Lecture 5 Flashcards
(17 cards)
Size of cells
0.5 μm to a few hundred micrometers
2 ways to see cells
- Light microscopes;use light to illuminate the specimen
- Electron microscopes use electrons to illuminate the specimen
Why are they so small?
- Cell limited to surface area to volume ratio
- The volume of a cell determines the amount of chemical activity that can take a place within the cell
Plasma membrane
- All cells are surrounded by the plasma membrane, a bilayer of lipids with embedded protein molecules
- Adds hydrophobic layer
Internal organization
- Genes are segments of DNA that code for individual proteins
- The cytoskeleton maintains cell shape and plays key roles in cell
division, chromosome segregation, and transportation within the cell
About Prokaryotic cell
- Three shapes are common among bacterial prokaryotes: spherical, rodlike, and spiral
- The nucleiod is in the cytoplasm
- Information from DNA is copied into messenger RNA (mRNA) molecules and carried to ribosomes in the cytoplasm, which assemble amino acids into proteins
- flagella the bacterial flagellum rotates in a socket and pushes the cell through a liquid medium
- Hairlike pili attach the cell to surfaces or other cells a special sex pilus joins bacteria during mating
About Eukaryotic cells
- The eukaryotes include animals, plants, fungi and protists
- Eukaryotic cytoplasm contains a system of membranous organelles, specialized to carry out functions of energy metabolism and molecular synthesis, storage, and transport
- The cytosol participates in energy metabolism and molecular synthesis and functions in support and motility
The Nucleus
- The nucleus is separated from the cytoplasm by the nuclear envelope, which consists of two membranes
- A channel through the nuclear pore complex, a nuclear pore, is the path for the assisted exchange of large molecules with the cytoplasm
Plasma membrane + cell wall
- The eukaryotic plasma membrane is responsible for many
Functions involving multiple types of integral membrane
proteins: - Channel proteins transport substances in and out of cells
- Receptors recognize and bind specific signal molecules in thecellular environment and trigger internal responses
- Immune system proteins label cells as “self”
Endomembrane system
- A series of interconnected organelles, that communicate with one another by Vesicles ,small membrane-bound sacs that transfer substances between parts of the system
- The components of the endomembrane system include:
*ER - Nuclear envelope
*GolgI apparatus
*Lysosomes
*Vacuoles
*Plasma membrane
Rough ER
- Many ribosomes on outer surface
- Proteins are then delivered to other regions of the cell (i.e. components of the endomembrane system such as golgi complex) using small vesicles that form from ER
Smooth ER
- 0 ribozymes
- Smooth er synthesizes lipids that become part of cell membrane
Golgi body
- stack of flattened, membranous sacs (cisternae)
- sorts transports and modifies both proteins and lipids
Endocytosis
- uptake of fluids or macromolecules in small vesicles
- Vesicles also form by the reverse process, endocytosis, which brings molecules into cell from exterior
Lysosomes
-pH significantly lower(ph=5) while cytosol is ph=7.2
- Lysosomal enzymes digest food molecules worn out organelles (autophagy) and materials engulfed by phagocytes(cells of immune system)
Mitochondria
- Cellular respiration occurs ;energy-rich food molecules are broken down to water and carbon dioxide by mitochondrial reactions, and energy is converted to ATP
- areobic
Cytoskeleton
-Interconnected system of protein fibers and tubes that extends throughout the cytoplasm
-The cytoskeleton maintains a cell’s characteristic shape and internal organization, and functions in movement
- The cytoskeleton of animal cells is comprised of microtubules, intermediate filaments, and microfilaments
