Anatomy and Physiology

Cell Structure

Structure• Cell (plasma) membrane - The

selectively permeableselectively permeable outer boundary of a cell consisting of a phospholipids bilayer embedded with proteins.

• Nucleus - Cellular organelle that is enclosed by a double layer, porous membrane, and contains DNA.

• Cytoplasm - The entire contents inside of a cell excluding the cell membrane and nucleus. Cytosol - liquid portion

Cell Structure

• Shape differs according to cell function.

Cell Membrane• Encloses the cell.• Internal cell

membrane forms membrane of nucleus and organelles.

• Composed mainly of phospholipids and protein.

• Described as being a fluid mosaicfluid mosaic model.

• Lipid layer

Lipid Layer

• Heads are made of phosphate groups and are considered hydrophilic = water loving.

• Tails are made of lipid molecules and are considered hydrophobic = water fearing.

Lipid Layer

• Proteins are embedded on and in the lipid layer.

• Some are attached to the surface, inner layer, and all the way through.

Function of the Cell Membrane

• Receives information from other cells.

• Transportation of molecules into and out of cells.

• Recognizes cells as belonging to a particular person.– Tissue typing for transplants.

Organelles

• Endoplasmic Reticulum– Network of tunnels

throughout the cytoplasm of the cell.

– Miniature circulatory system for the cell.

• 2 Types– Smooth (SER)

• Synthesizes lipids

– Rough (RER) - has ribosomes

• Synthesizes proteins

Organelles

• Ribosomes– Function to make

proteins for the cell.

• 2 Locations– Free floating in

the cytoplasm.– Attached to

endoplasmic reticulum.

Organelles• Golgi Apparatus

– AKA Golgi Body or Golgi Complex

– Consists of tiny sacs stacked on top of one another.

– Synthesizes large carbohydrates and combines with proteins=glycoprotein

– Transport vesicles form, carrying substances to different parts of the cell.

Organelles• Mitochondria

– “Powerhouse of the cell”

– Consists of a double membrane wall.

– Inner membrane folds into extentions-cristae

– This is the site of cellular respiration for production of ATP - cellular energy molecule.

Organelles

• Mitochondria continued…

• The more work a cell completes, the more mitochondria.– Ex. Muscle cells

Organelles

• Lysosomes– “Suicide bags or

garbage disposals”

– Contain enzymes that break down cell parts.

– Destroy bacteria when it enters the body.

• White blood cells engulf bacteria and lysosomes destroy them.

Organelles

• Peroxisomes– Located in all

human cells but most abundant in liver cells.

– Among many functions, it helps in the detoxification of alcohol.

Organelles

• Centrioles– Appear as two

dots located near the nucleus.

– Forms spindle fibers during cell division (mitosis/meiosis).

Organelles• Cell Fibers

– Made of proteins

• Form a 3-D lattice which helps support the cell. (cytoskeleton)– Serves as the

muscle of the cell.

• Ex.- microfilaments and microtubules.

Organelles

• Nucleus– Largest cell

structure.– Contains DNA.– The center of

the nucleus contains the nucleolus.•Nucleolus

manufactures ribosomes.

Inclusions

•Lifeless chemicals •In a cell temporarily•Store

– Nutrients - glycogen and lipids– Pigments - ex. Melanin

• http://www.wiley.com/legacy/college/boyer/0470003790/animations/cell_structure/cell_structure.htm