The Cell Flashcards
cell theory
four basic tenets:
- all living things are composed of cells
- the cell is the basic functional unit of life
- cells arise only from preexisting cells
- cells carry genetic information in the form of deoxyribonucleic acid (DNA); this genetic material is passed on from parent to daughter cell
eukaryotic cells
contain a true nucleus enclosed in a membrane
prokaryotic cells
do not contain a nucleus
lack mitochondria
primitive cytoskeleton
different size of ribosome
organelles
in eukaryotic cells, most are membrane-bound, which allows for compartmentalization of functions
cytosol
allows for the diffusion of molecules throughout the cell
nucleus
within which genetic material encoded in DNA, organized into chromosomes
contains all of the genetic material necessary for replication of cell
surrounded by double membrane that maintains a environment separate and distinct from the cytoplasm
mitosis
how eukaryotic cells reproduce, forming two identical daughter cells
nuclear envelope
double membrane that maintains an environment separate and distinct from the cytoplasm
nuclear pores
in nuclear membrane, allow for selective two-way exchange of material between the cytoplasm and the nucleus
genes
coding regions of DNA
histones
linear DNA wound around these organizing proteins
chromosomes
once linear DNA wound around histones, wound further into these linear strands
nucleolus
subsection of the nucleus where ribosomal RNA (rRNA) is synthesized
only takes about ~25% of volume of entire nucleus
mitochondria
“the power plants of the cell” – reference to important metabolic functions
contain two layers: outer and inner membranes
semi-autonomous
contain some of their own genes and replicate independently of the nucleus via binary fission
thought to have evolved from an anaerobic prokaryote engulfing an aerobic prokaryote and establishing a symbiotic relationship
capable of killing the cell by release of enzymes from the electron transport chain –> kick-starts apoptosis
outer membrane of mitochondria
serves as barrier between cytosol and inner environment
cristae
numerous infolding of the inner membrane, which contains molecules and enzymes necessary for electron transport chain
highly convoluted structures that increase the surface area available for electron transport chain enzymes
intermembrane space
space inside the inner and outer membranes
mitochondrial matrix
space inside the inner membrane
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
autolysis
release of hydrolytic enzymes of the lysosome
results in apoptosis
directly lead to degradation of cellular components
endoplasmic reticulum (ER)
series of interconnected membranes that are actually contiguous with the nuclear envelope
single membrane folded into numerous invaginations, creating complex structures with a central lumen
two varies: smooth and rough
rough ER (RER)
studded with ribosomes
ribosomes
permit the translation of proteins destined for secretion directly into its lumen
smooth ER (SER)
lacks ribosomes and is utilized primarily for lipid synthesis and the detoxification of certain drugs and poisons
transports proteins form the RER tot he Golgi apparatus
Golgi apparatus
consists of stacked membrane-bound sacs
materials from ER transferred here in vesicles, may be modified by the addition of various groups, including carbohydrates, phosphates, and sulfates
may also modify cellular products through introduction of signal sequences, which direct the delivery of the product to a specific cellular location
after modification, cellular products are repackaged in vesicles, which are subsequently transferred to the correct cellular location
exocytosis
if product in Golgi apparatus is destined for secretion, secretory vesicle merges with cell membrane and its contents are released
peroxisomes
contain hydrogen peroxide
one of primary functions: breakdown of very long chain fatty acids via ß-oxidation
participate in 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
provides a conduit for the transport of materials around the cell
three components: microfilaments, microtubules, and intermediate filaments
microfilaments
made up of solid polymerized rods of actin
organized into bundles and networks and are resistant to both compression and fracture, providing protection for the cell
can use ATP to generate force for movement by interacting with myosin (i.e. muscle contraction)
cytokinesis
division of materials between daughter cells
role of microfilaments: create cleavage furrow
- actin filaments contract to pinch off connection between the two daughter cells
cleavage furrow
formed from microfilaments
organize as a ring at the site of division between the two new daughter cells
microtubules
hollow polymers of tubulin proteins
radiate throughout the cell, providing the primary pathways along which motor proteins (i.e. kinesin/dynein) carry vesicles
cilia and flagella are motile structures composed of these
cilia
projections from a cell that are primarily involved in movement of materials along the surface of a cell (i.e. line the respiratory tract and are involved in movement of mucus)
composed of nine pairs of microtubules forming an outer ring, with two microtubules in the center
flagella (eukaryotes)
structures involved in movement of the cell itself, such as the movement of sperm cells through the reproductive tract
composed of nine pairs of microtubules forming an outer ring, with two microtubules in the center
9 + 2 structure
nine pairs of microtubules forming an outer ring, with two microtubules in the center
structure of cilia and flagella, seen only in eukaryotic organelles of motility
centrioles
found in region of the cell called the centrosome
organizing centers for microtubules and structured as nine triplets of microtubules with a hollow center
during mitosis, these migrate to opposite poles of the dividing cell and organize the mitotic spindle
- microtubules emanating from these attach to the chromosomes via complexes called kinetochores and can exert force on the sister chromatids, pulling them apart
intermediate filaments
diverse group of filamentous proteins, including karting and desmin
many involved in cell-cell adhesion or maintenance of the overall integrity of the cytoskeleton
able to withstand a tremendous amount of tension, making the cell structure more rigid
help anchor other organelles, including the nucleus
identity of proteins within a cell is specific to the cell and tissue type
epithelial tissues
cover the body and line its cavities, providing a means for protection against pathogen invasion and desiccation
its cells are involved in absorption, secretion, and sensation; tightly joined to each other and to an underlying layer of connective tissue known as the basement membrane
- highly diverse and serve numerous functions depending on the identity of the organ in which they are found
parenchyma
in most organs, epithelial cells constitute this
functional parts of the organ
i.e. nephrons in the kidney, hepatocytes in the liver, and acid-producing cells of the stomach are all composed of epithelial cells
epithelial cells
polarized, meaning that one side faces a lumen (the hollow inside of an organ or tube) or outside world, while the other side interacts with blood vessels and structural cells
i.e. in the small intestine, one side of the cell will be involved in absorption of nutrients from the lumen, while the other side will be involved in releasing those nutrients into circulation for use in the rest of the body