Chapter 7.2: Cell Structure
Why is the cell membrane sometimes referred to as a fluid mosaic? What part of the cell membrane acts like a fluid? And what makes it like a mosaic?
Because the proteins embedded in the lipid bilayer can move around and "float" among the lipids, and because so many different kinds of molecules make up the cell membrane, scientists describe the cell membrane as a "fluid mosaic."
How do contractile vacuoles help maintain water balance?
By contrasting rhythmically, a contractile vacuole pumps excess water out of the cell.
What are the functions of chloroplasts?
Chloroplasts capture the energy from sunlight and convert it into food that contains chemical energy in a process called photosynthesis.
Why do you think it's important that cell membranes are selectively permeable?
If a cell membrane isn't selectively permeable, then it wouldn't be able to control what substances can pass in or out of the cell.
Describe the steps involved in the synthesis, packaging, and export of a protein from a cell.
In eukaryotic cells, proteins produced in the rough ER move next into the Golgi apparatus. From the Golgi apparatus, proteins are "shipped" to their final destination inside or outside the cell.
What are the functions of lysosomes?
Lysosomes break down lipids, carbohydrates, and proteins into small molecules that can be used by the rest of the cell. They are also involved in breaking down organelles that have outlined their usefulness.
What is the function of a mitochondria?
Mitochondria convert the chemical energy stored in food into compounds that are more convenient for the cell to use.
What organelles help make and transport proteins?
Proteins are assembled on ribosomes. Proteins made on the rough ER include those that will be released, or secreted, from the cell as well as many membrane proteins and proteins destined for lysosomes and other specialized locations within the cell. The Golgi apparatus modifies, sorts, and packages proteins and other materials from the endoplasmic reticulum for storage in the cell or release outside the cell.
What is the difference between rough ER and smooth ER?
Rough ER has ribosomes on its surface, but smooth ER does not.
What are the 2 major parts of the cell?
The 2 major parts of the cell are the nucleus and the cytoplasm.
What is the function of the cell membrane?
The cell membrane regulates what enters and leaves the cell and also protects and supports the cell.
You examine an unknown cell under a microscope and discover that the cell contains chloroplasts. From what type of organism does the cell likely come?
The cell probably came from a plant.
What is the function of the cytoskeleton?
The cytoskeleton helps the cell maintain its shape and is also involved in movement.
How do the properties of lipids help explain the structure of a cell membrane?
The head groups of lipids in a bilayer are exposed to the outside of the cell.
How is the role of the nucleus in a cell similar to the role of the captain on a sports team?
The nucleus and the captain both have instructions to tell the rest of the organelles or team members for what to do.
What is the role of the cell nucleus?
The nucleus contains nearly all the cell's DNA and, with it, the coded instructions for making proteins and other important molecules.
What are the functions of vacuoles?
Vacuoles store materials like water, salts, proteins, and carbohydrates.
lipid bilayer
a double-layered sheet which makes up most cell membranes that gives cell membranes a flexible structure that forms a strong barrier between the cell and its surrounding
cell wall
a strong supporting layer around the membrane, produced by many cells, including most prokaryotes
endoplasmic reticulum (ER)
an internal membrane system only in eukaryotic cells, where lipid components of the cell membrane are assembled, along with proteins and other materials that are exported from the cell
Golgi apparatus
an organelle where proteins that come from rough ER go to it, found in only eukaryotic cells, which appears as a stack of flattened membranes
centrioles
located near the nucleus and help organize cell division
selectively permeable
meaning that some substances can pass across them and others cannot, and are most biological membranes
chloroplasts
the biological equivalents of solar power plants
vacuoles
the large, saclike, membrane-enclosed structures
cytoplasm
the portion of the cell outside the nucleus
mitochondria
the power plants of the cell
lysosomes
the small organelles filled with enzymes
ribosomes
the small particles of RNA and protein found throughout the cytoplasm in all cells
organelles
the structures that act like specialized organs, literally "little organs"