Cell Structure & Function

Cell Theory All living things are made up of cells Cells are the smallest unit of all living things All cells come from pre-existing cells through cell division

Definition of Cell A cell is the smallest unit that is capable of performing life functions.

Examples of Cells Amoeba Proteus Plant Stem Red Blood Cell Nerve Cell Bacteria

Two Types of Cells Prokaryotic Eukaryotic

Prokaryotic Do not have structures surrounded by membranes Few internal structures One-celled organisms, Bacteria

Prokaryotic organisms No organelles with membranes around them No nucleus free floating DNA Usually reproduce asexually Very small and simple Contain ribosomes, cytoplasm, cell membrane and cell wall with DNA floating Example: Bacteria

Eukaryotic Contain organelles surrounded by membranes Animals, Plants, Protists Plant Animal

Eukaryotic organisms have organelles with membranes around them DNA is inside the nucleus Usually reproduce sexually Example: Animal and Plant Cells

“Generic” Animal Cell /~ acarpi/NSC/images/cell.gif

“Generic” Plant Cell

Membrane-bound organelles: specialized parts inside a cell that perform a particular job and is surrounded by its own membrane

Structures found in all cells : -Cell Membrane -Cytoplasm -Genetic Material -Ribosomes

Cell Membrane Function: –Outer, flexible membrane of cell that controls movement in and out of the cell, acts as a gatekeeper –Is semi-permeable: only lets certain things in –Maintains homeostasis (internal balance)

Structure: –Double layer, called the phospholipid bilayer –Hydrophilic heads, hydrophobic tails

Cytoplasm Function: –Site of many chemical reactions –Contains the organelles Structure: –Gel-like material bound within the cell membrane

Genetic Material All cells have genetic material (DNA) In eukaryotes, the DNA is found in chromosomes located in the nucleus In prokaryotes, the DNA is free-floating Contain instructions for traits & characteristics

Ribosomes Some cells contain thousands and some cells contain millions of ribosomes! What kind of cells might contain millions?

Ribosomes Function: –Site of protein synthesis (make proteins) Structure: –Composed of RNA and protein –Are not membrane- bound organelles –Either attached to the ER (only in eukaryotes) or free- floating in cytoplasm

A Look at Organelles in Eukaryotic Cells

Nucleus Function: –Control activities of a cell –Contain the genetic material, DNA Structure: –Bounded by a double membrane called the nuclear membrane –Nuclear pores allow RNA to go to ribosomes

Endoplasmic Reticulum (ER) Moves materials around in cell & carries proteins to the golgi apparatus for packaging Smooth type: lacks ribosomes Rough type (pictured): ribosomes embedded in surface “canal system” Found in eukaryotes only

Nucleolus Inside nucleus Creates the ribosomes

Mitochondria Function: –Produce energy through respiration (breakdown of food for energy) –Powerhouse of the Cell Structure: –Rod Shaped –Double Layer of membranes –Inner membrane folds to increase surface area, called the cristae

Mitochondria Some cells contain many mitochondria and some contain only a small number. What kinds of cells do you think have many? Did you know mitochondria have their own unique DNA (different from the nuclear DNA)? It comes from your mother only!

Golgi bodies Protein 'packaging plant' Move materials out of the cell Found in Eukaryotes only Surrounded proteins called vessicles

Which structure would have the most surface area and be the most efficient? Most Surface Area!

Vacuoles Function: –Stores substances such as water, waste, digested materials Structure: –Clear, fluid-filled cavity bound by a membrane –Plants have a large central vacuole filled with water to keep cells rigid –Smaller or not present in animal cells Large central vacuole in a plant cell filled with water

Structures Unique to Plant Cells: has a square shape *Don’t forget about the large central vacuole

Cell Wall Function: –Provides plant cells structure, support, and protection Structure: –Made of cellulose –Rigid wall that is not flexible –Gives plant cell square shape –Outside of cell membrane

Chloroplast Function: –Site of photosynthesis in plants (uses sun to convert water and CO 2 into glucose and oxygen-waste) Structure: –Contains pigment chlorophyll that makes plants green –More commonly found in the leaves –Has stacks of inner membranes called grana to trap light –Chloroplasts also have their own unique DNA just like mitochondria

Structures Unique to Animal Cells: has a circular shape *Don’t forget about the small or small or not present vacuole!

Centrioles Function: –Play a role in cell division Structure: –Barrel shaped structure that produces spindle fibers –Spindles attach to chromosomes to divide cell –Similar to microtubules

Lysosomes Digestive 'plant' for proteins Cell breaks down if lysosome explodes Nicknamed “suicide sacs or recyclers of the cell” Lysosome ruptures and releases enzymes to kill the cell if it is not doing its job anymore. in animal cells only

Cilia and Flagella Cilia – small hairlike projections for movement and feeding Found in many protists Flagellum – 1 whip like tail for movement Found in many protists and sperm cells

Viewing Cells in the Microscope You can’t view all cell structures with a compound light microscope Can see the nucleus, cell membrane, chloroplasts, cytoplasm, large vacuoles

Determining if it’s a prokaryote or eukaryote: If there is no visible nucleus and the cell is small, most likely it’s a prokaryote (bacteria).

Determining if it’s a plant or animal cells in microscope Plants : –If you seen green discs floating about cytoplasm, these are chloroplasts –It has a square shape from the cell wall Animal: –No chloroplasts –Circle Shape

Animal Cell

Plant Cell