TOPIC 2 Flashcards
What is the fluid mosaic model?
The fluid mosaic model of the plasma membrane is composed of a phospholipid bilateral building the membrane . Also shows cholesterol, membrane proteins and carbohydrates
What are the 3 major regions of the generalised cell?
Plasma membrane
Cytoplasm
Nucleus
Functions of the plasma membrane?
Mechanical barrier: Separates two of the body’s fluid compartments.
- Selective permeability: Determines manner in which substances enter or exit the cell.
- Electrochemical gradient: Generates and helps to maintain the electrochemical gradient required for muscle and neuron function.
- Communication: Allows cell-to-cell recognition (e.g., of egg by sperm) and interaction.
- Cell signaling: Plasma membrane proteins interact with specific chemical messengers and relay messages to the cell interior.
Function of the cytoplasm?
Cellular region between the nuclear and plasma membranes. Consists of fluid cytosol containing dissolved solutes, organelles (the metabolic machinery of the cytoplasm), and inclusions (stored nutrients, secretory products, pigment granules).
Function of the nucleus?
Control center of the cell; responsible for transmitting genetic information and providing the instructions for protein synthesis.
Chemical composition of plasma membrane?
Membrane made of a double layer of lipids (phospholipids, cholesterol, and so on) within which proteins are embedded. Proteins may extend entirely through the lipid bilayer or protrude on only one face. Most externally facing proteins and some lipids have attached sugar groups.
What is a cell?
Basic structural and functional unit of living organisms (smallest unit of life). All organisms are made up of one or more cells
What are the 2 types of cells?
Somatic- mitosis
Sperm/ ova- meiosis
What are extracellular materials?
- extra cellular fluid ( interstitial fluid, blood plasma, CSF)
- cellular secretions ( substances aiding digestion, intestinal and gastric fluids that act as lubricants, saliva , mucus and serous fluids
- extracellular matrix ( jellylike, proteins and polysaccharides, molecules assembling into mesh in extracellular space where they serve as universal ‘cell glue’ that helps bind body cells together.
What are extracellular materials?
Substances contributing to body mass that are found outside of cells.
What is a plasma membrane?
Flexible membrane that seperate the EF to the Intracellular fluid.
What is the phospholipid belayer made up of?
Polar hydrophilic head ( with phosphate group) facing EF and IF.
No polar hydrophobic tails ( with fatty acids) facing in
What do cholesterol do on the cell membrane?
wedges its platelike hydrocarbon rings between the phospholipid tails, which stabilize the membrane, while decreasing the mobility of the phospholipids and the fluidity of the membrane.
What do carbohydrates/ glycocalyx do on the cell membrane?
consists of gly- coproteins and glycolipids that form a fuzzy, sticky, carbohydrate- rich area at the cell surface.
glycocalyx provides highly specific biological markers by which approaching cells recognize each other
What are the types of proteins on the membrane and their functions?
Integral proteins
Peripheral proteins
Glycoproteins
What are the types of cell junctions?
Tight
Desmosomes
Gap junctions
Tight junctions?
Impermeable junctions that form continuous seals around the cells prevent molecules from passing through the intercellular space.
Desmosomes?
Anchoring junctions that bind adjacent cells together act like molecular “Velcro” and also help form an internal tension-reducing network of fibers.
Gap junctions?
Gap junctions: Communicating junctions that allow ions and small molecules to pass are particularly important for communication in heart cells and embryonic cells.
What are the passive cell transport methods?
Simple diffusion
Facilitated diffusion
Osmosis
What is diffusion?
tendency of molecules or ions to move from an area where they are in higher concentration to an area where they are in lower concentration, that is, down or along their concentration gradient
What increases rate of diffusion
Temperature, particle size
not concentration
T or F cell membrane is selectively permeable?
True
What is simple diffusion?
Energy- Kinetic energy
Description- Net movement of molecules from an area of their higher concentration to an area of their lower concentration, that is, down their concentration gradient
Examples- Fats, oxygen, and carbon dioxide move through the lipid bilayer of the membrane
What is facillitated diffusion?
Energy source- Kinetic energy
Description- Same as simple diffusion, but the diffusing substance is attached to a lipid-soluble membrane carrier protein (carrier-mediated facilitated diffusion) or moves through a membrane channel (channel-mediated facilitated diffusion)
Example- Glucose and some ions move into cells
What are the 2 types of facilitated diffusion?
Carrier mediated facilitated diffusion- via protein carrier specific for 1 chemical
Channel-mediated facilitated diffusion- diffusion through a channel protein ; mostly ions selected on basis of charge
What is osmosis?
Energy source- Kinetic energy
Description-Diffusion of water through a selectively permeable membrane
Eg. Movement of water into and out of cells directly through the lipid bilayer of the membrane or via membrane channels (aquaporins)
What is osmolarity?
The total concentration of all solute particles in a solution is referred to as the solution’s
What is tonicity?
ability of a solution to change the shape or tone of cells by altering the cells’ internal water vol- ume
What is an isotonic solution?
solutions have the same concentrations of nonpenetrating solutes as those found in cells (0.9% saline or 5% glucose). Cells retain their normal size and shape in isotonic solutions (same solute/water concentration as inside cells; water moves in and out).
What is a hypertonic solution?
Hypertonic solutions have a higher concentration of non- penetrating solutes than seen in the cell (for example, a strong saline solution). Cells immersed in hypertonic solutions lose water and shrink, or crenate
What is a hypotonic solution?
Hypotonic solutions are more dilute (contain a lower concen- tration of nonpenetrating solutes) than cells. Cells placed in a hypotonic solution plump up rapidly as water rushes into them (Figure 3.9c). Distilled water represents the most extreme example of hypotonicity. Because it contains no solutes, water continues to enter cells until they finally burst, or lyse.
Are all passive methods of diffusion specific and saturable? ( max rate of transport )
All passive methods except simple diffusion And aquaporin facillitated diffusion
What are aquaporins?
Membrane channels for water molecules
What is active transport!
Transport that uses apt to move against or up the concentration gradient
What are the types of active transports!
Active transport ( primary and secondary )
Vascular transport ( exocytosis, endocytosis, pinocytosis, phagocytosis, receptor mediated endocytosis)
What are the types of vesicular transports?
( exocytosis, endocytosis, pinocytosis, phagocytosis, receptor mediated endocytosis)
What is primary active transport?
Energy source is ATP, Transport of substances against a concentration (or electrochemical) gradient. Performed across the plasma membrane by a solute pump, directly using energy of ATP hydrolysis.
Ions
(Eg. Na+, K+, H+, Ca2+, and others)
What is secondary active transport?
Energy source is Ion concentration gradient maintained with ATP.
Cotransport (coupled transport) of two solutes across the membrane. Energy is supplied indirectly by the ion gradient created by primary active transport. Symporters move the transported substances in the same direction; antiporters move transported substances in opposite directions across the membrane.
What are the types of endocytosis
Phagocytosis- A large external particle (proteins, bacteria, dead cell debris) is surrounded by a pseudopod (“false foot”) and becomes enclosed in a vesicle (phagosome).
Eg. In the human body, occurs primarily in protective phagocytes (some white blood cells and macrophages)
Pinocytosis (fluid-phase endocytosis)-
Plasma membrane sinks beneath an external fluid droplet containing small solutes. Membrane edges fuse, forming a fluid-filled vesicle.
eg. Occurs in most cells; important for taking in dissolved solutes by absorptive cells of the kidney and intestine
Receptor-mediated endocytosis - Selective endocytosis and transcytosis. External substance binds to membrane receptors. Means of intake of some hormones, cholesterol, iron, and most macromolecules
What is vesicular trafficking?
Vesicular trafficking
- Vesicles pinch off from organelles and travel to other organelles to deliver their cargo.
Intracellular trafficking between certain organelles, e.g., endoplasmic reticulum and Golgi apparatus
What is exocytosis?
Secretion or ejection of substances from a cell. The substance is enclosed in a membranous vesicle, which fuses with the plasma membrane and ruptures, releasing the substance to the exterior.
eg. Secretion of neurotransmitters, hormones, mucus, etc.; ejection of cell wastes
Mitochondria structure
Rodlike, double-membrane structures; inner membrane folded into projections called cristae.
Mitochondria function
Site of ATP synthesis; powerhouse of the cell.
Ribosome structure
Dense particles consisting of two subunits, each composed of ribosomal RNA and protein. Free or attached to rough endoplasmic reticulum.
Rough ER structure
Membranous system enclosing a cavity, the cistern, and coiling through the cytoplasm. Externally studded with ribosomes.
Smooth ER structure
Membranous system of sacs and tubules; free of ribosomes.
Golgi apparatus structure?
A stack of flattened membranes and associated vesicles close to the nucleus.
Perioxomes structure?
Membranous sacs of catalase and oxidase enzymes.
Ribosome function
The sites of protein synthesis.
Rough Er function
Sugar groups are attached to proteins within the cisterns. Proteins are bound in vesicles for transport to the Golgi apparatus and other sites. External face synthesizes phospholipids.
Smooth Er function
Site of lipid and steroid (cholesterol) synthesis, lipid metabolism, and drug detoxification.
Golgi apparatus functions
Packages, modifies, and segregates proteins for secretion from the cell, inclusion in lysosomes, and incorporation into the plasma membrane.
Perioxomes function?
The enzymes detoxify a number of toxic substances. The most important enzyme, catalase, breaks down hydrogen peroxide.
Lysosomes structure
Membranous sacs containing acid hydrolases.
Microtubules structure?
Cylindrical structures made of tubulin proteins.