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Types of Cells
Prokaryotic (bacteria) - lack a nucleus and other membrane bounded structures (simple)
Eukaryotic (plant and animal) - have a nucleus and other membrane bounded structures (more complex)
Why Are Cells So Small?
Cell volume to surface area ratios favor small size.
Nucleus to cytoplasm consideration (control).
Metabolic requirements.
Plasma Membrane
Separates the cell from the environment.
Regulates the movement of materials in/out of a cell.
Cytoplasm
Cell substance between the cell membrane and the nucleus.
The “fluid” part of a cell. Contains all organelles
Chromatin
Chrom: colored - tin: threads DNA and Protein in a “loose”
format. Will form the cell’s chromosomes.
Ribosomes
Structure: 2 subunits made of protein and ribosomal RNA (rRNA)
No membrane.
Function: protein synthesis.
Ribosome Locations
Free in the cytoplasm - make proteins for use in cytosol.
Membrane bound (attached to a membrane) - make proteins that are exported from the cell.
Endomembrane System Related membranes throughout the cell Nuclear envelope endoplasmic reticulum golgi apparatus lysosomes vacuoles plasma membrane
Endoplasmic Reticulum
Often referred to as the ER. Often continuous with
(connects to) the nuclear membrane.
Types of ER
Smooth ER: no ribosomes. Used for lipid synthesis,
carbohydrate storage, detoxification of poisons.
Rough ER: covered with ribosomes Makes secretory proteins.
Golgi Apparatus
Structure: parallel array of flattened cisternae. (looks like a stack of Pita bread)
Found close to the ER
Structure Has 2 Faces
Cis face - side toward the nucleus. Receiving side.
Trans faceface - side away from - side away from the nucleus. Shipping side.the nucleus. Shipping side.
Function of Golgi Bodies
Processing - modification of ER products
Distribution - packaging of ER products for transport. ER products packaged into vesicles
and shipped out
Group Questions
Which of the following structures would be found in a prokaryotic cell? A. Endoplasmic reticulum B. Ribosome C. Golgi apparatus D. Nuclear envelope E. Flagellum
Group Questions
Why are most animal cells, regardless of species, relatively small and about the same size? A. small cells avoid excessive osmosis and subsequent
lysis B. small cells have a small surface to volume ratio C. small cells have a large surface to volume ratio D. small cells require less energy E. small cells fit together more tightly
Group Questions
To manufacture the components of the plasma membrane, activity from all of the following are required EXCEPT: A. lysosomes B. rough ER C. mRNA D. Golgi apparatus E. vesicles
Group Questions
In the inherited disorder Pompe’s disease, glycogen breakdown in the cytosol occurs normally and blood glucose levels are normal, yet glycogen accumulates in lysosomes. This suggests a malfunction with: A. catabolic enzymes in the mitochondria B. anabolic enzymes in the lysosomes C. catabolic enzymes in the lysosomes D. membrane transport during exocytosis E. membrane transport during endocytosis
Group Questions
All of the following are membrane bound bodies in eukaryotic cells EXCEPT: A. lysosome B. mitochondrion C. endoplasmic reticulum D. nucleolus E. Golgi body
Vacuoles
Structure - single membrane, usually larger than the Golgi vesicles.
Function - depends on the organism. Pump out water Store food or water
Plant Vacuole
Large single vacuole when mature making up to 90% of the cell's volume.
Tonoplast - the name for the vacuole membrane.
Mitochondria Structure
2 membranes ATP generated at inner membrane
Matrix: inner space. Intermembrane space: area
between the membranes.
Mitochondria Functions
Cell Respiration - the release of energy from food.
Major location of ATP generation.
“Powerhouse” of the cell.
Mitochondria
Have ribosomes. Have their own DNA. Can reproduce themselves. May have been independent
cells at one time.
Chloroplasts
Contain ribosomes. Contain DNA. Can reproduce themselves. Often contain starch. May have been independent
cells at one time.
Cytoskeleton Functions
Cell structure and shape. Cell movement. Cell division - helps build cell
walls and move the chromosomes apart.
Cilia and Flagella
Cilia - short, but numerous. Flagella - long, but few. Function - to move cells or to
sweep materials past a cell.
Centrioles
Usually one pair per cell, located close to the nucleus.
Found in animal cells. Help in cell division.
Cytoskeleton
Very dynamic; changing in composition and shape frequently.
Cell is not just a "bag" of cytoplasm within a cell membrane.
Cell Wall
Nonliving “jacket” that surrounds some cells.
Found in: Plants Prokaryotes Fungi Some Protists
Extracellular Matrix - ECM
“Fuzzy coat” on animal cells. Helps glue cells together. Made of glycoproteins and
collagen.
Evidence suggests ECM is involved with cell behavior and cell communication.
Intercellular Junctions Join neighboring cells Plant cells
Plasmodesmata
Animal cells Tight junctions Desmosomes Gap junctions
Tight Junctions
Very tight fusion of the membranes of adjacent cells.
Seals off areas between the cells.
Prevents movement of materials around cells.
Desmosomes Bundles of filaments which
anchor junctions between cells.
Does not close off the area between adjacent cells.
Gap Junctions
Open channels between cells, similar to plasmodesmata.
Allows “communication” between cells.