Anatomy of Cells Typical Cell Typical Cell vs

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/endoplasmicreticulumfigure 1. jpg

Ribosomes • Attached to Rough ER or scattered throughout cytoplasm • Composed of a large and a small subunit – Each subunit contains RNA (r. RNA) 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 r. RNA

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 17 th Edition. Thibodeau, Gary A. Ph. D and Patton, Kevin T. Ph. D. Mosby, Inc.