PART 1: CELL BASICS & THE TOOLS AVAILABLE TO STUDY THEM

Chapter 6

UNIT II: CELLS, CELL PROCESSES, AND BIOENERGETICS

• Cell Basics

• Cell Types

• Cell Components

• Cell Transport

• Cell Communication

• Bioenergetics: Photosynthesis and Cellular Respiration

• AP Biology Standards addressed: Big Idea 2,4

AP BIO VOCABULARY OF THE DAY(STEMS, PREFIXES, AND SUFFIXES…OH MY!)

carpal- wrist

Example: carpal tunnel syndrome

(a hand and arm condition caused by

a pinched nerve in the wrist)

FABULOUS FACT

The risk of being struck by a falling

meteorite for a human is one occurrence

every 9,300 years.

WHAT YOU MUST KNOW

• To understand cell basics and the tools available for studying them.

• The differences between prokaryotic and eukaryotic cells.

AP Biology Standards addressed: Big Idea 2

HOMEWORK

•Take notes or summarize the

notes “Part 1.5: The Tour of

the Cell”

•Find in Sophia – Unit 2

PEOPLE TO PONDER

LYNN MARGULIS

• Born in Chicago in 1938

• At age 14 she entered the University of Chicago: “I wanted to go, and they let me in.”

• At 19 she met Carl Sagan- a graduate student- and married him- they had two sons

• She and Sagan moved to Berkeley where she enrolled as a graduate student- they divorced while she was there

• Margulis got her PhD and moved to work at Boston University as a professor

• While at Boston in the 60s she started studying eukaryotic cells

• At the time it was becoming clear that there was a difference between eukaryotic and prokaryotic cells

• Margulis studied how eukaryotes might have originated

• She searched for genes in the cytoplasm and found they weren’t the same as those in the nucleus

LYNN MARGULIS

• Her findings led her to develop the endosymbiotic theory- eukaryote organelles were once prokaryotic cells

that entered into a symbiotic relationship

• Her paper about the theory was rejected by 15 science journals- finally was accepted by the Journal of

Theoretical Biology

• After the paper was published it was harshly criticized by mainstream biology

• Despite the opposition Margulis pushed her theory forward

• In 1967 she married scientist Thomas Margulis and had two more children- they divorced in 1980

• In the 80s new evidence was found to support her theory- mitochondria and chloroplasts have their own

DNA- different than that in the nucleus and similar to bacteria

• Today her theory is accepted as the key way organelles formed

LYNN MARGULIS

• In 1988 Margulis retired from Boston and became the Distinguished Professor of the University of

Massachusetts

• In 1999 she was awarded the National Medal of Science by President Clinton

• Margulis died in November, 2011 of a hemorrhagic stroke

• Her work is well documented- she wrote over 130 articles and 10 books in her career including What is

Life?

HOW DID WE GET HERE??? HOW DO WE KNOW ANYTHING ABOUT CELLS?

CELL BASICS

Cell Theory:

1. All living things are made of cells.

2. Cells are the basic unit of structure

and function of life.

3. Cells only come from other existing

cells.

ALL CELLS…

•Are living units (unlike viruses)

•Have a plasma membrane

•Have cytosol inside (semifluid jelly-like liquid)

•Contain chromosomes (DNA)

•Contain ribosomes

•Most are microscopic: Cell size is limited by the ratio of their area and volume. (allows nutrients to go in and out of the cell quickly).

• Vary in shape. Shape matches function.

2 TYPES OF CELLS:

1. Prokaryotes: Domain Bacteria & Archaea

2. Eukaryotes: (Domain Eukarya): Protists,

Fungi, Plants, Animals

PROKARYOTIC CELLS

• Meaning: “before nucleus”

• Organisms from the Bacteria and Archaea domains

• Are smaller (0.1-5 µm)- size relates to function

• DNA is concentrated in a region that is not

membrane bound: nucleoid region

• DNA condenses in a circular chromosome called a

plasmid

• Filled with cytoplasm, but cytoplasm is organized into

distinctive regions

EUKARYOTIC CELL

• Meaning: “true nucleus”

• Organisms from Eukarya domain (protists, fungi, animals, plants)

• Are bigger in size (10-100 µm)

• DNA is located in the nucleus and is organized into multiple chromosomes made of condensed chromatin

• Contains membrane-bound organelles that perform specific functions

• Cytoplasm fills the space between organelles and is not specialized by region

PROKARYOTE VS. EUKARYOTE

• “before” “kernel”

• No nucleus

• DNA in a nucleoid

• Cytosol

• No organelles other than ribosomes

• Small size

• Primitive

• i.e. Bacteria & Archaea

• “true” “kernel”

• Has nucleus and nuclear envelope

• Cytosol

• Membrane-bound organelles with specialized structure/function

• Much larger in size

• More complex

• i.e. plant/animal cell

LEVELS OF CELL ORGANIZATION IN EUKARYOTES

cells tissues organs organ system organism

Ex: heart cells heart tissue heart cardiovascular system human

CELL SIZE AND SCALE – TWO VERY COOL

SITES!

Cell Size & Scale:

Scale of the Universe:

• Cells must be small to maintain a large surface area to volume ratio

• Large S.A. allows rates of chemical exchange between cell and environment

SURFACE AREA EXAMPLE (ANIMAL):

Small Intestine: highly folded surface to increase

absorption of nutrients

• Villi: finger-like projections on SI wall

• Microvilli: projections on each cell

FOLDS VILLI MICROVILLI

SURFACE AREA EXAMPLE (PLANT):

Root hairs: extensions of root epidermal cells;

increase surface area for absorbing water and

minerals

TOOLS FOR STUDYING CELLS

• Light Microscope (LM)- light passes through the specimen and glass lens,

refracts, and magnifies up to 1000xs

• Electron Microscope (EM)- focuses beam of electrons through a

specimen- a 100 fold improvement over LM

• Scanning Electron Microscope (SEM)- scans the surface of the

specimen and excites the electrons so the image appears 3D

• Transmission Electron Microscope (TEM)- used to study internal cell

structure by staining with heavy metals that attach to structures

• Cell Fractionation- uses centrifuges to take cells apart and separate

major organelles and structures for study

INNER LIFE OF A CELL

• Directions: Watch the video clip. See how many cell

components and functions you recognize. Make notes

if needed and be ready to share.

• http://www.youtube.com/watch?v=wJyUtbn0O5Y

• For narration version of the above video

EVOLUTION OF MITOCHONDRIA AND CHLOROPLASTS

EndosymbiontTheory

• Ancestor of eukaryotes engulfed a smaller prokaryote

• A symbiotic relationship formed between the two

• Over time the prokaryote lost some of its characteristics- no longer a true cell

Evidence:

• Double membrane

• Unique DNA that’s circular

• Ribosomes

• They are autonomous organelles (not part of a system)

• Both have dynamic shape- can grow and reproduce

Credit: Modified from Anna VanDordrecht (SCOE) & Mrs. Chou (Longmont High School)