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Cell Biology-MCAT


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Centrifugation can be used to separate cells or mixtures of cells without destroying them in the process.
Prokaryotes, such as cyanobacteria and bacteria, have an outer cell membrane but do contain membrane bound organelles. There is no true nucleus, instead DNA is concentrated in the nucleoid area. Also, plasmids (rings consisting of a few genes) can replicate independently and can allow the cell to survive harsh conditions.
Bacteria have a cell wall, a cell membrane and cytoplasm, ribosomes and flagella. Respiration occurs at cell membrane.
All multicellular organisms and non-bacteria unicellular organisms. Bound by a cell membrane and contain cytoplasm, the cytoplasm contains organelles. Organelles are suspended in a semi-fluid medium called cytosol. Genetic material consists of DNA organized into chromosomes, and located in the nucleus.
Cytosola is fluid component of cytoplasm, which is free of proteins, nutrients, and other solutes.
The cytoskeleteton is composed of mictrotubules, microfilaments, intermediate fiber, and other proteins, is in the cytosol. These fibers serve to give the cell shape, anchor the organelles, help with cell maintainance, and intracellular transport.
Fluid Mosaic Model
The Fluid Mosaic Model describes the cell membrane in the following way.
The cell membrane consists of a phospholid bilayer, with proteins embedded throughout.
Transfer Proteins
Transfer Proteins allow certain molecules to pass through the lipid bilayer, and span the lipid bilayer.
Cell Adhesion Molecules
Cell Adhesion Molecules contribute to cell recognition and adhesion and are very important in development.
Receptors are complex proteins embedded in membrane and have sites that bond with specific molecules in the cells external environment. The receptor may take the molecule into the cell via pinocytosis or it may signal across the membrane via a second messenger.
Carrier Proteins
Carrier Proteins help large charged molecules pass through the cell membrane.
Nuclear Membrane
The nuclear membrane is a double membrane that maintains a nuclear environment distinct from that of the cytoplasm.
Nuclear Pores
Nuclear Pores are interspersed through the nuclear membrane. Allow exchange of selected materials between the nucleus and the cytoplasm.
The nucleolus is dense structure in nucleus where synthesis of ribosomal RNA occurs.
Rough ER
ER with ribosomes lining its outer surface
Smooth ER
ER without ribosomes lining its outer surface
Secretory Vesicles
Secretory Vesicles are produced by the Golgi apparatus and release their contents to the cells exterior through a process of exocytosis.

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