The Living Cell

Chapter 21

Great Idea:Life is based on chemistry,

and chemistry takes place in cells

Chapter Outline

• The Nature and Variety of Cells• How Does a Cell Work?• Metabolism: Energy and Life• Cell Division

The Nature and Variety of Cells

The Cell Theory

• All living things are composed of one or more cells

• The cell is the fundamental unit of life

• All cells arise from previous cells

Science in the Making

• The discovery of cells– Robert Hooke– Anton van Leeuwenhoek

Cork Cells

Observing Cells: The Microscope

• Early microscopes• Light microscope• Electron microscope

Light Microscope

Electron Microscope

Electron Microscope and Photograph

How Does a Cell Work?

The Cell Is Like a Refinery

Cell Membranes

• Cell membranes– Isolate cell– Separates cell parts

• Transport– Individual molecules– Specific materials

•Channels

Membrane Lipid Bilayer

Cell Membranes – cont.

• Receptors– Bind molecules

• Cell Wall– Plants

The Action of Cell Receptors

Plant Cell

Plant Cell

The Nucleus

• Nucleus– Contains genetic material

• Prokaryotes– No nucleus

• Eukaryotes– Nucleus

• Double Membrane

Nucleus Surrounded by a Double Membrane

Terms Related to Cells and Single-Celled Organisms

Plant Cell

Animal Cell

Energy Organelle - Chloroplasts

• Organelle– Specialized structure in cell

• Chloroplasts– Energy transformation

•Chlorophyll

– Plant cells only– Double membrane– Own DNA

Energy Organelle –Mitochondria

• Mitochondria– Produces cells energy– Double membrane– Own DNA

Cytoskeleton

• Cytoskeleton– Gives cell shape– Anchors– Allows movement– Transport system

•Within cell

• Structure– Strong filaments– Complex web

Cytoskeleton

Organelles and Their Functions

Metabolism: Energy and Life

The Cell’s Energy Currency

• Adenosine triphosphate (ATP)– Provides energy

• Structure– 3 phosphate groups– Sugar molecule: ribose– Adenine

• Function– Removal of phosphate group provides energy

Structure of ATP

Photosynthesis

• Photosynthesis– Convert sunlight to energy

• Process– Energy + CO2 + H2O carbohydrate + O2

• Colors

Photosynthesis

Glycolysis: The First Step in Energy Generation in the Cell

• Respiration– Oxidation of carbohydrate– Retrieves energy in glucose– Aerobic

Glycolysis

• Process– Glycolysis

•Split glucose•Result

– 2 pyruvic acid– 2 ATP– 2 energy carriers

•Convert energy carriers to 2–3 ATP

– 1 molecule glucose = 6–8 ATP

Glycolysis

Fermentation: A Way to Keep Glycolysis Going

• Fermentation– Anaerobic– Inefficient

• Yeast– Alcohol

• Animal cells– Lactic acid

Uses of Fermentation

The Final Stages of Respiration

• Krebs cycle– Glucose broken down

– CO2 produced

– ATP – Energy-carrying molecules

• Result– 36–38 ATP

Water Vapor Expelled during Respiration

Cell Division

Mitosis

• Mitosis– Cell division– Not for sexual reproduction

• Chromosomes• Process

– Copy chromosomes– Spindle fibers– Migration of chromosomes– Nuclear membrane reforms

Mitosis

Human Cell Dividing

Meiosis

• Meiosis– Sexual reproduction– 1 cell forms 4 gametes

•Gametes are genetically unique•Contain half the number of chromosomes

Process of Meiosis

• Process– Copy chromosomes– Crossing over– Segregation– Segregation again

• Result– 4 daughter cells– ½ normal number of chromosomes

Meiosis

Crossing Over

Thinking More about Cells

• Biochemical evidence for evolution