AP Bio cell membrane

plasma membrane

The membrane surrounding the cytoplasm, consisting of a phospholipid bi-layer with embedded proteins. The function is to control the exit and entrance of molecules from the cell.

Phospholipid Bilayer

What the plasma membrane mainly consists of. The hydrophilic heads of the phospholipids face outwards and the hydrophobic, nonpolar tails face inwards. Embedded inside are protein molecules and lipids like cholesterol.

fluid mosaic model

A model for the plasma membrane. It is based on the changing location and pattern of protein molecules in the fluid bilayer.

Selective Permeability

One of the properties the plasma membrane has. It allows some substance to enter the cell, but stops the movement of others like large molecules or charged ions.

concentration gradient

A change in concentration between two different areas. This goes from high to low.

diffusion

The movement of molecules going with the concentration gradient (high to low). It requires no energy (passive transport) and when equilibrium is reached, the net movement will be zero.

osmosis

The diffusion of water through the cell membrane goes with the concentration gradient (high to low).

tonicity

The solute concentration compared to that of a cell. In an isotonic solution, there is no net movement of water. In a hypotonic solution, the cell gains water. In a hypertonic solution, the cell loses water

isotonic

When the solution is in equal concentration to the cytoplasm in a cell. This causes a cell to have no net water movement in osmosis.

hypotonic

WHen a solution contains a lower solute to water concentration than the cytoplasm of a cell. In this situation, the cell will gain water.

hypertonic

When a solution contains a higher solute to water concentration than in the cytoplasm of a cell. This can cause the cell to lose water through osmosis.

facilitated transport

The passive transfer of a substance in or out of the cell along the concentration gradient (high to low) by a process which requires a protein carrier.

channel protien

The protein which forms a channel. This allows a specific molecule or ion to cross the plasma membrane into the cell.

carrier protien

A type of protein in the plasma membrane. It combines with and transports molecules or ions across the plasma membrane.

active transoprt

The use of the plasma membrane carrier protein to move a molecule or ion against the concentration gradient (low to high). This can oppose equilibrium and requires cellular energy (ATP).

sodium-potassium pump

The carrier protein within the plasma membrane that specialises in moving sodium ions out of the cell and potassium into the cell. This is very important in the function of muscle and nerve cells.

exocytosis

Process in which a vesicle fuses with the plasma membrane. This results in the vesicles contents being released outside the cell.

endocytosis

The process by which substances can be moved into the cell from the environment. This can be done through Phagocytosis, pinocytosis, and receptor mediated endocytosis.

phagocytosis

A process a cell goes through to engulf a large substance. This process forms an intracellular vacuole

pinocytosis

The process by which a cell can bring macromolecules or liquids into the cell.

receptor-mediated endocytosis

The uptake of molecules into the cell through vacuole formation after binding to a specific receptor protein within the plasma membrane

extracellular matrix (ECM)

It is composed of proteins and polysaccharides. The non-living substance some animal cell secrete

What is an adhesion junction?

A junction between cells where the adjacent plasma membranes do not touch, but are held together by intracellular filaments attached in a buttonlike fashion.

What is a gap junction?

The junction between cells formed by the joining of two adjacent cell membranes, allowing ions, sugars, and other small molecules to pass between cells.

What is a junction protein?

A protein in the plasma membrane which assists in cell to cell communication.

What is a neuromuscular junction?

A region where the axon bulb approaches a muscle fiber, containing a presynaptic membrane, a synaptic cleft, and a postsynaptic membrane.

What is a tight junction?

The junction between cells where adjacent plasma membrane proteins join to form an impermeable barrier.

cel junctions

Adhesion junction: a junction between cells where the adjacent plasma membranes do not touch, but are held together by intracellular filaments attached in a buttonlike fashion Gap junction: the junction between cells which are formed by the joining of two adjacent cell membranes. This lends strength, allowing ions, sugars, and other small molecules to pass between cells. Junction Protein: a protein in the plasma membrane which assists in cell to cell communication. Neuromuscular junction: a region where the axon bulb will approach a muscle fiber. It contains a presynaptic membrane, a synaptic cleft, and a postsynaptic synaptic membrane. Tight junction: the junction between cells when adjacent plasma membrane proteins will join to form the impermeable barrier, which nothing can get through

What is the primary function of the plasma membrane?

To separate the internal cytoplasm from the external environment and allow incompatible chemical reactions to occur simultaneously.

What model describes the structure of the plasma membrane?

The fluid mosaic model.

What are the two main components of the plasma membrane?

Phospholipid bilayer and protein molecules.

What characterizes the phospholipid bilayer of the plasma membrane?

It has hydrophilic polar heads on both surfaces and hydrophobic fatty-acid tails sandwiched in between.

What are the two types of membrane proteins?

Peripheral proteins (found on the inner membrane surface) and integral proteins (partially or wholly embedded in the membrane).

How does cholesterol affect the plasma membrane?

responsible for the fluidity of the membrane.

What role do glycoproteins and glycolipids play in the plasma membrane?

They contribute to the cell's 'fingerprint' and are important for cellular identification in tissue transplantation and blood transfusions.

What are channel proteins?

Proteins that allow the passage of molecules through the membrane via a channel.

What is the function of carrier proteins?

They combine with the substance to be transported and assist its passage through the membrane.

What are cell recognition proteins?

Glycoproteins that help the body recognize foreign substances.

What do receptor proteins do?

They bind with specific molecules and allow a cell to respond to signals from other cells.

What is the function of enzymatic proteins in the plasma membrane?

They carry out metabolic reactions directly.

What are junction proteins?

Proteins that attach adjacent cells to each other.

What is the significance of the MHC glycoproteins?

They are unique to each person, making organ transplants challenging as cells with foreign MHC glycoproteins are attacked by the immune system.

What is the process of signaling in cells?

Signaling molecules serve as chemical messengers, binding to cell receptors and initiating a cascade of events that elicit a cellular response.

What is diffusion?

The net movement of molecules down a concentration gradient from high to low concentration until equilibrium is reached.

What is osmosis?

A special case of diffusion focusing on the movement of water across a selectively permeable membrane.

What is the difference between isotonic, hypotonic, and hypertonic solutions?

Isotonic: equal solute and water concentrations; Hypotonic: lower solute concentration outside the cell, causing swelling; Hypertonic: higher solute concentration outside the cell, causing cell shrinkage.

What is osmotic pressure?

The pressure that develops due to osmosis.

What is the role of aquaporins?

Specialized proteins that speed up water transport across the plasma membrane.

What is active transport?

The movement of molecules against their concentration gradient, requiring energy.

What is exocytosis?

The process of moving particles outside the cell by the fusion of a vesicle with the plasma membrane.

What is endocytosis?

The process of moving particles into the cell through vesicle formation.

What is the significance of turgor pressure in plant cells?

It is caused by swelling in hypotonic solutions, helping maintain plant structure.

What can happen to animal cells in a hypotonic solution?

They may lyse (rupture) due to excess water intake.

What causes turgor pressure in plants?

The presence of water in the vacuoles of plant cells.

What happens to animal cells placed in a hypertonic solution?

They will shrink due to water loss, a process known as crenation.

What is plasmolysis in plant cells?

It occurs when plant cells lose water in a hypertonic solution, causing the cell membrane to pull away from the cell wall.

What is facilitated transport?

The movement of molecules across the cell membrane via specific carrier proteins, following the concentration gradient without using energy.

What types of molecules typically require facilitated transport?

Glucose and amino acids.

What is the sodium-potassium pump?

An active transport mechanism that moves sodium ions out of cells and potassium ions into cells against their concentration gradients.

What is phagocytosis?

A form of endocytosis where large, solid materials are taken in by the cell.

What is pinocytosis?

A form of endocytosis where vesicles form around liquids or very small particles.

What is receptor-mediated endocytosis?

A specific form of pinocytosis that uses receptor proteins to engulf specific substances.

What is the extracellular matrix (ECM)?

A meshwork of proteins and polysaccharides that provides structural and biochemical support to surrounding cells.

What role does collagen play in the ECM?

It resists stretching and provides structural support.

What is the function of integrin in the ECM?

Integrin plays a role in cell signaling and helps cells adhere to the extracellular matrix.

What are desmosomes?

Structures that provide adhesion between cells by connecting internal cytoplasmic plaques.

What are tight junctions?

Specialized connections between cells that form impermeable barriers.

What is the function of gap junctions?

They allow communication between adjacent cells through plasma membrane channels.

What is the primary component of plant cell walls?

Cellulose.

What are plasmodesmata?

Channels that penetrate plant cell walls and allow the passage of materials between cells.

What is the fluid-mosaic model of the plasma membrane?

A model that describes the plasma membrane as a dynamic and fluid structure with various proteins embedded in or associated with a phospholipid bilayer.

What is the role of channel proteins in the plasma membrane?

They allow specific molecules or ions to cross the membrane freely.

What is the significance of cell recognition proteins?

They help the immune system recognize foreign cells, which is crucial for organ transplants.

What is the function of enzymatic proteins in the membrane?

They catalyze specific biochemical reactions, such as adenylate cyclase in ATP metabolism.

What is the role of junction proteins?

They join cells together to enable tissues to function cohesively.

What is a transduction pathway?

A series of relay proteins that ends when a protein is activated.

What happens during the response phase of a transduction pathway?

Targeted proteins bring about a cellular response.

How do inactivated receptor proteins become activated?

They get activated by attaching to signaling molecules.

What are the three types of targeted proteins involved in cellular responses?

Structural proteins, enzymes, and gene regulatory proteins.

What is the effect of structural proteins in a cellular response?

They alter the shape or movement of the cell.

What is the role of enzymes in cellular responses?

They alter metabolism or cellular function.

What do gene regulatory proteins influence?

They alter gene expression and the types and amounts of proteins produced.

What occurs during osmosis?

Water molecules move from a region of higher concentration to a region of lower concentration through a selectively permeable membrane.

What happens to an animal cell in a hypotonic solution?

Water enters the cell, which may lead to bursting (lysis).

What is the outcome for an animal cell in a hypertonic solution?

Water leaves the cell, causing it to shrivel (crenation).

What is turgor pressure in plant cells?

It develops when vacuoles fill with water in a hypotonic solution, keeping the cell firm.

What occurs in a plant cell in a hypertonic solution?

Vacuoles lose water, leading to cytoplasm shrinkage (plasmolysis).

What are the steps of the sodium-potassium pump?

1. Carrier takes up 3 sodium cations. 2. ATP is split, and phosphate attaches to the carrier. 3. Carrier releases sodium outside. 4. Carrier takes up 2 potassium cations. 5. Phosphate is released. 6. Carrier releases potassium inside.

What is the extracellular matrix in animal cells?

A structure where collagen and elastin provide support, and fibronectins assist communication between the ECM and cytoskeleton.

What is an adhesion junction?

A junction where cells are connected by cytoskeletal filaments and adhesion proteins.

What characterizes a tight junction?

Cells are held together by tight junction proteins, reducing intercellular space.

What is a gap junction?

A junction that allows communication between cells through membrane channels.

What is the main structure of the plasma membrane?

the phospholipid bi-layer. It consists of a double layer of Phospholipids, with their hydrophilic heads pointing outwards and the hydrophobic tails pointing inwards.

Describe the "fluid mosaic model" and why the membrane is described as both fluid and a mosaic.

The fluid mosaic model is used to describe the interactions between cholesterol, carbohydrates, phospholipids, and proteins within the phospholipid bilayer. The lipids in the phospholipid bilayer are responsible for the fluidity and are responsible for the flexible properties cells have. The mosaic aspect of the plasma membrane comes from the presence of proteins, both integral and peripheral

What are the major components of the plasma membrane, and what are their functions?(Phospholipids, proteins, cholesterol, carbohydrates)

The cholesterol in the membrane keeps the cell membrane from becoming too fluid or solid by stiffening at higher temperatures and not allowing the phospholipid tails to come in contact in lower temperatures. Carbohydrate chains, which are attached on the outward facing side of the plasma membrane. These are attached to lipids and proteins, making them glycoproteins and glycolipids. Carbohydrates are important for cell-to-cell recognition, meaning that they are critical in the immune system and organ transplants. The cell membrane mainly consists of phospholipids. These phospholipids are amphipathic, meaning one side is polar and the other is non-polar. They create a bilayer, with their polar heads facing outwards and the nonpolar tails facing inwards. There are a myriad of different types of proteins within the plasma membrane which can be either integral or peripheral. Different types of proteins and their function include che channel protein, which provides a channel in which a particular ion or molecule can easily pass through, a carrier protein, which will interact with a specific molecule in order to allow it to cross, the cell recognition protein, which are glycoproteins that are able to signal an immune response in the body, the receptor protein, which brings about cellular responses when a molecule is bonded to the protein, an enzymatic protein carries out metabolism through a catalysed reaction, and finally a junction protein can join cells.

Explain how the plasma membrane is selectively permeable.

it lets some substances through, but keeps others out. For example, non-charged molecules and water easily pass through the membrane while charged ions and macromolecules cannot.

What is passive transport, and what drives it?

the movement of substances across a cell membrane without the use of cellular energy. It is driven by the concentration gradient of a substance, or from a high concentration to a low concentration.

Define diffusion and give a biological example.

the movement of molecules down the concentration gradient, in other words, from a region of higher concentration to an area of lower concentration, which will continue until equilibrium is reached. Diffusion occurs during photosynthesis when carbon dioxide diffuses into a plant through stomata in the leaves. After photosynthesis is complete, oxygen diffuses out of the leaves.

Define osmosis and describe how it affects cells placed in isotonic, hypotonic, and hypertonic solutions.

the diffusion of water across the plasma membrane along the concentration gradient. It can occur across the plasma membrane when cells are placed in different solutions like isotonic, hypotonic, or hypertonic. The concentration of the solute in the solution determines what direction the water will flow.

What molecules require facilitated diffusion?

Facilitated diffusion transports molecules like glucose and amino acids across the plasma membrane.