A&P Chapter 3

Question 1

3.1 Describe the cell theory and the process of cellular differentiation. p. 95

Answer 1

Cell theory:

1. Cells are the building blocks of all plants and animals
2. All new cells come from the division of pre-existing cells
3. Cells are the smallest living units that carry out all vital functions

Cellular differentiation is a process of gradual specialization of cells during which daughter cells begin to develop specialized structural and functional characteristics to that form the tissues of the body (epithelial, connective, muscle, nervous)

Question 2

3.2 Describe the cell and its organelles, including the structure and function of each. p. 96

Answer 2

Cells consist of:

• plasma membrane - separates cytoplasm from interstitial/extracellular fluid
• cytoplasm - material between the the plasma membrane and the membrane around the nucleus (cytosol + organelles)
• cytosol - intracellular fluid
• organelles - intracellular structures within the cytosol that perform specific functions (membranous or non-membranous)

Membranous Organelles:
- cytoskeleton, microvilli, centrioles, cilia, flagelle, ribosomes

Nonmembranous Organelles:
- mitochondria, nucleus, endoplasmic reticulum, golgi apparatus, lysosomes, peroxisomes

Question 3

Identify the membranous organelles, and describe their functions.

Answer 3

- Mitochondria 
structure = double membrane, with inner membrane folds enclosing important metabolic enzymes
function = produces 95% of the ATP required by the cell

- Nucleus
structure - a fluid nucleoplasm containing enzymes, proteins, DNA, and nucleotides; surrounded by a double membrane, the nuclear envelope
function - controls metabolism, stores and processes genetic information, controls protein synthesis

- Endoplasmic reticulum
structure = network of membranous sheets and channels extending throughout the cytoplasm
function - synthesis of secretory products; intracellular storage and transport; detoxification of drugs or toxins
1. Smooth ER, which has no attached ribosomes, synthesizes lipids and carbohydrates
2. Rough ER, which has ribosomes bound to the membranes, modifies and packages newly synthesized proteins

- Golgi apparatus
structure = stacks of flattened membranes (cisternae) containing chambers
function = stores, alters, and packages synthesized products

- Lysosomes
structure = vesicles (membranous sacs) containing digestive (oxidative) enzymes
function = breakdown of organic compounds and damaged organelles or pathogens 

- Peroxizomes
structure = vesicles (membranous sacs) containing degradative enzymes 
function = breakdown of organic compounds; neutralization of  toxic compounds generated in this process

Question 4

3.3 describe the structural and functional features of the plasma membrane. p. 98

Answer 4

The plasma membrane is a selectively permeable barrier that separates the inside of the cell from the surrounding extracellular fluid.
It’s a thin and delicate phospholipid bilayer, with each half-layer consisting of a hydrophilic head at the surface and a hydrophobic tail at the middle.
Structural features include:
- integral (transmembrane) proteins - SOME contain pores and channels through which waters and solutes may pass. Integral proteins greatly outnumber peripheral proteins.
- peripheral proteins - bound to the inner or outer layer of the plasma membrane; may have regulatory or enzymatic functions. (Easily separated from the surface, like sticky notes)
- glycocalyx - a layer of superficial membrane carbohydrates that is important in cell recognition, binding to extracellular structures, and lubrication of the cell surface
- cholesterol - stiffens the plasma membrane to make it less fluid and permeable; an important component of plasma membranes; almost one cholesterol molecule for each phospholipid molecule.

Question 5

3.4 Differentiate among the structures and functions of a cytoskeleton p. 100

Answer 5

3 types of fibers:
Microfilaments
Intermediate filaments
Microtubules

Centriole - 9 groups of microtubule TRIPLETS form a short cylinder
Cilia - 9 groups of microtubule DOUBLETS form a cylinder (motile or primary)
Flagella - same microtubule structure as motile cilia but are longer and beat in a wavelike fashion (sperm)