Chapter 7 Cell Structure and Function Section: 7-1 Life Is

Chapter 7 Cell Structure and Function Section: 7-1 Life Is Cellular

Slide 1 of 31 Copyright Pearson Prentice Hall

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7-1 Life Is Cellular

The Discovery of the Cell

Approximately how Many Cells are in the Human Body? 100 trillion or 1 X 1014 Cell Size – How large are they?


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Early Microscopes In 1665, Robert Hooke used an early compound microscope to look at a thin slice of cork, a plant material. Cork looked like thousands of tiny, empty chambers. Hooke called these chambers “cells.” Cells are the basic units of life. Slide 3 of 31 Copyright Pearson Prentice Hall

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Hooke’s Drawing of Cork Cells


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What is the cell theory?


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The Cell Theory In 1838, Matthias Schleiden concluded that all plants were made of cells. In 1839, Theodor Schwann stated that all animals were made of cells. In 1855, Rudolph Virchow concluded that new cells were created only from division of existing cells. These discoveries led to the cell theory. Slide 6 of 31 Copyright Pearson Prentice Hall

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The cell theory states:

• All living things are composed of cells. • Cells are the basic units of structure and function in living things.

• New cells are produced from existing cells. Slide 7 of 31 Copyright Pearson Prentice Hall

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Exploring the Cell

Electron Microscopes Electron microscopes reveal details 1000 times smaller than those visible in light microscopes. Electron microscopy can be used to visualize only nonliving, preserved cells and tissues.


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Exploring the Cell

Transmission electron microscopes (TEMs)

• Used to study cell structures and large protein molecules

• Specimens must be cut into ultra-thin slices


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Exploring the Cell

Scanning electron microscopes (SEMs)

• Produce three-dimensional images of cells • Specimens do not have to be cut into thin slices


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Exploring the Cell

Scanning Electron Micrograph of Neurons


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Prokaryotes and Eukaryotes

Prokaryotes and Eukaryotes Cells come in a variety of shapes and sizes. All cells:

• are surrounded by a barrier called a cell membrane (aka - plasma membrane)

• contain DNA.


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Cells are classified into two categories, depending on whether they contain a nucleus. The nucleus is a large membrane-enclosed structure that contains the cell's genetic material in the form of DNA. The nucleus controls many of the cell's activities.


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Eukaryotes are cells that contain nuclei. Prokaryotes are cells that do not contain nuclei.


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What are the characteristics of prokaryotes and eukaryotes?


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Prokaryotes

Prokaryotic cells have genetic material that is not contained in a nucleus. •Prokaryotes do not have membrane-bound organelles. •Prokaryotic cells are generally smaller and simpler than eukaryotic cells. •Bacteria are prokaryotes. Copyright Pearson Prentice Hall

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Eukaryotes Eukaryotic cells contain a nucleus in which their genetic material is separated from the rest of the cell.


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• Eukaryotic cells are generally larger and more complex than prokaryotic cells. • Eukaryotic cells generally contain many structures and internal membranes. • Many eukaryotic cells are highly specialized. • Plants, animals, fungi, and protists (algae, protozoa, slime molds, amoeba, plankton) are eukaryotes. Slide 18 of 31 Copyright Pearson Prentice Hall

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7-1

The cell theory states that new cells are produced from a. nonliving material. b. existing cells. c. cytoplasm. d. animals.


7-1

The person who first used the term cell was a. Matthias Schleiden. b. Lynn Margulis. c. Anton van Leeuwenhoek. d. Robert Hooke.


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Which organism listed is a prokaryote? a. protist b. bacterium c. fungus d. plant


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One way prokaryotes differ from eukaryotes is that they a. contain DNA, which carries biological information. b. have a surrounding barrier called a cell membrane. c. do not have a membrane separating DNA from the rest of the cell. d. are usually larger and more complex. Slide 23 of 31 End Show Copyright Pearson Prentice Hall

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7-2 Eukaryotic Cell Structure


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Comparing the Cell to a Factory The eukaryotic cell is much like a living version of a modern factory. The specialized machines and assembly lines of the factory can be compared to the different organelles of the cell. Cells, like factories, follow instructions and produce products.



Eukaryotic Cell Structures

Eukaryotic Cell Structures Structures within a eukaryotic cell that perform important cellular functions are known as organelles. Cell biologists divide the eukaryotic cell into two major parts: the nucleus and the cytoplasm. The cytoplasm is the portion of the cell outside the nucleus. Slide 27 of 49 Copyright Pearson Prentice Hall

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Plant Cell Nucleolus Nucleus Smooth endoplasmic reticulum

Nuclear envelope Ribosome (free)

Rough endoplasmic reticulum

Ribosome (attached) Golgi apparatus

Cell wall Cell membrane Chloroplast

Mitochondrion Vacuole Slide 28 of 49 Copyright Pearson Prentice Hall

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Animal Cell Nucleolus

Smooth endoplasmic reticulum

Nucleus Ribosome (free)

Nuclear envelope

Cell membrane

Rough endoplasmic reticulum

Ribosome (attached) Centrioles

Golgi apparatus

Mitochondrion


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Nucleus

What is the function of the nucleus?


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Nucleus

Nucleus The nucleus is the control center of the cell. The nucleus contains nearly all the cell's DNA and with it the coded instructions for making proteins and other important molecules.


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Nucleus

The Nucleus The nucleus is surrounded by a nuclear envelope composed of two membranes and dotted with thousands of nuclear pores that allow materials to move in and out of the nucleus.

Nuclear envelope

Nucleolus

Nuclear pores

Most nuclei also contain a small, dense region known as the nucleolus. The nucleolus is where the assembly of ribosomes begins. Copyright Pearson Prentice Hall



Ribosomes

What is the function of the ribosomes?


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Ribosomes

Ribosomes One of the most important jobs carried out in the cell is making proteins. Proteins are assembled on ribosomes. Instructions for protein production come from DNA. Ribosomes are small particles of RNA and Slide protein found throughout the cytoplasm. 34 of 49 Copyright Pearson Prentice Hall

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Ribosomes

What is the function of the endoplasmic reticulum?


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Endoplasmic Reticulum

There are two types of ER—rough and smooth. Smooth ER – contains enzymes that help to cell membrane lipids and also detoxify drugs. A lot of smooth ER is found in liver cells.

Ribosomes


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Endoplasmic Reticulum

Lipid portions of the cell membrane and proteins are made by the endoplasmic reticulum. New proteins leave the ribosomes on roughendoplasmic reticulum and may be chemically altered in the ER. Newly assembled proteins are carried from the rough-ER to the Golgi apparatus in vesicles.


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Golgi Apparatus

What is the function of the Golgi apparatus?


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Golgi Apparatus

The Golgi apparatus appears as a stack of flattened membranes. The Golgi apparatus modify, sort, and package proteins received from the ER for shipment inside or outside of the cell


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Golgi Apparatus

What is the function of lysosomes? Lysosomes breakdown and recycle old cell parts, and also breakdown macromolecules such as lipids, carbohydrates and proteins into smaller molecules. Remove the “junk” that may accumulate and clutter up the cell. They are found in both animal and plant cells. Slide 40 of 49 Copyright Pearson Prentice Hall

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Vacuoles

What is the function of vacuoles?


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Vacuoles

In many plant cells there is a single, large central vacuole filled with liquid (water, salts, proteins and carbohydrates).

Vacuole


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Vacuoles are also found in some unicellular organisms and in some animals.

Vacuoles

Contractile vacuole

The paramecium contains a contractile vacuole that pumps excess water out of the cell.


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Mitochondria and Chloroplasts

What is the function of the mitochondria?


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Mitochondria Nearly all eukaryotic cells contain mitochondria. Mitochondria convert the chemical energy stored in food into compounds that are more convenient for the cell to use.

Mitochondrion Slide 45 of 49

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What is the function of chloroplasts?


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Chloroplasts


Chloroplast

Plants and some other organisms contain chloroplasts. Chloroplasts capture energy from sunlight and convert it into chemical energy in a process called photosynthesis. Slide 47 of 49 Copyright Pearson Prentice Hall

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Cytoskeleton

What are the functions of the cytoskeleton?


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Cytoskeleton

The cytoskeleton is a network of protein filaments that helps the cell to maintain its shape. The cytoskeleton is also involved in movement. The cytoskeleton is made up of:

• Microfilaments (made-up of the protein actin) • Microtubules (made-up of tubulin) – examples are centrioles, cilia and flagella Slide 49 of 49 Copyright Pearson Prentice Hall

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Cytoskeleton

Cytoskeleton Cell membrane

Endoplasmic reticulum Microtubule Microfilament Ribosomes

Mitochondrion Copyright Pearson Prentice Hall



Cytoskeleton

Centrioles are located near the nucleus and help to organize cell division.

Cell Organelle Interactive Plant and Animal Model Interactive Copyright Pearson Prentice Hall


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7-2

In the nucleus of a cell, the DNA is usually visible as a. a dense region called the nucleolus. b. the nuclear envelope. c. granular material called chromatin. d. condensed bodies called chloroplasts.


7-2

Two functions of vacuoles are storing materials and helping to a. break down organelles. b. assemble proteins. c. maintain homeostasis. d. make new organelles.


7-2

Chloroplasts are found in the cells of a. plants only. b. plants and some other organisms. c. all eukaryotes. d. most prokaryotes.


7-2

Which of the following is NOT a function of the Golgi apparatus? a. synthesize proteins. b. modify proteins. c. sort proteins. d. package proteins.


7-2

Which of the following is a function of the cytoskeleton? a. manufactures new cell organelles b. assists in movement of some cells from one place to another c. releases energy in cells d. modifies, sorts, and packages proteins


END OF SECTION

Chapter 7 Cell Structure and Function Section: 7-3 Cell Boundaries


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7-3 Cell Boundaries

7-3 Cell Boundaries

All cells are surrounded by a thin, flexible barrier known as the cell membrane. Many cells also produce a strong supporting layer around the membrane known as a cell wall.


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7-3 Cell Boundaries

Cell Membrane

Cell Membrane The cell membrane regulates what enters and leaves the cell and also provides protection and support.


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7-3 Cell Boundaries

Photograph of a Cell Membrane


7-3 Cell Boundaries

Cell Membrane

Cell Membrane Outside of cell Proteins

Carbohydrate chains

Cell membrane

Inside of cell (cytoplasm)

Protein channel

Lipid bilayer


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Cell Membrane (Plasma Membrane)

• Separates the cytoplasm of the cell from its environment • Protects the cell & controls what enters and leaves • Cell membranes are selectively permeable only allowing certain materials to enter or leave. CO2, O2, and H2O enter and leave easily. • Maintains a balanced cell environment or homeostasis

Selectively Permeable

Structure of the Cell Membrane Composed of a lipid bi-layer (two layers) made up of phospholipid molecules

Phospholipids Make up 2 thefatty cell Contains membrane acid chains that are nonpolar Head is polar & contains a (PO4-) phosphate group

Fluid Mosaic Model Phospholipids move within the membrane like water molecules within lake currents.

Proteins within the membrane move among the phospholipids like boats within the lake – and create a mosaic (pattern) on the membrane surface.

Membrane Proteins • A variety of protein molecules are attached and embedded in the cell’s lipid bi-layer. • “Transport proteins” help move materials into and out of the cell (membrane). – “Channel proteins” have holes or pores that enable certain substances – like ions Na+, Ca+ and K+ to cross the cell membrane. – “Carrier proteins” can change shape to move material from one side of the membrane to the other

• Some embedded proteins have carbohydrate chains attached to them to serve as chemical signals to help cells recognize each other or for hormones or viruses to attach • Cholesterol – also found in the cell membrane stabilizes the phospholipids and prevents the fatty acid tails from sticking together

Three Forms of Transport Across the Membrane

Passive Transport Simple Diffusion

Doesn’t require energy

Moves high to low concentration Example: Oxygen or water diffusing into a cell and carbon dioxide diffusing out.

Passive Transport Facilitated Diffusion Doesn’t require energy Uses transport proteins to move high to low concentration Examples: Glucose or amino acids moving from blood into a cell.

Types of Transport Proteins • Channel proteins are embedded in the cell membrane & have a pore for materials to cross • Carrier proteins can change shape to move material from one side of the membrane to the other

Facilitated Diffusion Molecules will randomly move through the pores in Channel Proteins.

Active Transport • Some carrier proteins do not extend through the membrane. • They bond and drag molecules through the lipid bi bi--layer and release them on the opposite side.

Active Transport

Requires energy or ATP

Moves materials from LOW to HIGH concentration

AGAINST concentration gradient

Active transport

Example: Pumping Na+ (sodium ions) into a cell and K+ (potassium ions) out of a cell against strong concentration gradients.

Called Na+ - K+ Pump

SodiumSodium -Potassium Pump

3 Na+ pumped in for every 2 K+ pumped out

Who Would Like to Explain This?

7-3 Cell Boundaries

Cell Walls

What is the main function of the cell wall?


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7-3 Cell Boundaries

Cell Walls

Cell Wall Cell walls are found in plants, algae, fungi, and many prokaryotes.


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7-3 Cell Boundaries

Diffusion Through Cell Boundaries

Measuring Concentration A solution is a mixture of two or more substances. The substances dissolved in the solution are called solutes. The concentration of a solution is the mass of solute in a given volume of solution, or mass/volume. Slide 83 of 47 Copyright Pearson Prentice Hall

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7-3 Cell Boundaries


What happens during diffusion?


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7-3 Cell Boundaries


Diffusion Particles in a solution tend to move from an area where they are more concentrated to an area where they are less concentrated. This process is called diffusion. When the concentration of the solute is the same throughout a system, the system has reached equilibrium. Slide 85 of 47 Copyright Pearson Prentice Hall

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7-3 Cell Boundaries



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Simple Diffusion • Requires NO energy • Molecules move from area of HIGH to LOW concentration

DIFFUSION Diffusion is a PASSIVE process which means no energy is used to make the molecules move, they have a natural KINETIC ENERGY

Diffusion of Liquids

Diffusion through a Membrane

Cell membrane Solute moves DOWN concentration gradient (HIGH to LOW)

7-3 Cell Boundaries

Osmosis

Osmosis Osmosis is the diffusion of water through a selectively permeable membrane.


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Osmosis • Diffusion of water across a membrane • Moves from HIGH water potential (low solute) to LOW water potential (high solute)

Diffusion across a membrane

Semipermeable membrane

Diffusion of H2O Across A Membrane

High H2O potential Low solute concentration

Low H2O potential High solute concentration

7-3 Cell Boundaries

Osmosis

How Osmosis Works

Dilute sugar solution (Water more concentrated)

Concentrated sugar solution (Water less concentrated) Sugar molecules

Selectively permeable membrane

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Movement of water Slide 94 of 47 End Show

7-3 Cell Boundaries

Osmosis

Water tends to diffuse from a highly concentrated region to a less concentrated region. If you compare two solutions, three terms can be used to describe the concentrations:

hypertonic (“above strength”). hypotonic (“below strength”). isotonic (”same strength”)


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Cell in Isotonic Solution 10% NaCl 90% H2O

ENVIRONMENT

CELL 10% NaCL 90% H2O

NO NET MOVEMENT

What is the direction of water movement? equilibrium The cell is at _______________.

Cell in Hypotonic Solution 10% NaCl 90% H2O


What is the direction of water movement?

Cell in Hypertonic Solution 15% NaCl 85% H2O

ENVIRONMENT



7-3 Cell Boundaries

Osmosis

Osmotic Pressure Osmosis exerts a pressure known as osmotic pressure on the hypertonic side of a selectively permeable membrane.


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Osmosis in Red Blood Cells

Isotonic

Hypotonic

Hypertonic

Moving the “Big Stuff” Out Exocytosis - moving

things out.

Molecules are moved out of the cell by vesicles that fuse with the plasma membrane. This is how various types of hormones are secreted. secreted

Exocytosis Exocytic vesicle immediately after fusion with plasma membrane.

Moving the “Big Stuff” In Large molecules move materials into the cell by endocytosis endocytosis.

Endocytosis and Exocytosis


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Unlike a cell wall, a cell membrane a. is composed of a lipid bilayer. b. provides rigid support for the surrounding cell. c. allows most small molecules and ions to pass through easily. d. is found only in plants, fungi, algae, and many prokaryotes. Slide 106 of 47 End Show Copyright Pearson Prentice Hall

7-3

The concentration of a solution is defined as the a. volume of solute in a given mass of solution. b. mass of solute in a given volume of solution. c. mass of solution in a given volume of solute. d. volume of solution in a given mass of solute.


7-3

If a substance is more highly concentrated outside the cell than inside the cell and the substance can move through the cell membrane, the substance will a. move by diffusion from inside the cell to outside. b. remain in high concentration outside the cell. c. move by diffusion from outside to inside the cell. d. cause water to enter the cell by osmosis. Slide 108 of 47 End Show Copyright Pearson Prentice Hall

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The movement of materials in a cell against a concentration difference is called a. facilitated diffusion. b. active transport. c. osmosis. d. diffusion.


7-3

The process by which molecules diffuse across a membrane through protein channels is called a. active transport. b. endocytosis. c. facilitated diffusion. d. osmosis.


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Chapter 7 Cell Structure and Function Section: 7-4 Homeostasis and Cells


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7-3 Cell Boundaries

Osmosis

• The Cell as an Organism • Single-celled organisms must be able to carry out all the functions necessary for life. • Unicellular organisms maintain homeostasis, relatively constant internal conditions, by growing, responding to the environment, transforming energy, and reproducing. • Unicellular organisms include both prokaryotes and eukaryotes. • Unicellular organisms play many important roles in their environments. Slide 113 of 47 Copyright Pearson Prentice Hall

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7-3 Cell Boundaries

Osmosis

• Multicellular Life • Cells of multicellular organisms are interdependent and specialized. • The cells of multicellular organisms become specialized for particular tasks and communicate with one another to maintain homeostasis. • Specialized cells in multicellular organisms are organized into groups:

• A tissue is a group of similar cells that performs a particular function.

• An organ is a group of tissues working together to perform an essential task.

• An organ system is a group of organs that work together to perform a specific function.


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7-3 Cell Boundaries

Osmosis

• The cells of multicellular organisms communicate with one another by means of chemical signals that are passed from one cell to another. • Certain cells form connections, or cellular junctions, to neighboring cells. Some of these junctions hold cells together firmly. • Other cells allow small molecules carrying chemical signals to pass directly from one cell to the next. • To respond to a chemical signal, a cell must have a receptor to which the signaling molecule can bind. Slide 115 of 47 Copyright Pearson Prentice Hall

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Chapter 7 Cell Structure and Function Section: 7-1 Life Is

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