Introduction There are huge differences between the forms of life but cells are the basic unit of life and have many characteristics in common

Introduction Cells are often divided into certain groups based on major characteristics. –Two main groups: Prokaryotic cells Eukaryotic cells

2.2 Prokaryotic Cells

Prokaryotic Cells Much smaller and simpler than eukaryotic cells –Most are less than 1 um

Prokaryotic Cells Features of prokaryotic cells –Cell wall –Plasma membrane –Flagella –Riboome –Nucleoid (region containing free DNA) Be Sure you can Identify all of these!!!

Prokaryotic Cell

Prokaryotic Cells Cell Wall and Plasma Membrane –Protects and maintains the shape of the cell Composed of a carbohydrate-protein complex called peptidoglycan –Some bacteria have an additional layer of a type of polysaccharide out the cell wall This layer makes it possible for some bacteria to adhere to structures such as teeth, skin, and food

Prokaryotic Cells Cell Wall and Plasma Membrane –The plasma membrane is just inside the cell wall and has a composition similar to the membranes of eukaryotic cells Controls the movement of materials in and out of cells Cytoplasm occupies the complete interior of the cell

Prokaryotic Cells Pili and flagella –Some bacterial cells contain hair-like growths on the outside of the cell wall These are pili and are used for attachment However their main function is in joining bacterial cells in preparation for the transfer of DNA from one cell to another (sexual reproduction) –If bacterium has flagella (plural) or flagellum (singular), they are longer than pili Allows cell motility

Prokaryotic Cells Ribosomes –Ribosomes occur in all prokaryotic cells and function as sites of protein synthesis The more protein produced the larger the number of ribosomes.

Prokaryotic Cells The nucleoid region –Is non-compartmentalized and contains a single, long, continuous, circular thread of DNA –In addition to the bacterial chromosome, bacteria may also contain plasmids These small, circular, DNA molecules are not connected to the main bacterial chromosome. Replicates independently of the chromosomal DNA It is not required by the cell under normal conditions but it may help the cell adapt to unusual circumstances

Binary Fission Prokaryotic cells divide by a very simple process called binary fission. –During this process: DNA is copied The two daughter chromosomes become attached to different regions on the plasma membrane The cell divides into two genetically identical daughter cells

Prokaryotic Cells divide by binary fission 2.2.4

2.3 Eukaryotic Cells

The Parts of the Cell Each living cell carries out the tasks of taking food, transforming food into energy, getting rid of wastes, and reproducing. Most eukaryotic cells have three main components: –Cell Membrane –Cytoskeleton –Nucleus

Animal Cell Now let Annotate this picture with all the functions of each structure named

Plant Cell Now let Annotate this picture with all the functions of each structure named

Liver Cell 2.3.3

Structure and Function of Organelles The Structure and Function of the following organelles will be discussed: –Cell Membrane –Nucleus –Cell Wall –Cytoplasm –Cytoskeleton –Ribosomes –Endoplasmic Reticulum –Golgi Apparatus –Mitochondria –Lysosomes –Peroxisomes –Cilia and Flagella –Basal Bodies –Centrioles –Vacuoles –Plastids

Cell Membrane Structure: phospholipid bilayer with proteins that function as channels, markers, and receptors -also contains cholesterol which provides rigidity Function: selectively permeable boundary between the cell and the external environment

Nucleus Structure: the nucleus is a sphere that contains another sphere called a nucleolus Function: -storage center of cell’s DNA -manages cell functions

Cell Wall Structure: rigid wall made up of cellulose, proteins, and carbohydrates Function: boundary around the plant cell outside of the cell membrane that provides structure and support

Cytoplasm Structure: gelatin-like fluid that lies inside the cell membrane Function: -contains salts, minerals and organic molecules -surrounds the organelles

Cytoskeleton Structure: a network of thin, fibrous elements made up of microtubules (hollow tubes) and microfilaments (threads made out of actin) Function: -acts as a support system for organelles -maintains cell shape

Ribosomes Structure: consist of two subunits made of protein and RNA Function: location of protein synthesis

Endoplasmic Reticulum Structure: a system of membranous tubules and sacs Function: intercellular highway (a path along which molecules move from one part of the cell to another) Two types: –Rough Endoplasmic Reticulum –Smooth Endoplasmic Reticulum

Rough Endoplasmic Reticulum Rough Endoplasmic Reticulum (rER): prominent in cells that make large amounts of proteins to be exported from the cell or inserted into the cell membrane –Covered with ribosomes

Smooth Endoplasmic Reticulum Smooth Endoplasmic Reticulum (sER): involved in the synthesis of lipids and breakdown of toxic substances –Not covered with ribosomes

Golgi Apparatus Structure: stacked flat sacs Function: receives proteins from the rER and distributes them to other organelles or out of the cell (receiving, processing, packaging, and shipping)

Mitochondria Structure: folded membrane within an outer membrane –The folds of the inner membrane are called cristae Function: -converts energy stored in food into usable energy for work –cellular respiration

Lysosomes Structure: spherical organelles that contain hydrolytic enzymes within single membranes Function: breaks down food particles, invading objects, or worn out cell parts

Peroxisomes Structure: spherical organelles that contain enzymes within single membranes Function: Degrade hydrogen peroxide, a toxic compound that can be produced during metabolism.

Cilia and Flagella Structure: hair-like organelles that extend from the surface of cells –When they are present in large numbers on a cell they are called cilia –When they are less numerous and longer they are called flagella –Both organelles are composed of nine pairs of microtubules arranged around a central pair. Function: cell motility

Cillia and Flagella

Basal Bodies The microtubule assembly of a cilium or flagellum is anchored in the cell by a basal body. Structurally identical to a centriole

Centrioles Structure: composed of nine sets of triplet microtubules arranged in a ring –Exist in pairs Function: centrioles play a major role in cell division (mitosis)

Vacuoles Structure: a sac of fluid surrounded by a membrane –Very large in plants Function: used for temporary storage of wastes, nutrients, and water

Plastids There are three types of plastids in plant cells: –Chloroplasts (discussed on next slide) –Chromoplasts: synthesize and store pigments –Leucoplasts: store food such as starches, proteins, and lipids Chromoplasts Red Pepper Flower Leucoplasts

Chloroplasts Structure: stacked sacs (thylakoids) that contain chlorophyll surrounded by a double membrane Function: photosynthesis (conversion of light energy to chemical energy stored in the bonds of glucose)

Structural Organization of Eukaryotic and Prokaryotic Cells 2.3.4

Eukaryotes vs. Prokaryotes Eukaryotes (animals, plants, fungi, protists) and prokaryotes (bacteria) differ greatly in structure

Prokaryotic cellsEukaryotic cells DNA in a ring form without proteinDNA with proteins as chromosomes/chromatin DNA free in cytoplasmDNA enclosed within a nuclear envelope No mitochondriaMitochondria present 70S ribosome80S ribosome Not internal compartmentalization to form organelles Internal compartmentalization present to form many types of organelle Size less than 10 micrometresSize more than 10 micrometres

Similarities between two types of cells: –Both types of cells have some sort of outside boundary that always involves a plasma membrane –Both types of cell carry out all the functions of life –DNA is present in both cell types

Plant cellsAnimal Cells Exterior of cell includes an outer cell wall with a plasma membrane just inside Exterior of cell includes only a plasma membrane. There is no cell wall Chloroplasts are present in the cytoplasm There are no chloroplasts Possess large centrally located vacuoles Vacuoles are usually not present or are small Store carbohydrates as starchStore carbohydrates as glycogen Do not contain centrioles within a centrosome area Contain centrioles within a centrosome area Because a rigid cell wall is present, this cell type has a fixed, often angular, shape Without a cell wall, this cell is flexible and more likely to be rounded shape

Plant Cells vs. Animal Cells Animal cells are very similar to plant cells except for the following major differences: –Animal cells do not contain chloroplasts –Animal cells are not surrounded by cell walls –The vacuoles in plants are much larger than those of animals 2.3.5

Microscope Pictures of a Plant Cell and an Animal CellElodea Human Cheek Cells

Extracellular components The extracellular matrix (ECM) is composed of collegen fibers plus a combination of sugars and proteins called glycoproteins in many animal cells –These form fiber-like structures that anchor the matrix to the plasma membrane. This strengthens the plasma membrane and allows attachment between adjacent cells.

Extracellular components The ECM allows for cell to cell interaction, possibly altering gene expression and bringing about coordination of cell action within the tissue. –Many researchers think the ECM is involved in directing stem cells to differentiate –Cell migration and movement also appear to be the result of the interactions between cells

Extracellular components 2.3.6

THE END!