anatomy of cells. “typical” cell “typical” cell vs. reality “typical” cells do not...
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Anatomy of Cells
“Typical” Cell
“Typical” Cell vs. Reality• “Typical” cells do not actually exist in
the body• Cell are specialized structure to carry out
specialized functions (see Table 3-1, pg. 73)– Nerve cells: have long extension transmit
nerve impulses throughout the body– Muscle cells: contain fibers that slide
together contracts/movement of body parts
– RBCs: contain hemoglobin carry oxygen from lungs to various parts of the body
Main Components of Cell Structure
1. Plasma Membrane2. Cytoplasm
– Cytosol (intracellular fluid)– Organelles
3. Nucleus 4. Cytoskeleton
– Cell’s internal supporting framework
Plasma Membrane1. Phospholipid bilayer
• Hydrophilic heads• Hydrophobic tails
• Majority of membrane is hydrophobic – water and water-soluble molecules cannot pass
• Cholesterol – steroid lipid; provides stabilization for the plasma membrane
Plasma Membrane
2. Embedded proteins • Penetrate into the hydrophobic regions
of the plasma membrane• Transport mechanism
• Transport proteins are often specific for certain molecules
• “Gates” can open or close
Plasma Membrane
3. Peripheral Proteins• Glycoproteins (carbohydrates and
proteins)• Identification markers• Recognize self vs. non-self (immune system)
• Receptors• Proteins that react in the presence of
hormones or other regulatory chemicals• Trigger metabolic changes within the cells• Signal transduction
Cytoplasm
• Cytosol– Watery solution– Intercellular fluid (ICF)
• Organelles– “tiny organs”– Thicken the cytosol to a gel-like
consistency
Endoplasmic Reticulum • Rough ER
– Presence of ribosomes
– Protein synthesis– Intracellular transport
• Smooth ER– Lipid and
carbohydrate synthesis
– Replenishes cell membrane material
http://micro.magnet.fsu.edu/cells/endoplasmicreticulum/images/endoplasmicreticulumfigure1.jpg
Ribosomes• Attached to Rough ER
or scattered throughout cytoplasm
• Composed of a large and a small subunit– Each subunit contains
RNA (rRNA) bonded to protein
• Function – Protein synthesis – Cell’s “protein factory”
Golgi Apparatus• Consists of tiny
sacs or cisternea• “processing &
packaging plant”– Export proteins
make in the Rough ER out of the cell
– Secretion – Fig 3-5, page 81
Lysosomes
• Vesicles that have pinched off from the Golgi apparatus
• Contain enzymes capable of breaking down cell components
• “digestive bags” or “cellular garbage disposals”– Ex: rid cells of bacteria; Scavenger
WBCs
Peroxisomes
• Similar to lysosomes• Small sac containing enzymes• Important in kidney and liver cells
– Detoxification functions in the body
Mitochondria • Structure:
– Two membranes (sac within a sac)– Inner membrane contains folds (cristae)
• Function:– Enzymes embedded in cristae – essential in
making adenosine tri-phosphate (ATP)– Cell “power plant”– # of mitochondria based on amt of work done
by cell• Ex: liver cells > sperm cells
– Self-replicating – based on energy needs• Aerobic exercise increases # of mitochondria in
skeletal muscle cells
Mitochondria
Nucleus • Large, spherical organelle• Enclosed by a two nuclear membranes
= nuclear envelope • Nuclear pores – selectively allow
molecules to enter/leave nucleus • Contains DNA (genetic information)
– Chromatin – uncondensed genetic material– Chromosomes – condensed genetic
material
• Nucleolus – synthesizes rRNA
Nucleus
Cytoskeleton • Cell Fibers
1. Microfilaments • “Cellular muscles”• Thin, twisted strains of protein• Can contract (ex: muscle cells)
2. Intermediate Filaments• slightly thicker• Main component of the supporting framework
in many cell types
3. Microtubules• Thickest of the cell fibers; tiny, hollow tubes• Cell “engine” – help with movement within
the cell and the cell itself
Cytoskeleton• Centrosome
– Located near the nucleus– “microtubule-organization center”– Important role in cell division – move
chromosomes around the cell
• Centrioles– Cylindrical structures within the
centrosome– Replicate prior to cell division– Roles in cell division
Cell Extensions• Microvilli
– Epithelial cells found where absorption is necessary (ex: small intestine)
– Increase surface area• Cilia
– Transport fluid across a cell surface– Ex: Line the respiratory tract – move mucous
upward– Ex: Assist the ovum to move towards the
uterus• Flagella
– Single, long structures; aids in locomotion– Ex: sperm cells
Anthony’s Textbook of Anatomy and Physiology 17th Edition.
Thibodeau, Gary A. PhD and Patton, Kevin T. PhD. Mosby, Inc.