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This chapter covers the fundamental concepts of cell structure and function, beginning with historical insights from key scientists like Robert Hooke and Anton van Leeuwenhoek. It introduces the Cell Theory, distinguishing between unicellular and multicellular organisms and highlighting cell specialization. The chapter explores the differences between prokaryotic and eukaryotic cells, focusing on essential organelles such as the nucleus, endoplasmic reticulum, golgi apparatus, and mitochondria. It also discusses transport mechanisms, including diffusion, osmosis, and active transport that are integral to cellular function.
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Cell Structure and Function Chapter 7 Biology Miller • Levine
The Scientists… • Robert Hooke (1665) • Viewed cork under a microscope • Called the chambers he saw “cells” • Anton van Leeuwenhoek (1674) • First to see living organisms in a drop of water
The Scientists… • Matthias Schleiden (1838) • All plants are made of cells • Theodor Schwann (1839) • All animals are made of cells • Rudolf Virchow (1855) • All cells come from preexisting cells
The Cell Theory • All living things are composed of cells • Cells are the basic units of structure and function in living things • New cells are produced from existing cells
Unicellular vs. Multicellular • Unicellular – single-celled organism • Multicellular – many-celled organism • Cell specialization – cells are specialized to perform certain functions • Cells → Tissues → Organs → Organ systems → Organism
Prokaryotes vs. Eukaryotes • Prokaryotes • Have a cell membrane & cytoplasm, but do not have a nucleus • Ex. Bacteria such as E.coli • Eukaryotes • Have a nucleus, cell membrane, cytoplasm & organelles • Ex. Plants, Animals, Fungi
Basic Cell Structures • Cell membrane – thin, flexible barrier around the cell; protects the cell • Present in all cells • Cytoplasm – material inside the cell membrane (not including the nucleus) • Prokaryotes & Eukaryotes
Cell Wall • Found in many organisms, including plants, algae, fungi and nearly all prokaryotes • Not found in animal cells • Lies outside the cell membrane • Main function is to provide support & protection for the cell
Nucleus • Almost all eukaryotic cells, including plants and animals have a nucleus • Prokaryotes do not have a nucleus • Controls most cell process and contains the DNA
Nucleolus and Nuclear Envelope • Nucleolus: • Inside the nucleus • Where ribosomes are made • Nuclear Envelope: • Double-membrane layer around the nucleus • Allows material to move into and out of the nucleus
Cytoskeleton • Found in all eukaryotic cells • Not found in prokaryotes • A network of protein filaments that helps the cell maintain its shape • It also is involved in cell movement
Ribosomes • Found in all cells • Main function is to make proteins • Can be found floating in the cytosol or attached to endoplasmic reticulum
Endoplasmic Reticulum (ER) • Found only in eukaryotic cells • Where components of the cell membrane are assembled • Two kinds: Smooth ER & Rough ER • Smooth ER: no ribosomes; makes lipids • Rough ER: has ribosomes; involved in making proteins
Golgi Apparatus • Found only in eukaryotic cells • Enzymes attach carbohydrates & lipids to proteins • Send proteins to their final destination
Lysosomes • Found in animal cells only • Break down lipids, carbohydrates & proteins from food into particles that can be used by the cell • Also break down “dead” organelles
Vacuoles • Not found in prokaryotes • Animal cells have small or no vacuoles • Plant cells have a large central vacuole • Store materials such as water, salts, proteins & carbohydrates
Chloroplasts • Found in all plant cells • Some prokaryotes have them, but most do not • Use the energy from sunlight to make energy-rich food molecules during photosynthesis
Mitochondria • Found in eukaryotic cells only • Release energy from stored food molecules
Cell Membrane • Regulates what enters and leaves the cell (selectively permeable) • Provides protection and support • Lipid bilayer – two layers of lipids • Proteins run through the layers • Carbohydrates are attached to some of the proteins • Fluid Mosaic Model
Diffusion • Molecules move from an area of high concentration to an area of low concentration • Movement continues until equilibrium is reached • Many substances move across the membrane by diffusion • Does not require energy (passive transport)
Osmosis • The diffusion of water • Isotonic – equal concentration • Nothing happens • Hypertonic – higher concentration • Water moves out of the cell • Hypotonic – lower concentration • Water moves into the cell • No energy is required
Osmotic Pressure • In pure water, an animal cell would burst • Plant cells are protected by their cell wall • Some freshwater organism have special structures like contractile vacuoles to get rid of extra water
Facilitated Diffusion • Some molecules cannot cross the membrane without help • Some of the proteins in the membrane form protein channels • Materials still move from higher to lower concentrations • No energy is required
Active Transport • Materials move from lower concentration to higher concentration • Requires an input of energy • Works kind of like a pump
Transport of Large Amounts • Endocytosis – movement into the cell • Phagocytosis – “cell eating” – solid particles • Pinocytosis – “cell drinking” – particles dissolved in water • Exocytosis – movement out of the cell
