1. Ion Channel (integral) 2. Receptor (Integral) 3. Carrier (Integral) 4. Enzyme (Integral and Peripheral) 5. Linker (Integral and Peripheral) 6. Cell Identity Marker (Glycoprotein)

CELLULAR LEVEL OF ORGANIZATION Flashcards by Monica Anne Colina

Cell Structure

— Plasma membrane
— Cytoplasm: cytosol + organelles
— Nucleus

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cytosol + organelles

Cytoplasm

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— Phospholipid bilayer
— Cholesterol
— Proteins (integral and peripheral)
— Attached carbohydrates (glycolipids and glycoproteins)

Cell Membrane

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integral and peripheral

Proteins

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glycolipids and glycoproteins

Attached carbohydrates

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Membrane Function

Ion Channel (integral)
Receptor (Integral)
Carrier (Integral)
Enzyme (Integral and Peripheral)
Linker (Integral and Peripheral)
Cell Identity Marker (Glycoprotein)

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Allows specific ion to move through water-filled pore. Most plasma membranes include specific channels for several common ions

Ion Channel (integral)

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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)

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Carrier proteins are also known as _________

Transporters

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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)

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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)

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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)

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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)

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• 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

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Cell Organelles;

• Cytoskeleton
• Flagella, cilia & centrioles
• Endoplasmic reticulum
• Golgi apparatus
• Mitochondrion
• Nucleus, nucleolus, nuclear envelope
• Vesicles, e.g. lysosome

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• Cell contents
• Includes organelles and cytosol
• Excludes nucleus

Cytoplasm

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a network of protein filaments

Cytoskeleton

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• 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

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moves chromosomes to ends of
cell during cell division

Centrosome

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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

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Composed of microtubules: 9 clusters of 3 (triplets)

Two centrioles arranged perpendicular to each other

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Composed of tubulin that grows the mitotic spindle

Pericentriolar material

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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

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Specialized for motion

Cilia and Flagella

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— 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.

1. RoughE.R. 2. 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

1. Lysosomes 2. Tay-Sachs Disease: 3. Peroxisomes 4. 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

1. transcription 2. 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:

1. Messenger RNA (mRNA) 2. Ribosomal RNA 3. 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

1. Messenger RNA 2. Ribosomes 3. 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

1. Sperm cell 2. Red Blood Cell 3. Smooth Muscle Cell 4. 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