Chapter 7: Cell Structure and Function The Discovery of the Cell  Early Microscopes allowed us to see cells for the first time! –The earliest lenses in Europe allowed us to see the quality of cloth and tiny insects, which appeared small and blurry. –Scientists didn’t use microscopes to study nature until the 1600’s. 7-1 Life is Cellular

 Anton van Leeuwenhoek ( ) Discovered the new world of microorganisms when he looked at pond water through his microscope. Discovered the new world of microorganisms when he looked at pond water through his microscope. Leeuwenhoek greatly improved the quality of lenses

“Cells” named by Robert Hooke Robert Hooke looked at cork (from the Cork Oak Tree). He thought the compartments looked like little rooms, or “cells”. The name stuck. Robert Hooke was one of the first to look at objects under the microscope.

The History of the Cell Theory  In 1838, Matthias Schleiden stated that all plants are made of cells.  In 1839, Theodore Schwann stated that all animals were made of cells.  In 1855, Rudolf Virchow stated that cells could only come from other cells. - This is unlike how we bake cakes or build automobiles.

The Cell Theory 1.All living things are made of cells. 2.Cells are the basic units of structure & function in living things. 3.New cells are produced from existing cells.

Cells come in all shapes & sizes But, all cells have 2 characteristics in common: 1. They have a cell membrane at some point in their lives. 2. They contain DNA.

 There are 2 categories of cells: –Prokaryotes  Cells that do not have a membrane-bound nucleus. –Eukaryotes  Cells that do have a membrane-bound nucleus. –Pro = before –Eu = true –Karyon =kernel

 The type of cell is based on the presence (or absence) of a nucleus & organelles. –Nucleus –large membrane bound organelle.  Contains the cell’s DNA.  Controls many of the cell’s activities. –Organelle –specialized structure that performs important functions w/in the cell.  “Tiny organs”

Prokaryotes  The first cells (bacteria)  Generally smaller & simpler than eukaryotic cells.  Have DNA, but it’s not contained in a membrane-bound nucleus.  Most are unicellular.  Despite their simplicity, prokaryotes: –Grow –Reproduce –Respond to their environment –Some are mobile.

Eukaryotes  Generally larger & more complex than prokaryotes.  Contain membrane bound organelles and a nucleus.  Can be unicellular or multicellular.  Found in animals, plants, fungi, and protists

Pro-k vs. Eu-k Review Prokaryotes Eukaryotes Cell membrane Contain DNA Nucleus Endoplasmic reticulum Golgi apparatus Lysosomes Vacuoles Mitochondria Cytoskeleton

Plant vs. Animal Cell Centrioles Cell membrane Ribosomes Nucleus Endoplasmic reticulum Golgi apparatus Lysosomes Vacuoles Mitochondria Cytoskeleton Cell Wall Chloroplasts Animal CellsPlant Cells

Cell Structures 7-2 Cell walls are found in plants, algae, fungi, and most prokaryotes But, NOT animals! Cell wall Cell wall – provides support & protection for a cell Cell walls are made from fibers of carbohydrates and proteins (p. 173) Follow along in your textbook...

 Cells can be subdivided into 2 main parts: 1.Cytoplasm – 1.Cytoplasm – portion of the cell between the nucleus and the cell membrane. Do not confuse the cytoplasm with the cytosol... Analogy: cytoplasm is like vegetable soup cytosol is like the broth Includes the organelles

2. Nucleus 2. Nucleus – the control center of the cell   Contains almost all of the cell’s DNA, the coded instructions for making proteins & other important molecules. On the nuclear envelope you will find nuclear pores. These pores allow materials to move in & out of the nucleus Proteins RNA Other molecules nuclear envelope The nuclear envelope is a double membrane that surrounds the nucleus. Found in eukaryotic cells only (p. 175)

 Chromatin –a granular material visible w/in the nucleus. –It consists of DNA tightly coiled around proteins. –Most of the time chromatin is spread throughout the nucleus. –However, when a cell divides, chromatin condenses to form chromosomes.

 Another structure found in most nuclei is a nucleolus. –The nucleolus assembles ribosomes. (p. 176) Figure 7-7

Analogy... Comparing the Cell to a Factory  Organelles “little organs”.  Organelles – means “little organs”. – –Specialized structures that carry out specific functions in a cell... They each have a job to do. Organelles are found within the cytoplasm. Now lets look at organelles: ribosomes, endoplasmic reticulum, Golgi apparatus, lysosomes, vacuoles, mitochondria, and chloroplasts As we learn about each organelle, we can compare it to parts of a factory. For example: the nucleus is like the boss who sends out instructions... DNA.

Ribosomes Ribosomes –small particles of RNA & protein found throughout the cytoplasm.  Ribosomes make proteins by following coded instructions that come from the nucleus. –These instructions are RNA –These instructions are RNA (ribonucleic acid)  Cells that are major protein producers often protein producers often have numerous ribosomes. have numerous ribosomes. (p. 177)... Like an assembly line

 Endoplasmic Reticulum (ER)– organelle in which components of the cell membrane are assembled and some proteins are modified.  Rough ER Involved in the synthesis of proteins. Involved in the synthesis of proteins. Called “rough” b/c ribosomes are found on its surface Called “rough” b/c ribosomes are found on its surface Newly made proteins enter the rough ER & are modified. Newly made proteins enter the rough ER & are modified. There are 2 portions to ER... Rough ER and Smooth ER Smooth ER  Smooth ER No ribosomes are found on the surface No ribosomes are found on the surface Contains collections of enzymes that perform special Contains collections of enzymes that perform special tasks such as:Synthesis of membrane lipids tasks such as:Synthesis of membrane lipids Detoxification of drugs Liver cells tend to have a large amounts of smooth ER. Endoplasmic reticulum

 RER  SER Cross section of ER Rough and Smooth Endoplasmic reticulum

Golgi Apparatus The GA looks like a stack of closely opposed membranes, (or a stack of pita bread) Proteins made in the ER move to the Golgi Apparatus Proteins made in the ER move to the Golgi Apparatus (GA) These proteins can be stored in the cell or secreted out of the cell.

Golgi apparatus See Figure 7-9 Sequence pathway of proteins... Central nucleus  Interconnected rough ER  Golgi  Outer plasma membrane Factory analogy: Like a factory’s customized shop, where finishing touches are put on the products.

Lysosomes The clean up crew, Or recycling container Lysosome –small organelles filled w/ digestive enzymes.  Lysosomes are involved in: –Breaking down old organelles. –Digesting foreign matter in the cell.

 Tay-Sachs -a disease is caused by lysosomes that fail to properly do their job. –Fatal by the age of 4. –More common in eastern European Jews Example of what can happen when cells don’t work

Vacuoles and Vesicles  Vacuoles –an organelle that stores materials such as: –Water –Salts –Proteins –Carbs  Plants have large central vacuoles that can hold water & wastes. (p. 179) Figure 7-10 Factory analogy – Storage and shipping containers Smaller vacuoles, especially those that transport substances within a cell, are called vesicles.

Mitochondria & Chloroplasts  The power plants of a cell.  Most cells get their energy (E) in 2 ways: –Food (Heterotrophs) –Sun (Autotrophs)

 Mitochondria: –Can be found in almost all eukaryotic cells.  Including plant cells. –Converts chemical E into compounds that are easy for the cell to use.  Ex: ATP (Adenosine Triphosphate) These high energy compounds are used to power growth, development, and movement (p. 180)

 Mitochondria are enclosed by 2 membranes. –An outer membrane –An inner membrane  Highly folded on itself.  Creates more surface area for chemical reactions.

 Chloroplasts: –Found in plants & some other orgs. –They capture sunlight & convert it into chemical E by photosynthesis.  This chemical E is then converted to ATP by mitochondria in the plant. –Also surrounded by 2 membranes. –Contains a green pigment called chlorophyll.

 Chloroplasts

Organelle DNA  Chloroplasts & mitochondria contain their own DNA. –No other organelles do.  It is believed that both of these organelles are ancient descendants of prokaryotes.  This is called the endosymbiotic theory.

Cytoskeleton  Cytoskeleton –a network of protein filaments that helps the cell maintain its shape. –It is also involved in movement.  The cytoskeleton is made up of: –Microfilaments –Microtubules

 Microfilaments: –Threadlike –Made of actin –Forms a tough, flexible framework that supports the cell. –Also responsible for cytoplasmic movement of the cell.

 Microtubules: –Hollow tube-like structures –Made of tubulin –Critical to maintaining cell shape. –Also form structures called spindles during cell division. –Tubulin is also used to make centrioles. –Located near the nucleus.  Help organize cell division. Microtubules also help w/ movement. –They make up cilia & flagella. P. 181, fig. 7-11

Section 7-3 Cell Boundaries

 All cells are surrounded by a thin barrier called the cell membrane.  Many cells also have a strong supporting layer around that membrane called the cell wall. Cell Boundaries 7-3

Cell Membrane  Cell membranes regulate what enters & leaves a cell.  They also aid in protection & support.  Nearly all cell membranes are a flexible, double layered sheet called a lipid bilayer. –P. 182, fig. 7-12

Along w/ lipids, the cell membrane also has proteins & carbohydrates embedded in it. The lipid bilayer is often called a mosaic, b/c it is made up of many different parts.

 The proteins form channels & pumps for moving materials across the membrane.  The carbohydrates act like ID cards, allowing individual cells to identify one another.

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Cell Walls (CW’s)  Found in: –Plants –Algae (Protists) –Fungi –Many prokaryotes (not all)  CW’s lie outside the cell membrane. cell membrane. Onion Ragweed

 Most cell walls allow certain substances to pass through.  Such as: –H20–H20–H20–H20 –CO 2 –O2–O2–O2–O2  Its main function is to support & protect the cell.

 Most CW’s are made of fibers of carbohydrate & protein.  Plant CW’s are made of cellulose. –Cellulose is a tough carbohydrate fiber. –The fiber in your diet.

Diffusion Through Cell Boundaries  The movement of molecules from one side of the cell membrane to the other.

Measuring Concentration  Recall what a solution is. –What’s a solute? –What’s a solvent?  Concentration –the mass of solute in a given volume of solution, or mass/volume.  Lets figure concentration of a solution. –If you dissolved 12g of salt in 3L of water, the concentration would be: 12g/3L = 4 g/L

Diffusion  Diffusion –process of molecules moving from an area of high concentration to an area of low concentration. –Equilibrium –when the concentration of a solute is the same throughout a solution.  Diffusion will go on until EQ is reached.

 What does diffusion have to do w/ a cell membrane? –P. 184, fig  Diffusion requires no E output by the cell. –It’s free!

Osmosis  Biological membranes are selectively permeable. –Some substances can pass & some can’t.  Water passes very easily.  However, many solutes can’t.  Osmosis –the diffusion of water through a selectively permeable membrane.

How Osmosis Works  H 2 O moves from an area of high H 2 O concentration to an area of low H 2 O concentration.  Water moves across the membrane until EQ is reached.

Osmosis Section 7-3

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3 types of Osmotic Solutions: P. 186, fig  Isotonic –Concentrations are equal on both sides of the membrane. –Normal looking cells  Hypertonic –Solution outside the cell has a higher solute concentration than the inside of the cell. –Water leaves the cell. –Cells shrink  Hypotonic –Solution has a lower solute concentration than the cell. –Water enters the cell. –Cells swell

Plant Cells

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Turgid Flaccid

Red Blood Cells

Osmotic Pressure  Osmosis exerts a pressure known as osmotic pressure.  Osmotic pressure -the pressure exerted by the flow of water through a semi permeable membrane.  This can cause serious problems for a cell. –Cells can swell to the point of bursting.

 Fortunately, animal cells are in a isotonic solution & don’t come into contact w/ pure H 2 O. –If they did they would burst.  Also, plant cells & bacterial cells have cell walls that prevent the cell from bursting.

Facilitated Diffusion  Facilitated diffusion –movement of specific molecules across CM’s via protein channels. –P. 187, fig  There are hundreds of protein channels that allow only certain substances to cross different membranes.

 This process does not require E.  It acts just as diffusion. –It goes from high to low concentrations.

Facilitated Diffusion  Membranes/diffusionanimation.html Membranes/diffusionanimation.html Membranes/diffusionanimation.html

Active Transport  When cells move materials against the concentration gradient, they are using Active Transport. –This process requires E.  Active transport is carried out by transport proteins or pumps found in the membrane.

 Transport of larger molecules can be done through 2 active transport processes: 1.Endocytosis – P. 188, fig Exocytosis –For each of these processes, the shape of the membrane changes.

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Molecular Transport  Endocytosis –process of taking material into the cell by infolding or pocketing of the CM. –This process forms a vacuole in the cell. –This process works for:  taking in food  larger molecules  other cells –2 examples of endocytosis are:  Phagocytosis  Pinocytosis

 Phagocytosis – extensions of cytoplasm surround a particle & package it w/in food vesicles. –Amoebas use this method  Fig. 7-18

 Pinocytosis –the process of taking in liquids from the surrounding env.

 Many cells also release large amounts of material from the cell.  This process is called exocytosis.  Ex: –The removal of water by a contractile vacuole is an example of this kind of active transport.

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Section 7-4 The Diversity of Cellular Life

Unicellular Organisms  Unicellular orgs. –made of one cell.  Unicellular orgs. can: –grow –respond to the env. –reproduce –transform E

 Unicellular orgs. dominate life on Earth.  Examples on P. 190, fig. 7-20

Multicellular Organisms  Orgs. made up of many cells.  Multicellular orgs. have cells that are specialized.  Cell Specialization –process in which cells develop in different ways to perform different tasks. –P. 191, fig. 7-21

Specialized Animal Cells  Examples of specialized cells in animals: –Red blood cells  Transport O 2 throughout the body. –Pancreatic cells  Produce enzymes that aid in digestion.  Contain cells specialized for making proteins. –These cells have numerous ribosomes. –Muscle cells  Able to contract & relax, causing movement of our bones.

Specialized Plant Cells  Guard cells of the stomata: –Monitor a plants internal conditions, & makes changes accordingly.

Levels of Organization  The levels of organization in a multicellular org. are as follows: –Individual Cells –Tissues –Organs –Organ systems –Organism  P. 192, fig. 7-22

Examples  neurons (nerve cells)  nervous tissue  brain  central nervous system  human

 Tissue –a group of similar cells that perform a specific function. – Ex:  The collection of cells in the pancreas that make proteins. –Most animals have 4 types of tx:  Muscle  Epithelial  Nervous  connective

 Organs –many groups of tx’s working together. –Each muscle is an organ. –However, it also contains nervous tx, & connective tx.

 Organ system –a group of organs working together to perform a specific function. –Digestive system –Reproductive system –Nervous system  Altogether, organ systems make up the organism.

Body Systems