06Feb17 Biology (Chapter 3)
06Feb17 Biology (Chapter 3)
Cell Structure and Function (Chapter 3)
Cells as Life's Fundamental Unit
With the possible exception of viruses, every form of life on Earth either is a cell or is composed of cells (unified cell theory)
Cells come into existence only through the activity of other cells
How Cells are studies
A microscope is an instrument that magnifies an object
Types of Microscopes: Light Microscope
In 1665 ,Robert Hooke coined the term "cell"
In 1670, van leeuwenhoek discovered bacteria
in 1830 scholedin and schran?? brought about the unified cell theory
Prokaryotic and Eukaryotic Cells
All cells can be classified as prokaryotic or eukaryotic
Prokaryotic cells are bacteria or other single celled organisms
have most of their DNA contained in a membrane-lined compartment called the cell nucleus; prokaryotic cells do not have a nucleuse
Tend to e much larger than prokaryotic cells by a factor of 10 to 100
Have more specialized internal structures called organelles than do prokaryotic cells (both types have ribosomes
The Eukaryotic Cell
There are 5 principal components to the eukaryotic cell
Contains all genetic information of the cell (aka DNA)
Tiny organs within the cell that carry out specialized functions, such as energy transffer, material recycling, and protection
Jelly-like fluid outside the nucleus in which these organelles are immersed.
This should not be confused with the cytoplasm, which is the region of the cell inside the plasma membrane but outside he nucleus.
network of protein filaments.
It functions in cell structure, cell movement, and the transport of materials within the cell.
is the outer lining of the cell
A membrane can be defined as the flexible chemically active outer lining of a cell or its components.
Tour of the Animal cell's protein production path
Information for the construction of proteins is contained in the DNA located in the cell nucleus.
The protein production path
This information is copied onto a length of
RNA (mRNA) that departs the cell nucleus through its nuclear pores and goes to the sites of protein synthesis, structures called
, which lie in the cytoplasm.
polypeptic chains produced by the ribosomal "reading" of the mRNA sequences are dropped from ribosomes into the internal spaces of the rough endoplasmic reticulum.
There the polypeptide chains folded up, thuse becoming proteins, and undergo editing.
Once protein processing is finished in the rough ER, proteins undergoing processing move, via transport vesicles, to the Golgi Complex (apparatus).
Cell structures outside the protein production path
The smooth endoplasmic reticulum is a network of membranes that functions to synthesize lipids and to detoxify potentioally harmful substances.
organelles that break down worn0out cellular structures or foreign materials that come into the cell
Once this digestion is compleed by the LYSOSOMES, the lysosomes return the molecular components of these materials to the cytoplasm for further uses through cellular recycling.
Diffusion, gradients, and osmosis
concentration gradient efines the difference between the highest and lowest concentrations of a solute within a given medium
Through diffusion, compounds naturally move from higher to lower concentrations, meaning down their concentration gradients
Energy must be expended to move compounds against their concentration gradients, meaning from a lower to a higher concentrations.
net movement of water across a semipermeable membrane from an area of lower solute concentration to an are of higher solute concentration
Osmosis is a major force of living things; it is responsble for much of the movement of fluids in and out of cells.
can couse cells either to dry out from losing too much water or, in the case of animals cells, to break from taking too much water in
Plant cells generally do not have this problem because their cell walls limit their uptake of water
Cells will gain or lose water relative to their surrounding in accordance with what the solute concentration is inside the cell as opposed to outside it. If ther is no difference , the cell is said to be isotonic.
A cell will lose water to a surrounding solution that is hypertonic - a solution that has a greater concentration of solutes in it thn does the cell's cytoplasm
A cell will gain water when the surrounding solution is hyper(something) to the surrounding fluid
The plant cell
Plant cells have three structure not found in animal cells:
A cell wall
gives the plant structural strength andhelps regulate the intake and retention of water
a large centra vacuole
stores nutrients and degrades waste products
the organelles called choloroplasts
the sites of photosynthesis.
plant cells have most of the structures found in animal cells - ribosomes, a cell nucleus, a rough ER, and so forth- although plant cells do NOT have lysosomes found in animal cells
Transport through the plasma membrane
active transport is any movement of molecules or ions accross a cell membrane that requires the expenditure of energy.
Passive transport is any movement of molecules or ions across a cell membrane that does not require the expenditure of energy.
There are two forms of passive transport; simple diffusion and facilitated diffusion
Materials move down their concentration gradient through phospholipid bilayer
basically exocytosis backwards
The nature of the plasma membrane
The plasma membrane is a thin, fluid entity that manages to be very flexible and yet is stable enough to stay together despits... something
The plasma membran has four principal components
Molecules of cholesterol interspersed withtin the bilayer
proteins, which are integral, meaning bound to the hydrophobic interior of the membrane, or peripheral meaning not bound in this way.
glycocalyx: sugar chains that attach to proteins and phospholipids serving as protein binding sties and cell lubrication.
The cytoskelleton: Internal scaffolding
Cells have within them a web of protein strands, called a cytoskeleton
the cytoskeleton provides the cell with structure, facilitates the movement of materials inside the cell.
play a structural role in cells and facilitate the movement of materials.
Cilia and Flagella
Cilia extend from cells in great numbers, serving to move the cell or to move material around the cell
By contrast ,one- or at most a few-flagella extend fromcells that have them
The function of flagella is cell movement.
Mitochondria and energy
Mitchondria are organelles that function to extract energy from food and to transform this energy into a chemical form the cell can use, the molecule ATP.
Cells are able to communicate with each other throuhg special structures.
Plant cells have channels called plasmodesmata, that are always open and hence have the effect of making the cytoplasm of one plant cell continuous with that of another.
Adjacent animal cells have channels, called gap junctions, that are composed of protein assemblages that open only as necessary.
Considering adding images to coggle..
Instructor mentioned warfare where you are exposed to ga that make you believe you are more thirst than you are so you drink water to death.
a transport vesicle moves from the interior of the cell to the plasma membrane and fuses with it, at which point the contents of the vesicle are released to the environment outside the cell.
Bringing molecules into the cells
Animal cell interior
Membran proteins can provide structural support, often when attached to parts of the cells scaffolding or "cytoskeleton
serv to identiy the cells as normal or infected.
Receptor proteins including out from plasma membrane, can be the point of contact for signals sent to the cell via traveling molecules, such as hormones
Proteins can serve as channels through whichs materials can pass in and out of the cells