Transcript Anatomy of Cells

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 Membrane
2. Cytoplasm
– Cytosol (intracellular fluid)
– Organelles
3. Nucleus
4. Cytoskeleton
– Cell’s internal supporting framework
Plasma Membrane
1. 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
• Structure:
Mitochondria
– 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
• Microvilli
Cell Extensions
– 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.