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Chapter 3. Cell Structure. Introduction. The cell is the basic unit of biological organization Basic composition Protoplasm Cell membrane Organelles Eukaryotic vs. prokaryotic. History of the Cell Theory. History of the Cell Theory. Proposed in 1830s by Schleiden and Schwann
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Chapter 3 Cell Structure
Introduction • The cell is the basic unit of biological organization • Basic composition • Protoplasm • Cell membrane • Organelles • Eukaryotic vs. prokaryotic
History of the Cell Theory • Proposed in 1830s by Schleiden and Schwann • Modern cell theory • Cells are smallest complete living things • All organisms are composed of one or more cells
History of the Cell Theory (cont’d.) • Modern cell theory • Cells arise only from other cells • All existing cells are descendants of the first cells
The Cell Membrane • Double phospholipid layer with embedded proteins
The Cell Membrane (cont’d.) • Membrane transport: selectively permeable membrane • Osmosis • Protein channels • Active transport • Fluid mosaic model
Cytoplasm of the Cell • Mostly water with chemical compounds in solution or colloid • Solution vs. colloid • Individual vs. clumped atoms or ions distributed in medium
Cytoplasm of the Cell (cont’d.) • Polar compounds go into solution • Nonpolar compounds go into colloidal suspension
The Nucleus • Control center of the cell • Nuclear membrane has pores to allow substances passage • Chromatin genetic material inside nucleoplasm • Nucleolus: site of ribosome formation
The Mitochondria • Powerhouses of the cell • Cristae: inner folds where cellular respiration occurs • Energy requirements of cell determine cristae number
Lysosomes • Digestive enzyme packages • Function • Digest stored food • Maintenance and repair of organelles • Suicide agents for old or weak cells
Endoplasmic Reticulum • System of membranes that makes up channels • Connects with outer nuclear and cell membranes • Cisternae: sac-like or channel-like cavities
Endoplasmic Reticulum (cont’d.) • Rough ER • For protein synthesis • Attached ribosomes • Smooth ER • Fat transport • Sex hormone synthesis
Endoplasmic Reticulum (cont’d.) • Golgi apparatus • Collection of flat saclike cisternae • Concentration and collection of cellular compounds • Storage warehouses of the cell • Carbohydrate synthesis site
Ribosomes • Distributed throughout cytoplasm • Attached to rough endoplasmic reticulum • No membrane covering • Site of protein synthesis
Ribosomes (cont’d.) • Protein functions • Structure, enzymes or catalysts, immune response • DNA contains the code for a particular protein • DNA found in nucleus
Ribosomes (cont’d.) • Transcription • Messenger RNA copies DNA code and leaves nucleus • Translation • Transfer RNA picks up amino acids • Ribosomes link amino acids together
Centrioles • Centrosome: two centrioles at right angles to each other • Composed of nine sets of triplet fibers • Form spindle fibers during cell division • Guide duplicated chromosomes to daughter cells
Cilia and Flagella • Hairlike protrusions from cell membrane • Nine double fibrils around two single central fibrils • Cilia move materials across cell surface • Flagellum propels cell through a medium
Animation – Anatomy of a Typical Cell Click Here to Play Anatomy of a Typical Cell Animation
Plastids of Plant Cells • Chloroplasts • Most common plastid • Photosynthesis: conversion of light into chemical energy • Granum • Made of thylakoids • Connected by lamella
Plastids of Plant Cells (cont’d.) • Chromoplasts: carotenoid pigments • Leucoplasts: store food • Cell membrane surrounded by cell wall
Plastids of Plant Cells (cont’d.) • Cell wall composed of cellulose • Cellulose • Dietary fiber • Synthesized by Golgi bodies • Animal cells do not have cell walls
Summary • Discussed the modern cell theory and its origins • Discussed the different parts of eukaryotic cells including the cell membrane, cytoplasm and organelles
Summary (cont’d.) • Discussed protein synthesis • Described some of the differences between plant and animal cells