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