Tour of A Cell

A. Introduction

            1. Robert Hooke - 1665

                        a. Sliced a wine bottle cork

b. Looked at it under the microscope - The microscope had just been invented

                        c. Found that the cork was made up of little “cells”

            2. Cell theory

                        a. All living things made up of cells

                                    1. Some are just one cell

                        b. All cells come from previous cells

            3. Simple parts of cell

                        a. Plasma membrane - forms outside border

                        b. Cytoplasm - semi-fluid medium inside cell

                        c. Organelle - “little organ” structures inside cell

B. How to see cells

            1. Light microscope

                        a. Limited magnification - about 1,000X

                        b. To get more magnification you need radiation with a shorter wavelength

            2. Electron Microscope

                        a. Electrons behave like waves - really short wavelength

                                    1. Result is high magnification

                                    2. An electron microscope can magnify 100,000 x

                        b. Great to look at cell organelles

C. Cell sizes

            a. Many are very tiny - 100 microns (1 millionth of a meter)

            b. Some cells are very large - some nerve cells are as long as you are tall

                        1. A chicken egg starts out as 1 gigantic cell

D. Why are there cells?

            a. Surface to volume problem

1. If you have to quickly get stuff into the cell you need to put it through the cell membrane

2. Mostly the speed at which you can get stuff into the cell is limited by the surface area

3. For a cell, as you increase the size you increase the volume faster than you increase the surface area

a. For a big cell, you have a smaller ratio of surface/Volume than for a             small cell

                                    b. Thus cells need to be small to keep the surface/volume large

E. The cell as a factory

            1. The cell is really a little factory

                        a. Some cells manufacture things - secretory cells

                        b. Some cells make things happen - nerve cells and muscle cells

F. Cell Structures

            1. Nucleus

                        a. If the cell is a factory - the nucleus is the shop foreman’s office

                        b. It contains the genetic material in the form of DNA

1. This genetic material is in the form of chromosomes and chromatin

                        c. The nucleus is surrounded by a plasma membrane

                        d. We classify cells by the presence or absence of a nucleus

                                    1. Prokaryotes - Bacteria

                                                a. They have no membrane-bound nucleus  

b. They do have a single circular chromosome - circular DNA

                                                c. These were probably the first organisms on earth

                                    2. Eukaryotes

                                                a. Have a membrane bound nucleus

                                                b. Chromosomes are linear arrangements of DNA

            2. Membranes

                        a. Lipid bilayer

            3. Ribosomes

                        a. Locations were proteins are assembled from amino acids

            4. Endoplasmic reticulum

                        a. Rough Endoplasmic Reticulum

                                    1. A lipid bilayer covered with ribosomes

                                    2. Makes secretory proteins

                                                a. Hair

                                                b. Fingernails

                                                c. Digestive enzymes

                        b. Smooth Endoplasmic Reticulum        

                                    1. Synthesis of lipids

                                    2. In liver

                                                a. Smooth ER detoxifies chemicals

                                                            1. Detoxifies drugs

                                                            2. Reduces efficacy of drugs

                        c. Golgi Apparatus

                                    1. Molecular warehouse and finishing location for proteins

            5. Lysosomes

                        a. digestion - safe storage of digestive enzymes

b. Digestive enzymes used to digest particulate food in single-celled organisms

c. Used to reconstruct the body during metamorphosis in tadpoles and insects

            6. Vacuoles

                        a. Membrane-bound sacs                  

                                    1. Central vacuole in plant cells

                                    2. Contractile vacuole in single-celled animals

            7.Energy-producing organelles

                        a. Mitochondria (plural) - the singular is mitochondrion

                                    1. Organelle for energy transfer

2. The cell takes in sugar, but that is not the way energy is used in the cell

a. The cell uses ATP - Adenosine tri-phosphate to provide energy            for chemical reactions           

3. The mitochondrion is the site of respiration - it takes in oxygen and “burns” sugar to produce ATP

                                    4. Intermediary metabolism

                                    5. Some cells have lots of mitochondria - these are cells with high                                                           metabolism and lots of work to do

                                                a. Muscle cells - contraction

                                                b. Sperm cells            - need lots of energy to swim

1. Mitochondria are arranged in a ring around the location where the flagella joins the rest of the cell

                                                            2. This is where the energy is needed

                        b. Chloroplasts - only in plants

1. Contain Chlorophyl - a green colored chemical that captures the energy             of light for the plant

2. The chloroplast takes in carbon dioxide and light to make oxygen and sugars

a. The energy from the light is captured as chemical bonds in the             sugar

b. This process is called photosynthesis - it is the source of all food on earth

                                    3. Plants cannot live where there is no light

a. The bottom of the sea - below 100m is absolutely dark so there can be no photosynthesis so there are not plants

1. Animals in the deep sea get their food from particles that fall from the upper 100 m of the ocean

2. A few bacteria at hydrothermal vents can get their energy             from chemical compounds

                                                b. The bottom of Cougar Lake is just like the deep sea

1. All light is gone by 2m in the lake - I have measured it

                                                            2. It is a lot more turbid than the ocean

3. There are no plants in the deep water of Tower Lake                                                                       

4. What about where there is light?

                                                a. The upper 100 m of the ocean

                                                            1. Plants do fine here

2. There are plants called phytoplankton that live floating in the water

                                                                        a. Phytoplankton are algae

                                                            3. There are two types of algae

                                                                        a. Eukaryotes

1. Just like land plants but they are one celled

2. Have chloroplasts, nuclei & chromosomes

                                                                                    3. They do standard photosynthesis

                                                                                                a. Take in carbon dioxide

                                                                                                b. Give off oxygen

                                                                        b. Prokaryotes - blue-green algae

                                                                                    1. Really photosynthetic bacteria

                                                                                    2. Take in carbon dioxide

                                                                                    3. Give off oxygen

                                                                                    4. No nuclei - circular chromosome

 

            8. Organelles of Movement - flagellae and cilia

                        a. Flagellae - long and whip-like

                                    1. On Euglena - flagellates

                                    2. Sperm cells - organelle of motion - allows sperm to swim

                        b. Cilia - short and hair-like

                                    1. On the surface of Paramecia

                                    2. Line air passages of human lungs

                                                a. Keep passages clean - remove soot and particles

b. Move particles to top of airway and into mouth for disposal

                        c. Anatomy of cilia and flagellae

                                    1. Really the same thing - only difference is the number

                                    2. 9+2 pattern of microtubules

                                                a. Contractile proteins that allow cilia and flagellae to move

                                    3. Seem to be controled by a structure called a basal body

G. Materials Transport in Cells

            1. Cells need to get materials in and out

                        a. There are a group of different methods to get stuff into cells

            2. Passive Transport - these require no input of energy

                        a.  Diffusion

                                    1. Perfume in a room

2. Random motion of molecules distributes them acroos cell membrane

                                    3. Gases diffuse into or out of cells

                                                1. Oxygen

                        b. Osmosis

                                    1. Transfer of water

a. The cell membrane is semipermeable - most solutes can’t pass through

1. Membrane allows water through but not solutes like salt

                                                b. Hypertonic Solution

                                                            1. Less salt than cell contents - water moves into cell

                                                c. Hypotonic

                                                            1. Saltier than cell contents - water moves out of cell

                                                d. Osmosis presents a problem for animals and plants

                                                            a. Water diffuses into cell from freshwater

1. Problem for freshwater organism - water will dilute its cell contents

a. Contractile vacuole - in one celled animals

                                                                                    b. Turgor pressure in plants                                                                                                            c. Constantly working kidneys in fish

                                                            b. Water diffuses out of organisms in salt water

                                                                        1. Problem for salt water organisms

a. Sea is hypotonic to some organisms

                                                                                                1. They need to get rid of salt

                                                                                                2. Salt glands

                                                                                                3. Sea turtles, fish

b. Some organisms adjust body fluids to match seawater

1. Shark - has a circulating protein in blood

 

                        3. Active Transport - takes energy

                                    a. This system is used to get materials into the cell that it needs

1. Transport proteins that capture material on the outside of the cell membrane and put it inside

                                                2. Nutrients in plants - transport mechanisms in roots

                        4. Endocytosis

                                    a. Phagocytosis

                                    b. Pinocytosis