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What do all organisms have in common on a cellular level?
cells have the same basic structure
what tool has become important in the study of biology?
- the microscope
- Microscope observations of organisms led to the discovery of the basic characteristics common to all living things.
The discovery of cells
- In 1665 Robert Hooke used a crude micoscope that magnified 30x. He named disscoveries cells.
- ten years later Anton van Leeuwenhoek used a microscope that magnified 300-fold. He named discoveries animalcules or tiny animals.
- All living things are made up of one or more cells
- Cells are the basic units of structure & function in organisms
- All cells arise from existing cells
- Matthias Schleiden ~ plants are made of cells
- Theodor Schwann~ Animals are made of cells
- Rudolph Virchow~ cells came from the division of other cells
- their observations formed the cell theory
What doe the cell's shape reflect?
its function. may be branched, flat, round, or rectangular, irregular, or constantly changing.
what do all substances that enter or leave a cell must pass through?
the surface of the cell
what is cell size limited by?
a cell's surface area-to-volume ratio. Cells with a greater ratio can exchange substances more efficiently. Smaller cells have greater surface area to volume ratio.
shared structural features of cells
cell membrane, cytoplasm, ribosomes, & DNA.
what is the cell membrane?
the cells outer boundary. It acts as a barrier between the outside enviroment & the inside of the cell. Its a phospholipid.
what is cytoplasm?
includes the cytosol- the fluid inside the cell full of dissolved particles- and almost all the structures suspended in the cytosol.
what is a ribosome?
a cellular structure on which proteins are made.
what does DNA do for the cell?
- the genetic material.
- provides instructions for making proteins, regulates cellular activities, & enables cells to reproduce.
Features of Prokaryotic cells
- a prokaryote- an organisms that is a single prokaryotic cell.
- simple in organization.
- genetic material is a single loop of DNA
- ribosomes & enzymes share cytoplasm w/ DNA
- has a cell wall that surrounds the membrane for structure & support
- some walls are surrounded by a capsule~ a structure that enables prokaryotes to cling to surfaces including teeth, skin,& food
- The first living organisms
- make up a very large & diverse group of cells
- are bacteria
Features of Eukaryotic Cells
- a eukaryote- an organism that is made up of one or more eukaryotic cells.
- some live as single cells
- all multicellular organisms are made up of these cells
- Because of their complex organization they can carry out more specialized functions then prokaryotic cells can.
- contains compartments that are separated by membranes
- The cell's DNA is housed in an internal compartment called the nucleus
- all have membrane- bound organelles
- organelle- a structure that carries out specific activities inside the cell.EAch performs distinct functions. many are surrounded by membrane. others are connected by channels that help move substances within the cell.
what is the cytoskeleton?
- a web of protein fibers found in eukaryotic cells.
- supports the cells like bones to the body
- helps the cell move, keep its shape, & organize its parts.
- there are three kinds of cytoskeleton fibers
What are microfilaments?
- Long thin fibers that are made of the proteins actin.
- some are attached to the cell membrane
- they contract to pull the membrane in in some places & Expand to push out in others.
what are microtubules?
Thick hollow fibers that are made of the proteins tubulin. Info molecules move through these tubes to various parts of the cell.
what are intermediate fibers?
moderately thick & mainly anchor organelles & enzymes to certain parts of the cell.
What is the framework of the cell?
Cytoskeleton, microfilaments, microtubules, & intermediate fibers.
How are DNA instructions copies?
copied as RNA messages which leave the nucleus. In the cytoplasm ribosomes use the RNA messages to assemble proteins.
- it is surrounded by a double membrane called the nuclear envelope. This envelope has many pores.
- Nuclear pores are small channels that allow certain molecules to move into & out of the nucleus.
- the prominent structure of the nucleus is the nucleolus. The region where ribosome parts are made. the parts of ribosomes pass through the nuclear pores into the cytoplasm. Outside the nucleus the parts are assembled to form a complete ribosome.
- each is made of RNA & many proteins.
- some are suspended in the cytosol( as is in prokaryotic) these "free" ribosomes make proteins that remain inside the cell, such as proteins that build new organelles or enzymes to speed chemical reactions.
- "bound" ribosomes are attached to the membrane of another organelle. THey make proteins that are exported form the cell. Some of these proteins are important in cell communication. They also make proteins that must be kept separate from the rest of the cytoplasm.
- Ribosomes can switch between being bound or free depending on the kind of protein that the cell needs to make.
what happens to the proteins that are sent outside of the cell
must be kept separate from the rest of the proteins. the cell packages these proteins into vesicles. Vesicle- a small often spherical shaped sac that is formed by a membrane. Vesicles help maintain homeostasis by storing & releasing various substances as the cell needs them.
in a eukaryotic cell what 2 structures are mainly responsible for modifying, packaging, & transporting proteins for use outside the cell?
the endoplasmic reticulum & the Golgi apparatus are organelles that prepare proteins for extracellular export.
what is the Endoplasmic reticulem? ( ER)
a system of internal membranes that moves proteins & other substances through the cell. its membrane is connected tot he outer membrane of the nuclear envelope.
rough ER - Ribosomes are attached to some parts of the surface of the ER This ER has a bumpy appearance when viewed w/ an electron microscope. As proteins are made they cross the ER membrane entering the ER then the ER membrane pinches off to form a vesicle around the proteins.
Smooth ER- has no attached ribosomes. it appears smooth when viewed w/ an electron microscope . Enzymes of this perform various functions. i.e. making lipids & breaking down toxic substances.
the Golgi Apparatus
a set of flattened membrane bound sacs. Cell products enter one side of the Golgi apparatus which modifies sorts & packages them for distribution.
repackaging- vesicles that contain newly made proteins move through the cytoplasm from the ER to the Golgi apparatus. The vesicle membrane fuses w/ the Golgi membrane. inside th eapparatus enzymes modify the proteins as they move through the organelle. on the other side the finished proteins are enclosed in new vesicles that bud form the surface of the golgi apparatus.
Exporting- Many of these vesicles then migrate to the cell membrane as the vesicle membrane fuses w. the cell membrane the completed proteins are released to the outside of the cell.
what is a lysosome?
- a vesicle that contains specific enzymes that break down large molecules. they can digest food particles to provide nutrients for the cell. They help recycle materials in the cell by diggesting the old damaged or unused organelles. they work by fusing with other vesicles.
- if made by the golgi apparatus prevent the enzymes from destroying the cell.
what is a vacuole?
central vacuole- contained in many plant cells, a large membrane bound compartment. stores water, ions, nutirents, & wastes. stores toxins or pigments. When filled w/ water is rigid when loses water wilts.
others- some protists have contractile vacuoles which pump excess water out of the cell. This controls the concentration of salts & other molecule & helps maintain homeostasis. also created when cell membrane surrounds food particles outside the cell & pinches off to form a vesicle inside the cell . When the food vacuole later fuses with a lysosome the enzymes that digest the stored food are released.
what is the energy for cellular function produced by?
chemical reactions that occur in the mitochondria and chloroplasts. Both organelles- chemical reactions produce ATP the form of energy that fuels almost all cell processes.
what is chloroplast?
an organelle that uses light energy to make sugar from CArbon dioxide & water. Plant cells have many. EAch is surrounded by a pair of membranes. Inside the inner membrane are many stacks of flattened sacs. The ATP producing chemical reactions take place on the membranes of these sacs.
what is mitochondria?
an organelle that uses energy from organic compunds to make ATP. most of the cells ATP is made here. ITs has a smooth outer membrane, which divides the organelle into two compartments. Many ATP- producing enzymes are located on the inner membrane .
prokaryotes are? eukaryotes?
prokaryotes always unicellular & limited in size. Eukaryotes often larger & can be either unicellular or multicellular. the different organelles and features of cells enable organisms to function in unique ways in different environments.
Diversity in Prokaryotes.
can cary in shape, & they way teh use & obtain energy, the makeup of the cell ways, & their ability to move. many have flagella- a long threadlike structure that rotate to quickly move an organism thorough its environment. many have pili- short thick outgrowths that allow prokaryotes to attach to the surfaces or to other cells.
diversity in eukaryotic cells
- animal & plant are two types of the cell. both have many of the same organelles. plant cells have chloroplasts & a cell wall.
- they vary in size & structure according to function.
- organelles are more prominent in some cell types.
- by varying in their internal makeup cells can become specialized for certain functions.
important to know
plants & animals have many highly specialized cells taht are arranged into tissues, organs, & organ systems.
what is a tissue?
a distinct group of cells that have similar structures & functions.
what is an organ?
Different tissues arranged inso a specialized structure that has a specific function.
organsystem- various organs that carry out a major body function.
more then half of the biomass of earth is composed of
what is a multicellular organism composed of?
many individual, permanently associated cells that coordinate their activities.
distinct types of cells have specialized functions that help the organism survive. Individual cells cannot survive alone and are dependent on the other cells of the organism.
what are colonial cells?
- cells taht live as a connected group but do not depend on each other for survival.
- cell groups are not considered multicellular because the cells can survive when separated.
when does true multicellularity occur?
only in eukaryotes. some protist, most fungi, and all plants & animals.