Chapter 5 Cell Structure

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Chapter 5Cell Structure Function
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Vocabulary

• Excretion Waste materials of cell activity are
  passed from the cell to the environment.
• Cytoplasm Cell substance outside the nucleus
  and inside the cell membrane.
• Mitochondria Produces energy for the cell.
• Organ Structure which is composed of several
  types of tissue.
• Colonial Unicellular organisms which tend to
  group or live together.
• Vacuoles Cavities or sacs filled with extra
  food or water.
• Organelles Small cell structures in the
  cytoplasm and means little organs.
• Lipid molecules Molecules of fatty acids and
  glycerol.
• Protoplasm - A living material within a cell.
• Cristae Folds in the inner walls of the
  mitochondria which increase the surface area.
• Carotenes The yellow or orange color in some
  plants.
• Cell Wall Found only in plants and it supports
  and protects the plant cell.
• Multicellular Complex organisms made of many
  cells.
• Unicellular Simple organisms made of one cell.
• Organ System Group of organs joined together to
  perform a common function.

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Homework

• Read p. 87 101
• Homework p. 110-111
• Multiple Choice 1-8
• True/False 1-8
• Word Relationship 1-4
• Concept Mastery 1-8

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The Cell

• It was in the 17th century that some great men
  developed and perfected tools and instruments
  which were of great value of Biology.
• This era was later to be called the beginning of
  the Scientific Revolution.
• One of the most important developments in this
  time was the microscope.
• It was continually improved until the 19th
  century when it helped to develop one of the most
  important principles of Biology, which was the
  Cell Theory.
• Leeuwenhoek, who developed one of the first
  microscopes, was also one of the first scientists
  to report his findings to people of authority.

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• These people were a group of scientists who
  joined together to form the Royal Society of
  London.
• At this time they were the ruling body of all
  sciences.
• Leeuwenhoek wrote letters explaining in detail
  each one of his experiments.
• The members of the society were required to
  reproduce each experiment to prove whether the
  results were true or false.
• All of Leeuwenhoeks experiments were proved to
  be true.
• In 1933, an experiment was started to determine
  the quality of Leeuwenhoeks microscopes.
• It was proven that his microscope magnified
  objects up to 270 times.
• A picture was taken through his microscope and it
  showed almost exactly what scientists saw through
  our modern day microscopes.
• Without his discovery, Biology may still be in
  the dark ages.

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• Robert Hooke held the position of Curator of
  Experiments for the royal society.
• In the early 1660s, Hooke had designed and built
  a compound microscope.
• All modern microscopes are simply extensions or
  improvements of Hookes microscope.
• He then wrote a book called Micrographia in which
  he described all of his experiments.
• The word micrographia has a two part meaning
• Micro means microscope
• Graphia means drawings
• So the word means microscope drawings.

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• Hooke is most famous for his experiment in which
  he studied cork to see why it floated.
• He found through his experiment that cork was
  filled with small pores which he called cells.
• He described them as being small, shallow boxes
  running throughout the cork.
• He also reported seeing the same structures in
  the stems of plants.
• Hooke did not realize how important his discovery
  was.
• He set the ground rules for the modern study of
  Biology by giving scientists a place to start.

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Schleiden Schwann

• These are the men who set up some ground rules
  about cells and cellular study.
• Schleiden was a Botanist who worked only with
  plants.
• Schwann was a Zoologist who worked only with
  animals.

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• Together they developed the Cell Theory.
• Their theory started scientists working on the
  cellular level.
• The cell became to Biology what the atom was to
  Chemistry.
• The cell became the basis for building complex
  organisms and substances.
• There are five steps to the cell theory.
• Every living organism is composed entirely of
  cells.
• Some organisms only have one cell but they too
  function as living independent organisms.
• Most cells are microscopic and contain the same
  basic units inside.
• The activities of all cells are the same.
• The molecules, of which all cells are made, are
  basically the same.
• Cells come only from other cells.
• These are the basic concepts of the cell theory
  and they show you the importance of the cell to
  the beginnings of Biology.

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Cell Size and Shape

• The cell varies in size but within a very small
  range.
• Only specialized cells such as nerve cells and
  some unicellular plants and animals can be seen
  with the unaided eye.

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• The metric system is used to measure cells and
  the word used to describe this measurement is
  called a micron.
• A micron is abbreviated by the Greek letter (µ).
• 1 micron is equal to one thousandth of a
  millimeter.
• The average size in microns of cells in many
  organisms measure between 10-30 µ across.
• There are smaller cells and there are larger
  cells.
• This is only an average.
• In the body of a newborn baby there are about 2
  trillion cells and each of these cells does not
  perform every body function.
• There is a specialization of cells.
• In humans the nerve cells do not produce after
  birth and they only perform one specific function
  which is to carry messages.
• Also red blood cells dont reproduce they just
  carry food and oxygen in the blood.
• There are many more types of cells in the human
  body, each doing its own job.
• This type of situation not only exists in animals
  but also in plants.
• The higher an organism is classified the more
  specialized cells doing special jobs.
• This is an example of Division of Labor.

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Structure of a Cell

• The first structure of the cell membrane.
• This is semi-permeable, which means it only
  allows certain size particles to pass through it.
• There are 4 major processes that control the
  moving of materials across the membrane.
• In any of these processes energy is required for
  them to work.
• No one cell uses all the processes, most cells
  use only 1 or 2.

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• The 4 processes are diffusion, osmosis, active
  transport, and pinocytosis.
• Diffusion The process where molecules move from
  an area of high concentration to an area of lower
  concentration.
• Osmosis This is also molecules moving from high
  to low concentration but in doing so the
  molecules cross a semi-permeable membrane.
• Active Transport This occurs when the substance
  trying to enter the cell is too large to pass
  through a membrane by itself.
• In this situation an enzyme attaches to the
  substance and carries it across the membrane.
• The enzyme breaks down the substance as it is
  carried across the membrane.
• Pinocytosis This occurs when a vacuole or
  pocket is formed in the cell membrane.
• The substance will enter it and be trapped by the
  membrane.
• Once the substance is inside, a vacuole is formed
  around it and the substance it broken down.

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• Endoplasmic Reticulum
• This area was not actually located and named
  until 1945.
• This is a system of very small tubes running from
  the cell membrane to the nucleus.
• It carries energy and supplies to the nucleus and
  removes wastes.
• Its tubes also divide the cytoplasm into small
  areas so that if part is damaged, the whole cell
  is not destroyed.
• Golgi Bodies
• These are the chemical factories of the cell, in
  which large sugar molecules are built.
• They are always near the nucleus.
• They are also now believed to help form new
  endoplasmic reticulum.

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• Mitochondria
• This converts chemical energy for all life.
• Each mitochondria are smooth on the outer surface
  and it contains a folded inner membrane.
• The mitochondria are also called the power house.
• The more active the cell is, the more
  mitochondria it will have.
• The folds in the inner wall are called cristae
  and they function to increase surface area.
• Lysosome
• This is a sac containing enzymes that break down
  large molecules that enter the cell.
• This sac has a tough membrane around it which
  prevents the enzymes from escaping into the
  cytoplasm.
• If the cell dies or is damaged the enzymes are
  released to help break down the cell.
• For this reason the lysosome is also called the
  suicide sac.

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• Ribosome
• These are found attached directly to the outer
  membrane of the endoplasmic reticulum.
• This organelle contains large amounts of a
  protein called ribonucleic acid (RNA).
• The ribosomes function to produce new proteins.
• Vacuoles
• In most cells there are 2 types of vacuoles which
  are food and water.
• They both store extra amounts of food and water
  for later use.
• The water vacuole will in some cases also store
  fat molecules and waste materials.
• Cytoplasm
• The word cytoplasm comes from two words, cyte
  meaning cell, and plasma meaning fluid.
• The cytoplasm is a semi-fluid or jelly-like
  substance within the cell.
• All organelles are found inside the cytoplasm.
• Sometimes, it will also store solid food for
  later use.

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• Nucleus
• The nucleus of a cell has 2 major functions.
• It controls all cell activities.
• It plays an important part in cell division and
  heredity.
• The material in the nucleus is held in place by
  the nuclear membrane.
• The protoplasm in the nucleus contains a special
  chemical called chromatin, which eventually forms
  chromosomes.
• The chromosomes contain specific nucleoprotein
  called deoxyribonucleic acid (DNA).
• This controls the functioning of chromosomes and
  genes it is not found anywhere else in the body
  and it is unique for each individual person.

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• Nucleolus
• This organelle is found inside the nucleus of
  some cells.
• The major function of this is to produce new
  ribosomes for the cell.
• During certain stages of cell division it will
  disappear completely and reappear later when cell
  division is completed.