Overview of the Cellular Basis of Life - Weeblyt1lara.weebly.com/uploads/1/6/3/2/1632178/ch3cellspdfnotes.pdfCells and Tissues Cells: Carry out all chemical activities needed to sustain

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings

Overview of the Cellular Basis of Life


Cells and Tissues

Cells:

Carry out all chemical activities needed to

sustain life

Cells are the building blocks of all living

things

Cells vary in length, e.g. 2 micrometers to

over a meter (nerve cells)

Cells vary in function

Tissues

Tissues are groups of cells that are similar in

structure and function


Anatomy of a Generalized Cell


Anatomy of the Cell

Cells are not all the same

All cells share general structures

All cells have three main regions

Nucleus

Cytoplasm

Plasma membrane

Figure 3.1a


The Nucleus


The Nucleus

Control center of the

cell

Contains genetic

material, DNA,

(genes) for cell

reproduction

Three regions

Nuclear envelope

(membrane)

Chromatin

Nucleolus


Nuclear envelope (membrane)

Barrier of the nucleus

Consists of a double

membrane

Where membrane fuses,

becomes nuclear pore

Contains nuclear pores that

allow for exchange of material

with the rest of the cell

Relatively large pores

allows substances to pass

freely than elsewhere


Nucleoli

Nucleus contains

one or more nucleoli

Dark staining,

round bodies

Sites of ribosome

assembly

Ribosomes migrate

into the cytoplasm

through nuclear

pores into the

cytoplasm serve as

sites of protein

synthesis


Chromatin

When the cell is not

dividing DNA

combined with protein

forms loose, bumpy

threads called

chromatin

Scattered throughout

the nucleus

Condenses to form

chromosomes when

the cell divides


The Plasma Membrane


Plasma Membrane (Cell Membrane)

Barrier for cell contents

Plays a dynamic role cellular

activities

Double phospholipid layer

Allows membranes to reseal

quickly

Hydrophilic (water loving) heads

Hydrophobic tails (water hating)

Impermeable to most water

soluble molecules


Plasma Membrane (Cell Membrane)

Proteins scattered in lipid bilayer

Specialized functions include:

Enzymes

Receptors

Anchoring the cell to fibers

Protein channels

Branching sugars

Glycoproteins

Blood type, receptors, cell-

to-cell interactions


Plasma Membrane

Figure 3.2


Specialization of the Plasma Membrane


Plasma Membrane Specializations

Microvilli

Finger-like projections

that increase surface

area for absorption



Membrane junctions (3 types)—

binds cells together

Tight junctions (zipperlike)

Impermeable junction

(e.g. in sm. Intestine

keeps enzymes from

bloodstream)

Desmosomes (buttonlike)

Anchoring junction

Keeps cell from being

pulled apart (e.g. skin

cells)



Membrane junctions (3

types)—binds cells together

Continued…

Gap junctions

Allows communication

between cells (e.g.

heart cells)

Neighboring cells

connected by

connexons


Cytoplasm


Cytoplasm

Cytoplasm is the material outside the nucleus and inside

the plasma membrane


Cytoplasm (factory area)

Site of most cellular activities

Contains 3 major elements (seen by electron microscope)

Cytosol

Largely water fluid that suspends organelles

Dissolved nutrients & solutes

Organelles

Metabolic machinery of the cell

“Little organs” that perform functions for the cell


Cytoplasm (factory area)

Continued…

Inclusions

Chemical substances specific to the cell type

such as stored nutrients e.g. glycogen

granules in the liver

Pigments in skin & hair

Lipid droplets in fat cells

Mucus & other secretory products


Cytoplasmic Organelles



Figure 3.4



Mitochondria

Change shape continuously

Consists of a double membrane

Smooth outside, shelflike protrusions called

cristae

Enzymes inside carry out reactions where oxygen is

used to break down food

Most energy lost as heat but some is used to form

ATP molecules (“Powerhouses” of the cell)

Metabolically busy cells have hundreds of

mitochondria (liver and muscle)



Ribosomes (tiny, bilobed dark bodies)

Made of protein and ribosomal RNA (rRNA)

Sites of protein synthesis

Found at two locations

Free in the cytoplasm

As part of the rough endoplasmic reticulum


Endoplasmic reticulum (ER)—fluid filled tubes

Mini-circulatory system for cell

Carries proteins from one to another part of cell

Two types of ER

Rough endoplasmic reticulum

Studded with ribosomes

Synthesizes proteins

E.g. pancreas cells producing digestive

enzymes to be delivered to sm. intestine

See next slide…


Rough Endoplasmic Reticulum

Figure 3.5

Ribosome

Protein

Protein inside

transport vesicle

Transport

vesicle buds off

mRNA

Rough ER

As the protein is synthesized

on the ribosome, it migrates

into the rough ER cistern.

In the cistern, the protein folds

into its functional shape. Short

sugar chains may be attached

to the protein (forming a

glycoprotein).

The protein is packaged in a

tiny membranous sac called a

transport vesicle.

The transport vesicle buds from

the rough ER and travels to the

Golgi apparatus for further

processing or goes directly to

the plasma membrane where its

contents are secreted.


Cell Diversity

Figure 3.8f


Endoplasmic reticulum (ER)—fluid filled tubes

Smooth endoplasmic reticulum

Functions in lipid metabolism

(cholesterol & fat synthesis &

breakdown) and detoxification of

drugs and pesticides

E.g. liver cells and testes that

manufacture testosterone


Cell Diversity

Figure 3.8d


Golgi apparatus—Traffic Director

Stack of flattened membranous sacs

Modifies and packages proteins sent by the rough ER

via transport vesicles

As the sac swells with proteins it pinches off to form

Secretory vesicles—3 pathways:

Vesicles fuse with plasma membrane, it ruptures,

& contents ejected to outside of cell, e.g. mucus &

digestive enzymes

Vesicles destined to form plasma membrane

Vesicles form Lysosomes that contain digestive

enzymes to rid cell of worn-out structures or

foreign substances


Figure 3.6

Extracellular fluid

Plasma membrane

Golgi vesicle containingmembrane componentsfuses with the plasmamembrane

Golgi vesicle containingdigestive enzymesbecomes a lysosome

Proteins in cisterna

Lysosome fuses withingested substances

Membrane

Transportvesicle

Pathway 3

Pathway 2

Secretory vesiclesPathway 1

Golgiapparatus

Golgi vesicle containingproteins to be secretedbecomes a secretoryvesicle

Cisterna

Rough ER

Proteins

Secretion by

exocytosis


Cell Diversity

Figure 3.8e


Peroxisomes

Membranous sacs of oxidase enzymes

Converts free radicals to H2O2 then catalase

converts to H2O & O2

Oxidase enzymes contain O2 to detoxify

harmful substances such as alcohol and

formaldehyde

Replicate by pinching in half, as do

mitochondria (NOT formed by Golgi

apparatus)


Cytoskeleton—cell’s bones & muscles

Network of protein structures that extend

throughout the cytoplasm

Provides the cell with an internal framework

Figure 3.7a


Figure 3.7b–d


Cytoskeleton

Three different types of

elements

Microfilaments—cell

motility/change shape, e.g.

muscle cells

Intermediate filaments—

resist pulling forces,

e.g.from desmosomes

Microtubules—determine

overall shape of cell


Cell Diversity

Figure 3.8c


Cell Diversity

Figure 3.8b


Centrioles

Rod-shaped bodies made of microtubules lie at right

angles to each other

Generate microtubules & mitotic spindle during cell

division

Centrioles make cilia (hair-like projections) & flagella

(tail-like projections)

Cilia move materials across the cell surface

Located in the respiratory system to move mucus

Flagella propel the cell

The only flagellated cell in the human body is

sperm


Cell Diversity

Figure 3.8g


Cell Diversity

Figure 3.8a


Video: A Tour of the Cell


Cell Physiology—Cell Division


Events of Cell Division

The cell life cycle is the series of

changes a cell goes through from the

time it is formed until it divides. The

cycle has two major periods:

Interphase: the cell grows & carries

its usual metabolic activities, longer

phase of cycle (metabolic phase)

Cell division:

the reproduction of itself

Function is to produce more

cells for growth and repair

processes


DNA Replication

Function of cell division to produce more cells for

growth & repair processes

All body cells have the same genetic material

DNA molecules duplicate exactly before cell division

Genetic material is duplicated and readies a cell for

division into two cells

Occurs toward the end of interphase

DNA uncoils and each side serves as a template

Two DNA molecules are formed that are identical to

the original: one old one & one newly assembled

strand


DNA Replication

Figure 3.14


Events Of Cell Division


Cell Division: Consists of 2 events:

Mitosis—division of the nucleus

Results in the formation of two daughter nuclei

Cytokinesis—division of the cytoplasm

Begins when mitosis is near completion

Results in the formation of two daughter cells with

the same genetic information


Prophase

(Remember, due to DNA

replication, for a short time the

nucleus contains a double dose of

genes)

First part of cell division

Centrioles migrate to the poles to

direct assembly of mitotic spindle

fibers

DNA appears as double-stranded

chromosomes

Nuclear envelope breaks down

and disappears


Metaphase

Chromosomes are aligned in the center of the cell on

the metaphase plate


Anaphase

Chromosomes are pulled apart and toward the opposite

ends of the cell

Cell begins to elongate


Telophase

Chromosomes uncoil to become

chromatin

Nuclear envelope reforms around

chromatin

Spindles break down and disappear

Cytokinesis

Begins during late anaphase and

completes during telophase

A cleavage furrow forms to pinch

the cells into two parts


Stages of Mitosis

Cell division takes between 5 minutes-2 hours

Two daughter cells exist

Each is smaller with less cytoplasm than mother

cell, but genetically identical

The daughter cells grow & carry out normal cell

activities unit it is their turn to divide for body

growth in youth & repair body tissue

Mitosis gone wild is the basis for tumors &

cancers


Video: How To Stain Cheek Cells


Stained Cheek Cells

Documents

Overview of the Cellular Basis of Life - Weeblyt1lara.weebly.com/uploads/1/6/3/2/1632178/ch3cellspdfnotes.pdfCells and Tissues Cells: Carry out all chemical activities needed to sustain