Organization of the cell Flashcards
The cell theory holds that…
1) Cells are the basic living units of organization and function in all organisms. 2) All cells come from other cells.
Essential similarities of all cells are…
Every cell is surrounded by a plasma membrane that separates it from its external environment. Cells hace many organelles. All cells have similar mechanisms for information transfer and chemical reactions that convert energy from one form to another.
What is the functional significance of cell size and shape?
A critical factor in determining cell size is the ratio of the plasma membrane (surface area) to the cell’s volume. The plasma membrane must be large enough relative to the cell volume to regulate the passage of materials into and out of the cell. For this reason, most cells are microscopic. The size and shape of a cell are largely dictated by the functions it must perform.
Prokaryotic cells…
Are enclosed by a plasma membrane but have little or no internal membrane organization. They have a nuclear area rather than a membrane-enclosed nucleus. Prokaryotic cells typically have a cell wall and ribosomes, and may have propeller-like flagella.
Eukaryotic cells…
Have a membrane-enclosed nucleus, and their cytoplasm contains a variety of organelles; the fluid component of the cytoplasm is the cytosol.
Difference between plant and animal cells
Plant cells differ from animal cells in that plant cells have rigid cell walls, plastids, and large vacuoles, which are important in plant growth and development.
Function of cell membranes
They divide the eukaryotic cell into compartments allowing it to conduct specialized activities within small areas of the cytoplasm. Small membrane-enclosed sacs, called vesicles, transport materials between compartments. They are important in energy storage and conversion. They are also work surfaces for certain chemical reactions.
The nucleus
It contains genetic information codec in DNA. It is bounded by a nuclear envelope, consisting of a double membrane perforated with nuclear pores that communicate with the cytoplasm.
DNA within associates with protein to form chromatin, which is organized into chromosomes. DNA also transcribes its information in messenger RNA molecules, which enter the cytoplasm to provide information for protein synthesis by ribosomes.
The nucleolus is a region in the nucleus that is the site of ribosomal RNA synthesis and ribosome assembly.
Smooth endoplasmic reticulum
It is a network of folded membranes in the cytosol. Is the site of lipid synthesis, calcium ion storage and detoxifying enzymes.
Rough endoplasmic reticulum
Is studded along its outer surface with ribosomes that manufacture polypeptides. Polypeptides synthesized may be moved into the ER lumen, where they are assembled into proteins and modified by the addition of a carbohydrate or lipid.
The Golgi complex
It consists of stacks of flattened membranous sacs called cisternae that process, sort, and modify proteins synthesized on the rough ER. It also manufactures lysosomes.
The trace path of proteins synthesized in the rough endoplasmic reticulum as they are processed, modified and sort by the Golgi complex.
Glycoproteins are transported from the ER to the cis face of the GC by transport vesicles, which are formed by membrane budding. The GC modifies carbohydrates and lipids that were added to proteins by the ER and packages them in vesicles. These glycoproteins exit the GC through vesicles that are formed at its trans face. The GC routes some proteins to the plasma membrane for export from the cell. Others are transported to lysosomes or other organelles.
Lysosomes
They contain enzymes that break down worn-out cell structures, bacteria and debris taken into cells.
Vacuoles
They store materials, water and wastes. They also mantain hydrostatic pressure in plant cells.
Peroxisomes
They are important in lipid metabolism and detoxify harmful compounds such as ethanol. They produce hydrogen peroxide, but contain the enzyme catalase, which degrades this toxic compound.
