Download Chapter 7: Cell Structure and Function

Chapter 7: Cell Structure and Function
A. Discovery of the Cell:
 Introduction of the Microscope
1. History:
 Hooke: observed cells of cork
 Van Leeuwenhoek: observed cells in pond water
 Schleiden: observed cells in plants
 Schwann: observed cells in animals
 Virchow: concluded that new cells can be produced from existing cells
2. Cell: basic unit of life
3. Cell Theory
a. All living things are composed of cells
b. Cells come from pre-existing cells
c. Cells are the basic unit for structure and function
 Are the smallest living part of the larger organism and function
collectively to keep the organisms alive
 cells -----› tissues -----› organs -----› organ systems -----› organisms
d. Exception to the cell theory = VIRUS
 They cannot reproduce without a host cell
 Contain genetic information
B. Types of Cells
1. Prokaryote:
 Generally small, simple cells
 Cell that contains DNA, but not contained in a nucleus
 Does not contain membrane-bound organelles
 Ex. bacteria
2. Eukaryote:
 Cells that contain membrane-bound organelles
 Genetic material is surrounded by a nucleus
 Ex. plant and animal cells
Animal Cell
Plant Cell
C. Eukaryotic Cell Structures
1. Organelles: cell structures that act as specialized “organs” that function
collectively (together) to keep the cell alive
2. Types of Organelles:
a. Cytoplasm:
 Liquid portion of the cell outside the nucleus
 Function is for transportation of materials around the cell
 Cyclosis: movement throughout the cytoplasm
b. Nucleus:
 Structure that contains DNA (genetic information) that has the
instructions for controlling cell activity
i. Nuclear Envelope: two-layered membrane that surrounds the
nucleus
ii. Chromatin: unwound DNA bound to protein
iii. Chromosomes: DNA that winds up forming “X” shaped
Structures when the cell prepares to divide
iv. Nucleolus: center of the nucleus that produces ribosomes
c. Ribosomes:
 Tiny particles of genetic information attached to the endoplasmic
reticulum that assembly proteins
 They read the DNA code and assemble proteins and enzymes by
putting together amino acids
d. Endoplasmic Reticulum (ER):
 Folded membrane where ribosomes attach to produce proteins
 Proteins produced by the ribosomes are then transported
through the ER to the Golgi Apparatus
e. Golgi Apparatus:
 A highly folded membrane that modifies, sorts, packages, and
stores proteins received from the endoplasmic reticulum
f. Lysosome:
 Contain enzymes that digest organic compounds into smaller units
to be used by the cell
 Breakdown old, worn-out organelles
 Lyse = to split
g. Vacuole:
 Saclike structure that store materials such as water
 Plants: usually have one very large vacuole
 Animals: several small vacuoles
 Paramecium: contractile vacuoles that pump out excess water
preventing the cell from bursting
h. Mitochondria:
 Converts chemical energy in food into energy that is used by the
cell
 Cellular respiration
i. Chloroplast:
 Convert sunlight into chemical energy
 “Solar power” for the plant cell
 PLANT CELLS ONLY
 Photosynthesis
 Chlorophyll: green pigment that captures the light energy
j. Cytoskeleton:
 Protein filaments that give the cell its shape
 “Bones” of the cell
k. Centrioles:
 Microtubules only in animal cells that help in cell division
l. Cilia and flagella:
 Function in the movement of the cell
 Cilia: hair-like projection along the cell membrane
 Flagella: single whip-like tail
3. Cell Boundaries
a. Cell Wall:
 Function to provide support and protection to the cell; rigid
 Lie outside the cell membrane
 Composed of carbohydrates (cellulose)
 Porous enough to allow water, oxygen, and carbon dioxide to pass
through
 Found in plant cells and other organisms but NOT ANIMAL CELLS
b. Cell Membrane:
 Function to regulate what enters and leaves the cell
 Thin, flexible barrier that provides some protection
 Lipid Bilayer: 2 layers of phosphates and lipids sandwiched together
i. Phosphate Heads: polar; face the outside watery
environment and the inside cytoplasm
ii. Lipid tails: non-polar; repel water, sandwiched between the
Phosphate heads so they don’t come in contact with water
and split the cell membrane apart
iii. Transport Protein/Protein Transport: structure that
allows substances to go in and out of the cell
***Selectively permeable: allows certain molecules to pass in
or out of the cell
iv. Receptor Molecules: structures on the outer surface of
the cell membrane; specific in shape and function; receive
signals from other cells; act like “antennas”
***Maintains Homeostasis by being Selectively Permeable***
D. Transport Through the Cell Membrane
1. Diffusion: movement of particles from and area of high concentration to an
area of low concentration
a. Equilibrium: when the particles stop moving (diffusing) because it is
equal throughout
2. Osmosis: diffusion of water; (in order to determine what will happen to the
cell, always consider the amount of water)
a. Isotonic solution: the concentration of water on both sides of the
membrane are the same
 no water movement
 Cell remains the same size
b. Hypotonic Solution: the cell contains less water than the solution it is
placed in
 Ex. Cell is placed in distilled water (98-100% water)
 Water will move in and the cell will swell (cells contain about 95%
water)
c. Hypertonic Solution: the cell contains more water than the solution it is
placed in
 Ex. Cell is placed in a 10% salt solution or sugar solution
 Water will move out and the cell will shrink
Isotonic
Hypotonic
Hypertonic
3. Facilitated Diffusion:
 Movement of molecules across the cell membrane through the protein
channels from an area of high concentration to an area of lower
concentration (diffusion)
 Protein channel acts as a “door” and “helps” (facilitates) the molecules
through the membrane
 NO ENERGY REQUIRED
4. Active Transport:
 The movement of molecules against the concentration gradient
 Movement from LOW to HIGH concentrations
 Requires protein pump
 REQUIRES ENERGY (ACTIVE)
 Ex. Amoeba must actively pump out freshwater so that it does not burst
(water tries to move in because the cell is in a hypotonic solution; in order
to maintain homeostasis the cell must actively transport the water out)
a. Endocytosis: cell membrane takes in larger molecules (too big to fit
through the protein transports) forming vacuoles around them and
pulling them into the cell; requires energy (ATP)
i. Phagocytosis: “cell eating”; single-celled organisms form food
vacuoles around particles and bring them into the cell
ii. Pinocytosis: cell membrane pinches in liquids from the
surrounding area forming tiny vacuoles that are brought into the
cell
b. Exocytosis: a vacuole containing large molecules within the cell fuses
with the cell membrane and forces out the contents; requires energy
(ATP)