KB The Cell

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Compare and contrast Eukaryotic cells and Prokaryotic cells.: Eukaryotic cells include protists,fungi, plants and animals. Cell wall present in fungi and plants only. Eukaryotic cells have a nucleus and membrane bound organelles. Eukaryotic cells have ribosomes whose subunits = 40S and 60S.
Prokaryotic cells include bacteria and cyanobacteria. All of the prokaryotes have cell wall present, they have no nucleus and nomembrane bound organelles.
Prokaryotes also have Ribosomes but they differ in subunits as compared to Eukaryotic cells. Ribosome subunits for the Prokaryotic cells are 30S and 50S.
Summerize the Cell Theory.: - all living things are composed of cells
- which is the basic functional unit of life
- cells only come from pre-existing cells
-cells carry genetic info in the form of DNA,that is passed from parent cell to daughter cell.
What are the 3 main components of a microscope and what are their functions?: * diaphragm - controls amount of light passing through specimen.

* course adjustment knob - roughly focuses the image.

* fine adjustment knob - sharply focuses the image.
In general compound light microscopes are used in the observation of nonliving specimens. Why?: light microscopes require contrast between cells and cell structures, often the techniques used to obtain the contrast needed kills the cell being observed.
techniques often used are stains and dyes.
The phase contrast microscope is a special type of light microscope that allows the study of living cells. How is this possible?: The differnces in refractive index are used to produce the contrast between cellular structures, therefore does not kill the specimen.
How does an electron microscope work?: an electron microscope uses a beam of electrons to allow magnification a 1000X greater than the light microscope. Tissues must be fixed and sectioned and sometimes stained with a heavy metal solution, therefore no live specimens can be examined.
What happens when you centrifuge an eukaryotic cell at high speed?: The components sediment at different levels in the test tube. Ribosomes which are high in density settle to the bottom of the test tube, while mitochondria and lysosomes remain at the top due to low desity.
How does the dye hematoxlin reveal the distribution of DNA and RNA within a cell?: it has an affinity for negatively charged molecules.
Autoradiography: A technique that utilizes radioactive molecules to trace and identify cell structures and biochemical activity.
examples: it can be used to study protein synthesis- labeling amino acids with radioactive isotopes allows the pathways of protein sythesis to be examined.
it can also be used to study the mechanisms of DNA and RNA synthesis using similar techniques as protein synthesis.
Eukaryotic Organelles: specialized structures of unique form & function. They include
the nucleus,ribosomes,endoplasmic reticulum (ER),Golgi apparatus, vesicles, vacuoles, lysosomes, microbodies, mitochondria, chloroplasts, & centrioles.
Cytosol: fluid component of the cytoplasm and consists of an aqueous solution containing free proteins, nutrients, and other solutes.
cell membrane is also known as the: plasma membrane
Cell Membrane: encloses the cell and exhibits selective permeability; it regulates the passage of materials into and out of the cell.
Where are the two regions of the phospholipid located in the lipid bilayer (phospholipid bilayer)?: the hydrophilic regions are found on the exterior surfaces of the membrane while the hydrophobic regions are found on the interior of the membrane.
what do the cholesterol molecules embedded in the hydrophobic interior contribute to the cell membrane?: contributes to the membrane's fluidity.
what are the transport proteins?: membrane spanning molecules that allow certain ions and polar molecules to pass through the lipid bilayer.
Cell adhesion molecules (CAMs)?: proteins that contribute to cell recognition and adhesion and are particularly important during development.
what two functions of the cell do the proteins of cell adhesion molecules contribute to?: cell recognition and adhesion.
Receptors.: complex proteins or glycoproteins embedded in the membrane with sites that bind to specific molecules in the cell's external environment.
How are small charged molecules and large charged molecules able to cross the plasma membrane?: --small charged molecules cross through the protein channels in the membrane.
--larger charged molecules cross the plasma membrane with the assistance of carrier proteins.
Nucleus What is its function? What does it contain? How is it protected?: -controls activities of cell including cell division.
-surrounded by a nuclear membrane or envelope.
-contains DNA and nucleolus where rRNA synthesis occurs.
Nuclear membrane/envelope: double membrane that maintains a nuclear environment distinct from that of the cytoplasm.
-interspersed throughout are nuclear pores.
nuclear pores: allow selective two-way exchange of materials between the nucleus and the cytoplasm.
histones: structural proteins that when complexed with DNA form chromosomes.
nucleolus: dense structure in nucleus where ribosomal RNA (rRNA)synthesis occurs.
Gyloxysomes: - microbodies usually found in fat tissue of germinating seedlings
- used by seedlings to convert fats into sugars until the seedling is mature enough to produce its' own sugars by photosynthesis
Describe the mitochondrion.: - bound by an outer and an inner phospholipid bilayer membrane
- outer membrane smooth acts as a sieve allowing molecules through on the basis of size
where are Free ribosomes found?: in the cytoplasm
intermembrane space: - area between the inner and outer membrane of the mitochodrion
- has many cristae
- high in protein content including proteins of the electron transport chain
mitochondrial matrix: area bounded by the inner membrane site of many of the rxns in cell respiration.
what pH are the hydrolytic enzymes involved in intracellular digestion most effective?: pH of 5
mitochondria: sites of aerobic respiration with in the cell and therefore the suppliers of energy.
Endoplasmic Reticulum. what is its' function in the cell?: involved in the transport of materials throughout the cell especially those that are meant to be secreted from the cell
Rough ER (RER): - Endoplasmic Reticulum with ribosomes lining its' outer surface (bound ribosomes)
- involved in protein synthesis
Smooth Endoplamic Reticulum: - Endoplasmic Reticulum without ribosomes
- involved in lipid synthesis and detoxification of drugs and poisons.
How are protins synthesized by the bound ribosomes transported to the Golgi Apparatus?: (1) they cross into the cisternae of the RER where they undergo chemical modification.
(2) they then cross into the smoothe ER where they are secreted into cytoplasmic vesicles and transported to the Golgi Apparatus
Golgi Apparatus: - consists of a stock of membrane enclosed sacs
- receives vesicles and their contents from smooth ER
- modifies them, repackages them into vesicles and distributes them
- is particularly active in the distribution of newly synthesized materials to the cell surface
- produces secretory vesicles
What do Lysosomes do?: - they fuse with endocytotic vesicles thereby breaking down the material ingested by the cell.
- they also aid in renewing a cell's own components by breaking down the old one's and releasing their molecular building blocks into the cytosol for reuse
In comparison to vesicles vacuoles are larger where are they more likely to be found?: in plant cells(vacuoles)
Autolysis: process in which a cell in an injured or dying tissue "may commit suicide" by rupturing the lysosome membrane and releasing its' hydrolytic enzymes which will digest cellular contents
microbodies: membrane bound organelles specialized as containers for metabolic rxns
2 important types are perioxisomes and glyoxysomes
Perioxisomes: microbodies that contain oxidative enzymes that catalyze a class of rxns in which hydrogen peroxide is produces by the transfer of hydrogen from a substrate to oxygen.
- breaks down fats into smaller molecules that can be used for fuel
- also used in liver to detoxify compunds harmful to the body such as alcohol
Secretory vesicles: produced by the Golgi and releases their newly synthesized contents to the cell's exterior by exocytocis
vesicles and vacuoles: membrane bound sacs involved in the transport and storage of materials that are ingested, secreted processed or digested by the cell.
Lysosomes: - membrane bound vesicles
- contain hydrolytic enzymes involved in intracellular digestion
- has acidic environment compared to the neutral cytosol
Ribosomes: - sites of protein production
- synthesized by nucleolus
- consists of 2 subunits 1 large, 1 small
- each subunit is composed of rRNA and proteins
Where are bound ribosomes found?: lining the outer membrane of the endoplasmic reticulum (ER)
How are ribosomes synthesized?: by the nucleolus
what are the subunits of the ribosomes composed of?: rRNA and proteins
Endoplasmic Reticulum. What is it?: - network of membrane enclosed spaces connected at points with the nuclear membrane.
Why are mitochondria considered different from the other organelles?: - they are semiautonomous
- they contain their own DNA (circular) and ribosomes
- which enables them to produce sme of their own proteins and to self replicate by binary fission
Chloroplasts: - aka plastids
- found only in algae and plant cells
- contain chlorophyll
- site of photosynthesis
- contains own DNA ribosomes
- semiautonomous like the mitochondria
Cell walls: - protects cell from external stimuli and dessication
- plant cell wall composed of cellulose
- fungi cell wall composed of chitin
- animal cells do not have a cell wall
dessicate: to dry out thoroughly; removing moisture
microfilaments: solid rods of actin involved in cell movement as well as support
centrioles: - specialized microtubule involved in spindle organization during cell division
- not bounded by a membrane
- found in animal cells oriented at right angles to each other in the centrosome
- not found in plant cells
cytoskeleton: - gives cells mechanical support, maintains its shape functions in cell motility
- composed of microtubles, microfilaments and intermediate filaments.
microtubules: - hollow rods made up of polymerized tubulins that radiate throughout the cell and provide it with support.
cilia and flagella: specialized arrangements of microtubules that extend from certain cells and are involved in cell motility
what is a muscle contraction based on?: the interaction of actin with myosin in muscle cells
Give an example of how microfilaments are involved in cell movement?: they move materials across the plasma membrane for instance in the contraction phase of cell division and in amoeboid movement
Simple diffusion: - aka passive diffusion net movement of dissolved particles down their concentration gradients
*from a region of higher concentration to a region of lower concentration*
Intermediate filaments: collection of fibers involved in maintainance of cytoskeletal integrity
Osmosis: simple diffusion of water from a region of lower solute concentration to a region of higher solute concentration
What affects the direction of osmosis: the differnces in the concentration of substances to which the membrane is impermeable.
When is a medium hypertonic to the cell? what happens as a result?: when the cytoplasm of the cell has a lower solute concentration than the extracellular medium, as a result water will flow out causing the cell to shrink.
IOW: the extracellular medium has more solute than the cytoplasm.
when is a medium hypotonic to the cell?what happens as a result?: when the cytoplasm of a cell has a higher solute concentration than the extracellular medium. As a result water will flow in causing the cell to swell if too much wateer flows in the cell may lyse.
IOW: the etracellular medium has less solute then the cytoplasm.

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