Chap. 4

Cells

A Brief History

Robert Hooke – In 1664, he saw the 1st cell and named it a cellWhat did he use to look at the cell?Schleiden, Schwann, and Virchow - made up cell theory.

Cell Theory

• All living things are made up of cells and only cells can make cells

• Two types of cells– Prokaryotes – cell that lacks membrane-bound

organelles. No nucleus. Primitive – ex. Bacteria– Eukaryotes – cell that has organelles protected by

membranes. More complex.• Evidence to support the idea that prokaryote cells

developed 1st and eukaryote cells resulted when prokaryotic cells ingested each other.

• Prokaryotic cells lack a nucleus and membrane-bound organelles.– All cells share certain characteristics.

• Cells tend to be microscopic.• All cells are enclosed

by a membrane.• All cells are filled with

cytoplasm.

Bacterium(colored SEM; magnification 8800x)

cell membrane

cytoplasm

Types of Eukaryotic Cells

Plant – has cell wall, large vacuole, plastids (ex. Chloroplast), no centrioles

Animal – no cell wall, small vacuole, centrioles, no plastids

Eukaryotic cells have a nucleus and membrane-bound organelles.– All cells share certain characteristics.

• Cells tend to be microscopic.• All cells are enclosed by a membrane.• All cells are filled with cytoplasm.

Eukaryotic Membranes

Parts of Cell --- organelle – “little organ”Plasma or cell membrane – outer membrane. Phospholipid (P+O+fat)Cell wall – outer membrane of plants. Made up

of cellulose (we can’t digest)

Nucleus – control center of cell. a. nuclear membrane – outside edge of

nucleus. b. nucleolus – makes ribosomal RNA c. chromosomes – contains genetic material

(DNA) d. nucleoplasm – fluid inside nucleus. Used

to protect organelles within nucleus.

Eukaryotic Nucleus

What differences do you notice between the cells?

Cell Wall No cell Wall

Rigid shape Round shape

Large Vacuole Small Vacuole

Green Color! Lacks chloroplast (plastids)

No centrioles Centrioles

• Cell membranes are composed of two phospholipid layers.– The cell membrane is made of a phospholipid bilayer.– There are other molecules embedded in the membrane.– The fluid mosaic model describes the membrane.– It is responsible for protection and entering and exiting of

moleculescell membrane

protein

cholesterol

proteincarbohydratechain

protein channel

Membrane ProteinsIntegral protein – any protein embedded into the membrane•Transmembrane proteins– receptor and transport proteins – extend across the plasma membrane

Peripheral proteins – aid in conformational changes to binded integral proteins

Video!

• Other organelles have various functions.– Mitochondria supply energy to the cell.

– Vacuoles are fluid-filled sacs that hold materials.

– Lysosomes (suicide sacs)- contain enzymes to digest material. Digest foreign bodies and recycle cell parts.

• Plant cells have cell walls and chloroplasts.– A cell wall provides rigid support.

– Chloroplasts are a type of plastid that converts solar energy to chemical energy.(photosynthesis)

- Endoplasmic Reticulum (ER)transports materials throughout cell.Smooth ER – contains no ribosomes

Rough ER – has ribosomes

Ribosomes - makes proteins

• Can be on an ER or freely within cytoplasm

Golgi Body (apparatus)-Packages proteins and lipids

Peroxisomesbreakdown H2O2 into water and O2

Microtubules/Microfilaments -cytoskeleton – shape and support

Cilia/Flagella-used in cell movement

• -- cilia – hair-like projections• -- flagella – longer and thicker

Centrioles-only in animal cells

-directs cell reproduction

Cytoplasmfluid part of cell – “shock-absorber”

• -- holds organelles in place

Contains ions, carbohydrates, proteins, lipids, water, etc