anatomy of cells. “typical” cell “typical” cell vs. reality “typical” cells do not...

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.