Chapter 7. Cell Structure and Function

Biology

7.1 Life is CellularThe Discovery of the Cell

1665, Robert Hooke used a microscope to look at a thin slice of cork.

Look like tiny, empty chambers.

Hooke named the chambers “cells”

Anton van Leeuwenhoek observed pond water, revealed tiny living organisms.

7.1 Life is CellularThe Cell Theory

Cells are the basic unit of life.

1838, Matthias Schleiden concluded all plants are made up of cells.

1839, Theodor Schwann stated that all animals were made up of cells

1855, Rudolf Virchow concluded that new cells could be produced only from the division of existing cells.

7.1 Life is CellularThe Cell Theory

These discoveries are summarized in the cell theory:

1. All living things are composed of cells.

2. Cells are the basic unit of structure and function in living things.

3. New cells are produced from existing cells.

7.1 Life is CellularExploring the Cell

Fluorescent labels and light microscopy

Confocal light microscopy High-resolution video

technology Scanning Electron

Microscope Transmission Electron

Microscope Scanning Probe

Microscopes

Let’s look at page 170…

7.1 Life is CellularProkaryotes and Eukaryotes

Cells are very diverse Size ranges from 5 to 50

micrometers in diameter Tiniest – mycoplasm, 0.2

micrometers Larger – Chaos chaos

(Giant Amoeba), 1000 micrometers

All are surrounded by a barrier called a cell membrane and contain DNA.

7.1 Life is CellularProkaryotes and Eukaryotes

Two categories depending on the presence of a nucleus

Nucleus – a large membrane-enclosed structure that contains the cell’s genetic material in the form of DNA

Eukaryotes – cells that contain nuclei.

Prokaryotes – cells that do not contain nuclei.

Prokaryotic Cell

Cell membrane

Cell membrane

Cytoplasm

Cytoplasm

Nucleus

Organelles

Eukaryotic Cell

7.1 Life is CellularProkaryotes

Smaller and simpler than eukaryotic cells.

Genetic material is not contained in the nucleus.

Carry out every activity associated with living things.

Ex. Bacteria

Can you name this bacteria?

7.1 Life is CellularEukaryotes

Larger and more complex than prokaryotic cells.

Contain dozens of structures and internal membranes.

Contain a nucleus in which their genetic information is separated from the rest of the cell.

Can be single celled, or multicellular.

Ex. Plants, animals, fungi, and protists.

Venn Diagram

http://live.bcps.org/web_flash/arcade/2011/prokaryotes_vs_eukaryotes.swf

SECTION 2- ORGANELLES

7.2 Eukaryotic Cell StructureComparing the Cell to a Factory

Eukaryotic cells have structures that can be compared to specialized organs called organelles, “little organs.”

Two major parts: the nucleus and the cytoplasm.

Cytoplasm – portion of the cell outside the nucleus.

7.2 Eukaryotic Cell StructureNucleus

Nuclear envelope – surrounds the nucleus, contains thousands of nuclear pores.

Chromatin – DNA bound to protein (condenses when a cell divides to form chromosomes).

Chromosomes – contain genetic information that is passed from one generation of cells to the next.

Nucleolus – small, dense region where the assembly of ribosomes begin.

The nucleus contains nearly all the cell’sDNA and with it the coded instructionsfor making protein and other importantmolecules.

7.2 Eukaryotic Cell StructureRibosomes

Proteins are assembled on ribosomes.

Produce proteins by following coded instruction that come from the nucleus.

Cell that are active in protein synthesis are often packed with ribosomes.

Can be free or fixed

7.2 Eukaryotic Cell StructureEndoplasmic Reticulum

Endoplasmic reticulum – the site where lipid components of the cell membrane are assembled, along with proteins and other materials that are exported from the cell.

Rough Endoplasmic Reticulum (RER) – synthesis of proteins where they can be modified

Smooth Endoplasmic Reticulum (SER) – synthesis of membrane lipids and the detoxification of drugs

7.2 Eukaryotic Cell StructureGolgi Apparatus

The function of the Golgi Apparatus is to modify, sort, and package proteins and other materials from the endoplasmic reticulum for the storage in the cell or secretion outside the cell.

Comparison – put on the finishing touches and then “shipped.” **Jeopardy Fact: Discovered by Camillo Golgi

7.2 Eukaryotic Cell StructureLysosomes

“Clean up crew” Small organelles filled

with enzymes that digest lipids, carbohydrates, and proteins that can be used by the rest of the cell.

Also, remove “old” organelles

7.2 Eukaryotic Cell StructureVacuoles

Vacuoles – saclike structure that store “things.”

Store water, salts, proteins, and carbohydrates

Ex. Central vacuole (plant) and contractile vacuole (paramecium)

7.2 Eukaryotic Cell StructureMitochondria

All living things need a source of energy.

Mitochondria are organelles that convert chemical energy stored in food into compounds that are more convenient for the cell to use.

“power house of the cell” Mitochondria have two

membranes Inherited from the female

7.2 Eukaryotic Cell StructureChloroplasts

Chloroplasts – organelles that capture the energy from sunlight and convert it into chemical energy in a process called photosynthesis.

“Solar power plants” Also contain a double

membrane. Green pigment -

chlorophyll

7.2 Eukaryotic Cell StructureOrganelle DNA

Mitochondria and chloroplast have their own DNA

Theory – descendants of ancient prokaryotes (developed a symbiotic relationship)

Predation, Competition, Symbiosis, Mutalism, Commensalism, Parasitism

7.2 Eukaryotic Cell StructureCytoskeleton

Cytoskeleton – network of protein filaments that helps the cell to maintain its shape. The cytoskeleton is involved in movement.

Microfilaments – threadlike, made up of actin, helps cell move

Microtubules – hollow, made up of tubulin, maintain cell shape, separate chromosomes during cell division (centrioles), help build flagella and cilia

Cell membrane

Endoplasmicreticulum

Microtubule

Microfilament

Ribosomes Mitochondrion

7.2 Eukaryotic Cell StructureAnimal Cell

Centrioles

NucleolusNucleus

Nuclearenvelope

Rough endoplasmic reticulum

Golgi apparatus

Smooth endoplasmicreticulum

Mitochondrian

CellMembrane

Ribosome(free)

Ribosome(attached)

7.2 Eukaryotic Cell StructurePlant Cell

Nuclearenvelope

Ribosome(attached)

Ribosome(free)

Smooth endoplasmicreticulum

Nucleus

Rough endoplasmic reticulum

Nucleolus

Golgi apparatus

Mitochondrian

Cell wall

CellMembrane

Chloroplast

Vacuole

7.3 Cell BoundariesCell Membrane

The cell membrane regulates what enters and leaves the cell and also provides protection and support

Called a “phospholipid bilayer.”

Also contains proteins (channels and pumps) and carbohydrates (identification), referred to as a mosaic

7.3 Cell BoundariesCell Membrane

Cellmembrane

Proteins

Proteinchannel Lipid bilayer

Carbohydratechains

7.3 Cell BoundariesCell Wall

Present in many organisms, including plants, algae, and many prokaryotes

Allows water, oxygen, and carbon dioxide to pass through

Main Function: provide support and protection

Composed of mostly cellulose.

7.3 Cell BoundariesDiffusion Through Cell Boundries

One of the most important functions of the cell membrane is to regulate movement of dissolved molecules from the liquid side of the membrane to the liquid on the other side

Measuring Concentration Concentration – the mass of

solute in a given volume of solution, or mass/volume

7.3 Cell BoundariesDiffusion

Diffusion – movement from an area of more concentration to an area of less concentration

Equilibrium – when the concentration of the solute is the same throughout the system

Why do we care? This occurs on both sides of

the cell membrane. Does NOT require energy Particles are constantly

moving

http://www.indiana.edu/~phys215/lecture/lecnotes/lecgraphics/diffusion2.gif

7.3 Cell BoundariesOsmosis

Some substances cannot pass through the cell membrane – impermeable

Most biological membranes are selectively permeable.

Water is permeable to most membranes.

Osmosis – the diffusion of water through a selectively permeable membrane.

7.3 Cell BoundariesOsmosis

Higher Concentrationof Water

Lower Concentrationof Water

Cellmembrane

Water molecules

Sugar molecules

7.3 Cell BoundariesHow Osmosis works

Movement of water from an area of high concentration to the area of low concentration – until equilibrium is met

Isotonic – “same strength”

Hypertonic – “above strength”

Hypotonic – “below strength”

7.3 Cell BoundariesOsmotic Pressure

Osmotic pressure can cause serious problems for a cell.

Cells are bathed in fluids, such as blood that are isotonic, to prevent this

Plant and bacteria cells are surrounded by tough cell walls, to prevent expansion

7.3 Cell BoundariesFacilitated Diffusion

Cell membranes have protein channels that make it easy for certain molecules to cross the membrane

The cell protein is said to facilitate, or help, the molecule. This is called facilitated diffusion.

Fast and specific Will only in occur with a

concentration gradient Does NOT need energy

HighConcentration

CellMembrane

LowConcentration

Proteinchannel

Glucosemolecules

7.3 Cell BoundariesActive Transport

Sometimes, molecules need to be moved against the concentration gradient

This is called active transport, because it requires energy.

Carried out by protein channels or “pumps.”

LowConcentration

CellMembrane

HighConcentration

Moleculebeing carried

LowConcentration

CellMembrane

HighConcentration

7.3 Cell BoundariesMolecular Transport

Many cells use proteins to move calcium, potassium, and sodium ions across cell membranes

A considerable amount of energy is used by cells to keep active transport working

7.3 Cell BoundariesEndocytosis and Exocytosis

Endocytosis – the process of taking material into the cell by means of enfolding's, or pockets, of the cell membrane– Pinocytosis – process by which

a cell takes in liquid from the surrounding environment

– Phagocytosis – process by which extensions of cytoplasm surround and engulf large particles and take them into the cell

Exocytosis – the membrane of the vacuole surrounding the material fuses with the cell membrane, forcing the contents out of the cell

7.4The Diversity of Cellular LifeUnicellular Organisms

A single celled organism is also called a unicellular organism

They grow, respond to the environment, transform energy, and reproduce

They dominate this Earth!

Leptospira interrogans

7.4The Diversity of Cellular LifeMulticellular Organisms

Organisms that are made up of many cells are called multicellular.

Cells throughout an organism can develop in different ways to perform different tasks, this is called cell specialization.

7.4The Diversity of Cellular LifeSpecialized Animal Cells

Ex. Red blood cells carry oxygen, pancreatic cells produce proteins for digestion, muscle cells to help us move

Can you identify these specializedAnimal cells???

7.4The Diversity of Cellular LifeSpecialized Plant Cells

Ex. Guard cells monitor the plants internal conditions, communicates with the stomata

What’s going on here???

7.4The Diversity of Cellular LifeLevels of Organization

The levels of organization in a multicellular organism are individual cells, tissues, organs, and organ systems.

Muscle cell Smooth muscle tissue Stomach Digestive system

7.4The Diversity of Cellular LifeTissues

Tissue – group of similar cells that perform a particular funtion.

Ex. Pancreatic tissues that make enzymes

Animal tissue: muscle, epithelial, nervous, and connective

Do you know what type of tissue this is?

7.4The Diversity of Cellular LifeOrgans

Organ – many tissues working together

Ex. Within a muscle there is more than one type of tissue…nerve, connective, etc.

Jeopardy question…What is OURLargest organ???

7.4The Diversity of Cellular LifeOrgan Systems

Organ system – a group of organs that work together to perform a specific function.

We rely on Interdependence