Download THE CELL – Chapter 3

THE CELL – Chapter 3
There are three main parts of the cell:
1. cell membrane
2. cytoplasm
3. nucleus
I. Cell Membrane
A. outermost limit of the cell
B. extremely thin
C. made of 3 layers—protein, lipid, protein
D. selectively permeable (semi) – allows some things through and not others
1. gases and nutrients pass through pores
E. intercellular junctions – connect cells
1. desmosone – holds adjacent skin cells together
2. gap junctions – tubular channels like in heart cells
II. Cytoplasm – contains organelles
A. Endoplasmic reticulum
1. canal system or network which connects the cell membrane to nuclear
membrane
2. function is the diffusion of materials for metabolism
3. functions in the synthesis of protein and lipid molecules
4. ER that has ribosomes is called rough ER; do not have ribosomes called
smooth ER
B. Ribosomes
1. small round bodies attached on the ER
2. function – site of protein synthesis (makes the proteins for life)
C. Golgi apparatus
1. flattened membranous sacs near the nucleus
2. function – refines and packages proteins resulting in glycoproteins
D. Mitochondria
1. rod-shaped bodies located throughout the cytoplasm
2. function – site of cellular respiration
3. cristae – inner foldings which increase the surface area for reabsorption
E. Lysosomes
1. membranous sacs called suicide sacs
2. functions as a phagocyte which engulfs and destroys foreign matter
F. Peroxisomes
1. membranous vessels that resemble lysosomes
2. function – produces peroxidase – an enzyme necessary for cell function
G. Centrosome
1. a central body located near the nucleus – a special zone of cytoplasm
2. function – cell division
H. Vacuoles - considered inclusions
1. membranous sacs that vary in size
2. function – stores food and water
I. Microfilaments and Microtubules
1. Microfilaments are tiny rods of protein and move the cell – like in muscle.
2. Microtubules – long, slender tubes – help to maintain shape and also aid in
moving
J. Inclusions – lifeless, often temporary, substances in the cell (granule)
III. Cell Nucleus
A. Function:
1. Controls and regulates metabolic activities
a. making protein
b. breaking sugar
2. Plays the leading role in cell division
B. Parts:
1. nuclear membrane – double membrane of protein and fat
2. Nucleolus – small, dense body, rich in RNA
3. Chromatin (chromosomes) – DNA + protein
4. Nucleoplasm – protoplasm inside nucleus
IV. Five major materials of protoplasm in the cell
A. Water
B. Electrolytes (ions)
C. Protein
D. Fat
E. Carbohydrate
Physical processes by which materials move through the cell membrane:
A. Diffusion – random movement of particles from an area of greater to lesser
Concentration
Example 1. oxygen and carbon dioxide move in and out of blood
Of
2. nutrients move in and out of cell
Diffusion 3. all movement of materials to and from a fetus
B. Facilitated Diffusion – when special carrier molecules on the surface of the membrane
combine with glucose
C. Osmosis – diffusion of water through a semi-permeable membrane
1. Three types of osmotic solutions:
a. isotonic-same amount of water outside cell as inside and there is equilibrium
b. hypertonic-when the solution has less water than the cell-water leaves the cell
and the cell shrinks
c. hypotonic-when solution has more water than the cell-water moves into cell
and cell swells
2. Osmotic pressure is the difference in concentration of particles, and this pressure
creates movement and water moves toward more particles
D. Filtration-molecules are forced through membranes by hydrostatic pressure and blood
pressure that is greater on one side of the membrane than on the other.
E. Active transport- a process by which energy is required to take place, and it moves
from lesser to greater—40% of cell’s energy is used for active transport.
F. Pinocytosis-cell drinking when taking in droplets of liquids – a portion of a cell
membrane is indented.
G. Phagocytosis – cell eating – a solid material is taken into the cell, characteristic of
white blood cells.
Mitosis
I. Cell Differentiation
1. a human begins as a single cell
2. during development, the cells begin to specialize and this is called differentiation
3. mechanaism involves DNA’s instruction
4. there seem to be “switch on” and “switch of” factors involved
II. Control of Cell Reproduction
A. Skin cells, blood-forming cells, and cells that line the intestine reproduce
throughout life
B. Nerve cells never reproduce
C. Growth-inhibiting substances
D. surface-volume relationship—a cell will accommodate what enters it, and if not,
it will divide. (All cells do not divide.)
III. Cancer-a group of closely related diseases that have the following characteristics:
1. Hyperplasic –uncontrolled reproduction of cells
2. Anaplasia – used to describe the appearance o abnormalities in cellular structure
3. Metastasis – tendency to spread (malignant)
4. Cause remains unknown
5. When untreated, cancer cells occur in large numbers and obstruct function
6. Treatment is: surgical removal, drugs, radiation