UAlberta Physl 210A Cell Phys

Cell Categories

Epithelial, connective tissue, nerve, and muscle.

Epithelial Tissue

Body tissue composed of cells laid together in sheets with the cells tightly connected. Have two surfaces that differ in structure and function.

Plamsa Membrane

Also called the cell membrane which surrounds the cell surface.

Organelles

compartments, particles, or filaments that perform specialized functions within a cell. Can be membrane bound or non-membrane bound.

Cytoplasm

Region outside of the nucleus that is composed of cytosol where organelles are suspended.

Functions of the Cell Membrane

Physical barrier between ICF and ECF, cell-to-cell communication, structural support, transport.

What is a Biological Membrane?

The cell/plasma membrane and the intracellular membranes surrounding organelles, composed of a phospholipid bilayer.

Phospholipid Bilayer

A double layer of phospholipids with embedded proteins. Hydrophilic outer layer and hydrophobic inner layer.

Components of a Biological Membrane

Phospholipids, cholesterols, and proteins.

Membrane Lipids

Amphipathic molecules including phospholipids, cholesterol, and glycolipids.

Amphipathic

A molecule containing both hydrophobic (non-polar) and hydrophilic (polar) regions.

Phospholipid Structure

Hydrophilic (polar) head and hydrophobic (non-polar) tail. Tail is made of fatty-acid chains that can be saturated or unsaturated.

Membrane Cholesterols

Found primarily in the outer cell membrane to help with fluidity. Slightly amphipathic.

Membrane Proteins

Can be integral transmembrane or peripheral.

Integral Transmembrane Proteins

Membrane proteins that are amphipathic and span the entire phospholipid bilayer.

Peripheral Membrane Proteins

Membrane proteins that are not amphipathic and are attached to the inner or outer surface of the membrane.

Membrane Glycolipids

Lipids with a carbohydrate attached. Found in the outer edge of the membrane and are amphipathic. Form the Glycocalyx.

Glycocalyx

The layer of carbohydrates linked to lipids or membrane proteins.

Membrane Glycoproteins

Proteins with carbohydrates attached, facing the extracellular surface of the plasma membrane. Form the glycocalyx.

Cell Junction

Specialized connections that stabilize interactions and promote communication between cells.

Tight Junctions

Type of junction found in epithelial tissue and are made of proteins that form nearly impermeable junctions, link adjacent cells together, and limit movement of molecules between cells, forcing molecules to pass through the cells or across the plasma membrane.

Desmosome

Type of junction that anchors cells together in tissues that experience a lot of stretch. They are the main structural integrity of tissue. Gap between cells is ~20nm.

Cadherins

Proteins that extend into extracellular space and bind with themselves on adjacent cells.

Keratin

Protein that anchors desmosomes to the cytoskeleton.

Types of Cell Junctions

Tight Junction, gap junction, desmosome.

Occludins and Claudins

Proteins found in tight junctions.

Gap Junctions

Type of junction that links the cytoplasm of adjacent cells. They allow the movement of ions and small molecules to move between cells. Gap between cells is ~2-4nm.

Connexons

Main group of proteins that form the gap junctions between cells.

Nucleus

Largest organelle in the cell. Transmits genetic information and contains the genetic information needed to make proteins.

Chromatin

Storage form of DNA in the nucleus.

Nuclear Envelope

Double layered, porous membrane that surrounds the nucleus. Made of 2 phospholipid bilayers.

Nuclear Pores

Holes in the nuclear envelope that allow molecules to move in and out of the nucleus.

Nucleolus

Found inside the nucleus is the site of rRNA synthesis and protein components of ribosomes.

Which Cells are the Exception to Having a Single Nucleus?

RBC have no nucleus, skeletal muscle cells have multiple nuclei.

Ribosomes

Smallest and most abundant organelle. They make proteins by translating RNA, can be free floating or bound to the rough ER.

Cytosolic Proteins

Proteins made by free-floating riibosomes.

Membrane-Bound Proteins

Proteins made by ribosomes attached to the rough ER.

Smooth Endoplasmic Reticulum ER

Fluid filled membrane system that is branched and tubular with no attached ribosomes.

Smooth ER Functions

Site fatty acid synthesis, stores calcium, and aids in detoxification in the liver.

Rough Endoplasmic Reticulum ER

Fluid filled membrane system made of flattened sacs that are covered in ribosomes.

Rough ER Functions

Site of protein synthesis and post-translational modifications of proteins.

Path of Protein Synthesis

Nucleus->ribosome->ER->golgi body->functional destination.

Path From the Nucleus to the Cytosol

Nucleus->nuclear envelope->rough ER->Smooth ER->golgi->cytosol

Golgi Apparatus

Organelle composed of flattened sacs called cisternae, which have a cis and trans side.

Golgi Apparatus Functions

Receives vesicles with proteins from the rough ER to perform post-translational modifications, sorts and packages proteins in vesicles to be sent through lysosomes, secretion, and to the membrane.

Lysosomes

Small, membrane-bound organelles that contain hydrolytic enzymes to break down molecules and are important in the body's defence system.

Peroxisomes

Small, membrane-bound organelles that contain oxidative enzymes which break down molecules by using oxygen to remove a hydrogen. They break down fatty acids through beta-oxidation and detoxify alcohol and other toxins and produce hydrogen peroxide as a by product.

Mitochondria

Double membraned organelle that create interconnected rod structures. Makes ATP from glucose through cell resp. Has its own DNA.

Where is DNA found?

In the nucleus and the mitochondria.

Cytoskeleton

Non-membrane bound organelle composed of protein filaments.

Cytoskeleton Functions

Maintain cell shape, maintain the position of organelles in the cell, and mediate cell and organelle motility.

Types of Cytoskeletal Filaments

Actin, intermediate filaments, and microtubules.

Actin

Cytoskeletal protein filament made of two G-___ subunits that twist and form F-___.

Intermediate Filaments

Cytoskeletal protein filament made of twisted strands of protein like keratin.

Microtubules

Cytoskeletal protein filament that are hallow tubes made of tubulin subunits.

Diffusion

Movement of molecules from an area of higher concentration to an area of lower concentration. Ability to ___ across a membrane depends on polarity and does not require energy. Unsaturable process.

Net Flux

The product of balance between one-way flux compartments. Direction of diffusion.

Equation that Describes Diffusion

Fick's First Law.

Substances That Can Use Diffusion

Nonpolar, uncharged particles, polar and uncharged particles if they are small enough can use ___.

Factors That Influence Diffusion

Size, lipid solubility, magnitude of the driving force, the membrane surface area, the membrane permeability, temperature, and distance all influence ___.

Osmosis

The net movement of water across a selectively permeable membrane driven by a difference in solute concentrations. Water moves the solution with low solute concentration (high water) to the solution with high solute concentration.

Cell-Mediated Transport

Movement of molecules across a cell membrane via a transport protein. Saturable process.

Types of Mediated Transport

Facilitated diffusion and active transport.

Facilitated Diffusion

Passive transport that does not require energy to move substances down their concentration gradient. Involves carrier proteins or channels.

Carrier Proteins

Protein transporters with a specific binding site for the substance to be transported across the membrane.

Protein Channels

Membrane proteins that help specific ions (Ca2+) or types of ions (cation) pass through the membrane. Channels can be open (activated) or closed (deactivated). Can also be voltage-, ligand-, or mechanically-gated.

Voltage-Gated Channel

Channel that opens of closes with a change in voltage.

Ligand-Gated Channel

Channel that opens or closes with the binding of a substance.

Mechanically-Gated Channel

Channel that opens or closes in response to a mechanical stimuli like swelling.

Active Transport

The transport of substances with the use of energy specific binding sites. Can be with or against a gradient and involved primary and secondary versions. Also called pumps.

Primary Active Transport

Directly uses ATP to drive the transport of substances. Example would be the Na+/K+ pump.

Na+/K+ Pump

Active transporter that moves 3 Na+ ions out and 2 K+ ions in for every molecule of ATP that is hydrolyzed, against their respective concentration gradients.

Na+/K+ Pump Functions

Contributes to establishing and maintaining the membrane potential of a cell and maintain Na+ and K+ concentrations.

Vesicular Transport

Transport of molecules and substances across biological membranes with the use of small bubble-like organelles.

Endocytosis

Process by which material is taken into the cell by using vesicles.

Types of Endocytosis

Phagocytosis, pinocytosis, receptor-mediated endocytosis.

Phagocytosis

"Cell eating" where extensions of plasma called pseudopodia surround the material to bring it in. Used for large particles like bacteria and debris.

Steps of Phagocytosis

Recognition, attachment, pseudopodia extension, fusion, destruction, release.

Pinocytosis

"Cell drinking" where plasma membrane "indents" around the particles to be brought in. It is non-specific and brings in extracellular fluid and all particles dissolved in it.

Receptor-Mediated Endocytosis

Specific process which involved clathrin lined vesicles and the binding of a ligand to a receptor which produces a conformational change to bring in small molecule like vitamins.

Caveolae

Invagination in the plasma membrane that is used to bring particles into the cell during receptor-mediated endocytosis.

Exocytosis

Process by which material is expelled from cell by using vesicles

Functions of Exocytosis

Replace cell surface membrane that was lost during endocytosis and allow for the secretion of membrane impermeable molecules

Driving Forces of Non-Vesicular Transport

Difference in energy across a membrane to move substances and concentration gradients. These can be electrical, chemical, or electrochemical.

Chemical Driving Force

A difference in concentration gradient of a substance on either side of a membrane. Substances flow from high concentration to low.

Electrical Driving Force

Force that effects substances with a charge due to membrane potential, also called the separation of charge across a membrane. The membrane potential will push or pull a charged substance in different directions, depending on its charge and the membrane potential.

Electrochemical Driving Force

The sum of the electrical and chemical driving forces acting on an ion. Direction that this force acts depends on the net direction of the electrical and chemical driving forces

Signal Transduction

A series of molecular changes that converts a signal on a target cell's surface to a specific response inside the cell.

Chemical Messengers

Used in communication between cells (inter), can be lipid-soluble or lipid insoluble.

Signal Transduction Receptor Properties

Have specific binding sites for specific messengers, have a defined number of binding sites, have different affinities to messengers, (weak affinity requires a higher concentration), and can be found on the plasma membrane or in the cytosol/nucleus.

The ___ nature of the signal impacts how the signal is ___.

Biochemical; transduced.

Intracellular Receptors

Receptors found inside the cell in the cytoplasm or nucleus that bind to lipid-soluble chemical messengers like steroid hormones. They have segments that bind the messenger, other segments that act as regulatory sites, and a segment that binds to DNA.

Endogenous Ligand

Ligand that is a cell signalling protein produced in the body.

Antagonist Ligand

Ligand that can bind to the receptor but have no effect. If agonist and antagonist ligands are both present, it can inhibit the proper cell response which can be good or bad.

Agonist Ligand

A mimetic of the natural ligand and produces a similar biological effect as the natural ligand when it binds to the receptor. If agonist and antagonist ligands are both present, it can inhibit the proper cell response which can be good or bad.

Transcription Factors

Are chemical messengers that bind to intracellular receptors to alter the rate of transcription mRNA in the nucleus by binding to a response element and alter the rate of protein sythesis.

Response Element

A specific sequence of DNA near the beginning of a gene that binds to a chemical messenger.

Membrane-Bound Receptors

Channel-, enzyme-, or G-protein-linked receptors on the membrane surface that bind to water-soluble messengers to help transduce the message.

Receptor Tyrosine Kinases RTK

High-affinity cell surface receptors for many polypeptide growth factors, cytokines, and hormones.

RTK Functions

The enzyme part (kinase) phosphorylates tyrosine amino acid residues on the receptor, the phosphorylated tyrosines act as docking sites for proteins, and produce responses after a protein binds.