Chapter 7
Need to Know!!!
Microscopes:
Compound light: good for living specimens, limit of 1000X
Electron: much greater detail, specimen can not be living
Transmission: electrons pass through specimen, flat image
Scanning: electrons scan surface, produce 3D image
The cell theory is the basic framework in which biologists try to understand living
things:
1. all living things are composed of cells
2. cells are the basic units of structure & function in living things
3. all cells come from pre-existing cells
4. Energy flow occurs within cells.
5. Heredity information (DNA) is passed on from cell to cell.
6. All cells have the same basic chemical composition.
Structures:
3 basic structures common to all cells:
cell membrane
genetic material
cytoplasm
Eukaryotic- cells that have DNA enclosed in nucleus
Prokaryotic- cells that do not have genetic material inside a nucleus
1. cell membrane: fluid mosaic model- phospholipid bilayer with carrier proteins
embedded and carbohydrates attached for ID; constantly changing
a. as a cell increases in size its vol increases faster than surface area so
smaller cells more efficient
b. controls what enters & exits cell
c. support & regulation
d. Semipermeable, protein channels & pumps to assist in crossing membrane
e. phospholipid heads- hydrophilic
f. phospholipid tails- hydrophobic
g. cholesterol wedged between the phospholipid molecules
2. cell wall: found in plant cells & some prokaryotes
a. structural support
b. Primary cell wall is composed of pectin.
c. secondary cell wall – several layers of cellulose
3. centriole: located near the nucleus and help to organize cell division (spindles)
Centrioles are not found in plant cells.
4. chloroplast: in plants, contain photosynthetic pigments that turn light, CO2 and
H2O into glucose
a. site of photosynthesis
5. chromosome: packaging of DNA in nucleus. Functions in cell division
6. cilia: on outside of cell, move materials past cells (e.g. in bronchi and kidney
tubules) or used in locomotion.
7. cytoskeleton: internal framework of filaments & tubules that support the cell and
move substances in cell and anchor organelles. Composed of:
a. microfilament: fibrous protein (actin) filaments used for structural support
(e.g. cytoskeleton) and anchoring.
b. microtubule: tubes of protein monomers (tubulin) used in cilia, flagella,
cytoskeleton
8. flagella: long whip like tail used for locomotion in sperm cells and some single
celled organisms
9.
Golgi body: for packaging, modification, secretion of substances for export
inside and outside the cell.
a. Proteins produced in the rough ER move next into the Golgi apparatus
which appears as a stack of flattened membranes.
b. The Golgi apparatus modifies, sorts, and packages proteins and other
materials from the ER
c. Golgi is extensive in secretion cells!
10. lysosomes: contain hydrolytic enzymes
a. Digests macromolecules, recycles : damaged cells, foreign particles,
“clean up crew”
11. mitochondria: make energy for the cell by converting O2 and glucose to CO2,
H2O and ATP
a. site of cellular respiration- produces ATP for cellular energy
b. 2 membranes: outer membrane-smooth
inner membrane-convoluted,
folds known as cristae- increase surface area
c. The number of mitochondria per cell depends on metabolic activity
12. nucleolus: site of ribosome production in nucleus.
13. nucleus: contains nearly all the cell’s DNA (chromatin) , the coded instructions
for making proteins
a. controls cell activities including cell division.
b. The nucleus is surrounded by a nuclear envelope composed of two
membranes.
c. Nuclear envelope is dotted with thousands of nuclear pores, which allow
material to move into and out of the nucleus.
14. plastids: special plant organelles such as a chloroplast
15. ribosome: site of protein synthesis
a. small particles of RNA and protein found throughout the cytoplasm in all
cells & studded on the rough endoplasmic reticulum in some cells
b. protein synthesis- following coded instructions that come from DNA.
16. rough endoplasmic reticulum: anchors ribosomes in protein synthesis, accepts and
modifies newly transcribed proteins and sends to Golgi apparatus
a. extensive network of membranes continuous with nuclear envelope
b. found in Eukaryotic cells
c. Many types of cells: pancreatic cells
17. smooth endoplasmic reticulum: Ribosomes- not found on surface
a. Enzymes important in synthesis of lipids including phospholipids &
steroids and the detoxification of drugs
b. types of cells: testes, ovaries, liver
18. vacuoles: large vesicles used for storage
a. plant cells have large water vacuole
19. vesicle: membrane-bound sacs for transporting materials in, around, and out of
the cell, also used for storage of various materials
Chloroplasts and mitochondria contain their own genetic information in the form of small
DNA molecules.
Movement of Materials through the cell membrane:
Passive Transport
Diffusion: Molecules move from an area of higher concentration to area of lower
concentration due to random motion of particles. No energy expended by cell.
Facilitated Diffusion: passive transport no energy expended by cell. Molecules move
from an area of higher concentration to area of lower concentration with help of a
carrier protein. Ex. glucose
Osmosis: Type of facilitated diffusion. Water molecules move from an area of higher
concentration to area of lower concentration. No energy expended by cell. Use
aquaporins to pass thru membrane.
contractile vacuoles-help pump water out of cells to compensate for osmotic
pressure
cells in hypertonic sol: water moves out cells shrink
cells in hypotonic sol: water moves into cells causing them to burst
Active Transport: energy requiring. Molecules form an area of lower concentration to
area of higher concentration.
Common molecules that will use active transport: Ca, Na & K.
Contractile vacuoles are a form of active transport also molecular pumps.
Types of active transport:
Endocytosis
Phagocytosis- type of endocytosis, extensions of cytoplasm
surround solid particle and bring into cell
Pinocytosis-bringing in pockets of liquid in same way
Exocytosis- forcing contents out of the cell
Solutions: strength refers to the amount of solute not water: tonicity
Isotonic- concentrations are the same on both sides
Hypertonic- more concentrated solute, cells shrink
Hypotonic- less concentrated solute, cells swell
Cell Specialization:
Differentiation: cells begin as stem cells but differentiate as specific cells according to
their own function
Cells need to communicate to work together
Pancreas: large numbers of organelles that produce proteins and enzymes.
Eyes: contain light sensitive cells with the pigment rhodopsin & many mitochondria
Lungs: “sweeper cells”- have cilia, alveoli-increase surface area of lungs for greater air
exchange
Levels of Organization:
1st level: Cells
2nd level: Tissues- group of similar cells that perform similar function
3rd: Organs- a group of tissues that work together to perform similar function. Many types
of tissues may be used.
4th: Organ Systems- group of organs that work together to perform a function. Muscular,
skeletal, circulatory & nervous.
Cellular communication:
Cells in multicellular organism communicate by chemical signals
To respond to a chemical signal a cell needs to have a receptor (lock & key)
Gap junction- allow for communication to many cells