Cells Structure and Function Input from Ms. Thomas (IB teacher) and Heinemann Book

Topic 2 Section 1: Introduction to the Cell

Discovery of Cells The invention of the lens Robert Hooke (1665): observed a thin slice of cork (dead plant cells) with a microscope. He described what he observed as “little boxes” (cells).

Discovery of Cells Anton van Leeuwenhoek (1675): was the first person to observe living cells.

Microscopes Magnification: refers to the microscope’s power to increase an object’s apparent size Resolution: refers to the microscope’s power to show detail clearly

Light Microscope

Elodea - Aquatic Plant 40X400X

Transmission Electron Microscope (TEM)

Herpes Virus Plant Root Cell

Scanning Electron Microscope (SEM)

Mosquito Head 200X2000X

Scanning Electron Microscope (SEM) Fly Eye

Scanning Electron Microscope (SEM) Inside of Stomach Surface of Tongue Neuron

Scanning Electron Microscope (SEM) Pollen Yeast Red Blood Cell, Platelet, and White Blood Cell

TEM vs. SEM Viruses leaving a cell

The Cell Theory Who developed the cell theory? –Matthias Schleiden (1838): concluded that all plants are composed of cells –Theodor Schwann (1839): concluded that all animals are composed of cells –Rudolph Virchow (1855): determined that cells come only from other cells Out line the cell theory

The Cell Theory What is the cell theory? 1.All living things are composed of one or more cells. 2.Cells are organisms’ basic units of structure and function. 3.Cells come only from existing cells Out line the cell theory

Functions of Life State that unicellular organisms carry out all functions of life Growth Metabolism All organisms exist in either a unicellular or a multicellular form. And all organisms carry out all the functions of life. These functions include:

Functions of Life State that unicellular organisms carry out all functions of life Response Nutrition homeostasis Reproduction

Functions of Life All of the functions are tied together to produce a functioning living unit

Cell Diversity Size Shape Internal Organization

Cell Diversity- Size Compare relative sizes of molecules, cell membrane thickness, viruses, bacteria, organelles and cells, sing appropriate SI units

Cell Diversity- Size 6 inches long, 5 inches wide, 3 pounds Smallest Cells: Longest Cells: Ostrich Egg Biggest Cells: 2.1.4

Cells and Sizes Magnification = size of image divided by the size of the specimen 2.1.5

Limiting Cell Size You may wonder why cells do not grow to larger sizes, especially since growth is one of the functions of life. –There is a factor called the surface area to volume ratio that effectively limits the size of the cells. –In the cell, the rate of heat and waste production and rate of resource consumption are functions of (depends on) its volume

Limiting Cell Size Most chemical reactions occur in the interior of the cell and its size affects the rate of these reactions. –The surface of the cell, the membrane, controls what materials move in and out of the cell. Cells with more surface area per unit volume are able to move more material in and out of the cell, for each unit volume of the cell

Limiting Cell Size As the width of an object such as a cell increases, the surface are also increases but at a much slower rate than the volume –This means that a large cell has relatively less surface area to bring in needed materials and to rid the cell of waste, than a small cell.

Limiting Cell Size Because of this, cells are limited as to the size they can attain and still be able to carry out the functions of the life.

Surface Area to Volume Ratio SA = 6 mm 2 SA = 24 mm 2 SA = 96 mm 2 V = 1 mm 3 V = 8 mm 3 V = 64 mm 3 SA/V = 6:1 SA/V = 3:1 SA/V = 1.5:1 V increases faster than SA SA = 6lw V = lwh 2.1.6

Cell Diversity- Shape Cells differ widely in shape. Most cells are roughly cuboidal or spherical.

Multi-cellular organisms show emergent properties Emergent properties arise from the interaction of the component parts; the whole is greater than the sum of the parts'

Cells Differentiate Differentiation: Cells within a multi cellular organism specialize their function. Specialized cells have switched on particular genes (expressed) that correlate to these specialist functions. These specific gene expressions produce particular shapes, functions and adaptations within a cell.

Stem cells : What they are and therapeutic uses

Stem cells They are a population of cells within organisms that retain their ability to divide and differentiate into various cells types –In the early 1980’s, scientist found pluripotent or embryonic stem cells in mice. These cells retain the ability to form any type of cells in a organism and can even form a complete organism

Stem cells When stem cells divide to form a specific type of tissue, they also produce some cells that remain as stem cells. –This allows for continual production of a particular type of tissue. –Medical experts immediately noted the possibilities of such cells in treating certain human diseases

Stem Cell Research and treatments Some of the most promising research recently has been directed towards growing large numbers of embryonic stem cells in culture so that they could be used to replace differentiated cells lost due to injury and disease. –Alzheimers, Parkinsons, diabetes

Stem Cell Research and treatments Besides embryonic or pluripotent stem cells, there are also tissue specific stem cells. –These cells reside in certain tissue types and can only produce new cells of that particular tissue. Leukemia patients

Stem Cell Research and treatments There are important ethical issues involved in stem cell research. –Especially controversial is the use of embryonic or pluripotent stem cells. –This is because the cells come from embryos often obtained from laboratories carrying out IVF To gather these cells involves death of the embryo and opponents argue that this represents the taking of a human life

Where do you stand in the debate about the nature of stem cell research? How do you feel about the source of pluripotent stem cells