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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
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
1. Prokaryotic
i. Has no membrane-bound organelles or nucleus
ii. Is divided into 2 domains
Bacteria – similar to 1st cellular life forms
2. Eukaryotic
Has membrane-bound organelles, including nucleus
Plasma Membrane
• Phospholipid bilayer
– 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
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