A&P: Ch 3: cellular form and function

Robert Hooke 

english scientist who created the word “cell” during the 17th century

cell theory 

All living organisms are composed of one or more cells: 

The cell is the basic unit of life

All cells arise from pre-existing cells 

cell shapes

Limit on cell size

an overly large cell cannot support itself,

may rupture

• For a given increase in diameter, volume increases more than surface

area

• Volume proportional to cube of diameter

• Surface area proportional to square of diameter

cell membrane

 act as a protective, selectively permeable barrier that separates the inside of the cell from the outside environment while controlling what enters and exits 

Composition: selectively permeable, transport, cell communication and recognition, provides structural support

Microvilli

increases surface area for absorption

Cilia

coordinated movement creates a unidirectional current that propels substances across cell surfaces 

Flagella

propels the cell

passive transport

lets small or balanced molecules slide naturally across the cell membrane (no ATP required)

active transport

forces molecules where the cell needs them, even if the area is already crowded (requires ATP)

 Simple diffusion

Net movement of particles from an area of high concentration to low concentration 

Diffusion through lipid bilayer

• Nonpolar, hydrophobic, lipid-soluble substances diffuse through lipid

layer

• Diffusion through channel proteins

• Water and charged, hydrophilic solutes diffuse through channel

proteins in membrane

• Cells control permeability by regulating number of channel

proteins or by opening and closing gates

Carrier mediated transport – specificity and saturation

Transport proteins in the plasma membrane that carry solutes from one side of the membrane to the other

facilitated diffusion

Facilitated diffusion is the passive movement of molecules or ions across a cell membrane through specific transmembrane proteins, moving from an area of high concentration to an area of low concentration without using cellular energy

Osmosis

the movement of water from high to low concentration

Osmotic pressure

amount of hydrostatic pressure required to stop osmosis

Endocytosis

 brings external materials into the cell by wrapping the cell membrane around them to form a small pocket. That pocket pinches off into a membrane-bound package called a vesicle 

Phagocytosis ("cell eating")

The cell engulfs large, solid particles or whole cells, such as immune cells destroying bacteria

Pinocytosis ("cell drinking")

The cell takes in surrounding extracellular fluid containing dissolved nutrients and small solutes.

Receptor-mediated endocytosis

Specific target molecules bind to dedicated receptor proteins on the cell surface before the membrane pinches inward.

Exocytosis

pushes internal materials out of the cell. A vesicle inside the cytoplasm moves toward the plasma membrane and fuses with it. The vesicle then opens up to release its contents into the fluid outside the cell. Cells use this process to export waste products, secrete hormones, and release neurotransmitters. 

Nucleus

 control center of the cell

Mitochondria

provides ATP to cell

Smooth er

 synthesizes lipids, processes toxins, and stores calcium ions.

Rough er

synthesize, fold, modify, and transport proteins destined for the cell membrane, other organelles, or export outside the cell 

Ribosomes

 synthesize proteins by translating genetic instructions from messenger RNA (mRNA) into chains of amino acids

Golgi apparatus

 packages, modifies, and sends proteins across cell or for secretion to send outside of the cell 

Centrioles

organize microtubule network. During mitosis, form the spindle and asters, form the bases of cilia and flagella

Lysosomes

breaking down old cell parts, foreign invaders, and complex molecules 

Peroxisomes

 enzymes detoxify a number of toxic substances. The most important enzyme, catalase, breaks down hydrogen peroxide.

Microtubules

support the cell and give it shape. Involved in intra cellular and cellular movements

Endosymbiotic theory

key organelles inside complex eukaryotic cells—specifically mitochondria and chloroplasts—originated as independent prokaryotic bacteria that were engulfed by a larger host cell. 

 Supporting evidence: 

Division: Mitochondria and chloroplasts reproduce independently through a splitting process very similar to bacterial binary fission.

DNA Structure: Both organelles contain their own circular DNA molecules, resembling bacterial chromosomes rather than the linear DNA found in eukaryotic nuclei. 

Membranes: Their inner and outer membranes share biochemical similarities and specific transport proteins (like porins) with modern bacteria.

osmosis

 the moment of water from high to low concentration

Histology

 study of the skin

Radiology

a medical specialty that uses imaging technology to diagnose and treat diseases inside the human body

 Auscultation

the medical practice of listening to the internal sounds of the body, usually using a stethoscope 

 Cytology

study of cells

 Hypertonic

• Higher solute level outside the cell.

• Water moves out of the cell.

• Cells shrink or shrivel

Hypotonic

• Lower solute level outside the cell.

• Water moves into the cell.

• Cells swell and can burst

Isotonic

-equal concentration of solute (ex. water) and solvent (ex salt)

- cell keeps shape

characteristics of life 

made of cells, use energy, grow, reproduce, respond to changes, keep internal balance, and adapt over time