Topic 1 - Cell Biology Flashcards
State three parts of the cell theory.
The cell is the basic unit of life (nothing smaller is alive).
All living things are composed of cells.
Cells come from preexisting cells.
Outline evidence that supports the cell theory.
Repeated observations and experiments support the cell theory.
We have never observed the cell theory not to be true.
Compare the use of the word theory in daily language and scientific language.
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.
Define “trend” and explain why trends are useful in scientific study.
A prevailing tendency, a generalization.
Trends lead to the development of predictions of what we expect to observe.
Define “discrepancy” and explain why discrepancies are useful in scientific study.
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.
List features that would be considered a “trend” related to the cell theory.
All living things are composed entirely of true cells.
Cells are small.
Typical cell structures (such as membrane and genetic material)
Describe features of striated muscle fibres that make them a discrepancy from a typical cell.
Striated muscle fibres are large cells that have multiple nuclei (while most eukaryotic cells have one nucleus).
Describe features of red blood cells that make them a discrepancy from a typical cell.
Red blood cells have no nucleus (while most eukaryotic cells have one nucleus).
Describe features of giant algae that make them a discrepancy from a typical cell.
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.
Describe features of aseptate fungal hyphae that make them a discrepancy from a typical cell.
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.
Outline the functional characteristics shared by all life, including organisms consisting of only one cell.
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.
Describe characteristics of Paramecium that enable it to perform the functions of life.
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.
Describe characteristics of Chlamydomonas, a photosynthetic unicellular organism, that enables it to perform the functions of life.
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.
Calculate the total microscope magnification.
Multiply the magnifying power of the ocular by the magnifying power of the objective lens that you are using.
Define “magnification.”
How much larger an object appears compared to its real size.
Define “field of view.”
The diameter of the area visible through the microscope.
Outline how to determine the diameter of a field of view using low power magnification.
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.
What is the formula for calculating the field of view diameter of a microscope under medium or high power?
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
Outline how to estimate the size of a sample in the microscope field of view.
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
Outline how to focus the microscope on a sample.
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.
Demonstrate how to draw cell structures seen with a microscope using sharp, carefully joined lines and straight edge lines for labels.
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.
Define “micrograph.”
A photograph taken through a microscope to show a magnified image of an item.
State why the magnification of a drawing or micrograph is not the same as the magnification of the microscope.
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.
Use a formula to calculate the magnification of a micrograph or drawing.
Drawing magnification indicates how many times larger the drawing is compared to life size.
Drawing magnification = drawing size / actual size
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
Define and provide an example of a unicellular organism.
An organism composed of a single cell.
For example: paramecium, amoeba and chlamydomonas.
Define and provide an example of a multi-cellular organism.
An organism composed of multiple cells.
For example: turtle, oak tree, eagle.
Define “emergent property.”
Characteristics and/or abilities that only arise from the interaction of the component parts of a structure.
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
Define “tissue.”
A group of cells that specialized in the same way to perform the same function.
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.
Define “differentiation.”
The development of specialized structures and functions in cells.
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.
Define “zygote.”
The cell that results from a sperm fertilizing an egg.
Define “embryo.”
Early stages of development after the zygote divides.
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.
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.
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)
Define “totipotent.”
A stem cell that can become any body cell (including placenta in placental mammals).
A zygote is totipotent.
Define “multipotent.”
A stem cell that has partially differentiated but can still become multiple, related cell types.
Umbilical cord stem cells are multipotent.
Define “pluripotent.”
A stem cell that can become any body cell.
The inner cell mass of a blastocyst is pluripotent.
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.
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.
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.
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.
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.
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.
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.
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
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.
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.
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.
List three adaptations of cells that maximize the SA: volume ratio.
- Long extensions, such as in neurons.
- Thin, flattened shape, such as in red blood cells.
- Microvilli, such as in small intestine epithelial cells.
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.
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.
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.
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
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.
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.
State the function of the prokaryotic cell plasmid.
Smaller, circular DNA not associated with DNA in the nucleoid. Often contains genes for antibiotic resistance.
State the function of the prokaryotic cell cytoplasm.
Primarily water and dissolved molecules, the location of many metabolic reactions.
State the function of the prokaryotic cell ribosome.
Responsible for catalyzing the formation of polypeptides during protein synthesis. Size is 70s.
State the function of the prokaryotic cell cell wall.
Found in most prokaryotic cells.
Provides shape and protection to the cell.
Composed of peptidoglycan.
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.
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.
State the function of the prokaryotic cell flagella.
Found in some (not all) prokaryotic cells.
Long extension used for cell locomotion.
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)
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.
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
Define “asexual reproduction.”
Asexual reproduction creates offspring from a single parent organism.
The offspring are genetic clones of that parent.
Outline the four steps of binary fission.
- The nucleoid DNA replicates to create an exact duplicate copy.
- The nucleoid DNAs attach to the cell membrane.
- The cell membrane (and wall, if present) grow, causing the cell to elongate and the DNA molecules to move apart from each other.
- The cell membrane pinches inward, creating two genetically identical cells.
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:
- Specialization of regions within the cell for specific functions.
- Molecules needed for a specific function to be concentrated in a region within the cell.
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
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
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
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.
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.
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.
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.
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.
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.
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.
Describe the function of the mitochondria in an exocrine gland cell.
The location of aerobic cellular respiration used to make ATP.
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
Describe the function of the lysosomes in an exocrine gland cell.
Contains digestive enzymes that are used to break apart cellular debris and waste.
Describe the function of the vesicles in an exocrine gland cell.
Transport materials within the cell and out of the cell via exocytosis.
