Cell Biology Part 1

Flashcards on Cell Biology major concepts, components, and communication.

Plasma Membrane

A double membrane that acts as a selective barrier, separating the inside of the cell from the rest of the environment, rich in lipids and proteins.

Cell Wall

A barrier that protects the plant cell, more rigid than the plasma membrane, providing structure and strength, made of chitin in fungi and cellulose in plant cells.

Cytosol

A gel-like substance inside the cell where everything else is suspended, allowing molecules to travel across the cell; it is a reducing environment.

Cytoplasm

The cytosol and all of the cell’s organelles.

Ribosomes

Tiny complexes scattered throughout the cell responsible for creating proteins from the genetic information of DNA; eukaryotes have 80S ribosomes, while prokaryotes have 70S ribosomes.

Nucleus

The cell’s information center containing DNA, featuring a double membrane with nuclear pores and an interior nuclear lamina to maintain shape.

Nucleolus

A region inside the nucleus that contains special DNA coding for ribosomal RNA (rRNA).

Endoplasmic Reticulum (ER)

An organelle containing an extensive amount of membranes, tubules and cisternae sacs which store proteins and lipids for transport. The inside of the ER is called the lumen.

Smooth ER

A region of the ER responsible for synthesizing lipids, detoxifying poisons, and storing calcium ions.

Rough ER

A region of the ER that is studded with ribosomes on the outside, synthesizing proteins signaled to be secreted and membrane phospholipids.

Golgi Apparatus

The shipping center of the cell, responsible for directing vesicles to the correct location, receiving vesicles from the ER through the cis face.

COPI Transport Vesicles

Responsible for moving molecules retrograde (backwards) from the Golgi Apparatus back to the ER.

COPII Vesicles

Moving molecules from the ER to the Golgi.

Clathrin Vesicles

Move molecules from the Golgi to the Plasma Membrane and are surrounded by a protein shell called a triskelion skeleton.

Lysosomes

Found only in animal cells, contain an acidic pH of around 4.5, and contain enzymes for degrading molecules and breaking down old organelles, the recycling center of the cell.

Peroxisomes

Similar to lysosomes except that they contain the enzyme catalase to break down hydrogen peroxide into hydrogen and oxygen.

Vacuoles

Large vesicles that have many important functions.

Food Vacuoles

Responsible for storing food, mostly merging with lysosomes to digest the food inside.

Contractile Vacuoles

Found in many unicellular protists living in freshwater environments, responsible for expelling excess water out of the cell.

Central Vacuoles

Found in plant cells, the main storage center for inorganic ions and water, important in maintaining turgor pressure.

SNARE Proteins

Used when membranes fuse together to make the process easier.

V-SNARE Proteins

R-SNARE in the vesicle due to the presence of arginine.

T-SNARE Proteins

Q-SNARE in the plasma membrane due to the presence of glutamine.

Mitochondria

The powerhouse of the cell, the location of cellular respiration, breaking down large molecules into usable energy, with the intermembrane space, cristae, and matrix.

Chloroplasts

Found in plants and some protists, the site of photosynthesis of converting solar energy to chemical energy, containing thylakoid stacks and stroma.

Simple Diffusion

Molecules diffusing from high concentration to low concentration.

Osmosis

The diffusion of water from a high concentration of water to a low concentration of water.

Hypertonic

Describes the environment when it is more concentrated than the interior of the cell, causing water to flow out of the cell.

Hypotonic

Describes the environment when it is less concentrated than the interior of the cell, causing water to flow into the cell.

Isotonic

Describes the environment when it has the same concentration of solutes as the interior of the cell, resulting in no movement of water.

Plasmolysis

Occurs in a hypertonic environment, the cell membrane peels away from the cell wall.

Facilitated diffusion

Molecules move from high to low, in which transport proteins provide a hydrophilic path for molecules to enter the cell.

Channel proteins

Form a tunnel for the molecule to pass through the membrane, such as aquaporins that transport water.

Carrier proteins

Have binding sites for the molecule, exposes to only one side of the cell a time but the binding of the molecule changes which side the protein faces, such as GLUT transporters.

Active transport

The energy to move the molecules against a concentration gradient must come from a different source, ATP.

Primary active transport

Directly uses ATP to move a molecule against its concentration gradient.

Secondary active transport

Uses the concentration gradient generated by primary active transport.

Endocytosis

Part of the membrane invaginates to create a pocket for molecules to enter before that pocket closes off and forms a vacuole.

Receptor-mediated endocytosis

Molecules must attach to a specific receptor to start the vesicle invagination process.

Pinocytosis

Creates invaginations, ingesting fluids rather than big molecules.

Phagocytosis

Ingests very large molecules and is found commonly in white blood cells that ingest bacteria.

Cytoskeleton

A network of fibers strung throughout the cell, which plays a major role in structural integrity and organization.

Microtubules

Hollow rods created from alpha-tubulin and beta-tubulin subunits, acting as support and tracks for vesicles, found in centrosomes, cilia, and flagella.

Microfilaments

Thin solid rods also known as actin filaments, made of globular actin proteins, bearing tension against forces, present in the cell cortical and responsible for forming the shape of a cell.

Intermediate Filaments

More permanent structures used for structural support and strength that keep organelles fixated in place.

Plasmodesmata

Small holes in cell walls that allow direct cytoplasmic exchange between plant cells.

Gap Junctions

Holes directly connecting the cytoplasm of two animal cells, made of connexins.

Tight Junctions

Create a watertight seal between two cells, preventing liquids from passing, especially important for epithelial cells in the bladder.

Desmosomes

Connect two cells together using intermediate filaments for structure.

Adherens Junctions

Connect two cells together using actin microfilaments, made of cadherins.

Extracellular Matrix (ECM)

A system of proteins outside of the cell membrane that helps provide structure and is useful in cell communication.

Phospholipids

Lipids containing two hydrocarbon tails and a hydrophilic head containing phosphate; the most abundant lipids in the cell membrane.

Cholesterol

Scattered throughout the cell membrane, responsible for maintaining cell fluidity, a sterol made of 4 carbon rings, found in every cell except bacteria.

Lipid Rafts

Microdomain regions consisting of sphingolipids, cholesterol, and protein receptors that are closely concentrated to each other.

Transmembrane Proteins

Proteins that are embedded into the plasma membrane and span its entirety, requiring hydrogen bonding for stability; they are used for signaling, transport, and protein trafficking.

Porin Channels

Transmembrane proteins which create water-filled channels to allow small hydrophilic molecules to cross the membrane; they are responsible for passive diffusion.

Aquaporins

Transmembrane proteins made of 6 alpha helices responsible for efficiently diffusing water, which only allow for one water molecule to enter the protein at a time.

Flippases

Transmembrane proteins that use ATP to translocate amino phospholipids to the cytosolic side to prevent signals of apoptosis.

Floppases

Transmembrane proteins that move cytosolic phospholipids to the extracellular side and use ATP.

Scramblases

Transmembrane proteins that move phospholipids down their concentration gradient and does not use ATP. Their activity increases with an increase of cytosolic Ca2+.

G-Protein Coupled Receptors (GPCR)

A transmembrane protein created by 7 alpha helices.

Receptor Tyrosine Kinases (RTKs)

Receptors embedded into the plasma membrane, a protein kinase (an enzyme responsible for transferring phosphate from ATP to activate another protein.)

Gated Ion Channels

A receptor embedded into the membrane which acts as a valve, allowing certain ions to enter when open.

Protein kinases

Add a phosphate to proteins, activating them.

Protein phosphatases

Remove a phosphate to proteins, de-activating them.

Second messengers

Molecules that typically have a low intracellular concentration to amplify a signal throughout the cell.