Cell Structure & Function

Cells: the basic units of life. The cell theory, set forth in the 1850s, says that: All living things are composed of cells. The cell is the smallest unit that retains the properties of life. Under current conditions, all cells come from preexisting cells.

Question Q01: Which of the following statements is NOT part of the cell theory? All living things are composed of cells. All cells are surrounded by an outer membrane. The cell is the smallest unit that retains the properties of life. Under current conditions, all cells come from pre-existing cells. All cells DO have an outer membrane (called the plasma membrane), but this observation is not considered part of the cell theory.

Light Microscope (LM) Shows the entire cell and its interior

Scanning Electron Microscope (SEM) Shows a cell’s surface structure

Transmission Electron Microscope (TEM) Shows internal details of a preserved cell

Question Q02: Biologists generally rely on the ________ microscope to study the surface structures of cells and the ________ microscope to study the internal structure of cells. light; electron light; transmission electron scanning electron; transmission electron transmission electron; scanning electron Specimens for both types of electron microscopes must be killed and preserved before they can be examined. For this reason, light microscopes are still useful for observing living cells.

Basic Cell Structure (sketch this diagram)

Question Q03: Which of the following correctly labels the three major parts of the cell shown below? 1-nucleus, 2-cytoplasm, 3-plasma membrane 1-cytoplasm, 2-plasma membrane, 3-nucleus 1-plasma membrane, 2-nucleus, 3-cytoplasm 1-nucleus, 2-plasma membrane, 3-cytoplasm 1 2 3 The plasma membrane encloses the cytoplasm, and the cytoplasm surrounds the nucleus. Plasma membrane

Internal Cell Structures Cell membranes divide the cytoplasm of eukaryotic cells into functional compartments called organelles. Organelle = “mini organs”

Plant Cell Structures

Animal Cell Structures

Eukaryotic vs. Prokaryotic

Internal Cell Membranes Organelle membranes physically separate important chemical reactions in the cytoplasm and allow them to take place in an orderly fashion.

Selective permeability Cell membranes are said to be selectively permeable membranes, meaning that they allow some, but not all, materials to simply pass through them.

Question Q04: Which of the following is NOT an accurate analogy for a cell membrane? a window screen the US – Mexico border the Kansas – Colorado border a university admissions department The Kansas – Colorado border is a permeable barrier—anyone can cross the border at any time. All of the other barriers in the list are selectively permeable because they allow some things but not others to pass through.

Membrane Composition A phospholipid bilayer forms the basic unit of the cell membrane.

Question Q05: Where in this diagram of a cell membrane would you expect to find the FEWEST water molecules? A The fatty acid “tails” of the phospholipids are hydrophobic. They would repel any water molecules that came into that area of the membrane. B C

Membrane Composition Proteins embedded in the bilayer help the cell transport materials in and out. Carbohydrate chains attached to some membrane proteins help the cell communicate with other cells.

Structure of the Cell Membrane

Question Q06: What type of membrane molecules are responsible for cell-to-cell communication? lipids proteins phospholipids carbohydrates Carbohydrate chains act like “ID tags.” Different cell types have different kinds of carbohydrate chains on their surfaces.

A “Fluid” Membrane The lipid molecules have hydrophilic (“water-loving”) heads and hydrophobic (“water-hating”) tails. Therefore, if you puncture a membrane, it will come together and seal itself.

Cell Membrane Analogy The cell membrane is similar to the walls that surround a house.

Both help protect the inside from the outside.

A house needs a way of receiving fuel and power from the outside A house needs a way of receiving fuel and power from the outside. Supply lines pass through the walls of the house to bring in these materials.

A cell receives fuel and power from the outside through protein channels in the membrane.

Doors are sometimes needed to bring in food and take out the trash.

Channels in the membrane allow the cell to bring in food and get rid of waste.

People in a house also need to communicate with the outside.

Carbohydrates in the membrane allow the cell to communicate with other cells.

Summary Video Click here to play video.