chapter 5 gases - mr. doyle suis...

Chapter 4

Cell Structure and

Function Sections 1-6

4.1 Food For Thought

• E. coli O157:H7A, strain of bacteria that causes severe illness

or death, occasionally contaminates foods such as ground

beef and fresh vegetables

• Outbreaks, which occur with disturbing regularity, also have

severe economic impacts

• Food growers and processors are now using procedures that

they hope will reduce E. coli O157:H7 outbreaks

E. coli O157:H7

4.2 Cell Structure

• The cell is the smallest unit that shows the properties of life

• All cells have a plasma membrane and cytoplasm, and all

start out life with DNA

Components of All Cells

• Plasma membrane

• Controls substances passing in and out of the cell

• DNA containing region

• Nucleus in eukaryotic cells

• Nucleoid region in prokaryotic cells

• Cytoplasm

• A semifluid mixture containing cell components

Organelles

• Organelles are structures that carry out special metabolic

functions inside a cell

• Membrane-enclosed organelles compartmentalize tasks such

as building, modifying, and storing substances

Prokaryotic and Eukaryotic Cells

• Eukaryotic cell

• Cell interior is divided into functional compartments,

including a nucleus

• Prokaryotic cell

• Small, simple cells without a nucleus

Figure 4-2 p54

A A prokaryotic cell.

cytoplasm DNA plasma membrane

nucleus

B A eukaryotic

(plant) cell. Only

eukaryotic cells

have a nucleus.

ANIMATED FIGURE: Overview of cells

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videos_animations/cell_features_v2.html

Preview of Cell Membranes

• Lipid bilayer

• A double layer of phospholipids organized with their

hydrophilic heads outwards and their hydrophobic tails

inwards

• Many types of proteins embedded or attached to the

bilayer carry out membrane functions

Figure 4-3 p54

cell’s exterior

plasma membrane

cell’s interior

Constraints on Cell Size

• Surface-to-volume ratio restricts cell size by limiting

transport of nutrients and wastes

The Cell Theory Emerges

• Van Leeuwenhoek was the first to describe small organisms

seen through a microscope, which he called animalcules and

beasties

• Hooke was the first to sketch and name cells

• Brown was the first to identify a cell nucleus

Cell Theory

• The cell theory, a foundation of modern biology, states that

cells are the fundamental units of life

• In 1839, Schleiden and Schwann proposed the basic

concepts of the modern cell theory

• All organisms consists of one or more cells

• A cell is the smallest unit with the properties of life

• Each new cell arises from division of a preexisting cell

• Each cell passes its hereditary material to its offspring

Take-Home Message:

How are all cells alike?

• All cells start life with a plasma membrane, cytoplasm, and a

region of DNA, which, in eukaryotic cells only, is enclosed by

a nucleus

• The surface-to-volume ratio limits cell size and influences cell

shape

• Observations of cells led to the cell theory: All organisms

consist of one or more cells; the cell is the smallest unit of life;

each new cell arises from another cell; and a cell passes

hereditary material to its offspring

4.3 How Do We See Cells?

• Most cells are 10–20 micrometers in diameter, about fifty

times smaller than the unaided human eye can perceive

• One micrometer (μm) is one-thousandth of a millimeter, which

is one-thousandth of a meter

• We use different types of microscopes to study different

aspects of organisms, from the smallest to the largest

Table 4-1 p56

Modern Microscopes

• Light microscopes

• Phase-contrast microscopes

• Reflected light microscopes

• Fluorescence microscopes

• Electron microscopes

• Transmission electron microscopes

• Scanning electron microscopes

Figure 4-5a p56

path of light rays (bottom to top) to eye

prism that

directs rays to

ocular lens ocular

lens

objective

lenses

specimen

condenser

lens

focusing

knob

light source

(in base)

illuminator

stage

Figure 4-5b p56

incoming electron beam

condenser

lens

specimen

on grid

projective

lens

phosphor

screen

objective

lens

ANIMATED FIGURE: How a light

microscope works




videos_animations/light_micro.html

ANIMATED FIGURE: How a light

microscope works




videos_animations/electron_micro.html

Different Microscopes,

Different Characteristics

Relative Sizes

human eye (no microscope)

largest organisms small animals frog eggs

100 m 10 m 1 m 10 cm 1 cm 1 mm 100 µm

Relative Sizes

electron microscopes

light microscopes

most

eukaryotic

cells

most

bacteria mitochondria,

chloroplasts

viruses molecules of life small molecules

DNA

proteins

carbohydrates

10 µm 1 µm 100 nm 10 nm 1 nm 0.1 nm

lipids

Take-Home Message:

How do we see cells?

• Most cells are visible only with the help of microscopes

• Different types of microscopes reveal different aspects of cell

structure

4.4 Introducing “Prokaryotes”

• Bacteria and archaea are the prokaryotes (“before the

nucleus”), the smallest and most metabolically diverse forms

of life

• Bacteria and archaea are similar in appearance and size, but

differ in structure and metabolism

General Prokaryote Body Plan

• Cell wall surrounds the plasma membrane

• Made of peptidoglycan (in bacteria) or proteins (in

archaea) and coated with a sticky capsule

• Flagellum for motion

• Pili help cells move across surfaces

• “Sex” pilus aids in sexual reproduction


• Ribosomes

• Organelles upon which polypeptides are assembled

• Nucleoid

• An irregularly shaped region of cytoplasm containing a

single, circular DNA molecule

• Plasmids

• Small circles of DNA carry a few genes that can provide

advantages, such as resistance to antibiotics


flagellum

cytoplasm,

with

ribosomes

plasma

membrane

capsule

DNA in

nucleoid

cell wall

pilus 1

2

3

4

5 6

7

ANIMATED FIGURE: Typical prokaryotic

cell




videos_animations/bacterium_v2.html

Bacteria

Archaeans

Biofilms

• Although prokaryotes are all single-celled, few live alone

• Biofilm

• Single-celled organisms sharing a secreted layer of

polysaccharides and glycoproteins

• May include bacteria, algae, fungi, protists, and archaeans

Dental Plaque: A Biofilm

Take-Home Message:

How are bacteria and archaea alike?

• Bacteria and archaea do not have a nucleus. Most kinds have

a cell wall around their plasma membrane; the permeable wall

reinforces and imparts shape to the cell body

• The structure of bacteria and archaea is relatively simple, but

as a group these organisms are the most diverse forms of life;

they inhabit nearly all regions of the biosphere

• Some metabolic processes occur at the plasma membrane of

bacteria and archaea; they are similar to complex processes

that occur at certain internal membranes of eukaryotic cells

4.5 Introducing Eukaryotic Cells

• All protists, fungi, plants, and animals are eukaryotes

• Eukaryotic (“true nucleus”) cells carry out much of their

metabolism inside membrane-enclosed organelles

• Organelle

• A structure that carries out a specialized function within a

cell

Importance of Organelles

• Membranes around eukaryotic organelles control the types

and amounts of substances that enter and exit them

• Such control maintains a special internal environment that

allows the organelle to carry out its particular function

• Some metabolic pathways take place in a series of different

organelles

Components of Eukaryotic Cells

Figure 4-12a p61

Cell

Wall Chloroplast

Central

Vacuole

nuclear

envelope

Nucleus Cytoskeleton

microtubules

microfilaments

intermediate

filaments

(not shown)

Ribosomes

Mitochondrion

Smooth ER Plasmodesma

Golgi Body

Plasma Membrane

Lysosome-Like

Vesicle

Rough ER

DNA in

nucleoplasm

nucleolus

3D ANIMATION: Tour of an Animal Cell

videos_animations/TourAnimalCell/index.html

Figure 4-11b p60

cell wall

central

vacuole

plasma

membrane

mitochondrion

nucleus

B Photosynthetic cell from a blade of timothy grass.

vacuole

chloroplast

Makes lipids, breaks down

carbohydrates and fats,

inactivates toxins

Smooth ER

Finishes, sorts, ships lipids,

enzymes, and proteins

Golgi Body

Modifies proteins made by

ribosomes attached to it

Rough ER

Digests, recycles materials

Lysosome

Stepped Art

p64

Figure 4-11a p60

mitochondrion

nucleus

A Human white blood cell.

vacuole

plasma

membrane

Take-Home Message:

What do eukaryotic cells have in common?

• All eukaryotic cells start life with a nucleus and other

membrane-enclosed organelles

ANIMATION: Common eukaryotic

organelles




videos_animations/eukaryotic_cell_v2.html

4.6 The Nucleus

• All of a eukaryotic cell’s DNA is in its nucleus

• The nucleus keeps eukaryotic DNA away from potentially

damaging reactions in the cytoplasm

• The nuclear envelope controls when DNA is accessed

Table 4-2 p60

Figure 4-13a p62

nuclear envelope

DNA

nucleolus

nuclear pore

ER

cytoplasm

nucleoplasm

Figure 4-13b p62

nuclear envelope

DNA

nucleolus

nuclear pore

ER

cytoplasm

nucleoplasm

The Nuclear Envelope

• Nuclear envelope

• Two lipid bilayers pressed together as a single membrane

surrounding the nucleus

• Outer bilayer is continuous with the ER

• Nuclear pores allow certain substances to pass through

the membrane

Structure of the Nuclear Envelope

Figure 4-14ab p63

A The outer surface of this nuclear

envelope was split apart to reveal the

pores that span the two lipid bilayers.

B Each nuclear pore is an organized

cluster of membrane proteins that

selectively allows certain substances

to cross it on their way into and out of

the nucleus.

nuclear pore

Figure 4-14b p63

nuclear envelope

(two lipid bilayers)

cytoplasm

nuclear pore

ANIMATED FIGURE: Nuclear envelope




videos_animations/nuclear_envelope.html

The Nucleoplasm and Nucleolus

• Nucleoplasm

• Viscous fluid inside the nuclear envelope, similar to

cytoplasm

• Nucleolus

• A dense region in the nucleus where subunits of

ribosomes are assembled from proteins and RNA

Chromosomes

• Chromatin

• All DNA and its associated proteins in the nucleus

• Chromosome

• A single DNA molecule with its attached proteins

• During cell division, chromosomes condense and become

visible in micrographs

• Human body cells have 46 chromosomes

A Condensed Chromosome

Take-Home Message:

What is the function of the cell nucleus?

• A nucleus protects and controls access to a eukaryotic cell’s

DNA

• The nuclear envelope is a double lipid bilayer. Proteins

embedded in it control the passage of molecules between the

nucleus and the cytoplasm

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