A&P: Cellular Biology

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Cellular Biology

Cellular Biology

The study of the system and function of the cell.

Cell Membrane

The structure that regulates the entry and exit of substances in a cell.

Phospholipid Biylar

Composed of hydrophobic tails and hydrophilic heads, making it selectively permeable.

Fluid Mosaic Model

The description of the plasma membrane as flexible and dynamic in structure.

Active Transport

The movement of substances across a membrane that requires energy. Involves sodium-potassium pump.

Passive Transport

The movement of substances across a membrane that does not require energy.

Cytoplasm

The material within a cell, excluding the nucleus, that houses organelles.

Nucleus

The organelle that contains genetic material and directs cell activity.

Nuclear Envelope

Surrounds the nucleus, and contains nuclear pores.

Nuclear Pores

Openings where molecules move between the nucleus and cytoplasm.

Cytoplasm

Houes organelles and is the site of most cellular activities.

Ribosomes

Organelles that serve as the site of protein synthesis.

Endoplasmic Reticulum

Network of membranous tubules and sacs (cisternae) within the cytoplasm. Has smooth and rough parts.

Smooth ER

Lacks ribosomes. Responsible for calcium storage, synthesis of fats, and detoxifies drugs.

Rough ER

Has ribosomes on the surface (hence, rough).

Golgi Apparatus

The organelle that modifies, packages, and distributes proteins from the rough ER.

Cis face

Side of the Golgi Apparatus where proteins from the ER enter.

Trans face

Side of the Golgi Apparatus where proteins exit.

Lysosome

An organelle that contains digestive enzymes to break down macromolecules.

Mitochondria

The organelle that converts oxygen into ATP, known as the powerhouse of the cell.

Outer Membrane of the Mitochondria

Smooth and porous, allowing ions and small molecules to pass.

Inner Membrane

Folded into cristae. Majority of mitochondrial proteins are embedded. Increased surface area allows for chemical reactions.

Cristae

Folds of the mitochondria’s inner membrane.

Intermembrane Space

Proteins are located within, used for transport and apoptosis regulation.

Matrix

Outermost part of the intermembrane space, where the krebs cycle takes place. Contains enzymes needed for krebs and fatty acid oxidation. Mitochondria DNA and ribosomes are also located.

Endomembrane System

A network of membranes that synthesize, modify, and transport biomolecules within a cell.

Parts of the endomembrane system

Nuclear envelope, endoplasmic reticulum, golgi apparatus, lysosomes, and vacuoles.

Gene expression

Information from a gene is used to create a protein. This involves two processes: transcription and translation.

Transcription

DNA is transcribed to RNA with the use of RNA polymerase and then mRNA is able to leave the nucleus and go into cytoplasm

Before leaving the nucleus the pre-mRNA has to undergo modifications such as the removal of introns and the addition of the polyA tail and 5’cap (part that gets cut off when leaving so no genetic information is lost)

Translation

Turns RNA into proteins. The ribosomes groups 3 nucleotides into codons, tRNA carries amino acids to ribosome. This makes a growing polypeptide chain, resulting in a protein.

Cytoskeleton

A network of fibers that supports the cell and holds organelles in place.

Microtubules

The thickest fibers of the cytoskeleton, involved in cell shape and organelle movement. It contains a protein called tubulin.

• Hollow tubes composed primarily of protein units called tubulin

• Radiate from cell’s center

• Determine cell shape

• Provide tracks for organelle movement

• Involved in separation of chromosomes during cell division

  • Forms mitotic spindle (what separates chromosomes into daughter cells).

Actin Filaments

The thinnest fibers of the cytoskeleton, involved in muscle contraction and cell movement.

• Forms the contractile ring during cytokinesis

• Maintains and regulates cell shape

• Motor proteins move along microfilaments to transport materials within the cell

• Made up of contractile protein (actin)

• Attach to the cytoplasmic side of plasma membrane

• Forms tight junctions

• Participate in muscle contraction

• Cell motility 

Intermediate Filaments

Stable cytoskeletal elements that provide mechanical support to the cell.

• The most stable and permanent cytoskeletal element

• Act as guy wires to resist pulling forces on the cell

• Forms nuclear lamina which maintains nuclear shape 

• Fix organelle position

  • Makes up desmosomes

• Forms nuclear lamina which maintains nuclear shape

Plasma Membrane

The boundary that separates intracellular substances from extracellular substances.

Glycocalyx

A combination of glycolipids, glycoproteins, and carbohydrates on the plasma membrane involved in cell recognition.

Integral Membrane Proteins

Proteins that penetrate deeply into the lipid bilayer of the plasma membrane. Used for passive facilitated diffusion.

Peripheral Membrane Proteins

Proteins attached to the membrane surface, involved in cell signaling, enzymatic activity and structural support.

Three types of membrane junctions

Tight junctions, desmosomes, and gap junctions.

Tight Junctions

Membrane junctions that create an impermeable barrier between adjacent cells.

Desmosomes

Anchoring junctions that provide mechanical stability to tissues. Made up of intermediate filaments.

Gap Junctions

Junctions that allow the passage of small molecules and ions between cells.

Osmosis

The diffusion of water through a selectively permeable membrane.

Hypertonic Solution

Solution with greater solute concentration than inside a cell.

Hypotonic Solution

Solution with a lower solute concentration than inside a cell.

Isotonic Solution

Equal parts solute in and out of the cell.

Osmolarity

Total concentration of all solutes in a solution.

Osmotic pressure

Amount of pressure require to prevent net movement of water into a solution.

Diffusion

Movement down a concentration gradient: movement of solutes from an area of high concentration to a lower concentration. Rate determined by viscosity, concentration gradient, temp., and size of particles.

Facilitated Diffusion

The process by which carrier proteins move substances across the membrane.

Three types of transport

Passive, active, and bulk transport.

Passive Transport

Type of transportation that does not require energy.

Passive Transport (Filtration)

When water and solutes are forced through membrane or capillary by pressure.

Active Transport

The process of moving substances against their concentration gradient using energy.

Bulk Transport

Movement of large quantities of substances into or out of the cell using vesicles. Includes phagocytosis and pinocytosis.

Exocytosis

The process of releasing substances from a cell via vesicles.

Endocytosis

The process of taking large substances into a cell by enclosing them in membrane-bound vesicles.

Phagocytosis

The process of "cell eating," where large particles are ingested by the cell.

Pinocytosis

The process of "cell drinking," where fluids are ingested by the cell.

Receptor-Mediated Endocytosis

A specific uptake of molecules via receptors on the plasma membrane. It involves coated pit (indents in the plasma membrane) supported by a protein called clathrin.