cell structure and function chapter 3. aks standards 8a - state the cell theory

Cell Structure and Function

Chapter 3

AKS STANDARDS

8a - state the cell theory

The size range of cells.

The History of the Microscope

Early studies led to the development of the cell theory.

Cells – The Basic Unit of Life The accumulated research of Schleiden, Schwann,

and Virchow can be summarized in the cell theory, one of the first unifying concepts in the field of biology:

All organisms are made of cells. All existing cells are produced by other living

cells. The cell is the most basic unit of life.

Prokaryotic cells lack a nucleus and most internal structures of eukaryotic cells. Prokaryotes:

NO NUCLEUS, but do have nucleoid region with DNA present Small and Simple – do not contain membrane-bound

organelles Have cell membranes and cytoplasm All are single-celled

Ex. Bacteria & Archaea

Eukaryotes: Contain nucleus that house genetic information Contains organelles that perform specialized functions Can be unicellular or multicellular

Ex. Protists, fungi, plants, and animals

Prokaryotic Cell v. Eukaryotic Cell

Diversity of Cellular Life Unicellular organisms are made of

a single cell. This grouping includes all prokaryotes

(i.e. bacteria & archaea) and some eukaryotes (such as algae and yeasts).

Multicellular organisms are made of many cells. These organisms are always

Eukaryotic (i.e. many protistans, most fungi, all plants and animals).

Cell Specialization

Cell specialization describes an event where a cell becomes specialized to perform a specific function for an organism. Muscle cells Skin cells Leaf cells Nerve Cells Etc.

Levels of Cellular Organization In multicellular organisms:

Individual cells – basic unit of life

Tissues – groups of similar cells working together for a similar function

Organs – groups of tissues working together

Organ systems – groups of organs working together

A Comparison of Cells

Prokaryotic Cell (Bacterium)

Not in Prokaryotic Cells:-nucleus-membrane bound organelles

Practice, Application & Critical Thinking The following virtual textbook activities are

highly recommended: Section 3.1 Assessment Questions (Textbook pp.

72) Classzone.com: Animated Biology – Cell

Structures Interactive Review: Concepts Maps – Section 1

AKS STANDARDS

8c - identify common cell organelles and describe the function of each (e.g. diagrams

and microscopic examinations), 8d - explain the role of cell organelles

(including the cell membrane) in maintaining homeostasis and cell reproduction for both

prokaryotic and eukaryotic cells (GPS),

Cells have an internal structure. On a small scale, your cells carry out a

necessary division of labor. They contain specialized structures that work

together to respond to stimuli and efficiently carry out other necessary processes.

Cell organelles and molecules are anchored to specific sites, which vary by cell type.

The division of labor provided by membrane-bound organelles works to increase the overall efficiency of cellular processes.

Animal Cell

Plant Cell

Cytoskeleton Each eukaryotic cell has a cytoskeleton, a network

of proteins that is constantly changing to meet the needs of the cell.

The cytoskeleton provides structural support, and aids in cell motility and cell regulation.

Organelleshttp://bcs.whfreeman.com/thelifewire/content/chp04/0402001.html

Organelles that function in control:*Nucleus (plant and animal)*Centrosome (plant and animal)

Organelles that function in assembly, transport, and storage:*Endoplasmic reticulum (plant and animal)*Ribosomes (plant and animal)*Golgi apparatus (plant and animal)*Vacuoles (plant has 1 large and animals have

many)*Lysosomes (animal)

Organelles that function in energy transformations:*Chloroplasts (plant only)*Mitochondria (plant and animal)

The Nucleus, Nucleolus, and Nuclear Envelop 

Ribosomes

Endomembrane System

Many of the different membranes of the eukaryotic cell are part of an ENDOMEMBRANE SYSTEM.

Membranes within cell are not identical in structure or function (modifications are present according to job).

Includes: nuclear envelope endoplasmic riticulum (smooth and rough) Golgi apparatus, lysosomes vacuoles plasma membrane

Relationships Among Organelles of the Endomembrane System 

Endoplasmic Reticulum

The ER is a membranous system of channels and flattened sacs that traverse the cytoplasm.

Exists in 2 varieties: Rough ER: the site of protein

synthesis resulting from the attached ribosomes

Smooth ER: assists in the synthesis of steroid hormones and other lipids Also connects rough ER to the Golgi

apparatus and carries out various detoxification processes in liver

Smooth and rough E.R. are actually connected, not distinct, separate sections

The Golgi Apparatus

Vesicles Cells need to separate

reactants for various chemical reactions until it is time to be used.

Vesicles are a general name used to describe small membrane-bound sacs that divide some materials from the rest of the cytoplasm.

They transport these materials from place to place within the cell.

Vesicles are generally short-lived and are formed and recycled when needed.

Vacuoles A vacuole is a fluid-filled sac

used for the storage of materials needed by the cell.

Most animal cells contain many small vacuoles.

A large central vacuole, as shown in the diagram to the right, is a prominent structure unique to plant cells. It is filled mostly with a watery fluid

that strengthens the cell and helps to support the entire plant.

When a plant wilts, its leaves shrivel because there is not enough water in each cell’s central vacuole to support the leaf’s normal structure.

Lysosomes Lysosomes are membrane-bound

sacs of hydrolytic enzymes…they are the principle site of intracellular digestion.

Different lysosomes break down each of the major classes of macromolecules – proteins, polysaccharides, fats, and nucleic acids.

Lysosomes defend a cell from invading bacteria and viruses and are also used in autophagy – the recycling of the cell’s own organic material for use.

The Formation and Functions of Lysosomes (Layer 1)

The Formation and Functions of Lysosomes (Layer 2)

The Formation and Functions of Lysosomes (Layer 3)

Centrosomes & Centrioles The centrosome is a small region of

the cytoplasm that produces microtubules.

In animal cells, it contains two small structures called centrioles.

Centrioles are cylinder-shaped organelles arranged in a circle.

Before an animal cell divides, the centrosome, including the centrioles, doubles and the two new centrosomes move to opposite ends of the cell.

Microtubules grow from each centrosome forming spindle fibers that attach to the chromosomes and aid during cell division.

Peroxisomes

Mitochondria

Chloroplasts

Endosymbiosis and the First Eukaryoteshttp://highered.mcgraw-hill.com/sites/9834092339/student_view0/chapter4/animation_-_endosymbiosis.html

The hypothesis of endosymbiosis proposes that mitochondria and chloroplasts were formerly small prokaryotes living within larger host cells.

An endosymbiont is a cell that lives within a host cell.

Theory of Endosymbiosis

Evidence for this hypothesis includes: Both organelles have enzymes and transport systems

homologous to those found in the plasma membranes of living prokaryotes.

Both replicate by a splitting process similar to prokaryotes.

Both contain a single, circular DNA molecule, not associated with histone proteins.

Both have their own ribosomes which translate their DNA into proteins.

Evidence Supporting the Endosymbiotic Theory

Cilia and Flagella

In plants, algae, fungi, and most bacteria, the cell membrane is surrounded by a strong cell wall.

This rigid layer provides protection, support, and shape to the cell.

The cell walls of multiple cells can adhere to each other and help support the entire organism.

Cell wall composition varies and is related to the different needs of each type of organism:

Plants & Algae: cellulose

Fungi: chitin

Bacteria: peptidoglycan

Cell Walls

Practice, Application & Critical Thinking The following virtual textbook activities are

highly recommended: Section 3.2 Assessment Questions (Textbook pp.

79) Classzone.com: Animated Biology – Cell

Structures Interactive Review: Concepts Maps – Section 2 Classzone.com: WebQuests: Organelle

Dysfunction Data Analysis (Textbook pp. 80) – Defining

Variables

AKS STANDARDS

8d - explain the role of cell organelles (including the cell membrane) in

maintaining homeostasis and cell reproduction for both prokaryotic and

eukaryotic cells

Cell Membrane The cell membrane, or plasma

membrane, forms a boundary between a cell and the outside environment and controls the passage of materials into and out of a cell.

The cell membrane consists of a double layer of phospholipids interspersed with a variety of other molecules. The phospholipid “heads” are polar

and are directed toward the outside of the membrane.

The phospholipid “tails” are nonpolar and are directed toward the inside of the membrane.

Structure & Function of Cell Membrane

Some Functions of Membrane Proteins

Fluid Mosaic Model of the Cell Membrane

Selective Permeability The cell membrane has the

property of selective permeability, which means it allows some, but not all, materials to cross.

Selective permeability enables a cell to maintain homeostasis in spite of unpredictable, changing conditions outside the cell.

How a particular molecule crosses the membrane depends on the molecule’s size, polarity, and concentration inside versus outside the cell.

Selective Permeability

Practice, Application & Critical Thinking The following virtual textbook activities are

highly recommended: Section 3.3 Assessment Questions (Textbook pp.

84) Interactive Review: Concepts Maps – Section 3

AKS STANDARDS

8g - describe processes whereby substances enter and leave the cell (passive and active transport

mechanisms), 8h - investigate factors that affect the rate of cellular

transport (e.g., molecule size, charge, concentration, temperature),

8i - compare the reaction of plant and animal cells in solutions of different solute concentrations (e.g.,

isotonic, hypotonic, hypertonic solutions),

Passive Transport Cells almost continuously import and export substances. Passive transport is

the movement of molecules across a membrane without energy input from the cell. Diffusion is the movement of molecules in a fluid or gas from a region of higher concentration

to a region of lower concentration. A concentration gradient is the difference in the concentration of a substance from one location

to another. Molecules generally diffuse down their gradient, from a region of high concentration to a region

of low concentration. Diffusion exists in TWO forms:

1. Dialysis: the PASSIVE movement of particles across a semi-permeable membrane from an area of high particle concentration to an area of low particle concentration (no energy).

2. Osmosis: the PASSIVE movement of water molecules across a semi-permeable membrane from an area of high water concentration to an area of low water concentration (no energy).

Molecules of dye Membrane (cross section)

WATER

Net diffusion Net diffusion Equilibrium

(a) Diffusion of one solute

Net diffusion

Net diffusion

Net diffusion

Net diffusion

Equilibrium

Equilibrium

(b) Diffusion of two solutes

Types of Solutions All of the components of a solution are evenly distributed

throughout the solution: The substance that is dissolved is the solute. The substance in which the solute is dissolved is the solvent. Example: salt/water mixture – salt is the solute and water is the solvent.

A solution may be : Hypertonic: more solutes than liquid. Hypotonic: less solutes than liquid. Isotonic: equal amount of solute and liquid.

Water Balance of Cells WITHOUT Walls

Water Balance of Cells WITH Walls

Hypotonic solution

(a) Animal cell

(b) Plant cell

H2O

Lysed

H2O

Turgid (normal)

H2O

H2O

H2O

H2O

Normal

Isotonic solution

Flaccid

H2O

H2O

Shriveled

Plasmolyzed

Hypertonic solution

Facilitated Diffusion In facilitated diffusion, transport proteins speed the

passive movement of molecules across the plasma membrane from high to low concentration – NO ENERGY REQUIRED!

Channel proteins provide corridors that allow a specific molecule or ion to cross the membrane

Channel proteins include: Aquaporins, for facilitated diffusion of water. Ion channels that open or close in response to a stimulus (gated

channels).

USEFUL ANIMATION: http://highered.mcgraw-hill.com/sites/0072507470/

student_view0/chapter3/animation__how_facilitated_diffusion_works.html

EXTRACELLULAR FLUID

Channel protein

(a) A channel protein

Solute CYTOPLASM

Solute Carrier protein

(b) A carrier protein

Practice, Application & Critical Thinking The following virtual textbook activities are

highly recommended: Section 3.4 Assessment Questions (Textbook pp.

87) Classzone.com: Animated Biology – Getting

Through a Cell Membrane Interactive Review: Concepts Maps – Section 4

AKS STANDARDS

8g - describe processes whereby substances enter and leave the cell (passive and active

transport mechanisms),

Active Transport

Active Transport uses energy to move molecules AGAINST their concentration gradients or in large quantity (bulk).

Active transport is performed by specific proteins embedded in the cell membranes.

Active transport allows cells to maintain concentration gradients that differ from their surroundings.

http://www.wiley.com/college/pratt/0471393878/student/animations/membrane_transport/index.html

Bulk Transport Across the Cell Membrane Small molecules and water enter or leave the cell

through the lipid bilayer or by transport proteins. Large molecules, such as polysaccharides and

proteins, cross the membrane in bulk via vesicles.

Bulk transport requires energy (ACTIVE). There are two types of bulk transport in cells:

Endocytosis Exocytosis

Endocytosishttp://highered.mcgraw-hill.com/olc/dl/120068/bio02.swf

In endocytosis, the cell takes in liquids or fairly large molecules by engulfing them in a membrane.

Exocytosishttp://highered.mcgraw-hill.com/olc/dl/120068/bio02.swf

Exocytosis is the opposite of endocytosis, it releases substances out of the cell by the fusion of vesicles with the membrane.

Practice, Application & Critical Thinking The following virtual textbook activities are

highly recommended: Section 3.4 Assessment Questions (Textbook pp. 91) Classzone.com: Animated Biology – Getting Through

a Cell Membrane Interactive Review: Concepts Maps – Section 5 Reviewing Vocabulary (Textbook p. 95) Reviewing Main Ideas (Textbook pp. 95) Critical Thinking (Textbook pp. 96) Analyzing Data (Textbook pp. 96) Connecting Concepts (Textbook pp. 96)