Cell structure and function
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Cell Structure and Function. Preview. Cell characteristics and cell theory Overview of cell membrane Eukaryotic cells Eukaryotic organelles Prokaryotic cells How Cells Move. Smallest unit of life Can survive on its own or has potential to do so Senses and responds to environment

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  • Cell characteristics and cell theory

  • Overview of cell membrane

  • Eukaryotic cells

  • Eukaryotic organelles

  • Prokaryotic cells

  • How Cells Move

Characteristics of cells

Smallest unit of life

Can survive on its own or has potential to do so

Senses and responds to environment

Has potential to reproduce

Differ in:




Characteristics of Cells

Cell theory
Cell Theory

1) Every organism is composed of one or more cells

2) Cell is smallest unit having properties of life

3) Continuity of life arises from growth and division of single cells

Structure of cells
Structure of Cells

All cells have three distinct sections:

Plasma Membrane

Nucleus (or nucleoid region in prokaryotes)


Cell structure and function


  • Plasma Membrane

  • Nucleus

  • Cytoplasm

Preview of cell membranes

one layer

of lipids

one layer

of lipids

Preview of Cell Membranes

Plasma membranes are composed mostly of a lipid bilayer that prevents free passage of water soluble substances across it.

Other names for a cell membrane
Other names for a cell membrane:

  • Cytoplasmic membrane

  • Semipermeable membrane

  • Phospholipid bilayer

Eukaryotic cells
Eukaryotic Cells

Have a nucleus 

Have organelles – small, membrane bound “organs” in the cell that perform a specific job for the cell.

Found in the Protista, Fungi, Plant, and Animal kingdoms

Have 1000 times more DNA than prokaryotic cells

Organelle functions
Organelle Functions

  • nucleus - controls the cell’s activities

    • Nuclear membrane – separates cytoplasm from nuclear material

    • Nucleolus – site of RNA and ribosome synthesis

    • DNA – genetic material

  • cytoplasm – Space between nucleus and plasma membrane

    • (cytosol) jellylike substance that fills the inside of a cell , gives structure and shape

Cell structure and function

  • endoplasmic reticulum - "tunnels" in the cytoplasm that allow materials to move through the cell easier (subway system of the cell)

    • Rough (RER) – makes proteins, covered in ribosomes

    • Smooth (RER) - makes lipids, degrades fats, detoxifies material

  • ribosomes – attached to ER and scattered in cytoplasm, make proteins

  • mitochondrion – powerhouse, produce energy in the cell 

  • Golgi body - stores, processes, and secretes proteins and lipids (post office)

Cell structure and function

  • vesicle- sacs that transport material in cell

  • centrioles – centers that produce and organize structures that help in cell reproduction (animal cells only)

  • lysosome – digest, recycles nutrients (suicide sack)

  • cytoskeleton – structurally supports, gives shape & helps move cell components

Quick check
Quick Check

  • List two parts of the cell theory.

  • Rough endoplasmic reticulum is responsible for making ___ for the cell.

  • List the four eukaryotic kingdoms

  • Centrioles are only found in ___ cells.

Plant cells only
Plant Cells Only

  • cell wall - rigid surrounding of plant cells, protects, structural to support

  • chloroplasts - contain chlorophyll in plants; this is where the plant’s food is produced by photosynthesis

  • vacuoles - large bodies in plant cells that hold water, waste, etc.

Nuclear envelope membrane
Nuclear Envelope/Membrane


  • Double lipid membrane with pores

  • Controls what goes in and out

    • Pores control ions & water soluble materials entrance and exit

  • Ribosomes on outer membrane

  • Membrane merges with ER

  • Nucleoplasm - semifluid interior of nucleus


  • Mass of proteins that codes for rRNA (ribosomal RNA)

  • Synthesis of ribosomes and proteins

Genetic material dna
Genetic Material (DNA)

Chromosome – one DNA molecule and the many proteins that are associated with it

Chromatin – total collection of all DNA molecules and their associated proteins

Cell structure and function

A closer look at er
A closer look at ER:

  • Endoplasmic reticulum

  • A flattened channel that starts at the nuclear envelope/membrane and folds back and forth

  • Two types

    Rough (RER)

    • Has ribosomes attached

      • Makes proteins

        Smooth (SER)

    • Detoxifies drugs, makes lipids

A closer look at golgi bodies
A closer look at Golgi bodies:

  • Vesicles pinch off of ER.

  • Fuse with Golgi bodies

  • Golgi bodies repackage and ship vesicles by adding or removing molecules to proteins and lipids.

  • Think post office

    and stacks of

    pancakes with


A closer look at lysosomes
A closer look at lysosomes:

  • membrane-enclosed vesicles that contain powerful digestive enzymes

    • internal pH reaches 5.0

  • Functions

    • digest foreign substances and recycles own organelles

    • Autolysis

    • Suicide sac

Tay sachs disorder
Tay-Sachs Disorder

Affects children of eastern European descent

Genetic disorder caused by absence of single lysosomal enzyme

enzyme normally breaks down glycolipid commonly found in nerve cells

as glycolipid accumulates, nerve cells lose functionality

chromosome testing now available

A closer look at mitochondria
A closer look at mitochondria:

  • Mitochondria resemble bacteria

    • Have DNA, ribosomes

    • Divide on their own

  • May have evolved from ancient bacteria that were engulfed but not digested

  • Mitochondrial DNA (genes) are usually inherited only from the mother.

Mitochondria cont
Mitochondria (cont.)

Double outer membrane

Inner folded membrane

Site of most of cells ATP production

Only in eukaryotic cells

Site of aerobic respiration (oxygen present)

Numerous in skeletonal cells

A closer look at chloroplasts and other plastids
A closer look at chloroplasts (and other plastids):

  • Plastids

  • Are organelles that function in photosynthesis or storage in plants.

  • Three types

    • Chloroplast

    • Chromoplasts

    • Amyloplasts

Cell structure and function


Chloroplast –

  • Conduct photosynthesis

  • Enclosed by a double membrane

  • Thylakoid stacks of grana

    • Contain pigments such as chlorophyll

  • Stroma fluid filled area

Other plastids
Other Plastids


No chlorophyll

Abundance of carotenoids

Color fruits and flowers red to yellow


No pigments

Store starch (tubers- potatoes)

A closer look at plant cell walls
A closer look at plant cell walls:

  • Surrounds the plasma membrane

  • Protects, supports and give shape to cell

  • Porous – allows water and solutes to pass in/out

  • In all plants

  • Some protist and fungi

  • Cuticle on outer most surfaces of plants

Even cells have a skeleton
Even Cells Have a Skeleton


  • Cyto means cell

    • So cytoskeleton means cell skeleton

  • It is organized system of protein filaments in the cytoplasm.

  • Some are permanent others are temporary

Cytoskeletal elements
Cytoskeletal Elements





Functions of cytoskeletal elements
Functions ofCytoskeletal Elements:

  • Move organelles within the cytoplasm

  • Assist in cell division

  • Provide structure and support for the cell

  • Can be used to identify cells

Prokaryotic cells
Prokaryotic Cells

DNA is not enclosed in nucleus

Generally the smallest, simplest cells

No organelles

Most ancient form of life

Archaeans and bacteria the only representatives

Prokaryotic means “before the nucleus

Prokaryotic cells1
Prokaryotic Cells

  • Permeable, semi-rigid cell wall outside plasma membrane gives shape

  • Plasma membrane- semi-permeable to control what goes in and out

    • Can contain pigments for photosynthesis

  • Polysaccharides are on surface to help them stick to objects or give a protective coating

  • 1-2 Flagella – movement

Prokaryotic cells2
Prokaryotic Cells

  • Pili – helps stick to surfaces and exchange genetic material

  • Cytoplasm – semifluid material inside cell

  • Ribosomes – scattered in cytoplasm, protein making site

  • Nucleoid – concentrated region where DNA is located. DNA is circular.

  • Plasmids – scattered in cytoplasm, these can confer selective advantages such as antibiotic resistance. Contain just a few genes.

Prokaryotic structure
Prokaryotic Structure



with ribosomes




cell wall

plasma membrane

How do cells move
How Do Cells Move?

  • Cells must have ATP in order for movement to take place.

  • Cilia, flagella and false feet are all ways that cells move.

Cilia flagella and false feet
Cilia, Flagella and False Feet

  • Cilia

    • many small projections on cell membranes working in together for movement

    • Along trachea, oviducts in humans

  • Flagella

    • generally 1-2 projections that move an object

    • Sperm is the only flagella in humans

  • Pseudopodia

    • False foot

    • Temporary extension of cytoplasm for movement

Protists use all three
Protists use all three.


Cilia pseudopodia



Lead to the ability to develop the Cell Theory

Create detailed images of something that is otherwise too small to see

Light microscopes

Simple or compound

Uses two sets of lenses to magnify the living or dead image

Electron microscopes

Transmission EM or Scanning EM

Uses electrons view either inside or surface of a dead cell



New terms
New Terms

Wavelength – distance from the peak of a wave to the peak of another wave

Ocular Lens enlarges 10x inside the eye piece

Objective lens magnify at various levels

Stage supports the object viewed on slide



Create detailed images of something that is otherwise too small to see

Light microscopes

Simple or compound

Electron microscopes

Transmission EM or Scanning EM



Limitations of light microscopy
Limitations of Light Microscopy small to see

Wavelengths of light are 400-750 nm

If a structure is less than one-half of a wavelength long, it will not be visible

Light microscopes can resolve objects down to about 200 nm in size


Electron microscopy
Electron Microscopy small to see

Uses streams of accelerated electrons rather than light

Electrons are focused by magnets rather than glass lenses

Can resolve structures down to 0.5 nm


Sem surface views
SEM- surface views small to see


Electron microscopes
Electron Microscopes small to see




Tem inside cell view
TEM- inside cell view small to see


Image comparison
Image comparison small to see

The electron microscope allows a smaller object to seen

The electron microscope is not limited by the wavelength of light