Please pick up a copy of the powerpoint notes Honors Only Place Homework in basket. Place cell encyclopedia in the sink.

Structure and Function of the Cell A cell is the smallest unit of matter that can carry on all of the processes of life.

Discovery of the Cell ► The discovery of the cell was made possible by the invention of the microscope in the early 1600’s. ► In 1665 Robert Hooke used a microscope to examine a slice of cork. ► He described it as consisting of “a great many little boxes.”

Hooke’s Microscope

Discovery of the Cellcont….. ► The “little boxes” reminded him of the small rooms where monks lived, which were called cells. ► In 1673 Anton van Leeuwenhoek created a microscope powerful enough to view living cells allowing him to become the first person to view living cells.

The Cell Theory – A unified theory developed from the observations of Hooke and van Leeuwenhoek (150 years later). ► All living things are composed of cells. ► Cells are the basic units of structure and function in an organism. ► Cells come only from the reproduction of other cells.

Cell Diversity Cells are not all alike. The human body has at least 200 different types of cells.

Cell Diversity Size ► Some cells are large enough to be seen without a microscope. Example: The nerve cells in a giraffe’s leg may be as long as 2 meters. ► Most are microscopic. ► Cells are limited in size by the ratio between their outer surface area and their volume. ► As cells grow larger, the surface area become too small to allow materials to enter the cell quickly enough to meet the cell’s needs.

Cell Diversity Shape ► Cells come in a variety of shapes. ► The diversity of form reflects a diversity of function. Shapes aid in the cell’s function.

Cell Diversity Nerve Cell

Cell Diversity Bone Cells

Cell Diversity Cartilage

Cell Diversity Muscle Cells

Cell Diversity Cardiac Muscle

Cell Diversity Skeletal Muscle

Cell Diversity Red Blood Cells

Cell Diversity Internal Organization ► Cells contain a variety of internal structures called organelles. ► Organelles are cell components that perform specific functions just like organs in multicellular organisms.

Cell Diversity Internal Organization ► Eukaryotes – Organisms whose cells contain membrane bound organelles and nucleus.  Eukaryote means “True Nucleus”  DNA separated by a nuclear membrane.  Examples-plant and animal cells. All of the cells in your body.

► Prokaryotes – Unicellular organisms that lack a membrane bound nucleus and other organelles.  DNA isn’t separated by nuclear membrane  Smaller in size than eukaryotes.  Much simpler in design than eukaryotes.  Examples: Bacteria

Parts of the Eukaryotic Cell

The Eukaryotic Cell ► The structures of the cell depends on the function of the cell. ► There is no typical eukaryotic cell. ► They generally have the presence of:  A cell membrane.  A nucleus  Other organelles.

The Cell Membrane ► Separates the inside of the cell from the environment. ► Controls the ease of which particles and substances move in and out of the cell. ► Selectively Permeable – Some substances may be allowed to move through the membrane others may not. ► Membranes are specialized to the function of the cell. ► All cell membranes are composed primarily of lipids and proteins.

Cell Membrane The lipid bilayer

Organelles

Cytoplasm ► Cytoplasm – Lies between the cell membrane and the nucleus.  Contains the various organelles. ► Cytosol – Gelatin-like aqueous fluid that bathes the organelles.  Contains dissolved salts, minerals and organic molecules.

Mitochondria ► The site of cellular respiration - chemical reactions that transform organic compounds to ATP. ► Mitochondria are numerous in cells with high energy requirements. As many as 2500 present in liver cells. ► Surrounded by two membranes: A smooth outer membrane and inner membrane with many folds called cristae. The cristae enlarges the surface area available for chemical reactions. ► They have their own DNA. New mitochondria arise only when existing ones grow and divide.

Mitochondria

Ribosomes ► The most numerous organelle in many cells. ► Ribosomes have no membrane. ► They consist of proteins and RNA. ► Ribosomes are produced by the cell’s nucleolus and transported to the cytosol. ► Some attach themselves to the endoplasmic reticulum and some sit freely. ► Play an important role in the synthesis of proteins.

Ribosomes

Endoplasmic Reticulum (ER) ► The ER functions as an intracellular highway in which molecules can move from one part of the cell to the other. ► A system of membranous tubules and sacs. ► Rough ER – Has ribosomes attached and gives a rough appearance under the microscope. More common in cells that make large amounts of protein. ► Smooth ER – Has an absence of ribosomes and appears smooth. Involved in the synthesis of steroids in gland cells, the regulation of calcium in muscle cells, and the breakdown of toxic substances by liver cells. ► Smooth ER and rough ER may be continuous and run together.

Endoplasmice Reticulum

Golgi Apparattus ► The processing, packaging, and secreting organelle of the cell. ► Works in association with the ER. ► Modifies proteins for export by the cell. ► Looks like a series of flattened sacs.

Golgi Apparattus

Lysosomes ► Small, spherical organelles that enclose hydrolytic enzymes within a single membrane. ► The enzymes may be used to digest proteins, carbohydrates, lipids, DNA, RNA, or old organelles, viruses, and bacteria. ► Common in animal, fungi, and protist cells but rare in plant cells.

Cytoskeleton ► A network of protein strands located in the cytosol that give support and structure to the cell. ► Microfilaments – Made of a protein called actin. These are the smallest strands. They contribute cell movement and to the contraction of muscle cells. ► Microtubules – Hollow tubes that also contribute to movement and structure. ► During cell division microtubules form spindle fibers which assist in the movement of chromosomes.

Cilia and Flagella ► The cilia and flagella are hair-like organelles that extend beyond the surface of the cell and assist in cell movement. ► Cilia – When they are short and in large numbers they are called cilia. ► Flagella – When they are long and much less numerous they are called flagella. ► Structurally composed of nine pairs of microtubules around one central pair.

Nucleus ► Stores hereditary information in its DNA. ► Nuclear Envelope – The double membrane that surrounds the nucleus. ► Nuclear Pores – Small holes in the nuclear envelope. ► Nucleoulus – Site for ribosome synthesis. A spherical area that is visible within the nucleus. ► Chromatin – Strands of DNA and protein combined located in the nuclear envelope. ► Chromosomes – Densely packed coils of chromatin that form when a cell is about to divide.

Nucleus

Plant Cells Plant cells are characterized by the presence of cell walls, central vacuoles, and chloroplasts.

Plant Cells Cell Wall ► Cell Wall – A rigid wall that lies outside the cell membrane. ► Composed of long chains of cellulose embedded in proteins and carbohydrates. ► There are two types of cell walls, primary and secondary.

Plant Cells

Plant Cell

Central Vacuoles ► Fluid filled organelles that store enzymes, water and waste. ► Some of the waste may be toxic and is therefore kept separate from the rest of the cell. ► May be 90% of the cell’s volume in some cases.

Chloroplasts ► Chloroplasts convert energy from sunlight into chemical energy in glucose and other organic compounds. ► Occurs during photosynthesis. ► Chloroplasts are green in color because of the presence of chlorophyll.

Chloroplasts

Chloroplasts