34 terms

Biology 8

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osmosis
diffusion of water through a selectively permeable membrane
isotonic solution
A solution in which the concentration of solutes is essentially equal to that of the cell which resides in the solution.
hypotonic solution
in cells, solution in which the concentration of dissolved substances is lower in the solution outside the cell than the concentration inside the cell; causes a cell to swell and possibly burst as water enters the cell
hypertonic solution
in cells, solution in which the concentration of dissolved substances outside the cell is higher than the concentration inside the cell; causes a cell to shrink as water leaves the cells
passive transport
movement of particles across cell membranes by diffusion or osmosis; the cell uses no energy to move particles across the membrane
facilitated diffusion
passive transport of materials across a plasma membrane by transport proteins embedded in the plasma membrane
active transport
energy-expending process by which cells transport materials across the cell membrane against a concentration gradient
endocytosis
active transport process where a cell engulfs materials with a portion of the cell's plasma membrane and releases the contents inside of the cell
exocytosis
active transport process by which materials are secreted or expelled from a cell
What factors affect the diffusion of water through a membrane by osmosis?
The permeability of the membrane and the amount of water on each side of the membrane. If there is less water on one side, the water will diffuse to that side to even out the concentration of both sides.
How do animals cells and plant cell react differently in a hypotonic solution?
In a hypotonic solution, animal cells expand and burst. Plant cells also expand but don't burst because of the cell wall.
Compare and contrast active transport and facilitated diffusion.
Both require transport proteins for substances to move through. However, in facilitated diffusion, the direction of movement is still from areas of high concentration to low concentration and therefore no energy needs to be added to the system. In active transport, molecules can be moved against the concentration gradient with the addition of energy to the system.
How do carrier proteins facilitate passive transport of molecules across a membrane?
Carrier proteins facilitate passive transport of molecules across a membrane by changing its shape to allow a substance to pass through the membrane.
A paramecium expels water when it is in freshwater. What can you conclude about the concentration gradient in the organism's environment?
The organism's environment has a larger concentration of solute then the paramecium has inside its cell membrane.
chromosome
cell structures that carry the genetic material that is copied and passed from generation to generation of cells
chromatin
long strands of DNA found in the eukaryotic cell nucleus; condense to form chromosomes
cell cycle
series of events that cells go through as they grow and divide
interphase
cell growth phase where a cell in creases in size, carries on metabolism, and duplicates chromosomes prior to division
mitosis
period of nuclear cell division in which two daughter cells are formed, each containing a complete set of chromosomes
prophase
first and longest phase of mitosis where chromatin coils into visible chromsomes
sister chromatid
identical halves of a duplicated parent chromosome formed during the prophase stage of mitosis; the halves are held together by a centromere
centromere
cell structure that joins two sister chromatids of a chromosome
centriole
in animal cells, a pair of small cylindrical structures composed of microtubules that duplicate during interphase and move to opposite ends of the cell during prophase
spindle
tiny fibers that are seen in cell division
metaphase
short, second phase of mitosis where where doubled chromosomes move to the equator of the spindle and chromatids are attached by centromeres to a separate spindle fiber
Describe how a cell's surface area-to-volume ratio limits its size.
A cells size determines it's function. for example, a nerve cell could not fit through a vein, blood vessel, etc. because its too big, unlike a blood cell, which is completely round and small-easily fitting into the vessel.
Why is it necessary for a cell's chromosomes to be distributed to its daughter cells in such a precise manner?
It is necessary because chromosomes contain genetic material such as DNA which is used to create proteins necessary for the cell. When chromosomes do not split in anaphase, it is called non-disjunction leaving one cell with to many chromosomes and one with not enough chromosomes. This will lead to both the daughter cells dying.
Relate cells to each level of organization in a multicellular organism.
The first level of organization are living cells, the smallest units of all living things. The second level of organization are tissues, which are groups of cells working together. The next level of organization is an organ, groups of tissues working together to perform a specific activity in the organism. Then there are organ systems, which are groups of organs that work in unison to perform a specific function for the body. Lastly, an organism, a group of organ systems put together to make a fully functional multicellular organism.
In multicellular organisms, describe two cellular specializations that result from mitosis
Cell growth and reproduction
At one time, interphase was referred to as the resting phase of the cell cycle. Why do you think this description is no longer used?
Interphase is no longer referred to as the 'resting phase' of the cell cycle because the cell is actually still functioning during this phase; it is preparing for mitosis. The cell grows and works as normal, as well as replicating its DNA ready for the next mitotic division.
cancer
malignant growth resulting from uncontrolled cell division
gene
segment of DNA that controls the production of a protein
Do all cells complete the cell cycle in the same amount of time?
No
Describe how enzymes control the cell cycle.
The cell cycle is controlled by enzymes that are attach to the cycling system. If a certain enzymes has failed to produce, the cell will lose control of the cell cycle.
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