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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