Biology: Membrane structure, Function and Transport.

How is a cell membrane different from a cell wall? Which types of cells contain cell membranes? Cell walls?

The cell membrane, also known as the plasma membrane, is a semi-permeable barrier that surrounds the cell and controls the movement of substances in and out. It comprises a lipid bilayer with embedded proteins

• present in all types of cells, including animal, plant, fungal, and bacterial cells.

• A cell wall, rigid layer, provides additional protection, support, and shape to the cell. It is located outside the cell membrane.

What are the three key components of membrane structure? What is the role of each of these?

• lipids, proteins, and carbohydrates.

• Lipids, specifically phospholipids, form the basic structure of a cell membrane.

• create a stable barrier between two aqueous compartments.

• Proteins are embedded within this lipid bilayer to allow the selective transport of molecules across it. They also play a role in signal transduction and cell recognition.

• Carbohydrates, typically attached to proteins or lipids, help in cell-cell recognition and interaction, and they may have additional roles in signal transduction.

What are glycolipids and glycoproteins? And what is their function?

• Glycolipids: Lipids with carbohydrate chains attached. They help in cell recognition and cell signaling. Interaction, recognition, communication

• Glycoproteins: Proteins with carbohydrate chains attached. They are involved in cell-cell recognition and immune response. stability of the cell membrane

Why are cells small/microscopic (with a few exceptions!)?

Cells are small to maintain a high surface area to volume ratio, allowing for efficient exchange of nutrients and waste products. Larger cells would struggle to transport materials effectively.

Which types of molecules can pass directly across the membrane? Which kinds cannot? Give examples of each?

• Molecules that can pass directly across the membrane: Small nonpolar molecules like oxygen and carbon dioxide.

• Molecules that cannot pass directly across the membrane: Large polar molecules like glucose and ions.

Understand the terms solute, solvent, and solution

• Solute: The substance being dissolved in a solution.

• Solvent: The substance doing the dissolving in a solution.

• Solution: A homogeneous mixture of solute and solvent.

• lemonade, the sugar and lemon juice act as solutes that are dissolved in water, which serves as the solvent. The resulting combination of these solutes with the solvent forms the lemonade solution.

Compare and contrast active and passive transport across membranes.

Active Transport vs. Passive Transport

• Active Transport:

  • Requires energy (ATP)

  • Moves molecules against the concentration gradient

  • Examples: Sodium-Potassium Pump

  • lower to higher

• Passive Transport:

  • Does not require energy

  • Moves molecules along the concentration gradient

  • Examples: Diffusion, Osmosis

  • higher to lower

What is diffusion?

Diffusion is the natural process by which molecules move from an area of high concentration to an area of low concentration until equilibrium is reached. perfume. When you first spray it, the concentration of the perfume molecules is highest right where you sprayed it. But soon, you'll start to smell the perfume in other parts of the room - that's because the perfume molecules are diffusing, or spreading out, from the area where they were highly concentrated (where you sprayed the perfume) to areas where they are less concentrated (the rest of the room).

What is facilitated diffusion?

Facilitated diffusion is a type of passive transport where molecules move across the cell membrane with the help of transport proteins without requiring energy input. You're the substance that must cross the membrane, the crowd is the cell membrane, and the security guard is the transport protein that assists you. Just like how the security guard uses no extra energy to help you move through the crowd, facilitated diffusion doesn't require extra energy from the cell.

What is osmosis?

Osmosis is the movement of solvent molecules from an area of low solute concentration to an area of high solute concentration through a semi-permeable membrane. magine you're at a spa day with your friends. You all decide to get those trendy gel manicures and the nail artist soaks your nails in a bowl of water before applying the gel. This is to soften your cuticles, making them easier to push back. The water molecules move from the bowl (where there's a lot of water) into your cuticles (which have less water) - that's osmosis in action! Just like the water molecules, osmosis doesn't require any extra energy and happens naturally.

TONICITY: Hypertonic vs. Hypotonic vs. Isotonic: define and describe. Remember that you are always COMPARING one thing to another in these situations.

• Hypertonic Solution: Higher solute concentration compared to another solution, causing water to move out of cells.

• Hypotonic Solution: Lower solute concentration compared to another solution, causing water to move into cells.

• Isotonic Solution: Equal solute concentration compared to another solution, resulting in no net movement of water.

Be able to identify what would happen if cells (both plant and animal) were placed in of solutions of varying tonicity.

When cells are placed in solutions of varying tonicity, they may experience changes in water movement. In a hypotonic solution, cells may swell or burst due to water entering. In a hypertonic solution, cells may shrink or shrivel due to water leaving. In an isotonic solution, there is no net movement of water.

Describe the mechanism of active transport aka how it happens

Active Transport Mechanism: Active transport is the movement of molecules across a cell membrane against their concentration gradient, requiring energy in the form of ATP. This process involves specific carrier proteins that bind to the molecules and use ATP to pump them across the membrane. Instead of letting molecules simply move from an area of higher concentration to an area of lower concentration (like in passive transport), active transport uses energy to move substances against their concentration gradient, i.e., from an area of lower concentration to an area of higher concentration.

What is bulk transport? What is the difference between endocytosis and exocytosis?

• Bulk transport is the movement of large quantities of substances across the cell membrane. It's a bit like trying to stuff a whole season's worth of clothes into your closet; they won't all fit through the door at the same time, so you need a different strategy.

• Endocytosis is the process of bringing materials into the cell, It's like the cell is opening its door and allowing the shopping bags (molecules or particles) to come in.

• exocytosis is the process of releasing materials out of the cell. In the cell, vesicles (small sacks) enclose the substances to be removed, move to the cell membrane, and then merge with it, releasing their contents outside the cell.

Can you describe the two types of endocytosis? Phagocytosis and pinocytosis?

• Phagocytosis: Cell engulfs solid particles by extending pseudopodia around them. Like when you walk into a store and fall in love with an entire outfit on display. You decide you need to have all of it - the dress, the shoes, the bag, the accessories - everything! In the cellular world, phagocytosis is a bit like this. It's the process the cell uses to 'swallow' large particles or even whole cells. It's like the cell is opening its door wide and taking in the entire outfit

• .Pinocytosis: Cell engulfs liquid or small particles by invaginating its membrane. In the cell, pinocytosis is the process the cell uses to take in small particles or liquids. It's like the cell is just browsing, taking in small 'sips' of the surrounding environment.

Labs: Be able to answer questions regarding the Egg Osmosis Lab.

The corn syrup was hypotonic because the water molecules it held was a smaller amount than the amount the egg held. This leads to the diffusion of water molecules flowing out of the egg and into the corn syrup.

Phospholipid

Forms the bilayer that functions as a barrier

Cholesterol

Prevents bilayer from solidifying when the temp goes down and prevents excessive fluidity when temp goes up

Glycolipid

Cell: cell recognition/ surface identifiers

Glycoprotein

Cell: surface receptors/ identifiers

İntegral protein

Transport enzymes, signal transduction, attach the cytoskeleton

Peripheral protein

Enzyme, signal transduction