mrs. p biology. cell theory in 1665, englishman robert hooke used an early light microscope to look...
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UNIT 3: CELL STRUCTURE AND FUNCTION
Mrs. P Biology
Cell Theory In 1665, Englishman Robert Hooke
used an early light microscope to look at a thin slice of cork.
Under the microscope, cork seemed to be made of thousands of tiny, empty chambers.
Hooke called the chambers “cells”.
Cell Theory
By 1855, it was clear that cells were the basic units of life, and the Cell Theory was born. The cell theory states:
1 All living things are made of cells2 Cells are the basic units of structure
and function in living things. 3 New cells are produced from
existing cells.
LEVEL OF ORGANIZATION
The levels of organization in multicellular organisms:
Cells g tissues g organs g organ systems g organism
TWO MAJOR TYPES OF CELLS Cells fall into 2 major categories:
prokaryotes and eukaryotes.
Prokaryotes (pro = before, karyon = nucleus, so
literally “before nucleus” Generally smaller than eukaryotes. Lack a nucleus and membrane
bound organelles.
Prokaryotes Store genetic material in one circular
DNA molecule called a nucleoid. Have a cell wall made of
peptidoglycan.
Eukaryotes eu = true, karyon = nucleus, so
literally “true nucleus” Generally bigger than prokaryotes Have a nucleus and cytoplasm (gel
like material inside)
Eukaryotes
Have membrane bound organelles (literally “little organs”) that carry out different functions.
Store genetic material in the nucleus.
PARTS OF THE CELL
A eukaryotic cell is like a microscopic factory. It is filled with organelles, each of which has its own job.
Most biologists divide the cell into two major parts: the nucleus and the cytoplasm.
The cytoplasm is the part of the cell outside of the nucleus.
Cell Structure Type of Cell Structure Function
Nucleus All cells except prokaryotes
In the center of the cell, surrounded by a nuclear envelope. Envelope has pores, which allow things to move in and out of the nucleus.
Controls all of the cell’s activities
Contains the genetic material for the cell (chromatin/chromosomes)
Plasma Membrane
Cell Structure Type of Cell Structure Function
Plasma Membrane
ALL cells Made of a lipid bilayer, with proteins embedded inside and carbs attached to the proteins. “Fluid Mosaic Model”
Regulates what enters and leaves the cell.
Provides protection and support.
Cell wall
Cell Structure Type of Cell Structure Function
Plasma Membrane
ALL cells Made of a lipid bilayer, with proteins embedded inside and carbs attached to the proteins. “Fluid Mosaic Model”
Regulates what enters and leaves the cell.
Provides protection and support.
Cell Wall PlantsFungiProkaryotes
Outside of the plasma membrane. Made of cellulose in plants, chitin in fungi, peptidoglycan in prokaryotes.
Structural support (grow tall)
Protection allows H2O,
O2, CO2 to diffuse in & out of cell
Cell Structure Type of Cell Structure Function
Ribosome ALL cells Small particles of RNA and protein found throughout the cytoplasm or attached to the Rough ER.
Synthesize (make) proteins.
Mitochondria
Cell Structure Type of Cell Structure Function
Ribosome ALL cells Small particles of RNA and protein found throughout the cytoplasm or attached to the Rough ER.
Synthesize (make) proteins.
Mitochondria All eukaryotic cells
Shaped like a peanut, it has a double membrane, the inner membrane has folds called cristae.
Converts energy stored in food into energy used in the body (ATP) in a process called cellular respiration.
Cell Structure Type of Cell
Structure Function
Endoplasm Reticulum
Eukaryotic cells
Rough ER has ribosomes attached to its surface, smooth ER does not.
Helps with protein synthesis
Where lipids in the cell are made
Golgi Apparatus
Cell Structure Type of Cell
Structure Function
Endoplasm Reticulum
Eukaryotic cells
Rough ER has ribosomes attached to its surface, smooth ER does not.
Helps with protein synthesis
Where lipids in the cell are made
Golgi Apparatus Eukaryotic cells
Stacks of flattened sacs
Modifies, sorts, and packages proteins and other materials made in the cell.
Helps to “ship” materials out of the cell.
Cell Structure Type of Cell Structure Function
Vacuoles Plant cells have one big vacuoleAnimal cells have smaller vacuoles (called vesicles)
Fluid filled sacsLargest organelle in plant cells
Store materials like carbohydrates water, salt, and proteins.
Structural support in plants.
Chloroplasts
Cell Structure Type of Cell Structure Function
Vacuoles Plant cells have one big vacuoleAnimal cells have smaller vacuoles (called vessicles)
Fluid filled sacsLargest organelle in plant cells
Store materials like carbohydrates water, salt, and proteins.
Structural support in plants.
Chloroplasts Plant cells Contain chlorophyll (green)Have small stacks of thylakoids called grana
Capture energy from sunlight and convert into chemical energy (photosynthesis)
Cell Structure Type of Cell Structure Function
Lysosomes Eukaryotic cells Small organelles filled with enzymes
Breaks down large food molecules into smaller molecules for the cell
Breaks down old cell parts
Cytoskeleton
Cell Structure Type of Cell Structure Function
Lysosomes Eukaryotic cells Small organelles filled with enzymes
Breaks down large food molecules into smaller molecules for the cell
Breaks down old cell parts
Cytoskeleton Eukaryotic cells Made of protein filamentsMicrofilaments (actin) and microtubules (tubulin)
helps the cell to maintain its shape
helps with cell division
Cell Specialization Organisms that are made up of many
cells are called multicellular Gene expression is especially
important in shaping the way a multicellular organism develops.
Each of the specialized cell types found in the adult develops from the same fertilized egg cell.
Cells throughout an organism develop in different ways to perform different tasks. This process is called cell specialization.
Different types of cells have different types of shapes and parts so that they can perform different functions.
A series of genes called the HOX genes control the differentiation of the cells and tissues in the embryo.
During the process of differentiation, only specific parts of the DNA are activated. Different parts of the genetic instructions are used in different types of cells (this is influenced by the cell’s environment)
Because all the cells in an organism contain the same DNA, they initially have the potential to become any type of cell; however, once a cell differentiates, the process cannot be reversed.
SPECIALIZED CELLS Neuron – cells that
carry messages throughout the nervous system. Have an axon to send electrical impulses over long distances and dendrites to pass and receive messages from other nerve cells.
Red Blood cells – have a small disc like shape to increase the surface area for oxygen absorption; hemoglobin binds and carries oxygen; no nucleus to make more space for the hemoglobin
Muscle cells - A muscle cell is generally elongated and elastic containing mitochondria in large number. The elongated and elastic feature helps muscle tissues to contract; the mitochondria make more ATP for the cell.
Xylem – have a thick cell wall and hollowed center; used to transport water upward from the roots of a plant
Phloem – a specialized plant tissue used for transporting nutrients and glucose; made of specialized cells called sieve tube cells and companion cells.
Stomata – Where transpiration occurs in a plant. Guard cells surround the stoma and open and close to let water in or out.
Stem Cells Stem cells – unspecialized cells that
continually reproduce. Stem cells can be turned into different specialized cells. Sources of stem cells include:
Embryonic stem cells – found in an embryo; controversial because have to destroy the embryo; are pluripotent (can turn into almost any type of cell)
Adult stem cells – found mostly in bone marrow, but also in liver, brain, skin, and some muscle cells; not as useful as embryonic stem cells.
Umbilical cord/placenta – doctors can now collect an infant’s cord blood; can be used to cure some cancers, blood disorders, and immune disorders.
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