Unit 4: Cell/Cell Transport

8A Miss Sabia

Essential Question

1. What is a cell?2. What scientific

contributions led to the development of the cell theory?

Do Now• Write down any structures you recognize in this

cell.

Cell• A structure within a living thing

that has a definite boundary enclosing the material inside

• The basic unit of structure and function in a living thing

How did people discover cells?• The invention of the

microscope made it possible for people to discover and learn about cells!

• Microscope: an instrument that makes small objects look larger– A simple microscope has

only one lens– A compound microscope

is a light microscope that has more that one lens

• Late 1590’s (approx)

Robert Hooke• English scientist and inventor, 1665• One of the 1st people to observe cells• Observed a cork under a microscope,

called the little structures cells because they reminded him of tiny rooms

Anton van Leeuwenhoek• Made his own lenses, then used them

to construct his own simple microscopes

• Studied pond water—found little animals in the water (one-celled organisms)

• Looked at teeth scrapings—was the 1st scientist to see bacteria!

Soon enough…• Numerous observations made it clear

that cells were the basic units of life• 1838: Matthais Schleiden said all

plants are made of cells• 1839: Theodor Schwann stated that

all animals are made of cells• 1885: Rudolf Virchow concluded that

new cells could be produced only from the division of existing cells

Cell Theory1.All living things are made of cells

2.Cells are the basic unit of structure and function in living things

3.All cells are produced from existing cells

Essential Question•How are cells organized?

Prokaryotes v. Eukaryotes

• No nucleus• Smaller and simpler• Contain cell

membrane and cytoplasm

• Ex: bacteria• Carry out every

activity associated with life

• Have a nucleus• Have cell membrane

and cytoplasm• Have organelles• Many are large,

multicellular organisms

• Ex: plants, animals, fungi

Organelles• Organelles: specialized structures

that perform important cellular functions

• “little organs”

Cell Membrane• Thin, flexible barrier around the cell• Semi-permeable—only lets certain

materials in/out• Separates the cell from its external

environment• Supports and protects the cell• More to come on this later…

Cell Wall• Plant cells only!• Supports and protects the cell• Prevents plant cell from bursting due

to turgor pressure (from water)• Made of cellulose (a tough

carbohydrate fiber)

Cytoplasm• Material inside the cell membrane—

not including the nucleus• Thick, fluid, gel-like substance

IN THE NUCLEUS…

Nucleus• “brain” or “control center”• Contains cell’s genetic material

(DNA) and controls the cell’s activities

• Chromatin: DNA bound to protein • Chromosome: condensed chromatin

Nucleolus• Small, dense region within the

nucleus• Makes ribosomes

Nuclear Envelope• Surrounds and protects the nucleus• Has thousands of pores—allow

material to move in/out

CYTOSKELETON…

Cytoskeleton• Network of protein filaments that

helps the cell to maintain its shape• Also involved in many forms of cell

movement• microtubules: hollow tubes of protein

about 25 nm; maintain cell shape and allow organelles to move on them like tracks

• Microfilaments: long, thin fibers that aid in movement and support; 7 nm

IN THE CYTOPLASM…

Ribosomes• Make proteins

Do Now• Write the function of the following

organelles:– Nucleus– Cell membrane– Ribosome– Cell wall

Endoplasmic Reticulum• An internal membrane structure• Assembles components of the

cell membrane and modifies proteins

• Rough ER—protein synthesis; contains ribosomes on its surface

• Smooth ER—lipid synthesis, among other tasks

Golgi Apparatus• Golgi body, Golgi complex• Enzymes in the Golgi attach

carbs and lipids to proteins. Proteins are then sent to their final destinations

• Golgi receives proteins from ER

Lysosomes• Small • Filled with enzymes that break down

carbs, lipids, and proteins into particles that can be used by the rest of the cell

• Also break down old organelles• Remove debris to de-clutter the cell

Vacuoles• Store materials like water, salt, and

proteins• Central Vacuole (in plants): filled

with liquid, makes it possible for plants to support heavy structures like leaves and flowers

• When vacuoles are used for transport, we call them vesicles

Chloroplast• Only in plants!• Use energy from sunlight to

make food (photosynthesis)• Contain green pigment chlorophyll in

photosynthetic membranes

Structure of a Chloroplast

(Mighty) Mitochondria• Use energy from food to make

high energy compounds that the cell uses for growth, development, and movement

• “powerhouse”

Structure of a Mitochondrion

Summary

Coming soon to a theater near you!

• Prokaryotes v. eukaryotes• Organelles• Cell membrane• State Lab—Diffusion Through a

Membrane

Organelle Project