Chap 3: Parts of the cell Flashcards
Parts of the cell
plasma membrane
Cytoplasm
Nucleus
The cell
is the basic living, structural, and functional unit of the body.
Functions of the Plasma Membrane
- Acts as a barrier separating inside and outside of the cell.
- Controls the flow of substances into and out of the cell.
- Helps identify the cell to other cells (e.g., immune cells).
- Participates in intercellular signaling.
the lipid bilayer
the basic structural framework of the plasma membrane, two back-to-back layers made up of three types of lipid molecules—phospholipids, cholesterol, and glycolipids
amphipathic (am-fē-PATH-ik) molecules,
which means that they have both polar and nonpolar parts
Integral proteins
extend into or through the lipid bilayer and are firmly embedded in it
peripheral proteins (pe-RIF-er-al)
are not as firmly embedded in the membrane. They are attached to the polar heads of membrane lipids or to integral proteins at the inner or outer surface of the membrane.
ion channels,
pores or holes that specific ions,
the ligand of that receptor.
A specific molecule that binds to a receptor
carriers,
selectively moving a polar substance or ion from one side of the membrane to the other.
enzymes
catalyze specific chemical reactions at the inside or outside surface of the cell.
linkers
anchor proteins in the plasma membranes of neighboring cells to one another or to protein filaments inside and outside the cell
selective permeability
Plasma membranes permit some substances to pass more readily than others.
A concentration gradient
is the difference in the concentration of a chemical between one side of the plasma membrane and the other
electrical gradient
is the difference in concentration of ions between one side of the plasma membrane and the other
electrochemical gradient
concentration gradient & electrical gradient make up the electrochemical gradient
passive processes,
a substance moves down its concentration or electrical gradient to cross the membrane using only its own kinetic energy
active processes,
cellular energy is used to drive the substance “uphill” against its concentration or electrical gradient
Simple diffusion
is a passive process in which substances move freely through the lipid bilayer of the plasma membranes of cells without the help of membrane transport
facilitated diffusion,
a substance moves across the lipid bilayer aided by a channel protein or a carrier protein.
facilitated diffusion
Solutes that are too polar or highly charged to move through the lipid bilayer by simple diffusion can cross the plasma membrane by a passive process
Channels
are integral membrane proteins that allow specific, small, inorganic ions to pass across the membrane by facilitated diffusion.
Carriers
are integral membrane proteins that undergo changes in shape in order to move substances across the membrane by facilitated diffusion.
Osmosis (oz-MŌ-sis)
is the movement of water molecules through a selectively permeable membrane.
tonicity (tō-NIS-i-tē; tonic = tension)
is a measure of the solution’s ability to change the volume of cells by altering their water content.
isotonic solution
A solution that has the same salt concentration as cells and blood
Active transport
is considered an active process because energy is required for carrier proteins to move solutes across the membrane against a concentration gradient
Primary Active Transport
In primary active transport, energy derived from the hydrolysis of ATP changes the shape of a carrier protein, which “pumps” a substance across a plasma membrane against its concentration gradient
pumps.
carrier proteins that mediate primary active transport are often called
Sodium–potassium pumps
maintain a low intracellular concentration of sodium ions.
Secondary Active Transport
In secondary active transport, the energy stored in a Na+ or H+ concentration gradient is used to drive other substances across the membrane against their own concentration gradients.
Receptor-mediated endocytosis
imports materials that are needed by the cell
Exocytosis
– membrane-enclosed secretory vesicles fuse with the plasma membrane and release their contents into the extracellular fluid
Transcytosis
– a combination of endocytosis and exocytosis used to move substances from one side of a cell, across it, and out the other side
Phagocytosis
is a vital defense mechanism that helps protect the body from disease
Bulk-phase endocytosis
Most body cells carry out bulk-phase endocytosis, the nonselective uptake of tiny droplets of extracellular fluid.
cytosol (intracellular fluid)
is the fluid portion of the cytoplasm that surrounds organelles
cytoskeleton
- is a network of three types of protein filaments—microfilaments, intermediate filaments, and microtubules—that extend throughout the cytoplasm
1. Serves as a scaffold that helps determine a cell’s shape and organize the cellular contents.
2. Aids movement of organelles within the cell, of chromosomes during cell division, and whole cells such as phagocytes.
Microfilaments (mī-krō-FIL-a-ments)
are the thinnest elements of the cytoskeleton. They are composed of the proteins actin and myosin and are most prevalent at the edge of a cell
Intermediate Filaments
As their name suggests, intermediate filaments are thicker than microfilaments but thinner than microtubules
Microtubules (mī-krō-TOO-būls′),
the largest of the cytoskeletal components are long, unbranched hollow tubes composed mainly of the nonmotile,
microvilli (mī-krō-VIL-ī; micro- = small; -villi = tufts of hair; singular is microvillus),
microscopic fingerlike projections of the plasma membrane tubulin
organelles
are specialized structures within the cell that have characteristic shapes, and they perform specific functions in cellular growth, maintenance, and reproduction
centrosome (SEN-trō-sōm), or
microtubule organizing center, located near the nucleus, consists of two components: a pair of centrioles and the pericentriolar matrix
pericentriolar matrix (per′-ē-sen′-trē-Ō-lar),
which contains hundreds of ring-shaped complexes composed of the protein tubulin
Cilia and Flagella
Microtubules are the dominant components of cilia and flagella, which are motile projections of the cell surface.
Cilia (SIL-ē-a = eyelashes; singular is cilium)
are numerous, short, hairlike projections that extend from the surface of the cell
Ribosomes (RĪ-bō-sōms; -somes = bodies)
are the sites of protein synthesis. The name of these tiny structures reflects their high content of one type of ribonucleic acid (ribosomal RNA, or rRNA), but each ribosome also includes more than 50 proteins.
The endoplasmic reticulum
is a network of membrane-enclosed sacs or tubules that extend throughout the cytoplasm and connect to the nuclear envelope.
Golgi complex
Most of the proteins synthesized by ribosomes attached to rough ER are ultimately transported to other regions of the cell. The first step in the transport pathway is through an organelle
cisterns,
small, flattened membranous sacs with bulging edges that resemble a stack of pita bread
Lysosomes
are membrane-enclosed vesicles that form from the Golgi complex
autophagy,
the digestion of worn-out organelles.
autolysis,
the digestion of an entire cell
autophagosome
the organelle to be digested is enclosed by a membrane derived from the ER to create a vesicle
peroxisomes
Another group of organelles similar in structure to lysosomes
proteasomes
The continuous destruction of unneeded, damaged, or faulty proteins is the function of tiny barrel-shaped structures consisting of four stacked rings of proteins around a central core
mitochondria
they generate most of the ATP through aerobic (oxygen-requiring) respiration, the mitochondrion is referred to as the “powerhouses” of the cell
apoptosis
the orderly, genetically programmed death of a cell
The nucleus
contains most of the cell’s genes, which are located on chromosomes Functions of the Nucleus 1.Controls cellular structure. 2.Directs cellular activities. 3.Produces ribosomes in nucleoli.
nucleoli
Inside the nucleus are one or more spherical bodies, that function in producing ribosomes.
chromatin
the complex of DNA, proteins, and some RNA
genome
total genetic information carried in a cell or an organism
A chromosome
is a highly coiled and folded DNA molecule that is combined with protein molecules.
nucleosome (NOO-klē-ō-sōm)
that consists of double-stranded DNA wrapped twice around a core of eight proteins called histones
histones,
which help organize the coiling and folding of DNA
linker DNA
The string between the beads, which holds adjacent nucleosomes together.
chromatin fiber
cells that are not dividing, another histone promotes coiling of nucleosomes into a larger-diameter, which then folds into large loops.
gene expression,
a gene’s DNA is used as a template for the synthesis of a specific protein
transcription,
the information encoded in a specific region of DNA is transcribed (copied) to produce a specific molecule of RNA (ribonucleic acid)
translation,
the RNA attaches to a ribosome, where the information contained in RNA is translated into a corresponding sequence of amino acids to form a new protein molecule
During transcription,
- which occurs in the nucleus, the genetic information represented by the sequence of base triplets in DNA serves as a template for copying the information into a complementary sequence of codons
1. Messenger RNA (mRNA) directs the synthesis of a protein.
2. Ribosomal RNA (rRNA) joins with ribosomal proteins to make ribosomes.
3. Transfer RNA (tRNA) binds to an amino acid and holds it in place on a ribosome until it is incorporated into a protein during translation.
homologous chromosomes
they contain similar genes arranged in the same (or almost the same) order
diploid (2n) cells
somatic cells contain two sets of chromosomes
interphase (IN-ter-fāz)
the cell replicates its DNA
G1 phase
is the interval between the mitotic phase and the S phase
G2 phase
is the interval between the S phase and the mitotic phase
In somatic cell division,
a single starting cell divides to produce two identical diploid cells.
mitotic (M) phase of the cell cycle,
which results in the formation of two identical cells, consists of a nuclear division (mitosis) and a cytoplasmic division (cytokinesis) to form two identical cells.
Aging
is a normal process accompanied by a progressive alteration of the body’s homeostatic adaptive responses
Gerontology
is the scientific study of the process and problems associated with aging.
telomeres (TĒ-lō-mērz),
specific DNA sequences found only at the tips of each chromosome
Carcinogenesis (kar′-si-nō-JEN-e-sis)
is a multistep process of cancer development in which as many as 10 distinct mutations may have to accumulate in a cell before it becomes cancerous
Anaplasia (an′-a-PLĀ-zē-a; an- = not; -plasia = to shape)
The loss of tissue differentiation and function that is characteristic of most malignancies.
Atrophy (AT-rō-fē; a- = without; -trophy = nourishment)
A decrease in the size of cells, with a subsequent decrease in the size of the affected tissue or organ; wasting away.
Dysplasia (dis-PLĀ-zē-a; dys- = abnormal)
Alteration in the size, shape, and organization of cells due to chronic irritation or inflammation; may progress to neoplasia (tumor formation, usually malignant) or revert to normal if the irritation is removed.
Hyperplasia (hī-per-PLĀ-zē-a; hyper- = over)
Increase in the number of cells of a tissue due to an increase in the frequency of cell division.
Hypertrophy (hī-PER-trō-fē)
Increase in the size of cells without cell division.
Metaplasia (met′-a-PLĀ-zē-a; meta- = change)
The transformation of one type of cell into another.
Progeny (PROJ-e-nē; pro- = forward; -geny = production)
Offspring or descendants.
Proteomics (prō′-tē-Ō-miks; proteo- = protein)
The study of the proteome (all of an organism’s proteins) in order to identify all of the proteins produced; involves determining the three-dimensional structure of proteins so that drugs can be designed to alter protein activity to help in the treatment and diagnosis of disease.
Tumor marker
A substance introduced into circulation by tumor cells indicates the presence of a tumor, as well as the specific type. Tumor markers may be used to screen, diagnose, make a prognosis, evaluate a response to treatment, and monitor for recurrence of cancer.
