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Discovery of Cells Robert Hooke, 1665 Cells in Cork Cellulae (little room)
Life 1402: Principles of Biology Chapter 4: A Tour of the Cell
Lecture Objectives: Know the cell theory of life Understand the difference between prokaryotic and eukaryotic cells Appreciate the difference between an animal and plant cell Understand the significance of cellular compartmentalization Sketch the basic structure of a cell membrane and identify its components Appreciate the basic functions of various organelles within the cell and how these structures work together to support the cell
Since the 1600s, scientists have made many discoveries about the cells of living things.
Robert Hooke – discovered and named cells while observing cork (1670)
Anton van Leeuwenhoek (1680?) Dutch fabric merchant and amateur scientistDutch fabric merchant and amateur scientist observed living cells; called some 'animalcules'observed living cells; called some 'animalcules'
Matthias Schleiden (1838) German botanist German botanist discovered that plants are made of cells discovered that plants are made of cells
Theodor Schwann (1839) German zoologist German zoologist discovered that animals are made of cells discovered that animals are made of cells
Rudolph Virchow (1855) German physician German physician stated that all living cells come only from other living cells stated that all living cells come only from other living cells
These discoveries are summarized in the cell theory. The cell theory states: All living things are made up of cells. All living things are made up of cells. Cells are the basic units of structure and function in living things. Cells are the basic units of structure and function in living things. New cells are produced from existing cells. New cells are produced from existing cells.
Cell theory Cell theory – the cell is the most fundamental and common unit of living organisms; therefore, the definition of life is the presence of cells.
Pro- vs. eukaryotic cells pro- “before” Eu – “true” Karyote “kernel” or Nucleus Prokaryote – no membrane bound nucleus Eukaryote – true nucleus
A Tour of the Cell Cells are the basic unit of all living things. Cells possess a plasma membrane, organelles and cytoplasm Cytoplasm – semifluid substance inside the cell membrane, between organelles
Cell Size Cell size and shape is related to function Nerve cells can be 1 meter long Ostrich eggs are the largest single cell The largest animal and plant cells are 100 m while the smallest cells are 10 m Prokaryotic cells are between 2 and 8 m
Cell Size Limits Surface Area : Volume Ratio limits cell size A cell must absorb all nutrients and excrete all wastes through the membrane surrounding it The more volume a cell has the more it must move across the membrane As a cell grows the volume increases faster then the surface area (size of membrane)
Prokaryotic Cells Prokaryotic cells have no clearly defined nucleus, but do have a nucleoid region The nucleoid region is a coiled loop of DNA, but isn’t contained in a membrane Ribosomes are used to make proteins
Prokaryotic Cells A bacterial cell wall surrounds the plasma membrane Some prokaryotes have a sticky layer called a capsule surrounding the wall Pili may attach the bacteria to a surface, while some use flagella for motility
Eukaryotic Cells Eukaryotic cells are divided into compartments or organelles The nucleus is the most obvious structure in a eukaryotic cell
Eukaryotic Cells Most of the cells chemical activities or cellular metabolism are conducted inside the organelles Plant cells contain some additional organelles and a cell wall
Nucleus The Nucleus is the genetic control center of a eukaryotic cell. Nuclear DNA is in very long fibers called chromatin Each fiber of chromatin is a chromosome During cell division, chromatin condenses so it is visible
Nucleus The nuclear envelope is the membrane that surrounds the nucleus. It contains pores that control the flow of material. The nucleolus is responsible for making ribosomes
Endomembrane System Organelles that are formed by interrelated membranes. Endoplasmic Reticulum “Network within the Cell” Two types smooth and rough Rough ER is covered with ribosomes and is used to produce membranes. Rough ER is also responsible for making proteins that are to be secreted by the cell, such as antibodies.
Golgi Apparatus The Golgi apparatus receives molecules from the ER, sorts, packages and ships them to the proper destination.
Lysosomes Lysosome (lyse – break down, some- body) consist of digestive enzymes in a membranous sac. These are used to digest nutrient particles, bacteria (wbc’s) and recycle worn out organelles.
Lysosomes Tay-Sachs and Pompe’s diseases are both caused by a missing gene for an lysosomal enzyme making victims unable to break down certain molecules.
Mitochondria Mitochondria Convert food into usable a form of Energy (ATP) for the cell. Mitochondria are made up of two membranes. The space between the two membranes is the intermembrane space, while the second membrane contains the mitochondrial matrix. .
Mitochondria Mitochondria The folds in the inner membrane are cristae. They increase the surface area of the inner membrane. Mitochondria have their own DNA and reproduce on their own resembling a prokaryotic cell. All of your mitochondria are inherited from your mother.
Plant Cells Being photosynthetic plants require a few more organelles, including vacuoles and chloroplasts as well as a cell wall.
Vacuoles Vacuoles are mainly used for water storage, but can also store starch or other nutrients.
Vacuoles By filling with water the central vacoule increases the cell’s volume putting pressure on the cell wall. This is called turgor pressure and helps to support plants. Plants wilt due to a loss of turgor pressure.
Chloroplasts Chloroplasts are the organelle of photosynthesis. Chloroplasts are similar to mitochondria in that they have two membranes, but they also contain stacks of disks called grana where chlorophyll traps light energy.
Chloroplasts As in mitochondria, chloroplasts have their own DNA and reproduce on their own.
Cilia and Flagella These structures are used by cells mainly for movement. Cilia are usually shorter and too numerous to count. Flagella are usually longer and few in number.
Cilia and Flagella Trachea cells are lined with cilia that help move foreign objects and mucous out of the lungs. Sperm cells have flagella to make them motile.