Modern Biology©2009 Holt, Rinehart, & Winston Chapter 4 Biology: Cell Review Modern Biology©2009 Holt, Rinehart, & Winston Chapter 4

Cell History Robert Hooke, 1665, saw cork under light microscope, and called individual units “cells”. van Leeuwenhoek, 1673, saw living cells under microscope with 10x greater magnification M. Schleiden, 1838, said all plants were made of cells T. Schwann, 1839, said all animals were too. R. Virchow (1821-1902) said all cells came from preexisting cells

Cell Theory Has 3 essential parts: Cells come only from reproduction of existing cells. Cells are basic unit of structure & function in organisms. All living organisms are composed of 1 or more cells.

Cell Structure Form follows function: Shapes evolve to allow cells to perform their function. Sizes range from nm to 2 m in length, but average cells are 10 – 50 mm. Surface-area-to-volume ratio limits size. Volume increases more quickly. Cells’ need for nutrient intake & waste disposal depends on proximity to cell membrane.

Cell Types Two basic types Prokaryotic Eukaryotic Has no membrane-bound organelles or nucleus Is divided into 2 domains Bacteria – similar to 1st cellular life forms Archaea Eukaryotic Has membrane-bound organelles, including nucleus

Plasma Membrane Phospholipid bilayer Regulates passage in/ out of cell Outer & inner phosphate heads are polar Inner portion composed of lipid tails Regulates passage in/ out of cell Separates cellular activities from environment Interfaces with environment Includes integral & peripheral proteins & lipids (sterols)  Fluid Mosaic Model

Cellular Organelles & Functions Nucleus: houses/protects genetic info (DNA) Nucleolus: site of ribosomal RNA production Mitochondrion: energy production Ribosomes: protein production Endoplasmic reticulum: intracellular highway RER: phospholipids & proteins; SER: lipids + detox Golgi apparatus: sort/package proteins + lipids Lysosomes: digest large molecules & invaders Peroxisomes: break down R-OH, f.a., bacteria

Cytoskeleton Network crisscrossing cytoplasm Gives shape to cell Acts as system of internal tracks Has 3 structural elements Microtubules: made of tubulin; make flagella/cilia Centrioles: organize microtubules in cell division Microfilaments: made of actin, help in cell movement Intermediate filaments: rods: anchor nucleus et al, make up hair shaft

Plant Cells Unique Structures but have no centrioles Cell Wall: primary + secondary Made of cellulose Central Vacuole Made as smaller vacuoles fuse together Stores water, enzymes, wastes, etc… Plastids Chloroplast: site of photosynthesis Chromoplast: has colored pigments + photosynthesis Amyloplasts: store starch