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.