Chapter 7 Cellular Structure & Function

• 7.1 Cell Discovery & Theory

• 7.2 Plasma Membrane

• 7.4 Cellular Transport

• 7.3 Structures & Organelles

7.1 Cellular Discovery & Theory• Main idea-The invention of the microscope led to

the discovery of cells• Objectives

– Relate advances in microscope technology to discoveries about cells

– Compare compound light microscopes with electron microscopes

– Summarize the principles of the cell theory– Differentiate between a prokaryotic cell and a

eukaryotic cell.• Review Vocabulary

– Organization: the orderly structure of cells in an organism

History of the Cell Theory

• 1665, Robert Hooke made a simple microscope

• Cell-the basic structural and functional unit of all living organisms

• Late 1600’s Anton Van Leeuwenhoek designed his own microscope

The Cell Theory

• Fundamental idea of modern biology that includes these three principles:– All living organisms are composed of one or more cells

– Cells are the basic unit of structure and organization of all living organisms

– Cells arise only from previously existing cells, with cells passing copies of their genetic material on to their daughter cells

Microscope Technology• Compound Light

Microscope

• Utilizes a series of glass lenses and visible light to produce a magnified image

• Maximum magnification is around 1000X.

Microscope Technology• Electron Microscope• Utilizes magnets to

aim a beam of electrons at a cell to produce images

• Specimens must be nonliving

• Magnifies images up to 500,000X

Basic Cell Types

• Cells exists in various shapes and sizes

• Cells differ based on their function they perform for the organism

• All cells have at least one physical trait in common - the plasma membrane

Two Categories of Cells

• Prokaryotic Cells– Cells without

specialized internal structures

– Unicellular

– Similar to the first organisms on Earth

Two Categories of Cells• Eukaryotic Cells

– More complex than prokaryotic cells– Contain a structure called a nucleus (a distinct central

organelle that contains the cell’s genetic material in the form of DNA) and other organelles (specialized structures that carry out specific cell functions)

– Generally one to one hundred times larger than prokaryotic cells

Origin of Cell Diversity• Why two basic cell types?

– Eukaryotic cells derived from prokaryotic cells?

• Endosymbiont Theory– A symbiotic mutual relationship involved one prokaryotic

cell living inside the plasma membrane of another

• Because eukaryotic cells are larger and have distinct organelles, these cells have developed specific functions.

• Specific functions has led to cell diversity, and thus more diverse organisms that can adapt better to their environment.

7.2 The Plasma Membrane

• Main idea: The plasma membrane help’s to maintain a cell’s homeostasis

• Objectives:– Describe how a cell’s plasma membrane

functions– Identify the roles of proteins, carbohydrates,

and cholesterol in the plasma membrane

• Review Vocabulary– Ion: an atom or group of atoms with a positive

or negative electric charge

Plasma Membrane

• Primarily responsible for homeostasis in the cell

• A thin, flexible boundary between a cell and its environment that allows nutrients into the cell and allows waste and other products to leave the cell

Selective Permeability• A key property of the

plasma membrane which allows some substances to pass through while keeping others out

• Controls the substances in and out of the cell

Plasma Membrane Structure

• The plasma membrane is composed of the phospholipid bilayer.

• Phospholipid is a molecule that has a glycerol backbone, two fatty acid chains, and a phosphate-containing group

• Phospholipid bilayer is two layers of phospholipids arranged tail to tail

Plasma Membrane Structure

Plasma Membrane Structure

• Phosphate group makes the head polar and are hydrophillic

• The two fatty acid tails are non-polar and hydrophobic

• The phospholipids are arranged in such a way that the polar heads can be closest to the water molecules and the non-polar tails can be farthest away from the water molecules

Other Components of the Plasma Membrane

• Proteins – Transmit signals inside the cells (receptor

proteins)– Acts as a support structure to give the cell its

shape– Provide pathways for substances to enter and

leave the cell (transport proteins)

Proteins

Cholesterol

• Prevents fatty acid tails of the phospholipid bilayer from sticking together

• Helps maintain cell homeostasis

Carbohydrates

• Help cells identify chemical signals

Fluid Mosaic Model• The components of the plasma membrane are in constant motion

(fluid)• The different substances in the plasma membrane creates a pattern

(mosaic) on the surface

7.4 Cellular Transport• Main idea – Cellular transport moves substances

within the cell and moves substances into and out of the cell

• Objectives– Explain the processes of diffusion, facilitated diffusion,

and active transport.– Predict the effect of a hypotonic, hypertonic, or

isotonic solution on a cell– Discuss how large particles enter and exits cells.

• Review Vocabulary– Homeostasis: regulation of the internal environment of

a cell or organism to maintain conditions suitable for life.

Passive Transport

• Movement of particles across the cell membrane without using energy is passive transport– Diffusion– Facilitated Diffusion– Osmosis

Diffusion• Movement of particles

from an area of high concentration to an area of lower concentration

• Diffusion Rate Factors– Concentration– Temperature– Pressure

Dynamic equilibrium• Reached when

diffusion of material into the cell equals diffusion of material out of the cell

• Molecules continue to move, but the overall concentration remains the same.

Diffusion in a cell

Facilitated Diffusion

• Movement of materials across the plasma membrane using transport proteins– Channel proteins-water filled transport protein

that opens and closes to allow the substance to diffuse through the plasma membrane

– Carrier proteins – change shape to move particles through the membrane

Channel Proteins

Carrier Proteins

Osmosis

• Diffusion of water across a selectively permeable membrane

• Three types of solutions– Isotonic – the cell is at equilibrium– Hypotonic – lower concentration of solute– Hypertonic – higher concentration of solute

Isotonic Solution

• Water and dissolved substances diffuse into and out of the cell at the same rate.

Hypotonic Solution• Solute concentration is higher inside the cell• Water diffuses into the cell• Cell swells and may burst

Hypertonic Solution• Solute concentration is higher outside the cell• Water diffuses out of the cell• Cell wilts or shrinks

Active Transport• Requires energy to move substances against a

concentration gradient or from low to high concentration

• Active transport using carrier proteins or pumps to maintain cell homeostasis. Ex. Na+/K+ ATPase Pumps – moving 3 Na+ ions out of the cell and 2 K+ ions into the cell

Transport of Large Substances

• Endocytosis - Process by which the cell surrounds and takes particles into the cell

• Exocytosis - Secretion of material out of the plasma membrane

7.3 Structures & Organelles• Main idea: Eukaryotic cells contain organelles that

allow the specialization and the separation of functions within the cell.

• Objectives– Identify the structure and function of the parts of a

typical eukaryotic cell– Compare and contrast structures of plant and animal

cells

• Review vocabulary– Enzymes: a protein that speeds up the rate of a

chemical reaction.

Cytoplasm and Cytoskeleton

• Cytoplasm - a semi-fluid material that constitutes the environment inside the plasma membrane (Plant & Animal Cells)

• Cytoskeleton - a supporting network of long, thin protein fibers that form a framework for the cell and provide an anchor for the organelles inside the cell (Plant & Animal Cells)

Cytoskeleton• A framework for the cell within the

cytoplasm that rapidly assemble and disassemble and slide past one another. This allows cells and organelles to move.– Microtubules-long, hollow protein cylinders

that form a rigid skeleton for the cell and assist in moving substances within the cell

– Microfilaments-thin protein threads that help give the cell shape and enable the entire cell or parts of the cell to move

Cytoskeleton

Cell Structures• Nucleus - brain of the cell; directs the cell

processes (Plant & Animal Cells)– Contains most of the cell’s DNA, which stores

information used to make proteins for cell growth, function, and reproduction

– Nuclear envelope - double membrane with nuclear pores that surrounds the nucleus

– Nuclear pores - allow larger-sized substances to move in and out of the nucleus

– Nucleolus – site of ribosome production

– Chromatin – the complex DNA attached to protein; spread throughout the nucleus

Nucleus

Ribosomes• Ribosomes are the most numerous of the cell’s

organelles (Plant & Animal Cells)• The ribosome is the site of protein synthesis.

(Protein factories)• Composed of RNA & protein• The concentration or distribution of ribosomes in

the cells depends on how the proteins they produce will be used.

• Proteins used by the cells are made by free floating ribosomes.

• Exported proteins are made by ribosomes that are attached to the ER.

Ribosomes

Endoplasmic Reticulum (ER)• The “ER” is a membrane system of folded

sacs and tunnels (Plant & Animal Cells)

• Rough ER are covered with ribosomes

• Smooth ER have little or no ribosomes and function primarily as an intercellular highway, a path which molecules can move from one part of the cell to another– Also the site of carbohydrate and lipid synthesis

ER

Golgi Apparatus• The processing, packaging and secreting

organelle of the cell (Plant & Animal Cells)• Notice that the Golgi Apparatus consists of

a stack of membranes.• It operates like a production line in a

factory, where a product is assembled at one end, then packaged, and finally shipped out.

• The protein vesicle is modified as it passes from sac to sac. Finally it is released to be sent out of the cell.

Golgi Apparatus

Vacuole

• A membrane-bound vessicle for the temporary storage of materials

• Plant cells-one large; Animal cells-a few small

Lysosomes• Lysosomes are organelles that contain

powerful digestive (Animal Cells Only)

• They destroy foreign bodies that get into the cell

• They also digest food vacuoles to help feed the cell

• They destroy the cell when it is too old or damaged. This is why they are sometimes called the “suicide sacs of the cell”

Lysosomes

Centrioles• Centrioles are tiny

t-shaped structures in the cell that function in helping the cell when it divides to form two new cells (Animal Cells and most Protists)

Mitochondria• The Mitochondria are the respiration

centers of the cell (Plant and Animal Cells)

• They are called the “powerhouse of the cell”

• They provide energy for the cell.

• Mitochondria have their own DNA.

• The number of mitochondria in a cell depends on the needs of the cell.

Mitochondria

Chloroplasts• The Chloroplast is an

organelle that is responsible for making food (Plants Cells Only)

• This process is called photosynthesis.

• They use sunlight + Water + Carbon dioxide and make glucose (sugar).

• The waste product of this is oxygen and water vapor.

Cell Wall• A Cell Wall is the rigid

covering of a plant cell that provides shape and protection (Plant Cell Only)

• It is made primarily of cellulose (carbohydrate)

• Pores in the cell wall allow ions and molecules to pass to and from the cell membrane.

Cellular Projections• The Cilia is a hair-like

cellular projection that functions in movement both of an organisms and of moving particles. Like in the illustration to the right (Some Animal Cells).

• The Flagella is a whip-like tail cellular projection that is long and help movement in unicellular organisms and some individual cells such as the sperm on the right (Some Animal Cells)

Animal Cell

Plant Cell