02 cell structures 2015 ss

PowerPoint Lecture prepared by Dr. Judi Roux,

University of Minnesota Duluth

Chapter 2

Cells & Their Structures

© 2016 Pearson Education, Inc.

Learning Outcomes

Compare and contrast

prokaryotic and eukaryotic cells.



Introduction

• In 1665, Hooke examined a piece of cork under a crude microscope and identified “little rooms” as cells.

• Leeuwenhoek, working at about the same time, used more refined lenses to describe living cells from blood, sperm, and pond water.

• Since the days of Hooke and Leeuwenhoek, improved microscopes have vastly expanded our view of the cell.

How small is small?

Most cells are microscopic

• Cells vary in size and shape; again Form = Function

• Think: What are the

largest cells?

Human height

Length of somenerve andmuscle cells

Chicken egg

Frog egg

Una

ided

eye

Ligh

t mic

rosc

ope

Ele

ctro

n m

icro

scop

e

10 m

1 m

100 mm(10 cm)

10 mm(1 cm)

1 mm

100 m

10 m

1 m

100 nm

10 nm

1 nm

0.1 nmAtoms

Proteins

Small molecules

Lipids

Viruses

Ribosome

Nucleus

Mycoplasmas(smallest bacteria)

Most plant andanimal cells

Most bacteria

Mitochondrion

All Cells are Contained within a -Plasma Membrane

- Holds the cell (metabolism & structures)

- Selectively permeable barrier between the cell and its environment

- Formed by molecules that are- water soluble at one end - lipid (water insoluble) at the other

Water

Water

Hydrophilicheads

Hydrophobictails

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH3

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH

CH

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH3

CH2

CH2

CH3

CH3

CH3N+

OO O–P

OCH2CHCH2

C O C O

O O

Phosphategroup

Symbol

Hydrophilic head

Hydrophobic tails

Phospholipids form Membranes


The plasma membrane forms a flexible boundary between the living cell and its surroundings.

Phospholipids form a two-layer sheet called a phospholipid bilayer in which

• hydrophilic heads face outward, exposed to water, and

• hydrophobic tails point inward, shielded from water.


The small size of cells relates to the need to exchange materials across the plasma membrane

• Membrane proteins are embedded in the lipid bilayer.

• Some proteins form channels (tunnels) that shield ions and other hydrophilic molecules as they pass through the hydrophobic center of the membrane.

• Other proteins serve as pumps, using energy to actively transport molecules into or out of the cell.

The membrane is a fluid mosaic of phospholipids and proteins

• With proteins and other molecules embedded in a phospholipid bilayer

Fibers of the extracellular matrix

Carbohydrate(of glycoprotein)

Glycoprotein

Microfilamentsof cytoskeleton

Phospholipid

CholesterolProteins

Plasmamembrane

Glycolipid

Cytoplasm

Prokaryotic and eukaryotic cells

All living things are made of cells.• Contain similar macromolecules and cell structures


Prokaryotic cells are structurally simpler than Eukaryotic cells

• There are two kinds of cells

Prokaryotic cellNucleoidregion

Nucleus

Eukar yotic cell Organelles

Col

oriz

ed T

EM

15,

000

Prokaryotes

• Small; microscopic

• Simple

• Genetic material is “naked” DNA - not as protein-bound chromosomesNo nucleus

• No organelles

• Cell walls (Peptidoglycan)

Eukaryotes• Larger; single-celled or

multicellular

• Complex

• Genetic material is DNA as a complex with proteins = chromosomes

• Chromosomes contained in a nucleus

• Membrane-bound organelles

• Some with cell walls (Cellulose, Chitin)© 2016 Pearson Education, Inc.

Prokaryotic cells are small, relatively simple cells that do not have a membrane-bound nucleus

Prokar yoticflagella

Ribosomes

Capsule

Cell wall

Plasmamembrane

Nucleoid region (DNA)

Pili

There is a size limitation on cells

The interior cytoplasm of a large cell cannot interact quickly enough with the cell’s environment to:

- Take up nutrients & oxygen - Release wastes & carbon dioxide

Solution: Bring the border with the environment inside the cell

• A small cell has a greater ratio of sur face area to volume

• Than a large cell of the same shape

30 m 10 m

30 m 10 m

Surface areaof one large cube 5,400 m2

Total surface areaof 27 small cubes 16,200 m2Figure 4.2B

Eukaryotic cells are compartmentalized• Distinguished by the presence of a true nucleus• Have internal membranes to contain and control

chemical reactions• Eukaryotic cells can form

• Single-celled organisms

• Colonial organisms

• Multicellular organisms

FUNCTIONAL CATEGORIES OF ORGANELLES

Eukaryotic organelles comprise four functional categories

• Eukar yotic organelles fall into four functional groups• Manufacturing• Breakdown • Energy processing• Support, movement, and communication between

cells

• Eukar yotic organelles and their functions

Roughendoplasmicreticulum

Smoothendoplasmicreticulum

Golgi apparatus

LysosomeMitochondrion

Centrosomewith pair ofcentrioles

Plasmamembrane

Peroxisome

Intermediatefilament

MicrofilamentMicrotubule

CYTOSKELETON

NUCLEUSNuclear envelopeNucleolusChromatin

Ribosomes


Eukaryotic cells are partitioned into functional compartments

Plant but not animal cells have• a rigid cell wall that contains cellulose,• plasmodesmata, cytoplasmic channels through cell

walls that connect adjacent cells,• chloroplasts, where photosynthesis occurs, and• a central vacuole, a compartment that stores water

and a variety of chemicals.

Roughendoplasmicreticulum

Smoothendoplasmicreticulum

NUCLEUSNuclear envelopeNucleolusChromatin

Ribosomes

Plasmamembrane

Peroxisome

Mitochondrion

MicrofilamentMicrotubule

CYTOSKELETON

Cell wall ofadjacent cell Golgi

apparatus

PlasmodesmaCell wall

Chloroplast

Centralvacuole


Cell StructurePlasma membrane

• Encloses all cells

• Defines outer boundary of cells

• Isolates cell contents from environment


Cell StructureCytoplasm: includes cytosol and organelles

• Organelles: perform specific jobs required by the cell and work with other organelles

• Cytosol: watery matrix with salts and enzymes; houses the organelles


3 Cell StructureCell structure


3.2 Cell StructureSubcellular structures

• Cell wall: helps protect certain cells (plants, fungi, bacteria) and maintains shape

• Nucleus: holds chromatin (DNA and proteins) in eukaryotic cells

• Nucleolus: synthesizes ribosomes; inside nucleus



• Mitochondrion: produces energy for the cell through cellular respiration

• Chloroplast: produces sugars through photosynthesis in plant cells

• Lysosome: contains digestive enzymes to recycle molecules



• Ribosomes: assemble proteins; free floating or attached to ER

• Rough endoplasmic reticulum (rough ER): membrane network with ribosomes attached for protein synthesis

• Smooth endoplasmic reticulum (smooth ER):involved in lipid synthesis; lacks ribosomes

• Golgi apparatus: modifies, sorts, and packages proteins



• Centrioles: move chromosomes during animal cell division

• Cytoskeletal elements: form cytoskeleton for maintaining shape and structural support

• Central vacuole: stores water, starch, and pigments in plant cells

Animation: A Comparison of Prokaryotic and Eukaryotic Cells


This animation may be available in our ebook, but not viewable on SlideShare.

2.5 An Introduction to Evolutionary Theory

The tree of life

Common ancestor(4 billion years ago)

• Led to 10 millionorganisms of today

• Diversity due tonatural selection
