1D Flashcards
The means by which substances get through plasma membranes
Membrane transport
function of membrane transport
- protein synthesis
- cell reproduction
Responsible for specialized membrane functions
role of proteins
- ion channels (Na+, K+, Ca2+, Cl-)
- enzymes
- Receptors for hormones or other chemical messengers
- Transport as channels or carriers
- Recognition site
branched sugars attached to proteins that abut the extracellular space
Glycoproteins
the fuzzy, sticky, sugar-rich area on the cell’s surface
Glycocalyx
Barrier for cell contents and separates them from the surrounding environment
Plasma Membrane
Double phospholipid layer is composed of
Hydrophilic heads
Hydrophobic tails
A phospholipid has a backbone derived in carbon molecule called __________, with long carbon called fatty acid.
GLYCEROL
functions of the plasma membrane
1) acts as a barrier separating inside and outside of the cell
2) controls the flow of substances into and out of the cell
3) helps identify the cell to other cells (eg. immune cells)
4) participates in intercellular signaling
a selectively permeable barrier
plasma membrane
_________ can enter the cell
_______________ are kept out
Nutrients
Undesirable substances
also a key determinant of membrane fluidity: at high temperatures, this acts to stabilize the cell membrane and increase its melting point; while at low temperatures, it inserts intophospholipidsand prevents them from interfering with each other to avoid aggregation
Cholesterol
homogeneous mixture of two or more components (ex: air that we breath, fluid of plasma membrane, seawater, rubbing alcohol)
SOLUTION
dissolving medium; typically water in the body
SOLVENT
components in smaller quantities within a solution
SOLUTES
Contains water, dissolved solutes, and suspended particles.
INTRACELLULAR FLUID (cytosol; nucleoplasm)
solution that bathes the exterior of our cell and contains thousands of nutrients
INTERSTITIAL FLUID
Fluid outside the cells
EXTRACELLULAR FLUID
fluid found in the body of an organism;
includes the fluid outside (extracellular) and inside (intracellular) the cell.
body fluid
two types of passive transport
diffusion and
(simple & facilitated diffusion)
osmosis
passive transport
high concentration gradient to low concentration gradient
active transport
low/high concentration gradient to low/high concentration gradient that uses ATPs’ energy
Particles tend to distribute themselves evenly within a solution
Kinetic energy (energy of motion) causes the molecules to move about randomly.
Diffusion
Movement is from high concentration to low concentration, or down a concentration gradient
Diffusion
affect the speed of diffusion
size of the molecule and temperature
Molecules will diffuse only if
(1) The molecules are small enough to pass through the membrane’s pores.
(2) The molecule are lipid soluble
(3) The molecules are assisted by a membrane carrier
Diffusion are influence by several factors:
- Steepness of the concentration gradient
- Temperature
- Mass of the diffusing substances
- Surface area
- Diffusion distance
An unassisted process
Solutes are lipid-soluble materials
- Fats
- Fat-soluble vitamins
- Oxygen
- Carbon dioxide
small enough to pass through membrane pores
simple diffusion
difussion types
simple & facilitated diffusion and osmosis
Highly polar water molecules easily cross the plasma membrane through aquaporins (water pores) created by proteins in the membrane.
OSMOSIS
is the net movement of solvent molecules from a region of high solvent potential to a region of lower solvent.
simple diffusion of water (osmosis)
same solute & water concentration
No changes in cells, RBCs retain their normal size & disc-like shape.
Isotonic
contains more solutes or dissolved subs, than there inside the cells
Cells begin to shrink
given to patients with edema (swelling of the feet and hands due to fluid retention)
Hypertonic
Saline solution used often in medical field, contact lens fluid to help keep contact lenses clean and free from dust and pollutants
Hypertonic example
water enters the cell causing it to swell, bloat or explode
hypotonic
solution contains fewer solutes (ex. Distilled water)
hypotonic
Substances require a protein carrier for passive transport
Transports lipid-insoluble and large substances
Facilitated Diffusion
Water and solutes are forced through a membrane by fluid, or hydrostatic pressure
Filtration
A pressure gradient must exist
Solute-containing fluid is pushed from a high-pressure area to a lower-pressure area
Filtration
used for transport
ATP
substances that were unable to pass by diffusion are transported by
active transport
Substances are transported when they are unable to pass by diffusion due to
- Substances may be too large
- may not be able to dissolve in the fat core of the membrane
- may have to move against a concentration gradient
Two common forms of active transport
Active transport (solute pumping)
Vesicular transport
Vesicular transport
Exocytosis and Endocytosis
Endocytosis
Phagocytosis
Pinocytosis
Amino acids, some sugars, and ions are transported by protein carriers called solute pumps
ATP energizes protein carriers
In most cases, substances are moved against concentration gradients
Active transport (solute pumping)
energizes protein carriers
ATP
Amino acids, some sugars, and ions are transported by protein carriers called
solute pumps
Moves materials out of the cell
Exocytosis
Extracellular substances are engulfed by being enclosed in a membranous vesicle
Endocytosis
Types of endocytosis
Phagocytosis—“cell eating”
Pinocytosis—“cell drinking”
one of the building blocks of body tissues
proteins
helps repair and build body’s tissues, allows metabolic reactions to take place and coordinates bodily functions
also maintain proper pH and fluid balance
proteins
is another type of passive transport, and refers to the movement of water and other molecules across the cell membrane due to hydrostatic pressure generated by the cardiovascular system.
filtration
a tightly regulated process that allows a cell to respond to its changing environment.
It acts as both an on/off switch to control when proteins are made and also a volume control that increases or decreases the amount of proteins made.
There are two key steps involved in making a protein, transcription and translation.
gene expression
Many eukaryotic genes have a conserved promoter sequence called the _________, located 25 to 35 base pairs upstream of the transcription start site.
TATA box
The resulting product of RNA modification is a ________________ that passes through a pore in the nuclear envelope to reach the cytoplasm, where translation takes place.
functional mRNA molecule
___________ in the cytoplasm carry out translation.
Ribosomes
The small subunit of a ribosome has a binding site for mRNA; the larger subunit has three binding sites for tRNA molecules:
P site
A site
E site
the nucleotide sequence in an mRNA molecule specifies the amino acid sequence of a protein
translation
binds the tRNA carrying the growing polypeptide chain
Peptidyl site
binds the tRNA carrying the next amino acid to be added to the growing polypeptide
Aminoacyl site
binds tRNA just before it is released from the ribosome.
Exit site
also the codon for the amino acid methionine
AUG
first amino acid in a growing polypeptide
methionine
the process by which the information encoded in a gene is turned into a function
gene expression
the process by which the instructions in our DNA are converted into a functional product, such as a protein
gene expression
refers to all of an organism’s proteins
proteome
the large-scale study of proteomes.
proteomics
This mostly occurs via the transcription of RNA molecules that code for proteins or non-coding RNA molecules that serve other functions.
gene expression
transcription happens in
DNA
translation happens in
RNA
3 types of RNA
messenger RNA (mRNA)
ribosomal RNA (rRNA)
transfer RNA (tRNA)
carries code from DNA to ribosome for protein synthesis
messenger RNA
assembles amino acids brought by tRNA in a specific order from mRNA to make proteins
made of RNA by the nucleolus
ribosomal RNA
transports specific amino acid to ribosome for protein synthesis
transfer RNA
2 phases of protein synthesis
transcription and translation
the process in which a gene’s DNA sequence is copied to make an RNA molecule.
is the process in which mRNA copies a sequence of DNA.
transcription
the main transcription enzyme
uses a single-stranded DNA template to synthesize a complementary strand of RNA
builds an RNA strand in the 5’ to 3’ direction, adding each new nucleotide to the 3’ end of the strand.
RNA polymerase
the first step in gene expression. It involves copying a gene’s DNA sequence to make an RNA molecule.
transcription
uses a strand of DNA as a template to build a molecule called RNA.
the process of producing a strand of RNA from a strand of DNA
transcription
DNA triplet
mRNA codon
AAT CGT TCG
UUA GCA AGC
stages of transcription
initiation
elongation
termination
a special nucleotide sequence located near the beginning of a gene where transcription begins
PROMOTER
do code for segments of a protein
exons
do not code for parts of proteins
introns
enzymes that cut out the introns and splice together the exons
snRNPs (small nuclear ribonucleoproteins)
the process in which the genetic code carried by mRNA is translated into a sequence of amino acids; occurs on ribosomes
translation
mRNA codon
anti-codon
UUA GCA AGC
AAU CGU UCG
E
P
A
Exit site
Peptidyl site
aminoacyl site
AUG
start codon
UAA, UAG, UGA
stop codon
division of the nucleus
- Results in the formation of two daughter nuclei
Mitosis
division of the cytoplasm
- Begins when mitosis is near completion
- Results in the formation of two daughter cells
Cytokinesis
resting phase
G0
growth and metabolism
G1
DNA replication
S
growth of structural elements
G2
Mitosis
M
the cell “double checks” the duplicated chromosomes for error, making any needed repairs
G2
cellular contents, excluding the chromosomes, are duplicated
G1
each of the 46 chromosomes is duplicated by the cell
S
DNA synthesis
S
formation of 2 new daughter cells
MITOTIC PHASE
First part of cell division
Centrioles migrate to the poles to direct assembly of mitotic spindle fibers
DNA appears as double-stranded chromosomes
Nuclear envelope breaks down and disappears
prophase
Chromosomes are aligned in the center of the cell on the metaphase plate
metaphase
Chromosomes are pulled apart and toward the opposite ends of the cell
Cell begins to elongate
anaphase
Chromosomes uncoil to become chromatin
Nuclear envelope reforms around chromatin
Spindles break down and disappear
telophase
Begins during late anaphase and completes during telophase
A cleavage furrow forms to pinch the cells into two parts
cytokinesis
associated with an increase in the incidence and severity of disease
aging
process by which cell ages and permanently stops dividing but does mot die
Occurs throughout life
Arresting growth of damaged/dysfunctional cells
Beneficial early in life; may continue to aging later
Cell Senescence and Death
senescence inducers
telomere dysfunction
chromatin perturbation
DNA damage
strong mitogenic signals
senescent phenotype
growth arrest
functional changes
resistance to apoptosis
can cause cancer
inducers
allows cells to respond to inducers, but cells withdraw from the growth cycle – incapable of tumorigenesis
senescence
allows cells to respond to inducers, but cells withdraw from the growth cycle – incapable of
tumorigenesis
senescence includes multiple stages:
initiation, promotion, progression, and metastasis.
Contributions of Cell Senescence to Aging
Altered secretions of cells
Proteases, inflammatory cytokines, growth factors
Erosion of structure and integrity of tissues
the cell never acts, it reacts
ernst haeckel
small proteins that are crucial in controlling the growth and activity of other immune system cells and blood cells. When released, they signal the immune system to do its job.
cytokines
affect the growth of all blood cells and other cells that help the body’s immune and inflammation responses.
Cytokines
specific DNA sequences found only at the tips of each chromosome
These pieces of DNA protect the tips of chromosomes from erosion and from sticking to one another
telomeres
can be induced byloss of telomeres after extensive proliferation, as well as exposure to a variety of stresses, such as oxidative stress, DNA-damaging agents or oncogene activation
Cellular senescence
________, which stimulate cell division, primarily by relieving intracellular negative controls that otherwise block progress through the cell cycle.
mitogens
hasbeneficial biological functions in the regulation of embryonic development, wound healing, resolution of fibrosis and tumour suppression. However, prolonged senescence can result in deleterious sequelae, including tumour development, chronic inflammation, immune deficit and stem cell exhaustion.
Cellular senescence
are remarkably resistant to apoptosis, and several studies indicate that host defense mechanisms can enhance anti-apoptotic signaling, which subsequently induces a senescent, pro-inflammatory phenotype during the aging process.
Senescent cells
a normal process accompanied by a progressive alteration of the body’s homeostatic adaptive responses. It produces observable changes in structure and function and increases vulnerability to environmental stress and disease.
aging
The specialized branch of medicine that deals with the medical problems and care of elderly persons is
geriatrics
the scientific study of the process and problems associated with aging
gerontology
Although many millions of new cells normally are produced each minute, several kinds of cells in the body—including ______ cells and _____ cells—do not divide because they are arrested permanently in the G0 phase
skeletal muscle cells and nerve cells
part of the genetic blueprint at birth
aging genes
