Cells Chapter 6 Notes

What does the word ‘Cell’ Mean? The word cell is derived from the Latin word 'cellula' which means small compartment.

A Famous Man in Science – Robert Hooke In 1663 an English scientist, Robert Hooke, discovered cells in a piece of cork, which he examined under his primitive microscope. Hooke only observed cell walls because cork cells are dead and without cytoplasmic contents. Hooke drew the cells he saw and also coined the word CELL.

Anton van Leeuwenhoek Today, he is known as the “Father of Microbiology” and discovered bacteria Used his own (single lens) monocular microscopes and was the first person to observe bacteria and protozoa

Anton van Leeuwenhoek Built microscopes that magnified over 200 times, with clearer and brighter images than any of his colleagues at that time.

Cell Theory The CELL THEORY, or cell doctrine, states that all organisms are composed of similar units of organization, called cells. The concept was formally articulated in 1839 by Schleiden & Schwann and has remained as the foundation of modern biology.

Cell Theory Components There are 6 Components to Cell Theory: All known living things are made up of cells. The cell is structural & functional unit of all living things. All cells come from pre-existing cells by division. (Spontaneous Generation does not occur). Cells contains hereditary information which is passed from cell to cell during cell division. All cells are basically the same in chemical composition. All energy flow (metabolism & biochemistry) of life occurs within cells.   

Two Major Classes of Cells Prokaryotic Cell Lacks a nucleus and most other organelles. Bacteria and another group of organisms called the archaea are prokaryotic cells. Prokaryotic organisms appear earliest in Earth's fossil record. Eukaryotic Cell Has a nucleus surrounded by its own membrane, and has other internal organelles bounded by membranes. Protists, fungi, plants, and animals consist of eukaryotic cells. Organisms with eukaryotic cells appeared later in Earth's history.

Prokaryotic Cells A bacterium is an example of a prokaryotic cell (pro means "earlier than"). Prokaryotic cells are much simpler in structure They do not have a true nucleus or membrane bound organelles that a eukaryotic cell would have. The DNA in a prokaryotic cell is concentrated in an area called the nucleoid region: This is not separated from the rest of the cell by a membrane. ONLY EUKARYOTIC CELLS HAVE MEMBRANE BOUND ORGANELLES

Prokaryotic Cells Notice how everything is floating around together – not bound separately from one another! Example: The DNA is not bound separately from the ribosomes

Eukaryotic Cells Protists, fungi, plants, and animals consist of eukaryotic cells. Eukaryotic cells are much more complex in structure They do have a true nucleus and membrane bound organelles The DNA in a eukaryotic cell is concentrated in an area called the nucleus

Eukaryotic Cells Notice how everything is bound in a membrane separate from one another. Example: The DNA is seen inside the nucleus which has a nuclear membrane separate it from everything else!

Compare, Compare! Prokaryotic Cell Eukaryotic Cell What are some similarities? What are some differences?

Question: Do you have prokaryotic or eukaryotic cells? EXPLAIN!! Stop and Freeze! Question: Do you have prokaryotic or eukaryotic cells? EXPLAIN!!

All of this Membrane talk! --Membrane Structure Membranes help keep the functions of a eukaryotic cell organized. Act as partitions, The membranes isolate teams of enzymes within a cell's compartments. Regulate the transport of substances across the boundary, allowing only certain substances to pass. NOT A WALL!

Plasma Membrane The plasma membrane and other membranes of a cell are composed mostly of proteins and a type of lipid called phospholipids

Phospholipids A phospholipid molecule is structured much like the fat molecules but has only two fatty acids instead of three. Composed of 2 Main Parts: Head Made up of a phosphate group, Negatively charged Hydrophilic (water loving) Tail The two fatty acids at one end (the tail) of the phospholipid are hydrophobic. So the tail end of a phospholipid is pushed away by water, while the head is attracted to water

Phospholipids The structure of phospholipids allows them to form boundaries, or membranes, between two watery environments.

Phospholipid Bilayer The phospholipids form a two-layer "sandwich" of molecules, called a phospholipid bilayer, that surrounds the organelle or cell.

Inside the Phospholipid Bilayer Many types of proteins are embedded in the membrane's phospholipid bilayer. Other molecules, such as carbohydrates, may be attached to the membrane as well, but the proteins perform most of the membrane's specific functions.

Protein Function Inside Cells Help Other Cells (especially cells that are part of a multicellular organism) Proteins help cells communicate and recognize each other. Example, chemical signals released by one cell may be "picked up" by the proteins embedded in the membrane of another cell. Transport Proteins (Protein Channel) Help move certain substances such as water and sugars across the plasma membrane

Moving Across the Plasma Membrane Molecules in a fluid are constantly in motion, colliding and bouncing as they spread out into the available space. So how do particles move across the plasma membrane?! Diffusion! The net movement of the particles of a substance from area of where they are in high(more) concentration to where they are in low(less) concentration

Diffusion Diffusion across a membrane is called passive transport because no energy is expended by the cell in the process. Only the random motion of the molecules is required to move them across the membrane.

Passive Transport Cellular membranes are barriers to the diffusion of some substances. A selectively permeable membrane allows some substances to cross the membrane more easily than others and blocks the passage of some substances altogether.

Osmosis The passive transport (diffusion) of water across a selectively permeable membrane is called osmosis.