Exam I Flashcards
What is the cell theory?
- All organism are composed of cells
- Cells are the smallest living things
- Cells arise only from pre-existing cells
What type of microscope can be used to view live cells?
Light microscopes
Describe the five steps in processing nonliving tissue for microscopy.
- Fixed
- Embedded
- Sectioned
- Stained
- Mounted on a slide for microscopy
Compare the resolution capability of the naked eye to light and electron microscopes.
Naked eye:
• objects must be at least 100 micrometers apart to resolve them as two objects rather than one
Light microscopes:
• Resolve structures at least 200 nm (0.2 micrometers) apart (e.g., cells, organelles)
Electron microscopes
• Resolve structures less than 1 nm apart
What techniques would enable the visualization of transparent tissue?
Differential interference contrast microscopy
Why is it optimal for cells to be smaller rather than large?
Distinguish between protozoan and metazoan.
Protozoan:
• Single cell eukaryotes
Metazoan:
• Multicellular eukaryotes
What are three possible outcomes of mutations in DNA?
- Harmful (deleterious: disease, developmental defects)
- Advantageous
- Neutral
What properties are common among all cells?
- Plasma membrane
- Cytostol
- Ribosomes
- DNA
How can you distinguish between interphase and a mitotic nucleus using microscopy?
Interphase nucleus: chromosomes are decondensed
Where does cellular respiration take place?
Mitochondria
What kinds of cells undergo photosynthesis? Why? Which contain chloroplasts?
Photosynthetic bacteria (cyanobacteria) and plant cells
Plant cells contain chloroplasts
What is the function of the endoplasmic reticulum? The Golgi?
Golgi Apparatus:
• Modifies, packages, and distributes molecules
How does the proportion of SER to RER reflect a cell’s function?
• Cells that synthesize proteins that are secreted have more RER (e.g., endocrine glands)
• Cells that carry out extensive lipid synthesis have more SER (e.g., liver, testes, intestines, brain)
How can materials enter and exit a cell?
Endocytosis and exocytosis
What are the components and respective function of the cytoskeleton? ECM?
- Actin filaments
- Microtubules
- Intermediate filaments
• Directed cell movements
• Overall cellular structure
• Movement of structures within cell (e.g., nuclear division, vesicular traffic)
What is a structural similarity between nuclei and mitochondria?
Both have a double membrane and their own DNA
Which organelles are enclosed by a double membrane?
Nucleus, mitochondria
What cells are visible to the naked eye?
Oocytes (eggs)
What does it mean to increase/decrease contrast?
• Increase the difference between light and dark parts
• Accentuates light and darker
• Decrease contrast: light and dark parts are closer together
What is the difference between cytosol and cytoplasm?
Cytosol - liquid portion of cell
Cytoplasm - liquid + all organelles minus nucleus
Where else is DNA found in cells?
Mitochondria and chloroplasts
What does membrane envelope mean?
What type of cells use endocytosis significantly?
Immune cells (e.g., macrophages)
Digestive system (taking in nutrients)
What type of cells use exocytosis significantly?
• Endocrine cells
• Anything that needs to be exported/secreted
• Not steroidal hormones (e.g., testosterone, estrogen)
Most cells are relatively small due to reliance on ______ of substances in and out of cells
Diffusion
What is the rate of diffusion affected by?
- Surface area available
- Temperature
- Concentration gradient
- Distance
How does temperature affect rate of diffusion?
• Molecules tend to have more motion
• Hot temperature = diffusion goes faster
Which effect on rate of diffusion is most related to cell size?
Distance
An organism made of many ________ has an advantage over an organism composed of fewer, ________.
Small cells; larger cells
As cell’s size increase, its ______ increases much more rapidly than its __________.
Volume; surface area
Ten-fold difference (100 to 1,000)
How do some cells overcome the limitations of being larger cells? Give an example.
By being long, skinny with numbers branches (e.g., neurons)
What is the difference between 1 micrometer and 1 mm?
1 micrometer is 1,000x smaller than 1 mm
What is the largest cell body with a nucleus?
Ostrich egg
Changes in DNA sequence can result from mutations. What are three possible consequences?
- Harmful (deleterious)
- Advantageous
- Neutral
What do catalysts do? Give an example
Lower activation energy, speeding up chemical reactions (e.g., enzyme)
Which microscope type has the highest resolution?
Electron microscope
Why is the resolution of a light microscope not as high as an electron microscope?
Light microscopes are limited by wavelength of light
Resolution
Minimum distance two points can be apart and still be distinguished as two separate points
Why are many cells not visible to the naked eye?
• Objects must be at least 100 micrometers (0.1 mm) apart to resolve them as two objects rather than one
• Most cells are less than 50 micrometers (0.05 mm) in diameter
What cells are visible to the naked eye?
Oocytes (eggs)
Describe the characteristics of light microscopes.
• Use magnifying lenses with visible light
• Resolve structures that are at least 200 nm apart
• Resolution is limited by wavelength of light
• Can magnify cells up 1000x
• More flexibility
• Allows seeing live things
Describe the characteristics of electron microscopes.
• Use beam of electrons
• Resolve structures less than 1 nm apart
• Cannot look at live things
What are the two types of electron microscopes and what do they do?
- Transmission electron microscopes (TEM) - transmit electrons through material (see internal structures)
- Scanning electron microscopes (SEM) - beam electrons onto specimen surface (see structures on surface)
What are the different types of lenses that make up a CLM? What are their respective functions?
• Tube lens - allows rays of light to be parallel
• Eyepiece - 10x magnification
• Objective lens
• Condenser lens - concentrates light
Magnification is achieved through:
• Eyepiece (usually 10x)
• Objective (range from 4x-100x)
What would be the total magnification of a specimen viewed through a microscope with a 10x objective lens?
Answer: 100x
• Eyepiece - 10x
• Multiple objective lens - 10x
• 10 x 10 = 100
H&E stains
• Hematoxylin - purple stains (e.g., DNA, nucleic acids)
• Eosin - stains cytoplasm
What does it mean to increase contrast? Decrease contrast?
Increase contrast:
• Increase difference between light and dark parts
• Accentuates light and darks
Decrease contrast
• Light and dark parts are closer together
How are non-living tissues processed for microscopy?
- Fixed
- Embedded
- Sectioned
- Stained
- Mounted on a slide for microscopy
What happens during the step of being fixed?
• Use of fixedants (formaldehyde)
• Macromolecules are cross linked
Why is important that non-living tissues are fixed before being processed for microscopy?
Prevents decay and necrosis
What happens during the step of embedding non living tissues?
• Use of microtomes
• Tissue is embedded in something (e.g., soldi wax, resin)
• Remains in soldi state (keeps it rigid)
How is non-living tissue sectioned?
Usually with a microtome
How is non-living tissues stained?
Using hematoxylin and eosin
Wildtype
Control group; typical thing found in the wild
What are the three domains of life and what are their characteristics?
- Bacteria
• Single cell
• Prokaryotes
• Single circular chromosome
• No introns
• Peptidoglycan in cell - Archaea:
• Single cell
• Prokaryotes
• Singular circular chromosome
• Some genes contain introns
• No peptidoglycan in cell wall - Eukaryota
• Single/multicellular
• Eukaryotes
• Multiple linear chromosomes
• Most genes contain introns (especially metazoans)
Extremophiles
Organisms that live in extreme environments
What are the characteristics of Prokaryotic cells (Archaea and Bacteria)?
• Simplest organisms
• Lack membrane-bound organelles
• Contain cell walls
• Some are aerobic (require O2) and others strictly anaerobic (do not require oxygen; can be poisoned by oxygen)
• Contain ribosomes
Where is DNA present in prokaryotes ?
Nucleoid
What is the difference between cells walls in bacteria vs archaea?
Bacterial cell walls contain peptidoglycan and archaea do not
T or F: ribosomes are membrane-bound organelles.
F: Ribosomes are organelles but not membrane-bound
List the shapes of bacterial cells, and give a description and example for each.
- Spherical cells (e.g., Streptococcus)
• Gram positive - thick cell wall of peptidoglycan - Rod-shaped cells (e.g., E. coli, Salmonella)
• Gram negative - thin cell wall of peptidoglycan sandwiched between two membranes - Spiral cells (e.g., Treponema pallidum)
• Causes syphillis
• Gram negative
What does it mean for a bacterial cell to be gram negative?
Thin cell wall of peptidoglycan sandwiched between two membranes
• Peptidoglycan less abundant
• Prevents staining from accessing cell wall
Describe E. Coli.
• Divides by binary fission
• Has an outer membrane and an inner membrane (plasma membrane) - with a thin cell wall in between (gram negative)
• No membrane-bound organelles
What is the main function of photosynthetic bacteria?
Carbon fixing (taking in carbon to make glucose)
What is another function of photosynthetic bacteria?
Nitrogen fixing
Photosynthetic bacteria are precursors to what organelle?
Chloroplasts
List examples of protozoans (protists)
• Ciliate
• Heliozoan
• Amoeba
• Dinoflagellate
• Euglenoid
List examples of metazoans.
• Insects
• Zebrafish
• Mammals
What is the difference between cytosol and cytoplasm?
• Cytosol - liquid portion of cell (contains dissolved ions and small molecules)
• Cytoplasm - liquid + all organelles minus nucleus
Describe the nucleus.
• Contains genetic instructions (DNA)
• Consists of a membrane envelope (nuclear envelope)
List and describe the structures within the nucleus.
Nucleolus
• Ribosome biogenesis
• Ribosomal genes
• Ribosomal RNA
Nuclear pore complex
• Allows for transport of material into and out of nucleus
• Structural proteins that regulate what comes in and out of
Where else is DNA found in cells other than the nucleus?
Mitochondria and chloroplasts
What does it mean for the nucleus to have a membrane envelope?
Envelope - double bilayer
In brief terms, what happens in mitosis in terms of the nucleus and chromosomes?
• Nuclear envelope breaks down early (prophase)
• Chromosomes condense and become more visible
• Chromosomes align on metaphase plate
Describe mitochondria.
• Organelles that produce energy
• Aids in production of energy
• Contain their own genome
• Where cellular respiration machinery is embedded
How was mitochondrial function originally discovered?
• Centrifuged
• Fractionate cell
• See what each organelle does
• Mitochondria found to produce ATP
Which organelles likely arose during evolution through endosymbiosis?
Mitochondria and chloroplasts
How did mitochondria evolve through endosymbiosis
Aerobic bacterium engulfed/internalized
What do chloroplasts do?
Capture energy from sunlight
How did chloroplasts evolve through endosymbiosis?
Photosynthetic bacterium engulfed/internalized
What are the two types of proteins synthesized in RER?
- Proteins secreted
- Proteins embedded in membrane
Why is the RER called the RER?
Attachment of ribosomes to membrane gives rough appearance
What are the functions of the SER?
- Lipid synthesis
- Stores calcium ions
- Detoxification
What is the Golgi apparatus composed of?
Flattened stacks of interconnected membranes (Golgi bodies)
Explain the directionality of the Golgi apparatus.
Cis face - things closer to nucleus
Trans face - things in exit point
Vesicles transport molecules to what two destinations?
- Other organelles
- Plasma membrane
What are lysosomes and their function?
• Membrane-bounded digestive vesicles (filled with enzymes)
• Enzymes catalyze breakdown of macromolecules
• Recycles old or damaged organelles
• Destroy cells or foreign matter that cell has engulfed by phagocytosis
Lysosome function in a _____ pH environment (___-___)
Low; 4.5-5.0
Why is it important for lysosomes to function in a low pH environment?
• Example of compartmentalization
• Organelles need different environments
________ arise from Golgi apparatus.
Lysosomes
Describe peroxisomes.
• Membrane bound vesicle
• Contain enzymes involved in oxidation (breakdown) of fatty acids
• Contains enzymes to breakdown toxins (e.g., metabolic waste products, alcohol, drugs)
What two organs have the highest level of peroxisomes?
Liver and kidneys
What happens to the membrane during endocytosis?
• Some of membrane subtracted
• Membrane shrinks
What happens to the membrane during exocytosis?
Membrane expands
T or F: endocytosis and exocytosis occur simultaneously.
True
What type of cells use the process of endocytosis significantly?
• Immune cells (e.g., macrophages)
• Digestive system (taking in nutrients)
What type of cells use the process of exocytosis significantly?
• Endocrine cells
• Anything that needs to be exported/secreted
What type of cells do NOT use the process of exocytosis and why?
• Steroidal hormones (e.g., testosterone, estrogen)
• Lipid hormones
• Diffuse across bilayer
What is the cytoskeleton responsible for?
• Directed cell movements
• Overall cellular structure
• Movement of structures within cell (e.g., nuclear division, vesicular traffic)
What is the difference between ECM and cytoskeleton?
• ECM: outside cell (e.g., collagen, elastin)
• Cytoskeleton: inside cell
What are the three components that make up the cytoskeleton?
- Actin filaments
- Microtubules
- Intermediate filaments
Describe actin filaments
• Highly abundant in muscle
• Underlying cortex of cell
• Important for cell migration
Describe microtubules
• Important for forming mitotic spindle, vesicular traffic, and allowing ER to spread out
• Arrange “architecture” for cell
Describe intermediate filaments
• Highly abundant in skin cells
• Tend to be more stable
Which cell types have cell walls?
Prokaryotes, plant cells
Which cell types have chloroplasts?
Plant cells
Which cell types have extracellular matrix?
Animal cells
Which cell types have nuclei?
Animal and plant cells
Which cell types have cytoplasm
Animal and plant cells
Which cell types have actin filaments?
Animal and plant cells
