CELLULAR LEVEL OF ORGANIZATION Flashcards
Cell Structure
— Plasma membrane
— Cytoplasm: cytosol + organelles
— Nucleus
cytosol + organelles
Cytoplasm
— Phospholipid bilayer
— Cholesterol
— Proteins (integral and peripheral)
— Attached carbohydrates (glycolipids and glycoproteins)
Cell Membrane
integral and peripheral
Proteins
glycolipids and glycoproteins
Attached carbohydrates
Membrane Function
- Ion Channel (integral)
- Receptor (Integral)
- Carrier (Integral)
- Enzyme (Integral and Peripheral)
- Linker (Integral and Peripheral)
- Cell Identity Marker (Glycoprotein)
Allows specific ion to move through water-filled pore. Most plasma membranes include specific channels for several common ions
Ion Channel (integral)
Transports specific substances across membrane by changing shape. For example, amino acids, needed to synthesize new proteins, enter body cells via carriers. Carrier proteins are also known as transporters.
Carrier (Integral)
Carrier proteins are also known as _________
Transporters
Recognizes specific ligand and alters cells function in some way. For example, antidiuretic hormone binds to receptors in the kidneys and changes the water permeability of certain plasma membranes.
Receptor (Integral)
Catalyzes reaction inside or outside cell (depending on which direction the active site faces). For example, lactase protruding from epithelial cells lining your small intestine splits the disaccharide lactose in the milk you drink.
Enzyme (integral and peripheral)
Anchors filaments inside and outside the plasma membrane, providing structural stability and shape for the cell. May also participate in movement of the cell or link two cells together.
Linker (Integral and Peripheral)
Distinguishes your cells from anyone else’s (unless you are an identical twin). An important class of such markers are the major histocompatability (MHC) proteins.
Cell Identity Markers (glycoprotein)
• Barrier between inside and outside of cell
• Controls entry of materials: transport
• Receives chemical and mechanical signals
• Transmits signals between intra- and extra- cellular spaces.
Membrane Function
Cell Organelles;
• Cytoskeleton
• Flagella, cilia & centrioles
• Endoplasmic reticulum
• Golgi apparatus
• Mitochondrion
• Nucleus, nucleolus, nuclear envelope
• Vesicles, e.g. lysosome
• Cell contents
• Includes organelles and cytosol
• Excludes nucleus
Cytoplasm
a network of protein filaments
Cytoskeleton
• a network of protein filaments
• Includes: microfilaments, intermediate filaments, microtubules
• help generate movement, provide mechanical support
• stabilize position of organelles
• Help determine cell shape
Cytoskeleton
moves chromosomes to ends of
cell during cell division
Centrosome
Structure of Centrosome:
• Two centrioles arranged perpendicular to each other
— Composed of microtubules: 9 clusters of 3 (triplets)
• Pericentriolar material
— Composed of tubulin that grows the mitotic spindle
Composed of microtubules: 9 clusters of 3 (triplets)
Two centrioles arranged perpendicular to each other
Composed of tubulin that grows the mitotic spindle
Pericentriolar material
- The prricentriolar material of the centrosome contains tubulins that build microtubules in nondividing cells
- The pericentriolar material of the centrosome formation the mitotic spindle during cell division
Functions of Centrosome
Specialized for motion
Cilia and Flagella
— in groups
• Found in respiratory system: move mucus
Cilia
— single tail like structure on sperm
• Propels sperm forward in reproductive tract
Flagellum
• Made within the nucleus (in nucleolus)
• Sites of protein synthesis (on E.R. or freely
within cytoplasm)
• Consist of ribosomal RNA (rRNA) + proteins
• Contain large and small subunits
• Can be attached to endoplasmic reticulum or free in cytosol
Ribosomes
Sites of protein synthesis (on E.R. or freely
within cytoplasm)
Ribosomes
Made within the nucleus (in nucleolus)
Ribosomes
Consist of ribosomal RNA (rRNA) + proteins
Ribosomes
Structure: network of folded membranes
Endoplasmic Reticulum (E.R.)
synthesis of glycoproteins & phosholipids,
intracellular transport
Endoplasmic Reticulum (E.R.)
Types of E.R.
- RoughE.R.
- Smooth E.R.
— studded with ribosomes (sites of protein synthesis)
RoughE.R.
lacks ribosomes
Smooth E.R.
lipid synthesis (FA & steroids)
Smooth E.R.
storage and release of Ca2+ in muscle cells (where smooth E.R. is known as ____________)
sarcoplasmic reticulum or SR
Flattened membranes (cisterns) with bulging
edges (like stacks of pita bread)
Structure of Golgi Complex
Modify proteins -> glycoproteins and lipoproteins that:
• Become parts of plasma membranes
• Are stored in lysosomes, or
• Are exported by exocytosis
Functions of Golgi Complex
Small Bodies
- Lysosomes
- Tay-Sachs Disease:
- Peroxisomes
- Proteasomes
— contain digestive enzymes
• Help in final processes of digestion within cells
• Carry out autophagy (destruction of worn out parts of cell) and death of old cells (autolysis)
Lysosomes
destruction of worn out parts of cell
autophagy
death of old cells
autolysis
— hereditary disorder most often affects children of Ashkenazi (eastern European Jewish) descent; one missing lysosomal enzyme (Hex A) leads to nerve destruction.
Tay-Sachs Disease
excess ganglioside GM2 in the nerve cells.
Tay-Sachs Disease
detoxify; abundant in liver
Peroxisomes
contain the enzyme catalase, which decomposes H2O2.
Peroxisomes
digest unneeded or faulty proteins
Proteasomes
Faulty proteins accumulate in brain cells in persons with Parkinson or Alzheimer disease
Proteasomes
— Sausage-shaped with many folded membranes (cristae) and liquid matrix containing enzymes
Structure of Mitochondria
— Have some DNA, ribosomes (can make proteins)
Structure of Mitochondria
Generate ATP through reactions of aerobic
cellular respiration.
Function of Mitochondria
Chemical reactions require oxygen
Mitochondria
Play an important early role in apoptosis.
Mitochondria
— Abundant in muscle, liver, and kidney cells
• These cells require much ATP
Mitochondria
Round or oval structure surrounded by nuclear envelope with nuclear pores
Nucleus
Contains nucleolus: makes ribosomes that pass into cytoplasm through nuclear pores
Nucleus
Store genetic material (DNA) in genes arranged in 46 chromosomes
Nucleus
Contains most of the cell’s genes, which are located on chromosomes
Nucleus
— DNA contains information for directing protein synthesis:
• In this cell
• In new cells (formed by cell reproduction)
Nucleus
2 steps of Protein Synthesis
- transcription
- translation
transcription
In Nucleus
translation
Ribosomes in the Cytoplasm
• RNA polymerase (enzyme) transcribes DNA into RNA; complementary base
— C-G, G-C, T-A, A-U
Transcription
complementary base pairs of Transcription
C-G,
G-C,
T-A,
A-U
DNA has the _______
ATCG nitrogenous bases
RNA replaces thymine with uracil, making its
AUCG nitrogenous bases
Types of RNA formed:
- Messenger RNA (mRNA)
- Ribosomal RNA
- Transfer RNA (tRNA)
Directs synthesis of polypeptide
Messenger RNA (mRNA)
Component of ribosomes
Ribosomal RNA
Carries amino acids to ribosome for reaction
Transfer RNA (tRNA)
Requires 3 different RNAs
Translation
from nucleus (mRNA) direct sequencing of amino acids
Messenger RNA
Requires 3 different RNAs
- Messenger RNA
- Ribosomes
- Transfer RNA
contain ribosomal RNA (rRNA) and are the sites of translation
Ribosomes
carry amino acids (tRNA) to sites on mRNA
Transfer RNA
In all body cells except gametes
Somatic Cell Division
— Period of growth and development of cell
— Preparation for reproduction: DNA synthesis
Interphase
Preparation for reproduction
DNA synthesis
— division of nucleus
• 4 phases (Prophase, Metaphase, Anaphase, Telophase)
Mitotic Phase
division of cytoplasm
Cytokinesis
Cell metabolically active; duplicates organelles and cytosolic components; centrosome replication begins.
G1 Phase
DNA replicated (8hours)
S Phase
Cell growth continues; enzymes and other proteins are synthesized; centrosome replication completed.
G2 Phase
Chromatin condenses into pairs of chromatids connected at centromeres
Prophase
• Centrosomes form the mitotic spindle (composed of microtubules) that extends from pole to pole of the cell
— Some chemotherapy drugs fight cancer cells by inhibiting formation of the mitotic spindle
Prophase
Nuclear envelope and nucleolus break down
Prophase
Centromeres of chromatid pairs are aligned along microtubules at the center (“equator”) of the metaphase plate
Metaphase
Centromeres split, separating “sister chromatids” (chromosomes)
Anaphase
Chromosomes are pulled to opposite ends of spindle by microtubules of the mitotic spindle
Anaphase
Cytokinesis (division of cytoplasm) begins by the formation of a cleavage furrow
Anaphase
• Chromosomes revert to threadlike chromatin • Nuclear envelope and nucleolus reappear
• Mitotic spindle breaks up
• Cytokinesis is completed
Telophase
usually begins in late anaphase with the formation of a cleavage furrow and is completed after telophase
Cytokinesis
Cell Destinies:
(1) to remain alive and functioning without dividing
(2) to grow and divide
(3) to die (can be through apoptosis or necrosis)
— Because structure determines function, cells differ in structure related to their functions.
• Nerve cells may reach several feet in length to carry nerve impulses from spinal cord to toe
• Muscle cells can produce effective contractions because they are cylindrical or spindle-shaped
• Microvilli increase surface area of intestinal cells to maximize absorptive ability
Cellular Diversity
Most cells are microscopic; the diameter of the largest human cell (an oocyte) can barely be seen with the unaided eye.
Cellular Diversity
largest human cell
an oocyte
Cellular Diversity
- Sperm cell
- Red Blood Cell
- Smooth Muscle Cell
- Nerve Cell
has a flagellum that it uses for locomotion
Sperm cell
disc shape RBC gives it a large surface area that enhances its ability to pass oxygen
Red blood cells
can produce effective contractions because they are cylindrical or spindle-shaped
Smooth muscle cell
nerve cells have long extensions that permit them to conduct nerve impulses over great distances
Nerve cell
• May be programmed genetically
• Decreased rate of mitosis; nerve cells and skeletal muscle cells cannot be replaced
• Telomeres (DNA at tips of chromosomes)
— Telomeres shorten with aging
— Progeria (rapid aging): profound telomere shortening
• Protein damage by glucose cross-links
• Free radicals damage
• Autoimmune responses
Aging
DNA at tips of chromosomes
Telomeres
(rapid aging)
— profound telomere shortening
Progeria
Progeria also known as __________
Hutchinson-Gilford Progeria Syndrome
(HGPS)
is a disease characterized by normal development in the first year of life followed by rapid aging
Progeria
Symptoms include dry and wrinkled skin, total baldness, and birdlike facial features.
Progeria
Death usually occurs around age 13.
Progeria
Werner Syndrome also known as _____________
“adult progeria”
is a rare, inherited disease that causes a rapid acceleration of aging, usually age twenties.
Werner Syndrome “adult progeria”
Most afflicted individuals die before age 50.
Werner Syndrome “adult progeria”
the tangled, spread-out form of
DNA found inside the nuclear membrane.
Chromatin
When a cell is ready to divide, DNA condenses into structures known as ___________
chromosomes
— has two back-to-back layers made up of
three types of lipid molecules – phospholipids,
cholesterol, and glycolipids.
— It also contains proteins (integral and peripheral).
The Lipid Bilayer
consist of two layers of phospholipids with a hydrophobic (non-polar),
or water-hating, interior (tails)
and a hydrophilic (polar),
or water-loving exterior (head).
Phospholipid Bilayer
• Maintains the structural integrity and regulating the fluidity of cell membranes.
• Gives the membrane rigidity.
Cholesterol
extend into or through the lipid
bilayer and are firmly embedded in it.
Integral Proteins
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.
Peripheral Proteins
— maintains membrane stability, but also
facilitates cell-to-cell communication acting as
receptors, anchors for proteins and regulators of signal transduction.
Glycolipids
— enable cells to recognize another cell
as familiar or foreign. They also help cells attach to and bind other cells, which is called cell adhesion. It also serves as protection and immune response.
— Cell Recognition
Glycoproteins
• does notrequire energy.
• From high concentration to low concentration.
• Polar molecules like water and glucose can pass through.
• Ions enter through special transmembrane proteins.
• Some small nonpolar molecules (O2 and CO2) can pass right through the membrane.
Passive Transport (facilitated diffusion)
• requires energy.
• From low concentration to high concentration.
Active Transport
