03 the cell-53 - biology things

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Chapter 3 The Cell: Module Hyperlinks

•  3.1 Cells are the fundamental units of life •  3.2 Plant vs. animal cells •  3.3 Membranes: structure •  3.4 Membranes: function •  3.5 The nucleus •  3.6 Organelles in protein production •  3.7 Chloroplasts and mitochondria •  3.8 Other organelles

© 2017 Pearson Education, Inc.

3.1 Opening Questions: Are all living things made of cells? •  What are at least five things you know

about cells?

© 2017 Pearson Education, Inc. Chapter Table of Contents

3.1 All living organisms consist of cells. •  Some living organisms

have just one cell.

•  Some living organisms have trillions of cells.


Cells are the fundamental units of life.

Chapter Table of Contents

3.1 Cells can be grouped into two categories.

•  Prokaryotic cells –  Small, simple cells –  No organelles –  First appeared 3.5 BYA –  Unicellular

•  Eukaryotic cells –  Larger, complex cells –  Membrane-enclosed organelles –  First appeared 2.1 BYA –  Unicellular or multicellular

Are you a prokaryote or a eukaryote?

Chapter Table of Contents © 2017 Pearson Education, Inc.

3.1 Cells can be grouped into two categories.

•  Prokaryotic cells –  Bacteria and Archaea

•  Eukaryotic cells –  Plants, Animals, Fungi,

and Protists


3.1 All prokaryotes are relatively simple single-celled organisms. •  There are two domains of prokaryotes:

Bacteria and Archaea. •  Prokaryotic fossils date back at least

3.5 billion years.


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3.1 Bacteria have some unique features and some features common to all cells.


3.2 Opening Questions: What are you really made of? •  Scientists estimate that only one in 10 of

the cells in your body are actually human! The rest are largely prokaryote cells. These good bacteria help us digest food, synthesize vitamins, and protect against disease.


•  How is it possible to have more bacteria cells than human cells?

•  Does knowing the above change your view of bacteria?


3.2 Animals and Plants are made of eukaryotic cells that contain organelles. •  Compared to prokaryotic cells, eukaryotic

cells are relatively large (10-fold bigger) and more complex.


•  Eukaryotic cells contain organelles, which are membrane-enclosed structures that perform specific functions.

Prokaryotes do not contain organelles! Chapter Table of Contents

3.2 Plant and animal cells have many organelles in common. •  All eukaryotic cells are fundamentally alike. •  All eukaryotic cells share:

– Plasma membrane – Nucleus – Mitochondria


3.2 Structure of an idealized animal cell


3.2 Structure of an idealized plant cell


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3.2 Animal and plant cells have some unique organelles. •  Animal cells have

lysosomes. •  Plant cells have

chloroplasts, cell walls, and central vacuoles.

Looking at cells under a microscope, you see cell walls and chloroplasts. What type of cells are these?

Chapter Table of Contents © 2017 Pearson Education, Inc.

3.3 Opening Questions: Where does a cell start and stop? •  What defines a cell? •  What are the boundaries of a cell? •  If we look in a microscope, how do we

know something is a cell? •  What criteria would you use?


3.3 Every cell is surrounded by a plasma membrane.

•  All cells are surrounded by a plasma membrane.

•  Membranes regulate the passage of materials.


3.3 Membranes are made of lipids

•  Plasma membranes are made from two layers of phospholipids and integrated proteins.


3.3 Structure of a plasma membrane


3.4 Opening Questions: Who makes it into the exclusive club? •  Imagine that you and a group of friends are

going out on a Saturday night. At the first club, the place is packed and there is even a line. At the second club, the room is almost empty. – Which club is more likely to have a cover charge? – Which one is going to be harder to get into?

•  Now imagine that you are a molecule trying to get into a cell—across the cell membrane. –  List all the scenarios that might make it harder

or easier to gain entrance.


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3.4 Membranes regulate the passage of materials. •  Cells are surrounded by a

plasma membrane. •  Organelles may have their

own outer and internal membranes.


The most important function of any membrane is to regulate the flow of materials.


3.4 Membranes regulate what substances can enter and leave the cell. •  Every membrane is

selectively permeable. •  Some substances

flow freely. •  Others pass under

certain circumstances. •  Some cannot pass.


STOP

GO

YIELD


3.4 Transport across membranes can be passive or active. •  Passive transport requires no energy.

–  Substances move along a concentration gradient from high to low.

•  Active transport requires energy. – Substances move against a concentration

gradient from low to high.


Active transport is like trying to get into a crowded club!


3.4 Passive transport: Diffusion

•  Diffusion is the movement of molecules from an area of higher concentration to an area of lower concentration.


Lower concentration

Higher concentration

3.4 Passive transport: Osmosis

•  The diffusion of water is called osmosis.

•  Water will always flow from an area of higher water concentration to an area of lower water concentration.


Lower concentration


3.4 Passive transport: Facilitated diffusion

•  Large molecules can move through embedded transport proteins via facilitated diffusion.

•  Substances still move from an area of higher concentration to an area of lower concentration.


Lower concentration


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3.4 Active transport requires energy to move substances. •  Active transport involves

moving a substance from an area of lower concentration to an area of higher concentration.

•  Moving a substance against its concentration gradient always requires an expenditure of energy.



Lower concentration


3.4 Active transport is usually driven by a protein that sits within the membrane.


Here, you can see a protein called the sodium-potassium (Na+/K+) pump moving three potassium ions into the cell.


3.4 Cells can also transport substances by fusing a portion of the cell membrane. •  Exocytosis is the export from the cell. •  Endocytosis is the import into the cell.


3.5 Opening Questions: Where did you get your chromosomes from? •  Human cells contain 46 chromosomes.

•  What are at least three things that you know about chromosomes?

•  Can you draw a chromosome?

•  What is it made of?


3.5 Only eukaryotic cells contain organelles surrounded by membranes.

•  The most prominent membrane-enclosed organelle is the nucleus.

•  Every eukaryotic cell (including plant and animal cells) contains a nucleus.


3.5 The nucleus contains most of the cell’s DNA stored in chromosomes. •  The nucleus, surrounded by an envelope

and containing DNA, directs the activities of the cell.


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3.5 The nucleus is surrounded by a double membrane called the nuclear envelope. •  Protein-lined nuclear pores in the nuclear

envelope allow certain molecules, such as RNA, to pass through.


3.5 The nucleus houses the chromosomes.

•  DNA molecules are wrapped around proteins to form fibers called chromatin.

•  Each very long chromatin fiber twists and folds to form a chromosome.


3.5 The nucleus contains a darker area called a nucleolus. •  The nucleolus is a

particular location within the nucleus.

•  This area produces ribosomal RNA (rRNA), an important component of a ribosome.


3.6 Opening Questions: Who’s in charge?

•  Think of the cell as analogous to a factory. However, instead of producing widgets, the cellular factory produces proteins.

•  What roles might the following organelles play in the cell factory? – Plasma membrane – Nucleus – Ribosomes – Mitochondria


3.6 DNA directs a cell’s activities through the production of proteins. •  DNA in the nucleus

contains the instructions for making proteins.

•  Proteins are very important molecules in our cells. They are involved in virtually all cell functions.


DNA

RNA

Protein


3.6 Several organelles are involved in protein manufacture.


Golgi Apparatus

Endoplasmic Reticulum (ER)

Ribosomes floating or attached to ER

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3.6 Protein production involves two steps:


1.  Transcription in the nucleus results in the production of RNA from DNA.

2.  Translation at the ribosomes results in the production of proteins.

3.6 After transcription, RNA travels from the nucleus to a ribosome. •  Ribosomes are where proteins are made. •  Some ribosomes are bound to the

membrane of the rough ER. •  Other ribosomes float freely in the

cytoplasm.


3.6 The endoplasmic reticulum (ER) is filled with membranes. •  The smooth ER contains enzymes that

produce lipids (such as steroid hormones). •  The rough ER contains ribosomes that

produce many kinds of proteins.


3.6 Proteins are finalized and packaged in the Golgi apparatus. •  The Golgi apparatus finishes, sorts, and

ships cell products. •  The Golgi apparatus finishes cell products

in vesicles, small bubbles made of membrane.


3.6 Lysosomes are a type of vesicle that contains digestive enzymes. •  Lysosomes can dissolve large food

molecules, old cellular components, or invasive organisms such as bacteria.


3.7 Opening Questions: What if your organelles went missing? •  What would happen if all the ribosomes in

your cells disappeared?

•  What would happen if half of the mitochondria in your cells disappeared?


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3.7 Two organelles help provide energy for the cell. •  Chloroplasts are

found in all plant cells and the cells of some algae.

•  Mitochondria are found in both plant and animal cells (mitochondrion is singular).


3.7 Chloroplasts are the organelle of photosynthesis. •  In photosynthesis, the energy of sunlight

is used to create molecules of sugar. •  Chloroplasts require a

supply of water and carbon dioxide (CO2).

•  The sugars produced by photosynthesis provide the energy to power the cell.


Within a cell, chloroplasts are visible as green blobs.


3.7 The chloroplast


3.7 Mitochondria are the organelle of cellular respiration. •  Cellular respiration uses oxygen (O2) to

harvest energy from molecules of sugar. •  The harvested energy is stored as

chemical energy in molecules of ATP, which can then be used to power many other cellular processes.


3.7 The mitochondrion


3.8 Opening Questions: Plant cells vs. animal cells •  List three structures in the plant cell that

are not found in animal cells. •  For each of these structures, explain why

it is useful for plant cells, but not for animal cells.


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3.8 Vacuoles function in the general maintenance of the cell. •  Vacuoles are

intracellular sacs. •  Some are for

storage, such as for food, nutrients, or pigments.

•  Some pump water out of a cell.

•  Many plant cells have a very large central vacuole.


3.8 Some cells have moving appendages.

•  Flagella propel the cell through their whip-like motion.

•  Cilia move in a coordinated back-and-forth motion.


3.8 Some cells are supported by a rigid cell wall surrounding the membrane. •  Plant, fungus, and some prokaryotic cells

have a rigid cell wall. •  Plants can stand upright in part because

their rigid cell walls are made of cellulose.


Note: Animal cells do not have a cell wall!


3.8 Animal cells maintain their shape with an internal cytoskeleton. •  The cytoskeleton is a network of protein

fibers that provides mechanical support, anchorage, and reinforcement.


The cytoskeleton network can be quickly dismantled and reassembled, providing flexibility.


3.8 Animal cells stick together.

•  Animal cells produce a sticky extracellular matrix that helps hold cells together.


Cells are held together into a tissue by the extracellular matrix.


03 the cell-53 - biology things

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