Biology: Life on Earth Eighth Edition Biology: Life on Earth Eighth Edition Lecture for Chapter 4 Cell Structure and Function Lecture for Chapter 4 Cell Structure and Function Copyright © 2008 Pearson Prentice Hall, Inc. Teresa Audesirk Gerald Audesirk Bruce E. Byers

What Is the Cell Theory?

Why are cells small? Cheek cells. microscopyu.com

All Cells Share Common Features Members of Bacteria, Eukaryota, and Archaea share common cellular features.

Plasma Membrane A plasma membrane encloses all cells and regulates material flow

Cytoplasm –Interior fluid –Where cell’s metabolic reactions occur –Contains organelles –Fluid portion (cytosol) contains water, salts, and organic molecules

Genetic Material All cells use DNA (deoxyribonucleic acid) as a hereditary blueprint All cells use RNA (ribonucleic acid) to copy DNA to make proteins

All Cells Share Common Features All cells obtain energy and nutrients from the environment All cells use common building blocks to build the molecules of life

There Are Two Basic Cell Types Cells are either: –Prokaryotic Before nucleus –Eukaryotic True nucleus alllife/eukaryota.html

Eukaryotic Cells Eukaryotic cells > 10 µm long Have membrane-enclosed organelles that perform specific functions

Cell Walls

The Cytoskeleton

Main functions of cytoskeleton –Maintaining and changing cell shape –Providing for cell movement –Providing for organelle movement, including vesicle endo- and exocytosis –Facilitating cell division in chromosome movements and cytokinesis

Cilia and Flagella Cilia and flagella are extensions of the plasma membrane Cilia –Short, hair-like structures, numerous Flagella –Longer, whip-like, fewer in number Functions –motility –Cilia - create currents of moving fluid in environment

The Nucleus Control center of cell Contains genetic information (in eukaryotes) Contains: –Nuclear envelope –Chromosomes –Nucleolus

System of Membranes Membrane system includes the plasma membrane and organelle membranes

Vesicles –membranous sacs that carry substances throughout the cell

Endoplasmic Reticulum A series of enclosed, interconnected channels within cell Two forms of ER –Smooth ER –Rough ER

Golgi Apparatus a set of stacked flattened sacs

Fate of Substances Made in the Membrane System (3) 1.Secreted proteins made in RER, travel through Golgi, then are exported through plasma membrane

Fate of Substances Made in the Membrane System (3) 2.Digestive proteins made in RER, travel through Golgi, and are packaged as lysosomes for use in cell Lysosomes fuse with food vacuoles and digest food into basic nutrients

Fate of Substances Made in the Membrane System (3) 3.Membrane proteins and lipids made in ER, travel through Golgi, and replenish or enlarge organelle and plasma membranes

Vacuoles Serve Many Functions Fluid-filled sacs with a single membrane Contractile vacuoles in freshwater organisms used to collect and pump water out

Vacuoles Serve Many Functions Plant central vacuoles used in several ways Maintain water balance Store hazardous wastes, nutrients, or pigments Provide turgor pressure on cytoplasm to keep cells rigid

Mitochondria Extract Food Energy Mitochondria - round, oval, or tubular sacs of double-membranes –Inner membrane is folded into cristae –Intermembrane compartment lies between inner and outer membranes –Matrix space within inner membrane

Mitochondria Extract Food Energy Mitochondria may be remnants of free-living prokaryotes (endosymbiotic hypothesis) thebrain.mcgill.ca

Plants Use Plastids for Storage Plastids found only in plants and photosynthetic protists –Ex. chloroplasts Surrounded by a double membrane Functions –Storage for photosynthetic products –Storage of pigment molecules

Chloroplasts Chloroplasts - specialized organelles surrounded by a double membrane –Outer membrane –Inner membrane encloses the stroma space Stacked hollow membranous sacs (grana) within stroma are called thylakoids

Chloroplasts Contain chlorophyll and other pigments that capture sunlight, CO 2, and water and are used to make sugar (photosynthesis)

Prokaryotic Cells Most prokaryotic cells (bacteria) are < 5 µm long

Prokaryotic Cell Wall A stiff cell wall is usually present

Prokaryotic Cells Motility by flagella May have capsules or slime layers on their surfaces Pili and fimbriae are protein projections in some bacteria that further enhance adhesion E. Coli with fimbriae. mgm.stonybrook.edu E. Coli with fimbriae. med.upenn.edu

Prokaryotic Cells Cell shapes: bacilli, cocci, or spirilla abe.ufl.edu

Prokaryotic Cells Single, circular chromosome of DNA in area called the nucleoid Small rings of DNA (plasmids) located in the cytoplasm

Prokaryotic Cells No nuclear membrane or membrane-bound organelles present Some have internal membranes used to capture light Cytoplasm may contain food granules

The End