Chapter 7

Cell Structure and Function

Anton van Leeuwenhoek

Father of the microscope - 1600’s

used lens technology

fabric quality

telescope same time

1st to see life in a drop of water (“animalcules”)

Robert Hooke

1665

1st to examine plant

tissue

Resembled monastery’s

tiny rooms

“Cells”

Matthias Schleiden

1838 - all plants are made of cells

Theodor Schwann

1839 - All animals are made of cells

Rudolf Virchow

1855 - Cells come from other preexisting cells

The Cell Theory

All living things are composed of cells

Cells are the basic units of structure and function in living things

New cells are produced from existing cells

What do all cells have in common?

Cell membranethin, flexible barrier surrounding the cell (protection)

Cytoplasmfluid within the cell

Genetic Material (DNA/RNA)

Major Groups of Organisms

1. Bacteria

2. Protists (amoeba, algae, seaweed)

3. Fungi

4. Plants

5. Animals

Basic Cell Types

Prokaryotic Cellscell membrane

cytoplasm

genetic material (lack a nucleus)

bacteria Cell membrane

cytoplasm

Genetic Material

Eukaryotic CellsCell membrane

Cytoplasm

Nucleus

Membrane-bound organelles

animals, plants, fungi and protists

Prokaryotic Cell

Cell membrane

Cell membrane

Cytoplasm

Cytoplasm

Nucleus

Organelles

Eukaryotic Cell

Section 7-1

Go to Section:

7-2 A Closer Look at the Cell

Your objective is to…

Describe the main functions of each

cell structure

Cell WallPlants, bacteria (prokaryotes), fungi, algae (protists)

Provides structure and protection

Gas and water exchange

Plants - made of polysaccharide cellulose

Nucleus

Controls cell processes

Contains DNAdeoxyribose nucleic acid

codes for protein and other molecules

ChromatinDNA bound to protein

Chromosomeschromatin condenses during cell division

Nucleolusmake ribosomes

Nuclear Envelope2 layers with pores that allow for the passage of material

Nucleus

The Nucleus

Nucleolus Nuclear envelope

Nuclear pores

Chromatin

Cytoskeleton

Network of protein filaments

(microtubules and microfilaments)

Maintains cell shape

Cell Movement

Intracellular Movementmoves organelles

important during cell division

Tracks for organelle movement

Cell membrane

Endoplasmicreticulum

Microtubule

Microfilament

Ribosomes Mitochondrion

Figure 7-7 Cytoskeleton

Structures for Movement:

Flagella-tail-like structures to propel cell in whipping motion

Cilia- hair-like projections that beat together to move the cell

Transportation

The Organelles

Specialized structures within the cytoplasm of the cell that

perform specific jobs

Ribosomes

Use genetic information to make protein

found free in cytoplasm or on RER

Endoplasmic Reticulum

2 typesRough and Smooth

Cell membrane assembly

Roughcontain ribosomes

certain proteins are modified

Smoothsynthesis of lipids

Endoplasmic Reticulum

Ribosomes

Endoplasmic Endoplasmic ReticulumReticulum

Golgi Apparatus

Receive proteins from RER

Use enzymes to attach carbohydrates and lipids to proteins

Sent to final destination

Lysosomes

Contain enzymes that breakdown large molecules into smaller molecules

Recycle old organelles and debris

Enzyme

Recycling

Vacuoles

Storage units for water, salts, proteins and carbohydrates

Provide support for plants “water”Central water vacuole

Vacuole

ChloroplastsFound in plants and algae (some bacteria)

photosynthesis

2 membranes

Contains DNA

Chloroplast

Mitochondria

Convert food into high-energy compounds (ATP) that the cell uses to power growth, development and movement

ATP = Energy

2 membranes

Contains DNA

Mitochondrion

Animal vs. Plant Cells

Plant Cells have the following (Animal Cells do not):

Cell Wall

Chloroplasts

Central Water Vacuole

Prokaryotes Eukaryotes

Cell membraneRibosomesCell wall

NucleusEndoplasmic reticulumGolgi apparatusLysosomesVacuolesMitochondriaCytoskeleton

Animal Cells Plant Cells

Lysosomes

Cell membraneRibosomesNucleusEndoplasmic reticulumGolgi apparatusVacuolesMitochondriaCytoskeleton

Cell Wall

Chloroplasts

Section 7-2

Venn Diagrams

Go to Section:

Animal vs. Plant Cells

Plant Cell

Nuclearenvelope

Ribosome(attached)

Ribosome(free)

Smooth endoplasmicreticulum

Nucleus

Rough endoplasmic reticulum

Nucleolus

Golgi apparatus

Mitochondrion

Cell wall

CellMembrane

Chloroplast

Vacuole

Figure 7-5 Plant and Animal Cells

Animal Cell

Centrioles

NucleolusNucleus

Nuclearenvelope

Rough endoplasmic reticulum

Golgi apparatus

Smooth endoplasmicreticulum

Mitochondrion

CellMembrane

Ribosome(free)

Ribosome(attached)

Figure 7-5 Plant and Animal Cells

7-3 The Cell Membrane

Objectives:

Describe the structure of the cell membrane

Describe how substances move through the cell

Cell Membrane Structure: Lipids, Proteins, Carbohydrates

• Lipid bilayer

• Functions:

1. Regulates entry and exit of materials

2. Protection and support

• Carbohydrate chains act as identification cards

Fluids

ICF = Intracellular Fluid (inside cell/cytoplasm)

ECF = Extracellular Fluid (outside cell)

Always dissolved particles in both of these fluids

Dissolved particles = solutes

Concentration of solutes can varyHigh = more solute

Low = less solute

Outsideof cell

Insideof cell(cytoplasm)

Cellmembrane

Proteins

Proteinchannel Lipid bilayer

Carbohydratechains

Figure 7-15 The Structure of the Cell Membrane

Diffusion

Movement of materials from a high concentration to a lower concentration until equilibrium is reached

requires no energy = passive

What materials diffuse across a cell membrane?

Permeability

Ability of membrane to allow substances to penetrate/pass throughLevels of permeability:

Permeable- any solutes can pass throughSemi-permeable/Selectively Permeable- certain solutes are selected to pass throughImpermeable- nothing is able to pass through

All cell membranes are selective = picky/choosyImpermeability is not an optioncell would die! Why???

Osmosis

Diffusion of water across a selectively permeable membrane

Types of Solutionshypertonic - higher concentration of dissolved particles (solute)

hypotonic - lower concentration of dissolved particles (solute)

isotonic - identical concentration

Osmosis occurs b/c the solute is unable to pass through the membrane. Water can always pass through the membrane.

Hydrophobic

•Lipid Tails

•Nonpolar

Hydrophilic

•Lipid Heads

•Polar

Continues until the concentrations are equal

Solutions outside of the cell…..

Problems in Organisms (Maintaining Homeostasis)

Plantsturgor pressure

rigid vs. wilting

Antibiotic effects on bacteria

Single Celled Organismscontractile vacuole

homeostasis

Animals cells bathed in isotonic fluids “blood”

Facilitated Diffusion• specific protein channels for specific substances that cannot diffuse on their own

•glucose channel

Facilitated Diffusion

Protein channel

Glucose molecules

Active Transport

movement of materials from lower concentration to higher concentration

requires energy = ATP

Molecule to be carried

Active Transport

Molecule tobe carried

Moleculebeing carried

Energy

Figure 7-20 Active Transport-going against concentration gradient (low to high). Natural is from high to low (diffusion and facilitated diffusion).

Phagocytosis

Large particles taken into cell

Extension of cytoplasm engulfs large particles outside cell

Pocket folds into cell with contents and breaks loose from cell membrane forming vacuole inside cell (in cytoplasm).

Other examples of

active transport

Unicellular Organisms

A single cell is the entire organism

Includes all prokaryotes and some eukaryotes

Examples include: algae, yeasts, bacteria

Multicellular Organisms

Cells are interdependent (like a team)

Cell specialization- separate roles for each type of cell (ex. Blood cell, nerve cell, muscle cell)

Cells are specialized to perform particular functions within organism

Levels of Organization

Individual cellstissuesorgansorgan systemsorganism

Tissue- group of similar cells that perform particular functionOrgan- groups of tissues working togetherOrgan Systems- group of organs working together to perform specific function (11 major systems in human body)

Muscle cell

Smooth muscle tissueStomach

Digestive system