CELL STRUCTURE AND FUNCTION

Cell Discovery and

Theory

The Cell

A cell is the basic unit of structure and function Humans have trillions and trillions of cells You can’t see cells with the naked eye

Cell Dudes Robert Hooke- 1665

Looked at cork, saw little box-shaped structures and called it cellulae

Anton van Leeuwenhoek- late 1600s Looked at pond water and milk and saw

“beasties”

Cell Dudes Matthias Schleiden- 1838-botanist

Studied plants and concluded that all plants are made of cells

Theodor Schwann- zoologist Concluded that all animal tissues were made

of cells

Rudolph Virchow- Suggested that cells come from cells

Hooke’s Microscope Hooke’s Drawing of

Cork

Back when… Had to draw images

No cameras! First images of nervous system

Maid (Harriet Cole) willed her body to Dr. Rufus Weaver (1888) He meticulously dissected her body

to analyze nervous system Understanding blood flow

Criminals sentenced to death had option to be dissected while alive – 16th century

William Harvey 1628 – dissect live and dead animals Heart pumps blood and then it is returned – continuous

flow

The Human Nervous System, 1888 Dr. Weaver took 5

months to carefully dissect Harriet and then remove and draw the nerves!

Still on display at Hahnemann Medical College, Philadelphia, PA

Nerve tissue is real and coated; eyes are models

The Cell TheoryPrinciple Explanation

1. All living organisms are made up of one or more cells.

An organism can have one or many cells. Most plants andanimals have many cells.

2. The cell is the basic unit of organization in living organisms.

Even in complex organisms such as humans, the cell is the basic unit of life.

3. All cells come from cells. Cells pass copies of their genetic material on to their daughter cells.

Cells contain hereditaryinformation that passes fromcell to cell during cell division.

How do we know cells come from other cells?

Problem? A compound light microscope has a 10X

ocular lens and a 46X objective lens. Where is the ocular lens?

____________________ Where is the objective lens?

_________________ What is the total magnification ___________X

Prokaryotes 2 Kingdoms

Eubackteria Archeabacteria

No nucleus DNA in a central nucleoid

region Contains ribosomes First organisms on earth

Eukaryotic Cells 4 Kingdoms

Protist (single celled) Plants (cell wall/chloroplasts) Animals (lack cell wall/lack chloroplasts) Fungi (cell wall/lack chloroplasts)

Contain membrane bound organelles Organelles are specialized structures that

carry out functions

The Cell Membrane The cell membrane is selectively

permeable Some things can pass but others can’t

Cell membranes are made from a phospholipid bilayer

Phospholipid Bilayer Structure Each phospholipid has a polar head and

two nonpolar tails Polar head is attracted to water Nonpolar tails are repelled by water

Outsideof cell

Insideof cell(cytoplasm)

Cellmembrane

Proteins

Proteinchannel Lipid bilayer

Carbohydratechains

Phospholipid Bilayer Function The function is to let some things in and

not others Polar molecules do not easily pass

H2O is an exception because it is small Allows membrane to separate environment

inside from outside the cell The plasma membrane is always in

motion Fluid mosaic model

Animal Cells vs. Plant Cells Eukaryotic cell

which makes up tissues in animals

Lack cell walls and chloroplasts, and have smaller vacuoles.

Appears to be circular because of the lack of a rigid cell wall.

Eukaryotic cell that makes up plants

Cell Wall Chloroplast Large Vacuoles

Animal Cell

Plant Cell

Cytoplasm Semi-fluid material inside the plasma

membrane Consists of cytosol and the cellular

organelles (all organelles except the cell nucleus)

Cytosol - fluid in which the cellular organelles are suspended

Cytoskeleton Network of long, thin

protein fibers provide an anchor for organelles

Microtubules-long hollow cylinders that assist in moving substances within the cell

Microfilaments-thin threads that give the cell shape and enable the cell to move

Cytoskeleton in Red and Green

Nucleus Contains genetic

material (DNA) Nuclear envelope Nuclear pores

allow substances in and out

Nucleolus in center Very dense center

Ribosomes Produce proteins Made of RNA and protein Made in the nucleolus Some float freely in the cytoplasm Others attach to endoplasmic reticulum

Endoplasmic Reticulum Interconnected

network of tubules Rough ER

Where ribosomes attach and make proteins

Appear to create bumps and rough areas on the membrane

Smooth ER No ribosomes Produces complex

carbohydrates and lipids

Golgi Apparatus Modifies, sorts, and

packs proteins in sacs called vesicles

Vesicles fuse with plasma membrane

They release proteins which move through membrane to get outside of the cell

Vacuoles Act as temporary

storage unit for materials in the cytoplasm

Store, transport, or digest food and waste

Plant cells have one large one

Animal cells have little ones

Lysosomes Vesicles that contain

digestive enzymes to digest excess or worn-out organelles and food particles

They also digest bacteria and viruses that enter the cell

They are built in the Golgi apparatus.

Centrioles Microtubules Found near nucleus Animal Cells only Aid in cell

replication

Mitochondria Powerhouse Converts organic

materials into energy ATP

Outer and inner membranes with lots of folds Provides large surface

area to break sugar molecule bonds (produce energy)

Chloroplasts- Plant only Capture light

energy and convert it to chemical energy through photosynthesis

Cell Wall Mesh of fibers that surrounds the plasma

membrane Protects and supports the cell Made of carbohydrate, cellulose

Cilia and Flagella Cilia- short projections that look like

hairs Move back and forth like oars on a rowboat Move substances along surface of the cell

Flagella- longer projections that move in a whip-like motion

Both are composed of microtubules Move cells through watery environment

Cell Transport

Diffusion -net movement of particles from high concentration to low concentration Doesn’t require energy

because the particle are in motion

Dynamic equilibrium- the overall concentration does not change, but molecules are still moving randomly

What affects the rate of diffusion?

What makes molecules move faster High

temperature High Pressure High

concentration

Facilitated Diffusion Some ions and molecules can’t diffuse

across the cell membrane Facilitated diffusion – uses transport

proteins to help move some molecules across the plasma membrane

Osmosis Osmosis – diffusion of water Most cells undergo osmosis because

they are surrounded by water

Hyper—Hypo– Iso tonic These are comparing words

Hypertonic -more solute than Hypotonic- less solute than Isotonic- same solute as

What would happen if you Put a red blood cell in a hypertonic solution Put a red blood cell in a hypotonic solution Put a red blood cell in an isotonic solution

Active Transport Goes from low to high concentration Requires Energy

ATP Moves large substances

Endocytosis

Endocytosis- moving large substances into the cell

Exocytosis Exocytosis- moving large substances out

of the cell