Unit 1- Cells and reproduction

• In this unit, we will be studying:– Cell theory– Animal cells and Plants Cells– Microscopy– Mitosis– Meiosis

Discovery of the cell• The discovery of the cell in the mid

1600’s was by Dr. Robert Hooke. With the use of a compound microscope he saw “ a great many little boxes” in a sample of cork from the bark of an oak tree. Later he called these boxes cells.

• Nearly 200 years after Dr. Hooke’s discovery of the cell, three German biologists, Schwann, Schleiden and Virchow developed a cell theory.

Timeline for the cell theory

• C 1590- Zarchiarias Janssen- Dutch eye-glass maker invented first compound microscope by lining up two lenses

• 1665- Robert Hooke- English scientist examined thin slices of cork which looked “room-like” compartments or cells.

• 1674- Anton van Leeuwenhook reports living beasties as small as 0.002mm. He observed these using a single lens microscope.

• 1700’s- Scientists began to doubt theory of spontaneous generation.

• 1831- Robert Brown was the first to consider “nucleus” as a regular part of a living cell.

• 1839- Theodor Schwann- all animals are made up of cells- this led to all living things are made of cells.

• 1840’s- improved microscopy allows scientists to observe live beasties in matter.

• C1845- “the cell is the basic unit of life”. Alexander Braun

• 1856- William Perkin at 18yrs old developed an intense new purple dye. Staining techniques developed.

• 1858- Rudolph Virchow states that where a cell exists, there must have been a pre-existing cell.

Cell theory

1. All living things are composed of one or more cells.

2. Cells are the basic units of structure and function in all organisms. In other words, cells make up living things and carry out the activities that keep a living thing alive.

3. All cells come from existing cells and are able to make more cells like themselves.

All cells carry out certain functions to ensure growth and

survival.•Take in nutrients and use energy

•Eliminate wastes

•Detect and respond to changes in their environment

•Build and repair parts

•Store information

•Reproduce

Work on questions 2,5, and 9 on page 10 for homework.

Complete the worksheet of plant and animal cells.

Types of cells

• Eukaryotic – all cells containing a membrane bound nucleus. An example would be plant and animal.

•Prokaryotic - Cells that lack a membrane- bound nucleus. An example would be bacteria.

Types of Cells

• Unicellular: Organisms made up of only one cell. This one single cell carries out all the activities that keep the organism alive and allow it to reproduce or make more of its own kind. Example: Bacteria

• Multicellular: Organisms made up of many cells. All the cells work together to keep the organism alive and help it reproduce. Examples: Animals, plants and fungi.

CellsAll cells have 3 things in

common:

1) They are surrounded by a membrane. This membrane has to be flexible, so that the cell can undergo changes, but also has to be tough, so the cell doesn't burst. 

2) They have a DNA-containing region. Deoxyribonucleic acid; a molecule

that stores the genetic information in

cells. A gene is a section of a DNA.

3) They have cytoplasm, which is a gel-like substance in which all cellular components outside the nucleus are immersed.

Parts of a Cell Seen With an Electron Microscope

• The cytoplasm, the working area of every cell, contains special structures called organelles.

• Organelles- tiny cell structures within the cytoplasm that are specialized to carry out a specific function.

• Many of these tiny structures can be seen only with a transmission electron microscope.

• The organelles that we are going to describe, are found in both plant and animal cells.

• Mitochondria- often referred to as the “powerhouse” of the cell. They provide the cell with energy.

• In a process called respiration, mitochondria release energy by combining sugar molecules with oxygen to form carbon dioxide and water.

• This energy is used in almost every other function of the cell.

Figure 7.17 The mitochondrion, site of cellular respiration

• Ribosomes- protein manufacturing. Proteins are put together on ribosomes using information from the nucleus and molecules from the cytoplasm.

• Proteins are large molecules that are needed for cell growth, for repair, and for reproduction.

Figure 7.10 Ribosomes

• Endoplasmic Reticulum- material transport. These are a series of folded membranes which carry materials through the cytoplasm.

• “Rough” endoplasmic reticulum has many ribosomes attached to it while “smooth” endoplasmic reticulum does not have ribosomes attached to it.

Figure 7.11 Endoplasmic reticulum (ER)

• The Golgi Apparatus- Protein Storage. Proteins are stored inside the Golgi Apparatus. This structure also puts proteins into packages, called vesicles.

• These vesicles carry the protein molecules to the surface of the cell where they are released.

Figure 7.12 The Golgi apparatus

• Lysosomes- Recycling. Lysosomes patrol the cytoplasm, cleaning up.

• They contain special proteins that are used to break down large molecules into many smaller molecules.

• In humans and other animals, lysosomes are also used to kill and digest invading organisms and are sometimes referred to as “suicide sacs”

• Nucleolus- structure that is found inside the nucleus. The nucleolus produces ribosomes, which move out of the nucleus to positions on the rough endoplasmic reticulum where they are critical in protein synthesis.

Organelles::

(1) nucleolus(1) nucleolus(2) nucleus(2) nucleus(3) ribosome(3) ribosome(4) vesicle(4) vesicle(5) rough (5) rough endoplasmic endoplasmic reticulum (ER)reticulum (ER)(6) Golgi apparatus(6) Golgi apparatus(8) smooth (8) smooth endoplasmic endoplasmic reticulumreticulum(9) mitochondria(9) mitochondria(10) vacuole(10) vacuole(11) cytoplasm(11) cytoplasm(12) lysosome(12) lysosome

• Organelles:

(1) nucleolus(2) Nucleus(3) Ribosome(4) Vesicle(5) rough endoplasmic reticulum (ER)(6) Golgi apparatus(8) smooth endoplasmic reticulum(9) Mitochondria(10) Vacuole(11) Cytoplasm(12) lysosome

Plant & Animal Cell Similarities

Plant and animal cells are very similar because they are both eukaryotic. (have a membrane bound nucleus) They both contain some of the same organelles. Both also contain similar membranes such as the cytoplasm, and cytoskeleton.

Plant & Animal Cell Differences

Plant cells can be larger than animal cells. Beyond size, the main structural differences between plant and animal cells lie in a few additional structures such as: chloroplasts, the cell wall, and vacuoles

Chloroplasts• Plant cells use sunlight as their energy

source; the sunlight must be converted into energy inside the cell in a process called photosynthesis. Chloroplasts are the structures that perform this function. They are rather large structures that contain the chlorophyll, which absorbs sunlight.

A mitochondria and a chloroplast

The Cell Wall• This wall is composed of fats and

sugars. The tough wall gives added stability and protection to the plant cell.

Vacuoles• Vacuoles are large, liquid-filled

organelles. Vacuoles can occupy up to 90% of a cell's volume and have a single membrane. Their main function is as a space-filler in the cell.

Animal cells do contain vacuoles but they tend to be much smaller