Notes From Reading
CHAPTER 7:I NSIDE THE CELL (PGS.125-156)
- The structure of cell components is closely related to their function.
- Inside cells, materials are transported to their destinations with the help of molecular “zip
codes” or postal codes.
- Cells are dynamic. Thousands of chemical reactions occur each second within cells;
molecules constantly enter and exit across the plasma membrane; cell products are shipped
along protein fibres; and elements of the cell’s internal skeleton grow and shrink.
- Life on earth is cellular
7.1 What’s Inside the Cell?
- Looking at cell structure, there are two broad groupings of life:
- Prokaryotes, which lack a membrane-bound nucleus.
- Eukaryotes, which have such a nucleus.
- Looking into groupings by evolutionary history, there are two types of prokaryotic cells,
called Bacteria and Archaea, in addition to the Eukarya.
- The prokaryotic plasma membrane surrounds the cytoplasm, a term that includes all the
contents of the cell.
- Most prokaryotic species have one supercoiled circular chromosome containing DNA that is
found in the nucleoid region of the cell.
- All prokaryotic cells contain ribosomes for protein synthesis. Ribosomes have a large and a
small subunit and contain both RNA and protein molecules.
- The inside of prokaryotic cells is supported by a cytoskeleton of protein filaments.
- Some prokaryotes have tail-like flagella on the cell surface that spin around to move the
- Prokaryotic cells generally have few or no substructures separated from the rest of the cell
by internal membranes.
- Prokaryotes have a tough cell wall that protects the cells and gives them shape and
- The relatively large size of the eukaryotic cell makes it difficult for molecules to diffuse
across the entire cell. This problem is partially solved by breaking up the large cell volume
into several smaller membrane-bound organelles.
- The compartmentalization of eukaryotic cells increases chemical reaction efficiency by
separating incompatible chemical reactions and grouping enzymes and substrates together. Notes From Reading
CHAPTER 7:INSIDE THE CELL(PGS.125-156)
Eukaryotes and Prokaryotes Compared
- Major differences between typical eukaryotes and prokaryotes are as follows:
(1) Eukaryotic chromosomes are found inside a membrane- bound compartment called a
(2) Eukaryotic cells are often much larger.
(3) Eukaryotic cells contain extensive amounts of internal membrane.
(4) Eukaryotic cells feature a diverse and dynamic cytoskeleton.
Location of DNA Internal Cytoskeleton Overall Size
Bacteria and In nucleoid (not Extensive internal Limited in extent, Usually small
Archaea membrane membranes only relative to relative to
bound); plasmids in photosynthetic eukaryotes eukaryotes
also common species; limited
Eukaryotes Inside nucleus Large numbers of Extensive –usually Most are larger
(membrane organelles; many found throughout than prokaryotes
bound); plasmids types of organelles volume of cell
- All eukaryotes have a large nucleus surrounded by a double-membrane nuclear envelope.
The nucleus contains the linear eukaryotic chromosomes.
- Ribosomal RNA synthesis occurs in a distinct region of the nucleus called the nucleolus.
- Eukaryotic ribosomes are made of RNA and protein, and have a large and a small subunit.
Many ribosomes are found in the cytosol, the fluid part of the cytoplasm.
Rough Endoplasmic Reticulum
- The rough endoplasmic reticulum (rough ER) is a network of membrane-bound tubes and
sacs studded with ribosomes for protein synthesis and is continuous with the nuclear
- The Golgi apparatus is formed by a series of stacked flat membranous sacs called cisternae.
It receives products from the rough ER and sends finished products to the cell surface in
vesicles. Notes From Reading
CHAPTER 7:INSIDE THE C ELL(PGS.125-156)
Smooth Endoplasmic Reticulum and then Endomembrane System
- The smooth endoplasmic reticulum (smooth ER) lacks ribosomes and is responsible for fatty
acid and phospholipid synthesis.
- The endomembrane system, composed of the smooth and rough ER and the Golgi
apparatus, is the primary system for protein and lipid synthesis.
Peroxisomes and Vacuoles
- Peroxisomes are globular organelles bound by a single membrane in which oxidation
- Plants and fungi have very large vacuoles that store water and/or ions to help the cell
maintain its normal volume.
- Lysosomes are single-membrane-bound centers for storage and/or waste processing.
Materials are delivered to the lysosomes by three processes: phagocytosis, autophagy, and
- Endocytosis is a process by which the cell membrane can pinch off a vesicle to bring outside
material into the cell. In addition to phagocytosis and receptor-mediated endocytosis, a
third type of endocytosis called pinocytosis brings fluid into the cell.
- Mitochondria have two membranes; the inner one is folded into a series of sac-like cristae.
The solution inside the cristae is called the mitochondrial matrix.
- Mitochondria have their own DNA and their own ribosomes. They grow and divide
independently of nuclear division and cell division.
- ATP production is a mitochondrion’s core function.
- Most plant and algal cells have chloroplasts that, like mitochondria, grow and divide
independently, have a double membrane, and contain DNA.
- Chloroplasts contain membrane-bound, flattened vesicles called thylakoids, which are
stacked into piles called grana. Outside the thylakoids is the solution called the stroma.
- Chloroplasts contain everything required to convert light energy to chemical energy—in