LIFE IS CELLULAR

THINK ABOUT IT What’s the smallest part of any living thing that still counts as being “alive?” Can we just keep dividing living things into smaller and smaller parts, or is there a point at which what’s left is no longer alive? As you will see, there is such a limit. The smallest living unit of any organism is the cell.

The Discovery of the Cell What is the cell theory? The cell theory states: - All living things are made up of cells. - Cells are the basic units of structure and function in living things. - New cells are produced from existing cells.

Early Microscopes Early Microscopes date back to the mid-1600s In 1665, Englishman Robert Hooke used an early compound microscope to look at cork. Saw tiny, empty chambers that Hooke called “cells”.

In Holland, Anton van Leeuwenhoek examined pond water and mouth swabs. Saw bacteria.

The Cell Theory Soon after Leeuwenhoek, observations made by other scientists made it clear that cells were the basic units of life.

In 1838, German botanist Matthias Schleiden concluded that all plants are made of cells.

The next year, German biologist Theodor Schwann stated that all animals were made of cells.

In 1855, German physician Rudolf Virchow concluded that new cells could be produced only from the division of existing cells. Confirming a suggestion made by German Lorenz Oken 50 years earlier.

The cell theory states: -All living things are made up of cells. -Cells are the basic units of structure and function in living things. -New cells are produced from existing cells.

Light Microscopes Can study living specimens.

A problem with light microscopy is that most living cells are nearly transparent. Hard to see Use stains or dyes (but kills the organism)

Electron Microscopes Electron microscopes use beams of electrons, not light. Much higher resolution than light microscopes. Study non-living things.

TEM – Inner Structures Transmission electron microscopes make it possible to explore cell structures and the insides of cells.

SEM – Surface Only In scanning electron microscopes, a pencil-like beam of electrons is scanned over the surface of a specimen.

Eukaryotic vs. Prokaryotic How are prokaryotic and eukaryotic cells different? Prokaryotic cells – No Nucleus Eukaryotic cells – Has a Nucleus

Prokaryotes Prokaryotic cells - Small - Simple - No Nucleus Bacteria are prokaryotes.

Eukaryotes - Large - More complex and more advanced Eukaryotic cells - Large - More complex and more advanced - Lot of Compartments - Highly Specialized Eukaryotes: - plants, animals, fungi, protists.

What is the role of the cell nucleus? Cell Organization What is the role of the cell nucleus? The nucleus contains nearly all the cell’s DNA and, with it, the coded instructions for making proteins and other important molecules.

The cytoplasm is the fluid portion of the cell outside the nucleus. Cell Organization The eukaryotic cell can be divided into two major parts: the nucleus and the cytoplasm. The cytoplasm is the fluid portion of the cell outside the nucleus.

The nucleus = control center. DNA is here. Surrounded by a nuclear envelope – has 1000s of pores. Why? Proteins, RNA move in and out of nucleus Nucleus contains the nucleolus. Ribosomes are made in nucleolus.

Organelles That Store, Clean Up, and Support What are the functions of vacuoles, lysosomes, and the cytoskeleton? “Vac” = Vaccuum Vacuoles store materials like water, salts, proteins, and carbohydrates.

“Lys” = Slice Lysosomes break down (slice) lipids, carbohydrates, and proteins into small molecules that can be used by the rest of the cell. They are also involved in breaking down pathogens.

The cytoskeleton helps the cell maintain its shape and is also involved in movement.

Make up the cytoskeleton Microfilaments Microfilaments are threadlike structures made up of a protein called actin. Make up the cytoskeleton

They are also components of flagella. Microtubules Microtubules are important in cell division, form the mitotic spindle, which separates chromosomes. They are also components of flagella.

Organelles That Build Proteins What organelles help make and transport proteins Ribosomes

Endoplasmic Reticulum The endoplasmic reticulum is where lipid components of the cell membrane are assembled.

Rough Endoplasmic Reticulum The portion of the ER involved in the synthesis of proteins. Ribosomes found on its surface.

Endoplasmic Reticulum Rough ER has ribosomes NO RIBOSOMES on smooth ER

Golgi Apparatus Proteins produced in the rough ER move to the Golgi apparatus, which appears as a stack of flattened membranes.

Golgi Apparatus – UPS of the cell The Golgi apparatus modifies, sorts, and packages proteins and other materials from the ER for storage in the cell or release outside the cell.

Organelles That Capture and Release Energy Chloroplasts (plants) capture the energy from sunlight and convert it into useable energy. Mitochondria (animals) convert the chemical energy stored in food into compounds that are more convenient for the cells to use.

You get your mitochondria from Mom! In humans, all or nearly all of our mitochondria come from the cytoplasm of the ovum, or egg cell. You get your mitochondria from Mom!

Cellular Boundaries What is the function of the cell membrane? The cell membrane regulates what enters and leaves the cell and also protects and supports the cell.

Cellular Boundaries Similarly, cells are surrounded by a barrier known as the cell membrane. Most prokaryotes and plants, also produce a strong supporting layer around the membrane known as a cell wall.

Cell Membranes All cells contain a cell membrane that regulates what enters and leaves the cell and also protects and supports the cell.

Cell Membranes Double-layered sheet called a lipid bilayer.

The Properties of Lipids The fatty acid portions of such a lipid are hydrophobic, or “water-hating,” While the opposite end of the molecule is hydrophilic, or “water-loving.”

The Properties of Lipids The head groups of lipids in a bilayer are exposed to water, while the fatty acid tails form an oily layer inside the membrane from which water is excluded.

The Fluid Mosaic Model Because the proteins embedded in the lipid bilayer can move around and “float” among the lipids, and because so many different kinds of molecules make up the cell membrane, scientists describe the cell membrane as a “fluid mosaic.”

The Fluid Mosaic Model Most biological membranes are selectively permeable, meaning that some substances can pass across them and others cannot. Selectively permeable membranes are also called semipermeable membranes.

http://elearning.nccsc.k12.in.us/mod/resource/view.php?id=34496

Passive Transport What is passive transport? The movement of materials across the cell membrane without using cellular energy is called passive transport.

One Type of Passive Transport - Diffusion The process by which particles move from an area of high concentration to an area of lower concentration is known as diffusion.

http://elearning.nccsc.k12.in.us/mod/resource/view.php?id=34498

2nd Type of Passive Transport - Facilitated Diffusion Molecules that cannot directly diffuse across the membrane pass through special protein channels in a process known as facilitated diffusion. The movement of molecules by facilitated diffusion does not require any additional use of the cell’s energy.

http://www.d.umn.edu/~sdowning/Membranes/diffusionanimation.html

Osmosis: An Example of Facilitated Diffusion Osmosis is the diffusion of water through a selectively permeable membrane. Osmosis involves the movement of water molecules from an area of higher concentration to an area of lower concentration.

Osmosis- The diffusion of water through a membrane Osmosis- The diffusion of water through a membrane. Membranes prevent most solutes from crossing; however, water may move freely 1. The concentration of dissolved solutes and water is inversely proportional. Therefore, diffusion and osmosis are opposites. 2. Cells may be in One of Three Conditions…

Water will move equally in and out of the cell A. Isotonic Environment- equal amount of solute and water on both sides of a membrane Cell 5% solute 95% H2O Beaker with 5% solute and 95% water Water will move equally in and out of the cell

Water will move out of the cell B. Hypertonic Environment- more solute outside the cell and more water in the cell Beaker with 10% solute and 90% water Cell 5% solute 95% H2O Shriveled Water will move out of the cell

C. Hypotonic Environment- less solute and more water outside the cell. Beaker with 0% solute and 100% water Cell 5% solute 95% H2O Cells with no cell wall Burst! Water will move into the cell

http://www.youtube.com/watch?v=0c8acUE9Itw&feature=related

Active Transport – Requires Energy What is active transport? The movement of materials against a concentration difference is known as active transport. Active transport requires energy.

Endocytosis In phagocytosis, extensions of cytoplasm surround a particle and package it within a food vacuole. The cell then engulfs it. Amoebas use this method for taking in food. Engulfing material in this way requires a considerable amount of energy and, therefore, is a form of active transport.

Endocytosis In pinocytosis, cells take up liquid from the surrounding environment by forming tiny pockets along the cell membrane. The pockets fill with liquid and pinch off to form vacuoles within the cell.

Exocytosis Many cells also release large amounts of material from the cell, a process known as exocytosis.  

Levels of Organization Cells make up tissues… A tissue is a group of similar cells that performs a particular function.

Levels of Organization To perform complicated tasks, many groups of tissues work together as an organ.

Levels of Organization A group of organs that work together to perform a specific function is called an organ system. For example, the stomach, pancreas, and intestines work together as the digestive system.