Exam 2 Flashcards
(37 cards)
What does the lipid bilayer consist of?
Phospholipids which have hydrophilic heads (water attracting) and hydrophobic tails (water repelling)
What is the Hydrophobic Core?
The hydrophobic tails form the inner part of the lipid bilayer, creating a hydrophobic core.
Channel Proteins Structure and Function
Forms pores or tunnels through the lipid bilayers, allowing certains ions and molecules to pass through the membrane and down their concentration or electrochemical gradient (passive transport). Highly selective channels, only allowing specific ions (such as sodium, potassium, or calcium) or small POLAR molecules (like water) to pass.
Channel Proteins
Forms pores or tunnels through the lipid bilayer, allowing certain ions or molecules to pass through the membrane and down their concentration or electrochemical gradient. Highly selective, allows only specific ions such as sodium, potassium, or calcium to pass.
Ion Channels
Channels open in response to a signal (voltage changes) permitting specific ions to flow in and out of the cell.
Aquaporins
Specialized channels for water molecules, allowing rapid movement of water across the membrane while excluding other solutes.
Mode of transport: Facilitated diffusion, no energy (ATP) is required
Carrier Proteins
- Carrier proteins bind to the specific molecules or ions they are transporting.
- They undergo conformational change that allows the molecule to be transported across the membrane.
- Can move substances both passively and actively.
Passive Transporters: Carrier Protein
These carrier proteins move substances down their concentration gradient through facilitated diffusion, similar to channels but with a slower rate due to the conformational requirements. For example, glucose transporters (GLUT) facilitate the diffusion of glucose.
Active Transporters
These proteins actively pump molecules against their concentration gradient, requiring energy, usually from ATP hydrolysis. Examples include sodium-potassium (Na+/K+ pump), which actively moves sodium out of and potassium into the cell, maintaining the electrochemical gradient necessary for cellular functions.
Symporters
These transporters move two different molecules in the same direction across the membrane. For example, the sodium-glucose symporter uses the energy from sodium ions moving down their gradient to transport glucose into the cell against its concentration gradient
Antiporters
These transporters move two molecules in opposite directions. For example, the sodium-calcium exchanger moves sodium into the cell while transporting calcium out, helping regulate calcium levels.
Passive Transport
Refers to the movement of solutes across the membrane without the use of energy. It helps the cell maintain balance with its environment for essential substances like nutrients, gases, and waste products.
Simple Diffusion
Small, nonpolar molecules like oxygen (O₂), carbon dioxide (CO₂), and lipophilic (fat-soluble) molecules can move directly through the lipid bilayer, bypassing the need for transport proteins. No energy or transport proteins are required.
Facilitated Diffusion
Larger or polar molecules (such as glucose, amino acids, or ions) cannot diffuse through the lipid bilayer on their own. They require the assistance of transport proteins—either channel proteins or carrier proteins.
Active Transport
Active transport refers to the movement of solutes against their concentration gradient, from an area of low concentration to an area of high concentration, and requires the input of energy, typically in the form of ATP.
Sodium-potassium pump
Example of primary active transport. It pumps 3 sodium ions (Na) out of the cell and 2 potassium ions (K) into the cell, both against their concentration gradient.
Concentration Gradient
The concentration gradient refers to the difference in the concentration of a solute between the inside and outside of the cell.
Membrane Potential (Eletrical Gradient)
An electrochemical gradient is the combined effect of two gradients:
- Concentration gradient: The difference in the concentration of ions across a membrane.
- Electrical gradient: The difference in charge (voltage) across the membrane.
Together, these gradients drive the movement of ions, such as sodium (Na⁺) or potassium (K⁺), across the membrane, influencing processes like ATP production, nerve signaling, and muscle contraction.
Electrochemical Gradient
The electrochemical gradient is the combination of the concentration gradient (chemical) and the membrane potential (electrical). It determines the net driving force for the movement of charged solutes (ions) across the membrane.
Cystic Fibrosis
Genetic disorder that affects thee respiratory and digestive system due to the mutations in the CFTR gene. The CFTR protein is a channel that regulates the movement of chloride ions across ephithelial cell membrane. When it malfunctions, it leads to the production of thick, sticky mucus that causes various symptoms
What are the general function of proteins?
Protein have many functions such as enzymatic activity, structural support, and transport.
What is the function of proteins in enzymatic activity?
Proteins act as enzymes to catalyze biochemical reactions, speeding up metabolic processes. Examples include amylase (breaks down starch) and DNA polymerase (synthesizes DNA strands).
What is the primary structure of a protein?
The primary structure is the linear sequence of amino acids in a protein, determined by the gene encoding it and stabilized by peptide (covalent) bonds.
What is the role of proteins in structural support?
Proteins like collagen and actin provide structural support, with collagen strengthening connective tissues and actin forming the cytoskeleton, which maintains cell shape.
