Cell Structure & Function

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

First person to observe a cell Robert Hooke – 1665 Used a microscope to observe a thin layer of cork cells

Cell Theory All living things are made up of cells. Cells are the smallest working units of all living things. All cells come from preexisting cells through cell division.

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

Levels of cell organization in multicellular organisms. 1.Cells 2. Tissues 3. Organs 4. Organ Systems 5. Organism

Two Types of Cells 1. Prokaryotic – cells without a nucleus (bacteria) 2. Eukaryotic – cells with a nucleus (plant and animal cells)

Prokaryotic Do not have structures surrounded by membranes No nucleus Few internal structures Contain ribosomes Bacteria

Eukaryotic Contains a nucleus and many organelles surrounded by membranes Most living organisms PlantAnimal

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

“Typical” Plant Cell

Cell Parts Organelles – little organs that are found in the cytoplasm

Primary Structures Major organelles found in cells –Cell membrane (present in all cells) –Cytoplasm (present in all cells) –Nucleus (present in Eukaryote cells only)

Secondary Structures All other organelles –Mitochondria –Ribosomes –Endoplasmic reticulum –Golgi apparatus –Chloroplast –Vacuole –Lysosome –Cell wall

Surrounding the Cell Cell Wall – A. outer boundary of the plant cell B. Composed of cellulose which you cannot digest C. Gives plant cells their rigid structure Cell membrane – A.Outer boundary of animal cells (protects cell) B.Also found in plant cells (inside cell wall) C.Composed of proteins and lipids D.Controls what enters and exits the cell

Cell Membrane Outer membrane of cell that controls movement in and out of the cell Double layer of lipids with proteins scattered throughout

Cell Wall Most commonly found in plant cells & bacteria Supports & protects cells Composed of cellulose

Inside the Cell

Nucleus Control center of the cell – Directs all the cell’s activities Contains genetic material – DNA DNA is in the form of chromosomes

Cytoplasm Gel-like mixture – 70% water Fills cell and holds organelles in place Surrounded by cell membrane Site for all chemical reactions - metabolism

Nuclear Membrane Surrounds nucleus Made of two layers Openings allow material to enter and leave nucleus

Chromosomes In nucleus Made of DNA Contain instructions for traits & characteristics

Nucleolus Inside nucleus (small and round) Build ribosomes

Endoplasmic Reticulum Function -Moves materials around in cell (highway) Smooth type: lacks ribosomes Rough type (pictured): ribosomes embedded in surface Structure -Network of tubes running from nucleus to cell membrane

Ribosomes Each cell contains thousands Make proteins Found on endoplasmic reticulum & floating throughout the cell Structure – small and round

Mitochondria Function - Produces ATP energy by cell respiration Powerhouse of the cell Structure - Hot dog shaped

Golgi Apparatus or Golgi Bodies Protein packaging plant (FedEx – packages and ships proteins out of cell) Structure – a stack of flattened pancakes

Lysosome Helps cell breakdown proteins and clean up (clean-up crew: proteins, fats, and carbohydrates) Produces enzymes for intracellular digestion Cell breaks down if lysosome explodes Structure – small and round

Vacuoles Membrane-bound sacs for storage, digestion, and waste removal (storage tanks: water, food and waste) Contains water solution Help plants maintain shape

Chloroplast Usually found in plant cells Contains green chlorophyll Where photosynthesis takes place