Cell Theory and Eukaryotic Cells Flashcards
Cell Theory
- All living things are composed of cells
- The cell is the basic functional unit of life
- Cells arise only from preexisting cells
More recently:
- Cells carry genetic info via DNA: this is passed on from parent to daughter cell
Nucleus
Contains all of the genetic material necessary for replication of the cell. Surrounded by the nuclear membrane or envelope
Nuclear membrane or envelope
A double membrane that maintains a nuclear environment separate and distinct from the cytoplasm
Nuclear pores
In the nuclear membrane; allow selective two-way exchange of material between the cytoplasm and the nucleus.
Genes
Coding regions on genetic material (DNA)
Nucleolus
Subsection of nucleus, where the ribosomal RNA (rRNA) is synthesized. Actually takes up approximately 25% of the volume of the entire nucleus; dark spot in nucleus.
Mitochondria structure
Outer membrane: serves as barrier between cytosol and inner environment of mitochondrion.
Inner membrane, arranged in foldings called cristae, contain molecules and enzymes of electron transport chain..
Intermembrane space: space between inner and outer membranes
Matrix: Space inside the inner membrane
Cytoplasmic/extranuclear inheritance and mitochondria
Mitochondria are semi-autonomous: the contain some of their own genes and replicate independently of the nucleus via binary fission.
How are mitochondria thought to have originated
When the engulfing of an aerobic prokaryote by an anaerobic prokaryote resulted in a symbiotic relationship.
Mitochondria’s roles in the cells
Can keep the cell alive by providing energy (ATP), and also can kill the cell by release of enzymes from electron transport chain –> kick-starts apoptosis, programmed cell death
Lysosomes
Membrane-bound structures containing hydrolytic enzymes that are capable of breaking down many different substrates, including substances ingested by endocytosis and cellular waste products
Endosomes
They transport, package, and sort cell material travelling to and from the membrane
Where do endosomes transport materials to?
The trans-golgi, the cell membrane, or the lysosomal pathway for degradation
Autolysis
Process that results when lysosomes release their hydrolytic enzymes: results in apoptosis by directly degrading cellular components.
Endoplasmic reticulum
Series of interconnected membranes that are actually contiguous with the nuclear envelope. Includes smooth and rough ER
Rough ER (RER)
Studded with ribosomes, which permit translation of proteins destined for secretion directly into its lumen
Smooth ER (SER)
Lacks ribosomes and is utilized primarily for lipid synthesis (such as the phospholipids in the cell membrane) and the detoxification of certain drugs and poisons. It also transports proteins from the RER to the Golgi Apparatus
Golgi Apparatus
Consists of stacked membrane-bound sacs; materials from ER are transferred to the Golgi apparatus in vesicles. Inside the Golgi Apparatus, cellular products are modified by adding signal sequences –> then repackaged into vesicles, which are directed to correct cellular location.
Peroxisomes
Contain hydrogen peroxide; one of the primary functions is the breakdown of very long chain fatty acids via Beta-oxidation. They participate in the synthesis of phospholipids and contain some of the enzymes involved in the pentose phosphate pathway
Cytoskeleton
Provides structure to the cell and helps it to maintain its shape. Also provides a conduit for the transport of materials around the cell
3 components of cytoskeleton
Microfilaments, microtubules, and intermediate filaments
Microfilaments
Made up of solid polymerized rods of actin. Actin filaments are organized into bundles and networks and are resistant to both compression and fracture, providing protection for the cell.
Functions of microfilaments
Actin filaments can also use ATP to generate force for movement by interacting with myosin, such as in muscle contraction.
Microfilaments also play a role in cytokinesis, or the division of materials between daughter cells.
During mitosis, the cleavage furrow is formed from microfilaments.
Microtubules
Hollow polymers of tubulin proteins. They radiate throughout the cell, providing the primary pathways along which motor proteins like kinesin and dynein carry vesicles. They make up cilia and flagella
Cilia
Projections from a cell that are primarily involved in the movement of materials along the surface of the cell
Flagella
Structures involved in the movement of the cell tiself, such as the movement of sperm cells through the reproductive tract
CIlia and flagella share the same structure –> what is it?
Composed of 9 pairs of microtubules forming an outer ring, with 2 microtubules in the center. Known as 9+2 strucutre, seen only in eukaryotic organelles of motility
Centrioles
Found in a region of the cell called the centrosome. They are the organizing centers for microtubules and are structured as 9 triplets of microtubules with a hollow center
What do centrioles do during mitosis
The centrioles migrate to opposite poles of the dividing cell and organize the mitotic spindle. The microtubules emanating from the centrioles attach to the chromosomes via complexes called kinetochores and exert force on the sister chromatids, pulling them apart.
Intermediate filaments
Diverse group of filamentous proteins, which includes keratin, desmin, vimentin, and lamins. Many intermediate filaments are involved in cell-cell adhesion or maintenance of overall integrity of the cytoskeleton. They help anchor other organelles, including nucleus –> also are able to withstand tremendous amount of tension.
The 4 tissue types
Epithelial, connective, muscle, and nervous tissue
Epithelial tissues
Cover the body and line its cavities, providing a means for protection against pathogen invasion and dessication.
Basement membrane
An underlying layer of connective tissue to which epithelial cells are tightly joined to (and each other).
Parenchyma
The functional parts of the organ: in most organs, epithelial cells constitute the parenchyma.
Characteristics of epithelial cells
They are often polarized, with one side facing a lumen or the outside world, and the other side interacting with underlying blood vessels and structural cells.
Simple epithelia
Have one layer of cells
Stratified epithlia
Have multiple layers
Pseudostratified epithelia
Appear to have multiple layers due to differences in cell height but are, in reality, only one layer
Cuboidal cells
cube-shaped
Columnar cells
Long and thin
Squamous cells
Flat and scale-like
Connective Tissue
Supports the body and provides a framework for the epithelial cells to carry out their functions.
Stroma
The support structure of the body which the connective tissue is the main contributor to
Examples of connective tissues
Bone, cartilage, tendons, ligaments, adipose tissue, and blood
Extracellular matrix
Materials such as collagen and elastin which most cells in connective tissues produce and secrete
