Life is Cellular Cell Structures & Functions Biology I Introduction to Cells • Before the 17th century, no one knew cells existed • Most cells are too small to be seen with the unaided eye • In the early 17th century microscopes were invented & cells were seen for the 1st time • Anton Von Leeuwenhoek, a Dutchman, made the 1st hand-held microscope & viewed microscopic organisms in water & bacteria from his teeth • In 1665, an English scientist named Robert Hooke made an improved microscope and viewed thin slices of cork viewing plant cell walls • Hooke named what he saw "cells“ • The Cell Theory The combined work of scientists Schleiden, Schwann, & Virchow is known as the Cell Theory : • Principles of the Cell Theory • All living things are made of one or more cells • Cells are the basic unit of structure & function in organisms • Cells come only from the reproduction of existing cells Cell Diversity • Not all cells are alike • Cells differ in size, shape, and function • The female egg cell is the largest cell in the body & can be seen without a microscope • Bacterial cells are some of the smallest cells & are only visible with a microscope Cells come in a variety of shapes, & the shape helps determine the function of the cell (e.g. Nerve cells are long to transmit messages in the body, while red blood cells are disk shaped to move through blood vessels) Basic Structure of a Cell Introduction to Cells Cells are the basic units of organisms Cells can only be observed under microscope Basic types of cells: Animal Cell Plant Cell Bacterial Cell Number of Cells Organisms may be: • Unicellular – composed of one cell • Multicellularcomposed of many cells Cells May be Prokaryotic or Eukaryotic Prokaryotes include bacteria & lack a nucleus or membrane-bound structures called organelles Eukaryotes include most other cells, have a nucleus and membrane-bound organelles Prokaryotes •Nucleoid region contains the DNA •Cell membrane & cell wall •Contain ribosomes to make proteins in their cytoplasm Prokaryotic Cell - Bacteria Eukaryotic Cell Contain 3 basic cell structures: • Nucleus • Cell Membrane • Cytoplasm with organelles Eukaryotic Animal Cell Eukaryotic Plant Cell Two Main Types of Eukaryotic Cells Plant Cell Animal Cell Cytoplasm • Entire region between the nuclear membrane and the cell (plasma) membrane. • This includes all organelles! • Jelly-like substance enclosed by cell membrane Cytoplasm cytoplasm Nucleus • Membrane-bound cellular organelle in eukaryotes. • Contains the genes (DNA) • Brain of the cell (controls all activities) nucleus Vacuoles Vacuole •Large membraneclosed sac for cellular storage. • Contains sugars, proteins, minerals, wastes, & pigments Organelles Found in Cells Nucleolus – makes ribosomes Golgi Bodies– wrap & export proteins (Modifies, stores and routes products from the ER to the plasma membrane) Lysosomes – digests & gets rid of wastes Ribosomes- site of protein synthesis 1 2 3 4 5 6 7 mRNA incoming polypeptide small subunit Smooth & Rough Endoplasmic Reticulum •Smooth ER lacks ribosomes & makes proteins used in the cell •Rough ER has ribosomes on its surface & makes proteins to export Mitochondria • Found in both plants and animal cells. • It is the site of cellular respiration, a process that uses energy extracted from organic macromolecules (like glucose) to produce ATP. • Also known as the “powerhouse” Outer membrane Inner membrane Chloroplast • Found in photosynthetic plants cells. • The site of photosynthesis, a process that uses light energy (sun) and water to produce organic macromolecules (glucose). Stroma Outer Membrane Inner Membrane Thylakoid Granum Plasma (Cell) Membrane • • • • The boundary of every cell Separates the living cell from its nonliving surroundings. Acts as a selective barrier Made of protein and phospholipids Hydrophobic region Hydrophilic region • Network of fibers through out the cytoplasm. • Aids in cellular support and movement. • Composed of three components: 1. Microfilaments - support and cellular contraction 2. Intermediate filaments - support 3. Microtubles - support and cell motility Cilia and Flagella • Extensions of the plasma membrane. • Aids in movement…. Cell Wall Cell wall • Strong cellulose fibers surrounding plant cells and some bacteria only! • Composed of polysaccharides and proteins. • Freely permeable • Protect and support the enclosed substances • Resist entry of excess water into the cell • Give shape to the cell Different kinds of animal cells white blood cell Amoeba red blood cell muscle cell cheek cells sperm nerve cell Paramecium Differences between plant cells and animal cells Animal cells Plant cells Relatively smaller in size Relatively larger in size Irregular shape Regular shape No cell wall Cell wall present Differences between Plant Cells and Animal Cells Animal cells Plant cells Vacuole small or absent Large central vacuole Glycogen as food storage Starch as food storage Nucleus at the center Nucleus near cell wall Levels of organization • Cells are grouped together and work as a whole to perform special functions Levels of Organization CELLS (muscle cells,nerve cells) TISSUES (muscle, epithelium) ORGANS (heart, lungs, stomach) SYSTEMS (circulatory system) ORGANISM (human) It’s You!