Chapter 3Cell Structure and Function

KEY CONCEPT: Cells are the Basic unit of life.

3.1: Cell Theory

The cell theory grew out of the work of many scientists and improvements in the microscope.Many scientists contributed to the

cell theory.More was learned about cells as

microscopes improved.The cell theory is a unifying

concept of biology.

• Many scientists contributed to the cell theory.

1665Identified and named cells

1674Observed living cells; could see greater detail due to better lenses

1838Noted that plants are made of cells

1839Concluded that all living things are made of cells

1855Proposed that all cells come from other cells

Early studies led to the development of the cell theory.The Cell Theory has three principles:

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.All cells share certain

characteristics.Cells tend to be microscopic.All cells are enclosed by a

membrane.

cell membrane

Bacterium (colored SEM; magnification 8800x)

cytoplasm

Prokaryotic cells lack a nucleus and most internal structures of eukaryotic cells. All cells share certain characteristics.

All cells are filled with cytoplasm: jellylike substance that surrounds all organelles

Organelle: small part of a cell that carries out

a specific job in a cell.

cell membrane Bacterium (colored SEM; magnification 8800x)

Cytoplasm

There are two cell types: Eukaryotic cells have a

nucleus and membrane-bound organelles.

Prokaryotic cells do not have a nucleus and membrane- bound organelles.

nucleus

cell membrane

organelles

cytoplasm

1. Which invention played the biggest role in the discovery of cells by early scientists?

A. telescopeB. lensC. eyeglassesD. microscope

2. The cell theory states that all organisms are made of cells; cells are the most basic unit of life; and

A. all existing cells spontaneously form

B. all cells are eukaryoticC. all existing cells are produced

by other living cells.D. All cells have a nucleus

3. Which of the following is a major principle upon which cell theory is based?

a. All cells form by free-cell formation.

b. All cells have DNA.c. All organisms are made of cells.d. All cells are eukaryotic.

4. What is the term for the jellylike substance that is contained inside the cell membrane?

A. CytoplasmB. DNAC. OrganelleD. Nucleus

5. Unlike a eukaryotic cell, a prokaryotic cell does not have

A. DNAB. a cell membraneC. cytoplasmD. a nucleus

6. Specialized structures that work together inside a cell are called

A. organellesB. prokaryotesC. eukaryotesD. nuclei

KEY CONCEPT Eukaryotic cells share many similarities.

3.2: Cell Organelles

Cells have an internal structure.The cytoskeleton has many

functions.supports and shapes cellhelps position and transport organellesprovides strengthassists in cell divisionaids in cell movement

Several organelles are involved in making and processing proteins.The nucleus stores and protects

DNA.Direct all the activities of the cell

The nucleus is enclosed in a double membrane – nuclear envelope. Has tiny holes (pores).

Pores allow molecules to move between nucleus and cytoplasm.

The nucleus contains the nucleolus. Region where ribosomes are

assembled. Ribosomes are essential for

making proteins.

The endoplasmic reticulum (ER) is a network of thin, folded membranes that helps in production of proteins and other molecules.

There are two types of ER:rough endoplasmic reticulum:has ribososmes attached looks bumpy - makes proteins rough ER – (has

ribosomes)

There are two types of ER:Smooth endoplasmic reticulum:no ribosomes attached - makes lipids - breaks down drugs and alcohol

Smooth ER (no ribosomes)

Ribosomes make proteins by linking amino acids.Found in two areas: - 1. on surface of the rough ER

- make membrane proteins

Ribosomes make proteins by linking amino acids.Found in two areas: - 2. Floating in the cytoplasm. - make proteins used in

chemical reactions in cytoplasm

The Golgi apparatus is a stack of layers of membranes that modifies, packages, and transports proteins.

Vesicles are membrane-bound sacs that hold materials.Help to separate reactants needed

for chemical reactionsCarry molecules to where they are

needed.

Mitochondria supply energy to the cell.site of cellular respiration: process used to obtain energy from food by organisms

“Powerhouse of the cell”

Vacuoles are fluid-filled sacs that store materials such as water, food molecules, ions, and enzymes.Plant cell have a large central vacuole.

Lysosomes contain enzymes to digest material.Also break down old cell parts

Centrioles are tubes found in the centrosomes.Centrioles help divide DNACentrioles form cilia and flagella.

Plant cells have cell walls and chloroplasts. A cell wall provides rigid support.

It surrounds the cell membrane

Plant cells have cell walls and chloroplasts. Chloroplasts convert solar energy to

chemical energy.Carry out photosynthesis

1. Which of the following is a network of proteins that supports and gives shape to a cell?

a. vesiclesb. vacuolec. cytoskeletond. cytoplasm

2. What is the main function of the Golgi apparatus?

a. communicate with other cellsb. convert solar energy to

chemical energyc. process and deliver proteinsd. copy genetic material

3. Which of the following organelles can be found in the cytoplasm and on the surface of the endoplasmic reticulum?

a. mitochondriab. centrosomesc. ribosomesd. centrioles

4. Which organelle contains enzymes that break down damaged cell parts?

a. centrioleb. lysosomesc. vacuoled. mitochondria

5. What are the main differences between plant and animal cells?

a. Animal cells are eukaryotes and plant cells are not.

b. Plant cells are eukaryotes and animal cells are not.

c. Animal cells have cell walls and chloroplasts; plant cells do not.

d. Plant cells have cell walls and chloroplasts; animal cells do not.

6. Which organelle is the storehouse for most of a cell’s genetic information?

a. mitochondrionb. chloroplastc. centrioled. nucleus

7. Which phrase best describes rough ER?

a. studded with ribosomesb. protected by vesiclesc. found inside the nucleusd. stored in the central vacuole

8. Which organelles supply energy to the cell?

a. ribosomesb. centrosomesc. mitochondriad. vacuoles

9. Which organelles contain enzymes that break down old cell parts?

a. centrosomesb. lysosomesc. vacuolesd. chloroplasts

10. Which organelles are unique to plant cells?

a. ribosomesb. vacuolesc. chloroplastsd. centrosomes

11. Which process occurs inside the chloroplasts?

a. detoxificationb. ribosome assemblyc. photosynthesisd. protein synthesis

KEY CONCEPT The cell membrane is a barrier that separates a cell from the external environment.

3.3: Cell Membrane

The cell membrane has two major functions.forms a boundary between inside

and outside of the cellcontrols passage of materials into

and out the cellcell membrane outside cell

inside cell

cell membrane

Cell membranes are mainly composed of two phospholipid layers. The two layers of phospholipid

molecules have protein molecules embedded in them

protein

cholesterol

proteincarbohydratechain

protein channel

Phospholipid Structure Two part molecule:

Hydrophilic polar phosphate group head is attracted to water faces outward towards water

Hydrophobic non-polar fatty acids tails face inward toward each other—away from water

The cell membrane is selectively permeable (semipermeable) . Some molecules can cross the

membrane while others cannot.

CELL MEMBRANES

Cell Membranes.url

Chemical signals are transmitted across the cell membrane. Receptors bind with ligands and change

shape. There are two types of receptors.

intracellular receptor membrane receptor

Molecules that cannot enter the cell bind to receptors in the membrane. When bound, the receptor transmits the cell by changing shape.

1. What is a phospholipid composed of?

A. a polar head and a nonpolar tail

B. a nonpolar head and a polar tail

C. a polar head and tailD. a nonpolar head and tail

2. Which phrase best describes the property of selective permeability?

A. some molecules passB. all ions passC. large molecules passD. all molecules pass

3. A ligand produces a response in a cell if it finds the right kind of

A. carbohydrate.B. hormone.C. membrane.D. receptor.

KEY CONCEPT Materials move across membranes because of concentration differences.

3.4: Diffusion & Osmosis

Passive transport A substance moves from an

area higher concentration to an area of lower concentration

Does not require energy input from a cell.

Concentration GradientsConcentration gradient:

difference in the concentration of a substance from one location to another

Molecules diffuse down their concentration gradient

This movement does not require that any energy be supplied

There are 3 types of passive transport.

•Diffusion: Molecules move from high to low concentration

•Osmosis: the diffusion of water molecules across a semipermeable membrane.

•Facilitated diffusion: diffusion through transport proteins.

Osmotic solutionsThis term refers to the relative

concentration of solutes in one solution versus another solution

There are three types of osmotic solutions

- isotonic - hypotonic - hypertonic

DIFFUSION

Diffusion.url

Isotonic Solution• Isotonic: the solution has the same concentration of solutes as the cell.

- Iso- means “equal”• Same concentration of water inside and outside the cell

• As a result, water moves into and out of the cell at equal rate and the cell size remains constant.

Cells in Isotonic Solutions

Hypertonic Solution• Hypertonic: the solution has a higher concentration of solutes than the cell. - Hyper- means “more”

• The cell has a higher concentration of water than the surrounding fluid.

• As a result, water diffuses out of the cell and the cell shrivels.

Cells in Hypertonic Solutions

Hypotonic Solution• Hypotonic: the solution has a lower concentration of solutes than the cell.

- Hypo- means “less”• The cell has a lower concentration of water than the surrounding fluid.

• As a result, water diffuses into the cell and the cell swells and may burst.

Cells in Hypotonic Solutions

Cells in Different Osmotic Solutions

Facilitated DiffusionFacilitated diffusion: the diffusion of a

substance across a membrane through transport proteins

- “facilitate” means to make easier - transport proteins make it easier

for molecules to enter and exit cells - molecules still move areas of higher concentration to lower concentration

Facilitated Diffusion

How Facilitated Diffusion Works.url

1. Which phrase best describes passive transport?

A. requires transport proteinsB. requires no energy from the

cellC. requires an isotonic solutionD. requires facilitation by

enzymes

2. Water moves into a cell when the solution surrounding the cell is

A. hypertonic.B. hypotonic.C. isotonic.D. concentrated.

3. What is the term for the diffusion of water across a semipermeable membrane?

A. osmosisB. equilibriumC. transportD. isotonic

4. The difference in the concentration of dissolved particles from one location to another is called a

a. concentration gradient.b. concentrated solution.c. saline solution.d. dynamic gradient.

5. The movement of molecules down a concentration gradient through transport proteins in the cell membrane is a type of

a. selective transport.b. osmosis.c. energy expenditure.d. facilitated diffusion.

KEY CONCEPT Cells use energy to transport materials that cannot diffuse across a membrane.

3.5: Active Transport, Endocytosis, and Exocytosis

Active transport Moves a substance from low to

high concentration - against its concentration

gradientRequires chemical energy or ATP

Active transport Active transport occurs through

transport protein pumps powered by chemical energy (ATP).

Requires energy or ATPCells use active transport to

maintain homeostasis.

Active transport A cell can import and export large materials or large amounts of material in vesicles in two processes

endocytosis exocytosis

Endocytosis & Exocytosis

•Cells use energy to transport material in vesicles. •Endocytosis: process of taking material into the cell.

•Phagocytosis is a type of endocytosis. •Exocytosis: process of expelling material

from the cell.

1. Unlike passive transport, active transport requires

A. concentration gradients.B. diffusion.C. energy from the cell.D. vesicles.

2. Which process uses proteins to move molecules against a concentration gradient?

A. active transportB. passive transportC. endocytosisD. phagocytosis

Identifying Eukaryotic Animal Cell Organelles.url

A typical Cell.url