Life is CellularCell Structures &

FunctionsBiology I

Introduction to Cells• Before the 17th century, no

one knew cells existed• Most cells are too small to

be seen with the unaided eye

• In the early 17th century microscopes were invented & cells were seen for the 1st time

• Anton Von Leeuwenhoek, a Dutchman, made the 1st hand-held microscope & viewed microscopic organisms in water & bacteria from his teeth

• In 1665, an English scientist named Robert Hooke made an improved microscope and viewed thin slices of cork viewing plant cell walls

• Hooke named what he saw "cells“

•

The combined work of scientists Schleiden, Schwann, & Virchow is known as the Cell Theory :

• Principles of the Cell Theory• All living things are made of one or more

cells• Cells are the basic unit of structure &

function in organisms• Cells come only from the reproduction of

existing cells

The Cell Theory

Cell Diversity

• Not all cells are alike• Cells differ in size, shape, and function• The female egg cell is the largest cell in the body &

can be seen without a microscope

• Bacterial cells are some of the smallest cells & are only visible with a microscope

Cells come in a variety of shapes, & the shape helps determine the

function of the cell (e.g. Nerve cells are

long to transmit messages in the body, while red blood cells

are disk shaped to move through blood

vessels)

Basic Structure of a Cell

Introduction to CellsIntroduction to Cells

Cells are the basic units of organismsCells can only be observed under

microscopeBasic types of cells:

Animal Cell Plant CellBacterial

Cell

Number of CellsOrganisms may be:• Unicellular – composed of one cell• Multicellular- composed of many cells

Prokaryotes include bacteria & lack a nucleus or membrane-bound structures called organelles

Eukaryotes include most other cells, have a nucleus and membrane-bound organelles

Cells May be Prokaryotic or Eukaryotic

Prokaryotes•Nucleoid region contains the DNA

•Cell membrane & cell wall

•Contain ribosomes to make proteins in their cytoplasm

Prokaryotic Cell - Bacteria

Eukaryotic Cell

Contain 3 basic cell structures:

•Nucleus•Cell Membrane•Cytoplasm with

organelles

Eukaryotic - Animal Cell

Eukaryotic - Plant Cell

Two Main Types of Eukaryotic Cells

Plant Cell

Animal Cell

Cytoplasm• Entire region between the nuclear membrane and

the cell (plasma) membrane.• This includes all organelles!• Jelly-like substance enclosed by cell membrane

cytoplasm Cytoplasm

Nucleus

• Membrane-bound cellular organelle in eukaryotes.

• Contains the genes (DNA)

• Brain of the cell (controls all activities)

nucleus

•Large membrane-closed sac

for cellular storage.

• Contains sugars, proteins,

minerals, wastes, & pigments

VacuolesVacuoles

Vacuole

Organelles Found in Cells Nucleolus – makes

ribosomes

Lysosomes – digests & gets rid of wastes

Golgi Bodies– wrap & export proteins (Modifies, stores and routes products from the ER to the plasma membrane)

Ribosomes- site of protein synthesis

incomingsmall subunit

polypeptidemRNA1 2 3 4 5 6 7

Smooth & Rough Endoplasmic Reticulum•Smooth ER

lacks ribosomes & makes proteins used in the cell

•Rough ER has ribosomes on its surface & makes proteins to export

Mitochondria• Found in both plants and animal cells.• It is the site of cellular respiration, a

process that uses energy extracted from organic macromolecules (like glucose) to produce ATP.

• Also known as the “powerhouse”Outermembrane

Innermembrane

Chloroplast

Outer Membrane

Inner Membrane

Stroma

Granum

Thylakoid

• Found in photosynthetic plants cells.

• The site of photosynthesis, a process that uses light energy (sun) and water to produce organic macromolecules (glucose).

Plasma (Cell) Membrane

• The boundary of every cell• Separates the living cell from its nonliving surroundings.• Acts as a selective barrier• Made of protein and phospholipids

Hydrophobic region

Hydrophilic region

• Network of fibers through out the cytoplasm.• Aids in cellular support and movement.• Composed of three components:

1. Microfilaments - support and cellular contraction

2. Intermediate filaments - support

3. Microtubles - support and cell motility

Cilia and Flagella

• Extensions of the plasma membrane.

• Aids in movement….

Cell Wall

• Strong cellulose fibers surrounding plant cells and some bacteria only!

• Composed of polysaccharides and proteins.

• Freely permeable

Cell wall

• Protect and support the enclosed substances

• Resist entry of excess water into the cell

• Give shape to the cell

Different kinds of animal Different kinds of animal cellscells

white blood cell

red blood cell

cheek cells

sperm

nerve cell

muscle cell

Amoeba

Paramecium

Differences between plant Differences between plant cells and animal cellscells and animal cells

Animal cells Plant cells

Relatively smaller in

sizeIrregular shape

No cell wall

Relatively larger in size

Regular shapeCell wall present

Animal cells Plant cells

Vacuole small or absent

Glycogen as food storage

Nucleus at the center

Large central vacuole

Starch as food storage

Nucleus near cell wall

Differences between Plant Differences between Plant Cells and Animal CellsCells and Animal Cells

Levels of organizationLevels of organization

•Cells are grouped together and work as a whole to perform special functions

Levels of OrganizationLevels of OrganizationCELLS (muscle cells,nerve

cells)TISSUES (muscle, epithelium)ORGANS (heart, lungs,

stomach)SYSTEMS (circulatory system)ORGANISM (human) It’s You!