Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Cell Structure Chapter 5 Copyright © McGraw-Hill Companies Permission required for reproduction or display

Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Cell Theory Schleidon and Schwann All organisms are composed of one or more cells.  Metabolism and heredity occur within these cells. Cells are the basic units of organization for all organisms. Cells arise only by division of a previously existing cell.

Three Main Features of ALL Cells 1. Surrounded by a plasma membrane that encloses the cell and separates its contents from its surroundings - phospholipid bilayer with embedded proteins (transport proteins and receptor proteins) 2. Genetic material is enclosed within a nucleus or a nucleoid 3. Cytoplasm Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Cells Are Small The human body has approx. 100 Trillion Cells Cell diameter range: 7.5 micrometers (RBC) to 150 micrometers (ovum)

Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Cells Are Small Advantage of small cell size is explained by surface area-to-volume ratio.  As a cell’s size increases, its volume increases much more rapidly than surface area.  Cell membrane plays a key role in controlling cell function. - Small cells have more surface area per unit volume thus more effective communication.

Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Prokaryotic Cells Bacterial cells are small, consisting of cytoplasm surrounded by a plasma membrane enclosed within a rigid cell wall of peptidoglycan (carbohydrate matrix crosslinked by short polypeptide units)  Categorized by cell wall structure: - Gram Positive - Thick, single-layered cell wall. Gram Negative - Multilayered cell wall (less peptidoglycan)  Many propelled by flagellum (flagella).  Lack internal organization.

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Eukaryotic Cells Interior of eukaryotic cells contain numerous membrane-bound structures (organelles) that close off compartments to allow multiple simultaneous biochemical processes.  Vesicles - Storage and Transport (Plants and Animals)  Nucleus – Chromosomes (DNA)  Cytoskeleton - Internal Structure  Central Vacuole - Storage (Plants Only)

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Nucleus Largest organelle: repository of genetic info. DNA is divided into chromosomes found in nucleus (chromatin) Nucleolus in center: synthesizes rRNA Nuclear envelope made of two phospholipid bilayers Nuclear pores in envelope filled with proteins allow passage of two types of molecules

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Endoplasmic Reticulum Internal membrane composed of phospholipid bilayer and embedded proteins.  Weaves through cell, creating series of cisternal channels between its folds (cisternae) Rough ER - Surface regions covered with ribosomes.  Synthesizes proteins for export. Smooth ER - Membrane has few embedded ribosomes, and is embedded with enzymes for lipid synthesis, carbohydrate synthesis

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Golgi Apparatus Collection of interconnected flattened stacks of membranes (Golgi bodies). Each membrane is called a cisternae.  Function in collection, packaging, and distribution of molecules synthesized in one place, and utilized in another place within the cell. - Cis face - Receiving end - Trans face - Discharging end

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Vesicles Lysosomes - Membrane-bound digestive vesicles that arise from Golgi apparatus.  Contain degrading enzymes. - Break down old organelles and other structures and recycles them Microbodies - Bear enzymes for metabolism  Glyoxysome - Convert fat into carbohydrates  Peroxisome – Detoxify (those of kidneys and liver contain degrading enzyme catalase to detoxify hydrogen peroxide) metabolic waste, drugs, etc.

Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Ribosomes Ribosomes are site of protein synthesis.  Made up of rRNA bound within complex of several dozen different proteins.  Composed of two subunits (large RNA and smaller ribosomal protein) - Join to form functional ribosome only when they attach to messenger RNA.  Assembled in nucleolus within the nucleus.

Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Organelles With DNA Mitochondria  Bound by smooth outer membrane and an inner membrane folded into cristae.  Contain own DNA.

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Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Organelles With DNA Chloroplasts  Contain photosynthetic pigment chlorophyll that gives most plants their green color.  Double membrane  Grana - Stacked membranes internal to inner membrane. - Contain disk-shaped Thylakoids which also contain light-capturing pigments on surface Stroma – fluid surrounding grana

Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Chloroplast Structure Copyright © McGraw-Hill Companies Permission required for reproduction or display

Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Organelles With DNA Centrioles - Barrel-shaped organelles usually located near nuclear membrane.  Help assemble microtubules.  Some appear to contain DNA.

Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Cytoskeleton Network of protein fibers supports cell shape.  Individual fibers formed by polymerization. - Actin Filaments – cell movement and formation of cellular extensions - Microtubules – cell movement and moving material within cell - Intermediate Filaments – line organs and body cavities

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Cell Movement Some cells crawl via a pseudopod. Moving Material Within the Cell  Short Distances – ER and Golgi Apparatus  Long Distances - Molecular Motors - Vesicle - Microtubule

Cell Movement Many eukaryotic cells contain flagellum consisting of a circle of nine microtubule pairs surrounding two central microtubules: “9+2 Structure” Flagella undulates with the help of flagella motor protein dynein. Cilia: short cellular projections often organized in rows that carry out a multitude of functions Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Plant Cells Central Vacuole - Functions as storage center and helps increase surface-to-volume ratio by stretching (swelling) cell Cell Walls Chloroplasts Plastids: organelle for photosynthesis and starch storage -Choroplasts -Leucoplasts -Amyloplasts

Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Endosymbiosis Theory of endosymbiosis proposes some eukaryotic organelles evolved by symbiosis.  One species of prokaryote was engulfed and lived inside another.