Cell Structure and Function
Chapter four
The Discovery of the Cell
• Robert Hooke – first to see and identify cork “cells.”
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The Cell Theory
• Cell Theory:
1. All living things are composed of cells.
2. Cells are the basic units of structure and function in living things.
3. New cells are produced from existing cells.
SchleidenSchwann
Virchow
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Prokaryotes and Eukaryotes
• Nucleus – large membrane-enclosed structure that contains the cell’s genetic information.
• Prokaryotes – cells that do not contain nuclei. (Bacteria)
• Eukaryotes – cells that contain nuclei. (All other organisms)
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Eukaryotic Cell Structure
• Organelles – structures in a cell that act like “little organs.”
• Cytoplasm – the jelly-like fluid where the organelles “float.”
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Inside the Nucleus
• Nuclear Envelope – membrane that surrounds the nucleus.
• Chromatin – consists of DNA wrapped around proteins. “Ball of string”
• Chromosomes – condensed string-like structure that forms from DNA just before the cell divides.
• Nucleolus – structure within the nucleus that makes ribosomes.
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Inside the Nucleus
Nuclear Envelope
Chromatin
Nucleolus
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Ribosomes
• Ribosomes – made of RNA and protein. Make Proteins!
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Ribosomes
Ribosome
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Endoplasmic Reticulum (ER)
• Endoplasmic reticulum – internal membrane system of the cell.– Lipids, proteins, and other
products are made here.– Rough ER – has ribosomes– Smooth ER – no ribosomes
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Endoplasmic Reticulum (ER)
Rough ER
Smooth ER
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Golgi Apparatus
• Golgi Apparatus – modifies, sorts, and packages proteins.
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Golgi Apparatus
Golgi Apparatus
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Lysosomes
• Lysosomes – small organelles filled with enzymes.– Digest molecules to be used by
the cell.
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Vacuoles
• Vacuoles – store materials.
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Vacuoles
Vacuoles
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Mitochondria
• Mitochondria – organelle that converts chemical energy stored in food into compounds that are more convenient for the cell to use.– “Powerhouse of the Cell!”
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Mitochondria
Mitochondria
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Chloroplasts
• Chloroplasts – organelles that capture energy from sunlight and convert it into chemical energy. (Photosynthesis)– Found only in plants.
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Chloroplasts
Chloroplast
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Cytoskeleton
• Cytoskeleton – helps cell to maintain shape, move, and move organelles.
• Centrioles – help organize cell division. Not found in plants.
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Cytoskeleton
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Cell Boundaries
• Cell membrane – thin, flexible membrane that surrounds the cell.
• Cell walls – rigid layer around the membrane found only in bacteria, fungi and plants.
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Cell Membrane
• Controls what enters/leaves cell, provides support/protection.
• Lipid Bilayer – double-layered sheet of phospholipids.
Two layers!
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Diffusion and Osmosis
• Diffusion – movement of particles from an area of high to low concentration.
• Osmosis – the diffusion of water through a selectively permeable membrane.– Water will move into/out of a cell
to equalize concentrations.
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Osmosis Practice
Cell
90% H2O10% NaCl
90% H2O10% NaCl
Concentrations areequal, so no netmovement of water!
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Osmosis Practice
Cell
90% H2O10% NaCl
80% H2O20% NaCl
Concentration ofwater is greater inthe cell than out, sowater will move out!
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Osmosis Practice
Cell
80% H2O20% NaCl
90% H2O10% NaCl
Concentration ofwater is greateroutside the cell than in, so water will move In!
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Facilitated Diffusion and Active Transport
• Facilitated diffusion – when the plasma membrane “helps” particles pass through protein channels.– No energy used.
• Active transport – when the plasma membrane uses energy to move particles against a concentration gradient.– Uses Transport Proteins
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Facilitated Diffusion and Active Transport
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Organization in Multicellular Organisms
Tissues
Organs
Organ System
Organism
Cells
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