Download Fundamentals of Anatomy and Physiology, Second Edition

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Chapter 3
Cell Structure
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Introduction
• The cell is the basic unit of biological
organization
• Basic composition
– Protoplasm
– Cell membrane
– Organelles
• Eukaryotic vs. prokaryotic
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History of the Cell Theory
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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
– Cells arise only from other cells
– All existing cells are descendants of the first
cells
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Anatomy of a Typical
Eucaryotic Cell
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Introduction
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The Cell Membrane
• Double phospholipid layer with embedded
proteins
• Membrane transport: selectively
permeable membrane
– Osmosis
– Protein channels
– Active transport
– Fluid mosaic model
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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
• Polar compounds go into solution
• Nonpolar compounds go into colloidal
suspension
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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
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The Mitochondria
• Powerhouses of the cell
• Cristae: inner folds where cellular
respiration occurs
• Energy requirements of cell determine
cristae number
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Lysosomes
• Digestive enzyme packages
• Function
– Digest stored food
– Maintenance and repair of organelles
– Suicide agents for old or weak cells
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Endoplasmic Reticulum
• System of membranes that makes up
channels
• Connects with outer nuclear and cell
membranes
• Cisternae: sac-like or channel-like cavities
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Endoplasmic Reticulum (cont’d.)
• Rough ER
– For protein synthesis
– Attached ribosomes
• Smooth ER
– Fat transport
– Sex hormone synthesis
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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
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Ribosomes
•
•
•
•
Distributed throughout cytoplasm
Attached to rough endoplasmic reticulum
No membrane covering
Site of protein synthesis
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Ribosomes (cont’d.)
• Protein functions
– Structure, enzymes or catalysts, immune
response
• DNA contains the code for a particular
protein
– DNA found in nucleus
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Ribosomes (cont’d.)
• Transcription
– Messenger RNA copies DNA code and leaves
nucleus
• Translation
– Transfer RNA picks up amino acids
– Ribosomes link amino acids together
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Ribosomes (cont’d.)
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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
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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
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Animation – Anatomy of a Typical
Cell
• [Insert typical cell.swf]
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Plastids of Plant Cells
• Chloroplasts
– Most common plastid
– Photosynthesis: conversion of light into
chemical energy
– Granum
• Made of thylakoids
• Connected by lamella
• Chromoplasts: carotenoid pigments
• Leukoplasts: store food
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Plastids of Plant Cells (cont’d.)
• Cell membrane surrounded by cell wall
• Cell wall composed of cellulose
– Cellulose
• Dietary fiber
• Synthesized by Golgi bodies
• Animal cells do not have cell walls
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Summary
• Discussed the modern cell theory and its
origins
• Discussed the different parts of eukaryotic
cells including the cell membrane,
cytoplasm and organelles
• Discussed protein synthesis
• Described some of the differences
between plant and animal cells
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