Chapter 3 - Cells Flashcards
apo-
away, off, apart
(apoptosis)
cyt-
cell
(cytoplasm)
endo-
within
(endoplasmic reticulum)
hyper-
above
(hypertonic)
hypo-
below
(hypotonic)
inter-
between
(interphase)
iso-
equal
(isotonic)
lys-
to break up
(lysosome)
mit-
thread
(mitosis)
phag-
to eat
(phagocytosis)
pino-
to drink
(pinocytosis)
pro-
before
(prophase)
-som
body
(ribosome)
vesic-
bladder
(vesicle)
micrometer
one thousandth of a millimeter
(μm)
How many cells does an adult human body have?
50 trillion to 100 trillion, or about 75 trillion
differentiation
cell specialization
3 major parts of a human cell
- nucleus
- cytoplasm
- cell membrane
nucleus
cellular organelle enclosed by a double bilayer nuclear envelope and containing DNA
cytoplasm
the contents of a cell including cytosol and organelles, excluding the nucleus, enclosed by the cell membrane
cell membrane
(plasma membrane)
- the selectively permeable outer boundary of a cell consisting of a phospholipid bilayer embedded with proteins
- maintains integrity of cell
- provides for signal transduction
organelle
a structure or compartment in cells that houses the biochemical reactions that carry out a specific function
cytosol
gel-like fluid portion of the cytoplasm
hydrophilic
water-soluble
cellular adhesion molecule (CAM)
- enable cells to stick to each other
- e.g. white blood cells at injury site or cells forming a placenta
integral proteins
- span the cell membrane
- form pores, channels, and carriers in cell membrane
- transduce signals
enzymes
catalyze chemical reactions
cell surface proteins
establish “self”
peripheral protein
projects from the membrane’s outer surface (includes CAMs)
transmembrane protein
- extends outside the cell membrane at one end and dips into the cytoplasm on the inside
- many act as receptors, binding to specific incoming molecules such as hormones, triggering responses from within the cell
ribosomes
- tiny, spherical, nonmembranous structures composed of protein and RNA
- synthesize proteins
- scattered in cytoplasm (free) or bound to endoplasmic reticulum (membrane-bound)
endoplasmic reticulum
- complex of interconnected membrane-bound sacs, canals, and vesicles
- transports materials within the cell
- provides attachment for ribosomes (rough ER)
- synthesizes lipids (smooth ER)
rough ER (endoplasmic reticulum)
- closer to nuclear envelope and studded with ribosomes
- proteins are bound to sugar molecules (glycoproteins) in ER and move to Golgi apparatus for processing
smooth ER (endoplasmic reticulum)
- closer to cell membrane
- no ribosomes
- synthesizes lipids
- contains enzymes important in fat absorption and drug breakdown
- abundant in liver
vesicles
- membranous sacs
- hold and transport substances that are newly synthesized or recently entered the cell
- vesicle trafficking: movement of substances into and out of cells by fleets of vesicles
Golgi apparatus
- stack of flattened, membranous sacs (cisternae)
- refines and packages proteins synthesized on rough ER for transport or secretion
exocytosis
a vesicle fuses with the cell membrane and releases its contents outside the cell
mitochondria
- “powerhouse” of the cell
- membranous sacs with double membrane
- inner partitions created by folds in the inner membrane (cristae)
- moves slowly and can divide
- releases energy from nutrients and converts it to a usable form (adenosine triphosphate, or ATP)
matrix
fluid inside mitochondria
lysosomes
- “garbage disposals” of the cell
- tiny, membranous sacs that bud off Golgi membranes
- contain enzymes capable of digesting worn cell parts or substances that enter cells
autophagy
- “eating self”
- process of the cell’s disposing of its own trash
peroxisomes
- membranous sacs
- contain enzymes that catalyze metabolic reactions
centrosome
(central body)
nonmembranous structure near nucleus composed of two rodlike centrioles
cilia
- microscopic hairlike extensions (motile projections) attached to a basal body beneath the cell membrane
- propel fluids over the cell’s surface
- some receive biochemical signals and guide cell movements
flagellum
- relatively long, motile projection attached to a basal body beneath the cell membrane of a sperm cell
- enables the cell to move
microfilaments
- tiny rods of the protein actin
- form meshworks or bundles and provide cellular movements (e.g. myofibrils)
microtubules
- hollow rod made of the protein tubulin
- usually rigid
- provide the framework of the cell, movement of cilia and flagella, and transportation of organelles
nuclear envelope
- selectively permeable double lipid bilayer membrane that separates nuclear contents from cytoplasm
- membranes are joined at openings (nuclear pores)
nuclear pore
channels that allow certain dissolved substances (e.g. RNA molecules, ribosomes) to move between nucleus and cytoplasm
nucleoplasm
fluid inside nucleus
nucleolus
- “little nucleus”
- dense, nonmembranous body made of RNA and protein
- site of ribosome formation
chromatin
- fibers composed of DNA and protein
- carries information for synthesizing proteins
centrioles
- cylinders made of nine groups of three microtubules
- lie at right angles to each other
- distribute chromosomes during cell division
- form parts of cilia and flagella (basal bodies)
cytoskeleton
- system of microtubules and microfilaments
- reinforces a cell’s form and provides scaffolding and transport pathways for organelles
myofibrils
threadlike bundles of filaments in muscle cells
diffusion (simple diffusion)
passive (physical) process in which molecules move through the phospholipid bilayer from regions of higher concentration toward regions of lower concentration
facilitated diffusion
passive (physical) process in which ions move through channels or molecules move by carrier molecules across the membrane from a region of higher concentration to one of lower concentration
osmosis
passive (physical) process in which water molecules move through a selectively permeable membrane toward the solution with more impermeant solute (greater osmotic pressure)
filtration
passive (physical) process in which smaller molecules are forced through porous membranes from regions of higher hydrostatic pressure to regions of lower hydrostatic pressure
active transport
active (physiological) process in which carrier molecules transport molecules or ions through membranes from regions of lower concentration toward regions of higher concentration
pinocytosis (endocytosis)
active (physiological) process in which a membrane engulfs droplets of liquid from surroundings
phagocytosis (endocytosis)
active (physiological) process in which the membrane engulfs solid particles from surroundings (e.g. white blood cell membrane engulfing bacteria)
receptor-mediated endocytosis
active (physiological) process in which in which the membrane engulfs selected molecules combined with receptor proteins
exocytosis
active (physiological) process in which vesicles fuse with membrane and release contents outside the cell
cell cycle (3 stages)
series of changes that a cell undergoes, from formation to division
- interphase
- mitosis
- cytokinesis (cytoplasmic division)
interphase (3 phases)
period between cell divisions when a cell metabolizes and prepares for division
- G₁ phase
- Restriction checkpoint
- S phase
- G₂ phase
(G stands for gap or growth)
mitosis (4 phases)
division of a somatic cell nucleus during cell division
- prophase
- metaphase
- anaphase
- telophase
prophase (mitosis)
> chromatin condenses into chromosomes
> centrioles move to opposite sides of cytoplasm
> nuclear membrane and nucleolus disperse
> microtubules assemble and associate with centrioles and chromatids of chromosomes
metaphase (mitosis)
> spindle fibers from the centrioles attach to the centromeres of each chromosome
> chromosomes align midway between centrioles
anaphase (mitosis)
> centromeres separate
> chromatids separate
> spindle fibers shorten and pull individual chromosomes toward centrioles
telophase (mitosis)
> chromosomes elongate and form chromatin threads
> nuclear membranes form around each chromosome set
> nucleoli form
> microtubules break down
cytokinesis (cytoplasmic division)
- begins during anaphase, continues through telophase
- cell membrane constricts around the middle via microfilaments and, after telophase, pinches off into two cells
How many times do most human cells divide when grown in a lab?
40-60
What are telomeres? How do they affect cell division?
- repeating sequence of six nucleotides at the tips of chromosomes that wears down during mitosis
- when worn down too far, the cell stops dividing
tumor
tissue mass formed when cells lose division control
two major types of genes that cause cancer
- oncogenes
- tumor suppressor genes
oncogenes
abnormal variants of genes that normally control the cell cycle, but are overexpressed, increasing cell division rate
What do tumor suppressor genes do? How can they cause cancer?
- normally control mitosis
- when absent or inactivated, uncontrolled cell division leads to cancer
G₁ and G₂ phases (interphase)
- cell growth
- specific molecules and structures duplicate
Restriction checkpoint (interphase)
- formed by actions of several types of proteins
- determines if it will divide, stop dividing, or die
What happens during S phase (interphase)?
genetic material replicates
What makes stem cells unique?
they retain the ability to divide repeatedly, have the potential to become any type of cell, and self-renew
When a stem cell divides, what kind of cells can be made?
two stem cells or one stem cell and a progenitor cell
What is a progenitor cell, what type of cell divides to produce it, and what kind of potential does it have?
- partly specialized cell
- comes from a stem cell
- is pluripotent
pluripotent
a cell whose daughter cells can follow any of several differentiation pathways
totipotent
stem cells that can divide to become any kind of cell in the body
apoptosis
programmed cell death
What functions does apoptosis serve? How is it initiated? How long does it take?
- aids in development by carving away webbing between digits, pruning extra brain cells, and getting rid of any immune system cells that don’t recognize the body’s cell surface
- peels away damaged skin after sunburn
- a “death receptor” on the cell’s surface gets a signal
- less than an hour
