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Cell Structure and Function
All living organisms are made up of cells.
Cells are:• The basic unit of structure and function of a living organism.
– Organisms can be unicellullar
– Organsims can be multicellular
History of the cell.• 1665 Anton van Leevwenhoek: constructed
first simple microscope.• Viewed pond water and saw tiny moving
structures • he called “wee little beasties” or
“animalcules
• .
• 1670 Robert Hooke– English scientist – invented first compound light microscope.– Viewed cork– Named tiny, hollow units and called them
“cells”.
Approximately 200 years later…
• 1833 Robert Brown– First to view a nucleus within a cell.– Scientist now knew that there were structures
within the “cells” and they were not hollow like the cork.
• 1835 Two German scientist, Theodor Schwann (Zoologist) and Matthias Schleiden (Botanist) collectively came to the conclusion:– that all plants and all animals are made up
of cells.
• 1855 Rudolf Virchow recorded that “all cells come from other like and pre-existing cells.
• 1869 Fredrick Miescher: – Discovered: DNA’s presence (not its
structure) but did not know its importance until much later.
– He called it nuclein.
• 1879 Walter Flemming: Identified chromosomes in the nucleus. Once again did not know the true importance of them.
The Cell Theory
• 1. Every living organism is made up of one or more cells.
• 2. Cells are the basic unit of structure and function of all living organisms.
• 3. All cells arise from like, pre-existing cells.
Two types of cells exist: Prokaryotic and Eukaryotic Cells
Prokaryotic Cells
• Word means “before nucleus”• Includes all bacteria
– Believed to be the first cells on Earth in the primordial soup
Traits:
• Lack a nucleus • Lacks all membrane bound organelles.• Genetic material just floats around the
center of the cell.
Eukaryotic Cells
• Word means “contains a true nucleus”
• Examples includes all animals, plants, fungi, and protist.
• TRAITS:
• Evolved from prokaryotic cells.– Theory is one prokaryotic cell engulfed
another and now there was a cell within another cell.
• Eukaryotic cells contain a nucleus and membrane bound organelles.
• Organelles are “tiny organs” within a cell, each having their own function.
Two types of eukaryotic cells:
Plant-like Animal-like
Traits common to both prokaryotic and eukaryotic
cells
-Plasma / cell membranes-Cytoplasm-Cell wall-Genetic material-Ribosomes
Cell Membrane
Plasma or Cell Membrane: Function:
1. Outer boundary of the cell-separates one cell from another
2. Allows for interaction between like cells within a tissue.
3. Acts as a “gatekeeper”-regulates what is allowed to enter or leave the cell.
4.Aids in protection and support.-keeps out bacteria-provides some shape
OxygenFood MoleculesWater
Carbon dioxideCellular WasteExcess water
Fluid Mosaic Model
-model of the structure of a cell membrane-discovered in 1972
The cell membrane:-Consist of a double layer of phospholipids
with proteins and some carbohydrates scattered throughout the bilayer.
-known as a phospholipid bilayer
Components of the Cell Membrane
Carbohydrate chains
Phospholipid bilayer
Proteins: - receptor proteins - transporting proteins - adhesion proteins
Used for cell recognition
Type of lipid
Phospholipid-type of lipid
-most abundant component in the membrane
Hydrophobic Tail-water fearing-nonpolar
Hydrophilic Head-water loving-polar
Extracellular Fluid: Cells watery environment
Intracellular Fluid: Cells liquid center/cytoplasm
Several types of proteins embedded in the bilayer:
1. Receptor proteins: act as a docking area for items to attach to like hormones.
2. Transporting proteins:
-transports items across the bilayer
3. Adhesion Proteins:
-project outward from bilayer and help cells within a tissue to stick together.
Cytoplasm:1. -liquid part of the cell2. -found in all areas between the nucleus and the cell membrane
3.-made mostly of water with salts, amino acids, nucleotides, etc… dissolved in it.
Function: -to suspend and allow structures to move about.
Cell Wall:1.-surrounds cell membrane
-found in plants, fungi, some bacteria and some protist.2.-located outside the cell membrane3.-provides shape and support
4. -has openings so items can pass through.
5. -made up of cellulose and pectin in plants and chitin in fungi.
Turgor Pressure:1. -Pressure created by water
-cell loses water-turgor pressure decreases-cell wall bows inward-cell shrinks in size
2. Cell takes in water- turgor pressure increases- cell wall bulges out- cell swells
Genetic Material:1.-made up of DNA2.-has instructions for making all cellular proteins.
Prokaryotic Cells:-Have no nucleus-DNA is free floating-DNA is in 1 circular
loop
Eukaryotic Cells:-DNA contained in a nucleus-many linear pieces of DNA known as
chromosomes.
Ribosomes:
The cells “workbench”
Job: Makes proteins, in their linear form, by assembling amino acids in the correct order based on DNA’s code.
Ribosomes are made up of RNA and proteins.
Found attached to the endoplasmic reticulum
or
Free floating in the cytoplasm
Continue on to Bacteria lecture
Continue on to Viruses
