Chapter 4: Membrane structure and function

phospholipid bilayer, active transport, facilitated transport, osmosis, integral proteins, peripheral proteins

What is the fluid-mosaic model?

The fluid-mosaic model describes the structure of cell membranes a mosaic of protein molecules embedded in a fluid bilayer of phospholipids

True or false

phospholipids give the membrane fluidity. The phospholipids themselves move within the bilayer

True, allowing for flexibility and self-healing properties.

can protiens drift w/in the bilayer

Do lipids in the bilayer remain fluid at lower temperatures?

if the phospholipids has unsaturated tails then they stay liquid

What does the cholesterol do in animal bilipid layers?

Cholesterol helps to stabilize the fluidity of the cell membrane, preventing it from becoming too rigid at lower temperatures and too fluid at higher temperatures.

A type of protein found int he bilayer is an integral protein. what is an integral protein?

transmembrane proteins w/ a hydrophobic region that spans the membrane

what are integral proteins?

proteins that only protrudes on one side pf the phospholipid bilayer

can membrane proteins move in the lipid bilayer?

Yes, membrane proteins can laterally move within the lipid bilayer, contributing to membrane fluidity and functionality.

What are some of the membrane protien functions?

transport, enzymatic activity, signal transduction, cell-to-cell recognition, intracellular joining, attachment to cytoskeleton extracellular matrix

What is the function of carbohydrate in the plasma membrane?

Carbohydrates in the plasma membrane play key roles in cell recognition, signaling, and adhesion, often forming glycoproteins and glycolipids that interact with other cells and the extracellular environment.

True or false

membranes surfaces are asymmetrical. The membranes have distinct insides and outsides . That is to say that the apical side is different from the basolateral side

True, membranes are asymmetrical, with different compositions and functions on each side.

Are there carbohydrates in the intracellular portion of the plasma membrane?

No, carbohydrates are primarily found on the extracellular surface of the plasma membrane, contributing to cell recognition and signaling.

Fill in the blank

there are some oligosaccharides covalently bonded to lipids these are called ______. there are some bounded to proteins these are called ______.

glycolipids; glycoproteins

what kind of permeability does the phospholipid bilayer have?

The phospholipid bilayer is semi-permeable, allowing certain substances to pass through while restricting others.

What substances easily pass through the lipid bilayer?

Small nonpolar molecules such as oxygen and carbon dioxide can easily diffuse through the lipid bilayer. and nonpolar molecules: lipids, CO2, O2, very small polar but uncharged molecules (water and ethanol)

How do polar or ions cross through the pm?

Polar molecules and ions typically cross the plasma membrane through specific protein channels or transporters, as they cannot easily pass through the lipid bilayer due to their charge or polarity.

what is passive transport?

Passive transport is the movement of substances across a cell membrane without the use of energy, relying on concentration gradients to facilitate the process. diffusion is a primary method of passive transport, where molecules move from an area of higher concentration to an area of lower concentration.

What is facilitated diffusion?

Facilitated diffusion is a type of passive transport that utilizes specific proteins to help move molecules across the plasma membrane from an area of higher concentration to an area of lower concentration, without requiring energy.

what is osmosis?

Osmosis is the process by which water molecules move across a selectively permeable membrane from an area of lower solute concentration to an area of higher solute concentration until equilibrium is reached.

Match the terms and the definition

hypotonic

hypertonic

isotonic

high solutes

low solutes

equilibrium

Hypotonic solutions have lower solute concentration compared to another solution, hypertonic solutions have higher solute concentration, and isotonic solutions have equal solute concentration. In osmosis, water moves towards high solute areas until equilibrium is reached.

what happens to the an animal cell in a hypotonic, hypertonic, and isotonic environment?

In a hypotonic environment, an animal cell swells and may burst due to water influx; in a hypertonic environment, it shrinks as water exits; and in an isotonic environment, the cell remains stable with no net movement of water.

what happens to the a plant cell in a hypotonic, hypertonic, and isotonic environment?

In a hypotonic environment, a plant cell becomes turgid as water enters, maintaining structural integrity; in a hypertonic environment, it undergoes plasmolysis and shrinks; in an isotonic environment, it remains flaccid with no significant water movement.

what is active transport?

A biological process that moves molecules across a cell membrane from an area of lower concentration to one of higher concentration, often using energy in the form of ATP.

what is cotransport?

the transport of a specific solute indirectly drives the active transport of other solutes.

How are large molecules such as proteins and polysaccharides transported outside of the cell?

Large molecules are transported outside the cell via exocytosis, a process where vesicles fuse with the plasma membrane, releasing their contents into the extracellular space.

what are the different types of endocytosis?

Endocytosis is the process by which cells internalize substances from their external environment, primarily through phagocytosis, pinocytosis, and receptor-mediated endocytosis.

what is pinocytosis?

a type of endocytosis where the cell engulfs small particles and liquids, forming vesicles.