Chapter Three

Cell Structure and Function

The Fundamental Discovery!

Curiosity led early investigators to the most fundamental of all discoveries about life:

Cells are the basic units of structure and function in living things. What does this mean???

Invention Led To This Discovery!

_________; Early 1600s… Two major inventions:

________ – Made distant objects visible. ________ – Made very small objects visible.

Early Scientists

Robert – 1665 Constructed a poor microscope. Could see very little detail. First to observe _____through a

microscope. Saw “many little boxes” Called them cells because they

reminded him of the small rooms called cells in a _________.

Cork was actually ________ outer walls of dead plant cells.

Early Scientists

Anton Van ___________ Improved the simple

microscope. Built more than 240

microscopes & ground the lenses himself.

First to observe ______ cells.

Saw Red Blood Cells & Bacteria from teeth scrapings.

Early Scientists

Modern Light Microscopes – 1825 Compound Light Microscope. Uses 2 or more glass lenses to magnify objects. Magnified up to 1500 times.

Robert Brown – _______ Discovered _________ of cells (dark region in

center).

Early Scientists

Schleiden & Schwann – _________s Schleiden – Concluded that all _______ are made of

1 or more cells (“You ‘SCHLip’ on a banana peel, which is a plant”).

Schwann – Concluded that all ________ are made of 1 or more cells (“A ‘SCHwan’ (Swan) is an animal”).

Rudolf Virchow – 1855 Discovered that all cells arise from the division of

____________ cells.

Cell Theory

All of the information collected by these early scientists was combined to form our modern…

The cell theory forms the basic framework in which biologists have tried to understand living things.

Cell Theory

1. _

2. _

3. _

Two Basic Types of Cells

The absence or presence of a ________ can be used to divide organisms into two general categories.

Organisms whose cells lack nuclei.

Organisms whose cells contain nuclei.

Karyon = “nucleus” pro- = “before”eu- = “true”

Prokaryotic vs. Eukaryotic

Prokaryotic Organisms: Include bacteria and their relatives. Usually smaller and unicellular.

Eukaryotic Organisms: Both unicellular & multicellular forms. Larger and more complex.

The Prokaryotes…

No membrane bound organelles. . Single strand of DNA. . “Live alone.” Primitive cell. .

The Eukaryotes…

Membrane bound organelles. True nucleus. . Mostly _________ organisms (some single

cells). Function with other cells to form organism. More advanced cell type. .

Cell Size

Cell size is limited by metabolic requirements.

Size limits are imposed by the surface area to volume ratio. As a cell increases in size, its volume grows proportionately more than its surface area.

A smaller surface area cannot support a large cell volume (import food, export wastes, etc).

Surface To Volume Ratio

Cell Structures/Organelles

__________ = A tiny structure that performs a specialized function in the cell (“little organ”).

The cells of animals, plants and related organisms have three basic structures: ___________ (outer boundary of cell) Nucleus (control center) ___________ (“fluid” material between cell

membrane and the nucleus)

Animal Cell!

Plant Cell!

Cell Membrane

The cell membrane is the “___________.” It controls what _______________ the cell. Outer boundary of the cell that holds the cell

together (aids in _________ and support of the cell).

Cells need to be able to communicate with other cells, take in food/water and eliminate wastes.

Structure of Cell Membrane

Cell membrane is composed of a double layer of _______, known as a bilayer.

Cell membrane also contains __________, many of which act as channels or pumps through which molecules can enter the cell.

Cell membrane contains carbohydrates as well that act like an “_______” (allow cells to recognize & interact with each other).

Where is the Cell Membrane?

Cell Wall

__________ of plant cells (outside the cell membrane).

Provides rigid support to the cell and protection for the plant.

Three layers: Middle Lamella (“gluey layer”) that connects two plant

cells. Primary Cell Wall (contains cellulose). Cellulose makes

the cell wall elastic so it can stretch & grow. Secondary Cell Wall (contains cellulose & lignin). Lignin

makes cellulose more rigid – found in woody plants.

Cell Wall

Nucleus

The “___________” of the cell. Contains genetic information (_____). “Information Center” that directs all the

activities of the cell. Prokaryotes do not have a nucleus.

Where is the Nucleus?

Nuclear Envelope

Two membranes surrounding the nucleus form the _______________ (a boundary).

There are many pores in the nuclear envelope that allow molecules to move in and out of the nucleus.

Nucleolus

Small, spherical region inside the nucleus.

Made up of _______ and proteins.

________ are made in the nucleolus.

Ribosomes are important in protein synthesis for the cell.

Chromosomes

Structures located in the nucleus that contain DNA (the hereditary information) attached to special proteins.

This genetic information must be passed to each new generation.

Cytoplasm vs. Cytosol

_________ = the space between the nucleus and the cell membrane.

_________ = Thick, jelly-like part of the cell (70% H2O).

Mitochondria & Chloroplasts

Mitochondria Chloroplasts

Both of these organelles change energy from one form to another.

Found in ______cells (and some plant cells).

Found in ______ cells only.

Converts chemical energy in food to ATP energy for use by the cell.

Traps energy from the sun and converts it to chemical (“food”) energy for plant.

Mitochondrion

Mitochondrion contians ________________:

1. Outer membrane surrounds organelle.

2. Inner membrane has many folds that increase surface area. (More space for energy reactions to take place.)

Chloroplast

Similar structure to mitochondrion.

Surrounded by two membranes.

Found only in plant cells and algae.

Location where ___________ takes place.

Ribosomes

___________________________________________________.

Site of protein synthesis in cells. Can be found attached to

membranes or free in the cytosol.

Cells that are active in protein synthesis have MANY ribosomes.

Endoplasmic Reticulum - “ER”

Complex network of sacs in the cytoplasm used to transport materials throughout the cell.

Rough & Smooth ER

___________ – Walls look smooth; no ribosomes. creates steroids/lipids and stores ions, detoxifies poisonous substances

___________– Walls are studded with ribosomes; involved in protein and glycoprotein synthesis.

Protein Destinations...

Proteins that are meant to be released from the cell (for other parts of the body) are made on ribosomes attached to the ____________.

Proteins that are meant to be used inside the cell are made on free __________ that are floating by themselves in the cytosol.

Golgi Apparatus

Flattened stack of membranes piled on top of each other (“pancakes”).

Proteins move from ER to Golgi Apparatus, where they are Packages and then released.

__________________________________

________________________________. Creates Glycoproteins, package lipids,

creation of lysosomes

Path of Proteins...

Proteins made by ribosomes on Rough ER.

Proteins then enter the Rough

ER.

Proteins moved around cell in

Rough ER, often ending up at Golgi

Apparatus.

Golgi Apparatus modifies proteins and sends them to

where they are needed.

Golgi Apparatus

Where is ER and Golgi Apparatus?

Lysosomes

Small spherical organelles that contain chemicals and _______ ______. (“Get rid of cell’s garbage.”)

Endocytosis = When cells engulf particles and bring them through the cell membrane.

These particles are then broken down by lysosomes. “______ _______” – Digest old organelles. Lysosomes are NOT found in plant cells!

Where are Lysosomes?

Vacuoles

Vacuole = A fluid-filled sac within _____ ____. Stores food, water, salts, proteins, carbohydrates, etc.

Many plant cells have a large central vacuole filled with liquid Creates PRESSURE in these cells Makes it possible for plants to grow quickly & to support heavy structures like leaves/flowers.

Why does a plant wilt?

Where is the Vacuole?

Plastids

Plastids = ______ organelle used to store food or pigments. Chloroplast – Contains chlorophyll. Leukoplast – Stores starch granules. Chromoplast – Contains colored pigment.

Cytoskeleton

Cytoskeleton = Composed of a variety of filaments and fibers that support cell structure ( _____________) and drive cell movement.

Microtubules

Microtubules = ______ tubes made of protein. Support cell shape, help move organelles, play a role in

cell division by forming centrioles. (Centrioles are NOT found in plant cells.)

Microtubules also support cilia and flagella (hair-like projections). _______ = Short hairs that move unicellular organisms

and help substances move across surface of cells. __________ = Longer whiplike structures that help

unicellular organisms move.

Microfilaments

Microfilaments = ____, _____ fibers that function in movement and support of the cell. Also permit movement of the cytoplasm within the cell (“________ ________”).

Diffusion!

Cells exist in a liquid environment ~ This makes it easier for materials (food, oxygen, water) to move into and out of the cell.

Diffusion = Molecules move from areas of

________ concentration of that substance to areas of ______ concentration.

Equilibrium

If two substances are present in ______ amounts on either side of a membrane, each substance will tend to move toward the area of lower concentration until equilibrium is reached.

Occurs when the concentrations of the substances on both sides of the membrane are the same.

Equilibrium Question…

When equilibrium has been reached, are molecules still moving through the membrane?

_____!!! Individual molecules move between the two sides at equilibrium, but ________ numbers of molecules move in each direction – so they balance each other out. (No change in concentration.)

Equilibrium

Permeability

Permeability determines whether diffusion occurs across a membrane.

__________: A substance can diffuse across a membrane.

_____________: A substance cannot move across a membrane.

Membranes…

Are most membranes permeable or impermeable?

Some materials can move across membranes and some cannot, so we say that biological membranes are…

Osmosis

Water can pass through most membranes VERY rapidly.

Osmosis = The ________ of water through a selectively permeable membrane from an area of high water concentration to an area of low water concentration.

Osmosis

Forms of Osmosis

__________solutions are those in which more solute and thus less water is present.

___________ solutions are those with less solute and thus more water is present.

___________ solutions have equal (iso-) concentrations of substances.

Solute, Solvent, Solution…

The __________ is what is being dissolved in a solution. Sugar, Salt, Dyes, Etc.

The __________ is what does the dissolving. Usually water.

The __________ is the end product after the solute has completely dissolved in the solvent.

Hypo, Hyper, Isotonic…

Examples!

Examples!

Review: Diffusion

Movement of molecules from a region of

higher concentration to a region of lower concentration.

________ Transport!

Review: Osmosis

Diffusion of water molecules from a region

of high concentration to regions of lower concentration.

Passive Transport!

Facilitated Diffusion

__________ protein helps transport molecules across a membrane.

Still travels from higher concentration to lower concentration.

Still PASSIVE transport! What’s the advantage of facilitated

diffusion? ____________________________________

_____________________________.

Facilitated Diffusion: with molecules

Ion channels also a type of Facilitated Diffusion with Ions

Active Transport

Active = Requires ________! Moves material from areas of lower

concentration into areas of ______ concentration.

This allows cells to concentrate certain molecules, even though normal diffusion might tend to move those molecules in the opposite direction.

Passive vs. Active Transport

Special Types of Active Transport

___________ “Cell Eating” Large particles are surrounded and taken in to the cell.

Pinocytosis “Cell Drinking”

Fluids are taken in to the cell through pockets along the cell membrane.

__________ “Outside The Cell”

Large particles are sent out of the cell.

Cell Specialization

Examples of specialization: Movement. Reaction to environment. Manufacturing of products.

When cells have unique characteristics that allow the cell to perform certain functions in an organism. (The cell is “custom made” for a certain purpose.)

Example 1…

Cells in the pancreas have MANY of the following organelles: rough ER and golgi apparatus.

What function do you think pancreas cells serve?

Protein synthesis – proteins that will be sent to other parts of the body.

Example 2…

Light-sensitive cells in the eye are heavily packed with MITOCHONDRIA.

What can you say about these eye cells? They require a lot of ENERGY!

Example 3…

Cells lining the passageways in the lungs have MANY cilia.

What can you say about the function of these cells?

“Sweeping action” that keeps vital passageways clean and open.

Levels of Organization

Multicellular organisms are studied through their LEVELS OF ORGANIZATION.

CELLS TISSUES ORGANS ORGAN SYSTEMS

Cells are the first and most basic level of organization.

Tissues

Cells are organized into groups called tissues.

Tissues = Groups of similar cells that perform similar functions.

Four main types of tissues: Muscle, Epithelial, Nerve, Connective.

Organs

Tissues are organized into organs.

Organs = Groups of tissues that work together to perform a specific function.

Organ Systems

Groups of organs combine to form organ systems.

Organ System = Group of organs that work together to perform a certain function.

Ten organ systems in the body (Muscular system, Nervous system, Circulatory system, Skeletal system, etc).