What name is given to the basic functional and structural unit of all living organisms?
The basic structural and functional unit of all known life-forms is the cell.
For the AP Biology exam, you'll want to be familiar with animal and plant cells, as well as the general structure of bacterial cells.
The cell theory, originally composed in 1838, includes three primary tenets. Name them.
- The cell is the basic unit of life.
- All living things are composed of cells, whether one or many.
- All cells arise from other cells.
All cells can be categorized into which two broad groups?
Prokaryotic and eukaryotic cells
Prokaryotic cells are generally simpler and include bacterial species. Eukaryotes can range from single-celled organisms (like yeast) to complex animals (like humans).
What main features characterize eukaryotic cells?
Eukaryotic cells have membrane-bound organelles, including nuclei, and linear chromosomes. They are also larger than prokaryotic cells and differ in specific aspects like flagellum structure.
Eukaryotic cells can comprise either unicellular or multicellular organisms.
What main features characterize prokaryotic cells?
Prokaryotic cells lack membrane-bound organelles. They generally contain one circular chromosome within a nucleoid region, but can also possess circular plasmids outside the genome.
Prokaryotic cells always comprise unicellular organisms.
How do eukaryotic and prokaryotic cells differ with respect to organelles?
Unlike eukaryotes, prokaryotes lack a nucleus, as well as all membrane-bound organelles.
Note that membrane-bound organelles include mitochondria, lysosomes, the ER, and the Golgi apparatus, but not ribosomes. Prokaryotes do contain ribosomes, a fact that may appear on the AP Biology exam.
How do eukaryotic and prokaryotic organisms differ in their cellular organization?
Prokaryotes are always unicellular, while eukaryotes can be either unicellular or multicellular.
One common example of a unicellular eukaryote is yeast, a fungus. Most other single-celled eukaryotes are classified as protists.
Determine if an organism with the following traits is a prokaryote or a eukaryote:
- composed of a single cell
- linear DNA
- has mitochondria
This organism is a eukaryote.
Only a eukaryote would possess mitochondria, since prokaryotes lack membrane-bound organelles. Eukaryotes also have linear, not circular, chromosomes. Note that both eukaryotes and prokaryotes can be unicellular.
The cytosol is the fluid contained within a cell.
In contrast, the cytoplasm includes both the intracellular fluid and all of the extranuclear organelles.
The cytoplasm includes both the intracellular fluid, or cytosol, and the organelles.
The only organelle that is not included in the cytoplasm is the nucleus.
An organelle is a separate, specialized structure within a cell.
Many organelles are enclosed by lipid bilayers, but some, including ribosomes, are not membrane-bound.
What is the cellular role of the plasma membrane?
The plasma membrane, also called the cell membrane, protects the interior of the cell from its environment. It also limits the movement of specific materials into and out of the cell.
Describe the composition of the plasma membrane.
The plasma membrane consists of a phospholipid bilayer, with polar heads on the exterior (pointing toward the extracellular fluid and cytoplasm) and nonpolar tails on the interior.
The membrane also contains cholesterol, associated large proteins, and sphingolipids, among other components.
Explain the fluid mosaic model.
The fluid mosaic model is used to describe the plasma membrane. It is composed of lipids with a "mosaic" of embedded proteins and other components, and its "fluidity" allows these macromolecule components to move laterally within the membrane.
In animal cells, which organelle serves as the location for DNA in the form of linear chromosomes?
The nucleus holds the cell's linear chromosomes. It is also the site of DNA replication and transcription.
While the mitochondria also include DNA, mitochondrial DNA is found in small circular chromosomes, not linear ones.
What structural features are present in the nucleus?
The nucleus is encased in a double membrane, known as the nuclear envelope. This membrane is marked by channels called nuclear pores. Inside, a fluid (the nucleoplasm) surrounds linear chromosomes.
In what part of the cell is the nucleolus located, and what function does it serve?
The nucleolus is located within the nucleus. It serves as the site of ribosomal RNA transcription and synthesis of ribosomal subunits.
Which organelle has two subunits and serves as the location for protein synthesis?
Ribosomes are small organelles found in both eukaryotic and prokaryotic cells. At these organelles, proteins are synthesized (translated). A typical ribosome includes a small and a large subunit, although the sizes of these subunits vary depending on the type of cell.
How do eukaryotic and prokaryotic organisms differ in the composition of their ribosomes?
Eukaryotic ribosomes are slightly larger, with a 40S and a 60S subunit combining to yield 80S. Prokaryotic ribosomes have a 30S and a 50S subunit, which combine to form 70S.
The abbreviation "S" refers to the rate at which a molecule settles in a centrifuge.
Describe the structural characteristics of the endoplasmic reticulum (ER).
The ER is a folded membrane divided into two regions: rough ER and smooth ER.
Rough ER contains ribosomes bound to its surface, while the smooth ER does not.
Within the cell, what is the role of the endoplasmic reticulum (ER)?
The ER is involved in a variety of processes, with smooth ER and rough ER performing different functions. The smooth ER is involved in lipid anabolism and detoxification, while the rough ER, with its many ribosomes, is the site of protein translation.
Both types of ER help synthesize macromolecules and shuttle them to the Golgi apparatus to be secreted from the cell.
What biological products are synthesized in the rough endoplasmic reticulum?
The rough ER synthesizes proteins.
These can include enzymes and peptide hormones, among other examples.
What biological products are synthesized in the smooth endoplasmic reticulum?
The smooth ER synthesizes lipids.
These include steroid hormones and phospholipids, among other examples.
What is the cellular role of the Golgi apparatus?
The Golgi apparatus modifies molecules that arrive from the ER. It has the ability to break off into vesicles and can thus facilitate the exocytosis of these modified products.
What main cellular function is performed by the mitochondria?
Mitochondria are involved in cellular metabolism, specifically the production of energy via aerobic respiration.
In the mitochondria, the Krebs cycle produces electron carriers, while the electron transport chain facilitates the formation of a proton gradient. This gradient is used to produce ATP.
What membranes and spaces are present in a mitochondrion?
Mitochondria contain both an outer and an inner membrane. The intermembrane space is located between the two, while the mitochondrial matrix is the innermost space, bounded by the inner membrane.
Both membranes are phospholipid bilayers.
Binary fission is most relevant to the production of which organelle?
Binary fission is the method of replication for mitochondria.
Just like prokaryotic asexual reproduction, which produces identical daughter cells, this method of division yields identical organelles.
Which organelle found in animal cells may have arisen as a result of mutualism?
Mitochondria may have evolved from a symbiotic relationship between small bacteria and larger cells. This is known as the endosymbiotic theory.
Like all instances of mutualism, this situation is thought to have provided benefits to both organisms. The smaller bacterium was given a livable environment while providing energy for the larger host.
What is the cellular role of lysosomes?
Lysosomes break down engulfed pathogens, nutrient molecules, and components of the cell itself that are no longer functional.
Like the stomach, a lysosome contains enzymes and an acidic interior.
What are peroxisomes, and what cellular function do they perform?
Peroxisomes are small membrane-bound organelles that contain enzymes. They function in fatty acid breakdown, detoxification, and facilitation of the pentose phosphate pathway.
Peroxisomes are named for hydrogen peroxide (H2O2), which can be both formed and broken down within the organelle. This is important because H2O2 is a poisonous radical initiator.