living).
172
Describe the evidence for the endosymbiotic theory.
Mitochondria and chloroplasts share the following with prokaryotic cells:
- shape
-size
-70s ribosomes
-circular, naked DNA
-genetic sequences
-movement
-division by binary fission
-inhibited by antibiotics
Additionally, mitochondria and chloroplasts have a double layer membrane.
173
Define spontaneous generation.
The theory, now discredited, that living organisms can routinely emerge from nonliving matter independently of other living matter.
174
Describe Pasteur's experiments about spontaneous generation.
Pasteur's experiments (1859) provided evidence that spontaneous generation of cells and organisms does not now occur on Earth.
Pasteur's experiment consisted of three parts. In the first part, the broth in the flask was boiled to sterilize it. When this broth was cooled, it remained free of microbial contamination.
In the second part of the experiment, the flask was boiled and then the neck was broken off. The broth in this flask became cloudy as it became contaminated with microbes from the air.
In the third part of the experiment, Pasteur created a flask with a curved neck. The curve allowed indirect exposure to air but prevented entry of microbes. The broth remained free of microbial contamination.
175
Explain why Pasteur's experiments did not support the idea of spontaneous generation.
If a life force was responsible for microbial growth within the sterilized flasks, it would have access to the broth, whereas the microorganisms would not.
However, because the broth in the flask remained clear, Pasteur's experiment showed that air does not contain a "vital force" that creates life. Life could not spontaneously generate.
176
Outline historical thinking about spontaneous generation.
Early philosophers and scientists were basing their ideas on what they could observe at the time.
Technological tools had not yet advanced to the point of being able to observe cells arising from other cells.
There was no reason or pressure to show that spontaneous generation wasn't accurate. It's hard to speak out against an idea when a majority support it.
Spontaneous generation was consistent with the other widely held cultural and religious beliefs of the time.
177
Summarize the Redi experiment.
Summarize the Redi experiment.
Redi placed meat three different jars. One jar was left open; the other two were covered. Later, the open jar contained maggots, whereas the covered jars contained no maggots. He did note that maggots were found on the exterior surface of the cloth that covered the jar (attracted to the smell). Redi successfully demonstrated that the maggots came from fly eggs and were not spontaneously generated.
178
Summarize the Spallanzani experiment.
Spallanzani put broth in a flask, sealed the flask so that way no air could get in, and boiled it. No organisms grew in that flask. This suggested that microbes were introduced into these flasks from the air. In response to Spallanzani's findings, others argued that life originates from a "life force" that was destroyed during Spallanzani's extended boiling.
179
List reasons why biologists now universally accept that cells only come from preexisting cells.
With improved observational tools and a focus on controlled experiments, we now know that cells only come from existing cells.
180
State the function of mitosis.
The function of mitosis is to create two daughter cells with genetically identical nuclei as the parent cell.
181
List four processes which involve mitosis.
1. Tissue repair (for example after injury)
2. Growth of the organism
3. Embryonic development
4. Replacement of cells that die naturally (for example, skin)
5. Clonal selection of B cells (for antibody production)
6. Asexual reproduction (for example budding)
182
State the names of the four phases of mitosis.
Mitosis is divided into four major phases:
1. prophase
2. metaphase
3. anaphase
4. telophase
183
Draw a typical eukaryotic cell as it would appear during the interphase.
Nucleus intact
Nucleolus visible
DNA as chromatin
DNA is unreplicated
184
Draw a typical eukaryotic cell as it would appear during the prophase.
Nuclear membrane breaking down
Nucleolus fading
DNA supercoiling into chromosome
Spindle fibers form
Centrioles more towards cell poles
185
Draw a typical eukaryotic cell as it would appear during the metaphase.
Replicated chromosome align at the cell equator
186
Draw a typical eukaryotic cell as it would appear during the anaphase.
Identical chromatids (now individual unreplicated chromosomes) are pulled towards the poles of the cell.
187
Draw a typical eukaryotic cell as it would appear during the telophase.
Nuclear membrane reforming
Nucleolus reforming
DNA uncoiling to become chromatin
Spindle fibers degrade
188
Outline four events that occur during prophase.
Nuclear membrane breaking down
Nucleolus fading
DNA supercoiling into chromosome
Spindle fibers form
Centrioles more towards cell poles
189
Outline the process of metaphase.
Replicated chromosome align at the cell equator
190
Outline the process of anaphase.
Identical chromatids (now individual unreplicated chromosomes) are pulled towards the poles of the cell.
191
Outline the events that occur during telophase.
Nuclear membrane reforming
Nucleolus reforming
DNA uncoiling to become chromatin
Spindle fibers degrade
192
Describe the structure of a replicated chromosome, include the centromere and sister chromatids.
Chromosomes are supercoiled strands of DNA
Replicated chromosomes means that there are identical copies of DNA called sister chromatids (formed during DNA replication in S phase) attached to each other at the centromere
193
Explain why chromosomes must condense during mitosis.
To "condense" means to make DNA denser, or more tightly packed. DNA condenses during mitosis so that it can more easily be moved to the poles of the cell without getting tangled and/or broken.
194
Define cytokinesis.
Cytokinesis is the division of the cytoplasm of a parent cell into two daughter cells.
195
State the difference between mitosis and cytokinesis.
Mitosis refers to the division of the nucleus (nuclear DNA) whereas cytokinesis is division of the cytoplasm (and organelles in it).
196
Contrast cytokinesis in plant and animal cells.
Cytokinesis is different in plant and animal cells because plant cells must create new cell wall between the daughter cells; animal cells do not have to form a cell wall.
197
List example metabolic reactions occurring during cell interphase.
The majority of the cell cycle is spent in interphase. During interphase "G1", the cell is performing its specialized function, which requires extensive protein synthesis. During interphase "S," DNA replication occurs.
198
Outline events of G1, S, G2 and G0 phases of interphase
G1: cell grows and performs its specialized function
S: the DNA replicates
G2: the cell makes the proteins required for mitosis and cytokinesis
G0: the cell is neither dividing nor preparing to divide
199
Explain the role of cyclin and cyclin-CDK complexes in controlling the cell cycle.
The cell cycle must be controlled so that cells are only dividing when necessary, not continuously. Cell also need to time the progression through the cell cycle so that it moves from one phase to the next only when all the steps are complete.
Cyclins are protein molecules whose concentration cycle up and down as the cell progresses through the cell cycle. Cyclins attach to other molecules, cyclin-dependent kinases (CDK) to activate progression through the cell cycle. If there is a low concentration of cyclin, the CDK will not be active and the cell cycle will freeze.
200
State the role of cyclins D, E, A and B in the cell cycle.
Cyclin D - causes progression of the cell through G1 and into S phase.
Cyclin E - causes the cell to prepare for DNA replication.
Cyclin A - initiates DNA replication in S phase and prepares the cell for mitosis during G2.
Cyclin B - progresses the cell through prophase and metaphase. Must degrade for the cell to begin anaphase.
201
Define tumor.
A mass of tissue caused by abnormal cell division.
202
Contrast benign and malignant tumors.
Benign - a tumor that lacks the ability to invade other tissues or metastasize.
Malignant - a tumor made of cells that can invade other tissues and metastasize.
203
Define cancer.
A disease caused by a malignant tumor.
204
Describe why mutagens are not necessarily carcinogens.
A mutagen induces mutations in DNA. If the mutation results in uncontrolled cell division and cancer, then the mutagen is also a carcinogen.
205
Describe how cancer arises.
Cells become cancerous after mutations accumulate in genes that control the cell cycle.
The Cancer Genome Project found that most (not all) cancer cells possess 60 or more mutations.
206
Explain the relationship between oncogenes and cancer.
Proto-oncogenes are normal genes that code for proteins (i.e. cyclins) that help the cell move through the cell cycle.
When proto-oncogenes mutate, they become oncogenes. Oncogenes move the cell through the cell cycle even when it shouldn't divide.
207
Explain the relationship between tumor suppressor genes and cancer.
Tumor-suppressor genes are normal genes that code for proteins that stop a cell from dividing when it shouldn't.
When tumor-suppressor gene mutate, the cell will divide even when it shouldn't.
208
Explain the use of correlations to determine the relationship between two variables.
Correlations are used to show how related two variables are to each other. Correlations do not necessarily show causation between variables.
Positive correlation (direct) - as X increases, Y increases
Negative correlation (indirect) - as X increases, Y decreases
209
Explain why the existence of a correlation does not necessitate a causal relationship between two variables.
For any two correlated variables, the following relationships are possible:
X causes Y
Y causes X
X and Y are consequences of a common cause, but do not cause each other
X causes Z which causes Y
The correlation between X and Y is a coincidence
210
Outline the relationship between smoking and cancer.
Epidemiologists noticed a relationship between smoking and rates of lung cancer. Since cancer rates when up as smoking rates went up, epidemiologists concluded that there is a positive (direct) relationship between smoking and lung cancer.
Substantial evidence has now been collected to determine that this is a CAUSAL relationship - smoking can cause the development of cancer.
211
Determine the phase of mitosis from the image.
212
Calculate the mitotic index of a tissue as seen in a micrograph.
Mitotic Index = # of cells in mitosis (shown in red) / total number of cells
M.I. = 17 / 60 = 0.3
213
State the formula for calculation of a mitotic index.
Mitotic Index = # of cells in mitosis / total number of cells
214
Outline the use of mitotic index calculations in diagnosis and treatment of cancer.
Diagnosis: the higher the mitotic index relative to a tissue specific standard, the more likely a tissue is cancerous.
Treatment: cancer treatments work by stopping cell division, so if a cancer treatment is working fewer cells will be in mitosis. As a result, the mitotic index will decrease if a treatment is working.
215
Define serendipity.
Serendipity is a chance event with a positive outcomes.
216
Outline the discovery of cyclins including the role of serendipity.
Tim Hunt was studying embryonic development when he by chance observed that a protein would increase and decrease in concentration with each cycle of cell division.
