UNIT 2 Flashcards
(14 cards)
What is the fundamental structure of all biological membranes?
The basic structure of all biological membranes is the same. They are formed by phospholipids and other amphipathic lipids which naturally assemble into continuous sheet-like bilayers in water.
What are the main components determining a substance’s ability to pass through a biological membrane?
The hydrophobic hydrocarbon chains at the core of a membrane provide low permeability to large molecules and hydrophilic particles, including ions and polar molecules. Whether a substance can pass depends on its size and its hydrophilic or hydrophobic properties. Additionally, the presence of channels and pumps allows for selective passage.
How does simple diffusion occur across membranes, and what types of particles use it?
Simple diffusion is a passive process that requires no energy. Particles spread from an area of higher concentration to an area of lower concentration, moving down their concentration gradient. Across membranes, particles pass between the phospholipids. Small non-polar particles such as CO2 and O2 diffuse easily, while ions hardly diffuse at all. NO PROTEIN NEEDED
What are integral and peripheral proteins, and how are they associated with the membrane?
Integral proteins have at least one part embedded in the phospholipid bilayer, and that portion is hydrophobic. Many integral proteins, called transmembrane proteins, cross the membrane completely. Peripheral proteins are hydrophilic on their surface and are never embedded in the bilayer. Most attach reversibly to integral proteins, though some are anchored by a hydrocarbon chain inserted into the membrane. The amount and type of protein in a membrane varies based on the membrane’s activity.
How do water molecules cross membranes, and what role do aquaporins play? WHAT IS OSMOSIS
Water is small enough to cross membranes of most cells despite being polar.
Osmosis is the net movement of water across a membrane from a side with a lower solute concentration to a side with a higher solute concentration.
This occurs because solute particles attract water molecules. Aquaporins are integral proteins that function as water channels, significantly increasing the membrane’s permeability to water.
What is facilitated diffusion, and what role do channel proteins play?
Facilitated diffusion allows polar molecules (if not too small) and ions to pass through membranes. It is a passive process that requires no energy. This movement is mediated by channel proteins, which are specific, allowing only one type of substance to pass through. Particles typically move from an area of high concentration to an area of low concentration. Channel proteins can control the flow of ions by opening or closing, making membranes selectively permeable.
FACILITATED NEED MEMBRANE PROTEIN
SIMPLE DIFF DOES NOT NEED PROTEIN
What is active transport, and how does it differ from passive transport?
Active transport uses energy from Adenosine Triphosphate (ATP). It typically transports a solute against its concentration gradient, moving it from a place of low concentration to one of high concentration.
In contrast, passive transport (simple and facilitated diffusion, and osmosis) does not require cellular energy and moves substances down their concentration gradients.
Are cell membranes semi-permeable or selectively permeable?
Cell membranes are selective, meaning their channels and pumps are substance-specific. This is different from a semi-permeable membrane, which allows free flow of the solvent and passage of some small solutes but does not match the specific permeability properties of cell membranes. Facilitated diffusion and active transport contribute to this selective permeability, while simple diffusion is not selective and depends solely on the particle’s size and hydrophilic/hydrophobic properties.
What are the functions of glycolipids and glycoproteins in cell membranes?
Glycolipids and glycoproteins are crucial for cell-to-cell recognition. Their carbohydrate components are always located on the extracellular side of the membrane, forming the glycocalyx. Glycoproteins are conjugated proteins, and glycolipids are found in the plasma membrane of all eukaryotic cells.
What is solvation, and how does water’s polarity contribute to it?
Solvation is the combination of a solvent (like water) with the molecules or ions of a solute. This process depends on water’s polarity. Hydrogen bonds form between solutes and water. Specifically, cations (positive ions) are attracted to the oxygen in water molecules, while anions (negative ions) are attracted to the hydrogen in water.
How does water move in relation to solute concentration across a membrane?
Water moves from a less concentrated solution (hypotonic) to a more concentrated solution (hypertonic). This net movement of water across a membrane due to attractions between solutes and water is called osmosis. The attractions between solute molecules and water are stronger than those between water molecules, which restricts water movement and makes solutions more viscous than pure water.
TYPES OF BONDS + what is maltose
Maltose: 2 glucose together
Alfa-1,4- glocosydic bond: side by side bond 2 glucose
Alfa - 1,6- Glycosidc bond: Creating branches
GLYCOSIDIC BONDS: SUGAR ONLY
UNSATURATED CIS AND TRANS FAT
Trans: straight shape: hydrogen up and down (human made) worst type
Cis: hydrogen on the same side (natural) curved
Structure of an amino acid
H H // O
H - N - C - C
R. \ O
R: 20 variable side chains
