Cell Growth and Reproduction

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Cell Growth and Reproduction

• Key Questions
• Why do cells grow and reproduce?
• How do cells grow and reproduce?

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Chapter 2

• 2.1 The Importance of Cell Division

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Importance of Cell Division

• Growth
• to increase size of organism
• Repair
• replace damaged or old cells
• Reproduction
• primarily unicellular organisms

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All Cells Undergo Cell Division
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Cell Theory

• The cell is the basic unit of life
• All organisms are composed of cells
• Some are composed of only one cell
  (unicellular)E.g. bacteria
• Some are composed of two or more cells
  (multicellular)E.g. turtles

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2.2 Cell Structures Involved In Cell Division
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Cells

• There are 2 main types of cells
• Animal cell
• Plant cell
• Within cells are smaller structures called
  organelles
• Carry out functions to ensure cell survival

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Animal Cell (pg.
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Plant Cell (pg
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Cell Structures

• Cell membrane
• Protective covering
• Allows for certain materials to enter/exit the
  cell
• Cell Wall (in Plant cells only)
• is a tough rigid structure that surrounds the
  cell membrane
• Gives a cell a boxlike shape.
• helps to protect the plants and provides support
  for the growing plant

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Cell Structures cont

• Nucleus
• control center for the cell
• surrounded by nuclear membrane
• contains nucleolus chromosomes
• Nucleolus
• site for production assembly of ribosomes

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Cell Structures cont

• Chromosomes
• each human cell has 23 pairs (46 total)
• made up of deoxyribonucleic acid (DNA) and
  protein
• DNA is a long molecule that looks like a twisted
  ladder
• DNA directs cells activities

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Cell Structures cont

• Cytoplasm
• contains all organelles in the cell
• most activities occur here
• Microtubules
• movement and support for the cell
• Centrioles
• special microtubules involved in cell division in
  animal cells only

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Cell Structures cont

• Mitochondria
• Produces energy for the cell through a process
  called cellular respiration
• Cellular respiration occurs when chemical energy
  taken from the food we eat is converted to energy
  ourselves can use.

Glucose Oxygen ? Carbon dioxide water Energy
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Cell Structures cont

• Chloroplasts
• (in Plant cells only)
• trap energy from the sun change it into
  chemical energy which the plant can use through a
  process called photosynthesis.

Carbon dioxide water energy ? glucose Oxygen
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Cell Structures cont

• Endoplasmic Reticulum (ER)
• series of tubes and flattened sacs used to
• transport materials in cell
• Rough ER
• ribosomes attached
• transports proteins
• Smooth ER
• contains no ribosomes
• makes and transports fats
• Ribosomes
• make proteins
• either free in cytoplasm or attached to
  endoplasmic reticulum (ER)

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Cell Structures cont

• Golgi Body
• sorts proteins and packages them into structures
  called vesicles.
• vesicles carry proteins, nutrients, and water in
  and out of the cell.
• Vacuole
• Storage compartments that store wastes and
  nutrients.
• PLANTS have a large central vacuole that stores
  WATER.

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Cell Structures cont

• Lysosome
• Recycle and break down organelles when they wear
  out.
• contain enzymes to break down food particles,
  cell wastes, and worn-out cell parts.

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2.3 From DNA to Proteins
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DNA

• Chromatin is the material inside the nucleus that
  contains DNA and proteins.
• Each strand of chromatin contains one molecule of
  DNA.
• Chromatin coils tightly into X-shaped chromosomes

• Genes are small segments of DNA located on a
  chromosome
• Genes store the information needed to produce
  proteins

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• Human cells have 46 chromosomes arranged in 23
  pairs
• The 23rd pair determines sex
• XX for females
• XY for males
• Each chromosome can carry thousands of genes

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DNA Structure

• DNA is made of 2 strands of smaller molecules
  called nucleotides
• Nucleotides consist of a sugar, a phosphate,
  and a nitrogenous base

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• Each nucleotide has one of 4 different bases
• adenine (A) cytosine (C)thymine (T) guanine
  (G)
• A always pairs with T (A T)
• C always pairs with G (C G).
• These pairs are often referred to as base pairs.

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The Genetic Code

• The bases in DNA combine to form 3-letter words
  (E.g. GGC or TAC)
• Each 3-letter word codes for the production of
  one of 20 different amino acids
• Amino acids are the building blocks of proteins

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From Genes to Proteins

• DNA molecules in a chromosome are organized into
  genes.
• RNA is a copy of the genetic information in the
  gene
• RNA carries instructions for making proteins from
  genes in nucleus to ribosomes in cytoplasm

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• There are several steps to making a protein from
  DNA, AKA Protein Synthesis.

1. Nucleus receives a signal to make a specific
   protein.
2. The DNA message for a specific protein is copied
   into a small molecule called ribonucleic acid
   (RNA). The RNA has only one strand.

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• 3. RNA leaves through a nuclear pore
• 4. The RNA message is delivered to the ribosome,
  and the ribosome makes the protein.
• 5. The manufactured protein enters the ER.
• 6. A vesicle forms off the end of the ER and
  carries the protein to the Golgi body

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• 7. The Golgi body repackages the protein for
  transport out of the cell.
• 8. A vesicle forms off the end of the Golgi body
  to carry the protein to the cell membrane.
• 9. The vesicle attaches to the cell membrane and
  its protein contents are released out of the cell

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Genes and Variation

• Genes are responsible for all the characteristics
  in a species
• All members of the same species have the same
  number and types of genes (E.g. eye colour) but
  within a species we can have different versions
  of the same gene (E.g. blue vs brown)
• Versions are called traits or alleles.

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2.5 Changes to a Cells DNA
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Changes to a Cells DNA

• Any change in the DNA of a cell is called a gene
  mutation.
• a change in the order of bases (A,C,T,G) that
  make up the gene.
• There are several types of gene mutation
• Deletion (base missing)
• Addition (extra base added)
• Substitution (one base substituted for another)

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• Mutagens are substances or factors that cause
  mutations
• Environmental mutagens such as
• Mercury
• cigarette smoke
• X-ray and UV radiation
• viruses
• Correcting mutations is difficult, but new
  techniques such as gene therapy offer hope.

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The CLONE!!!

• http//www.youtube.com/watch?v8wLiOp4LreIfeature
  related
• Merricks Speech
• http//www.youtube.com/watch?v54q_46SXPQ4feature
  related
• Birthing scene

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Effects of Mutations

• Gene mutations may produce proteins that are
  beneficial or harmful to the organism, or may
  have no effect at all.
• Beneficial (positive)
• Neutral (no effect)
• Harmful
• (E.g. genetic diseases, cancer).

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Beneficial Mutation (positive mutation)

• There are millions of people infected with HIV
  and AIDS
• still no known cure or vaccine
• Some individuals have been found to be resistant
  to the AIDS virus
• because they carry a mutated gene that produces
  instructions for a protein that can prevent HIV
  infection

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Neutral Mutation

• A mutation that does not affect an organism.
• Ex. The gene mutation that results in the white
  coat colour of the spirit bear, since it does not
  increase or decrease the bears survival rate.

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Harmful Mutation (AKA negative mutation)

• Causes genetic diseases, such as Cystic Fibrosis
• CF is caused by a mutation in a gene which codes
  for a protein that helps move certain chemicals
  into out of the cell.
• So the shape of the protein changes which and it
  can no longer do its job which cause the many
  symptoms of CF.
• May cause Cancer

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Cancer Characteristics

• Cancer is a disease in which cells divide very
  rapidly and uncontrollably.
• Cells accumulate in masses called tumours. There
  are 2 types.
• Benign stay in one place and dont interfere
  with surrounding tissues
• Ex. Warts
• Malignant invade surrounding tissues and
  interfere with normal functions
• Visible because of enlarged nuclei.

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Cancer cont

• When cancer cells spread from original location
  this is called metastasis.
• Substances that cause cancer are called
  carcinogens.
• E.g. pesticides, X-rays, some viruses, chemicals
  in tobacco.
• Treatment methods include surgery, radiation, and
  chemotherapy.