Bio 156 Chapter 4

hydrophillic

having a tendency to mix with, dissolve in, or be wetted by water.

What will happen to a red blood cell placed in a hypotonic solution?

swell and possibly lyse (disintegrate)

hydrophobic

tending to repel or fail to mix with water. Non polar.

Label cell membrane parts.

Phospholipids form the basic structure of a cell membrane, called the lipid bilayer. Scattered in the lipid bilayer are cholesterol molecules, which help to keep the membrane fluid consistent. Membrane proteins are important for transporting substances across the cell membrane

what will happen to a red blood cell if placed in an isotonic solution?

Remain the same. This is the ideal environment.

What will happen to an plant cell placed in an isotonic solution?

become flaccid (limp)

What will happen to an plant cell placed in an hypotonic solution?

becomes turgid (swollen)

osmoregulation

the maintenance of constant osmotic pressure in the fluids of an organism by the control of water and salt concentrations.

what is meant by a concentration gradient?

the process of particles, which are sometimes called solutes, moving through a solution or gas from an area with a higher number of particles to an area with a lower number of particles. The areas are typically separated by a membrane

solute

the substance that is being dissolved (salt/sugar)

Name and describe 4 kinds of membrane proteins and explain what they do. (membrane transport proteins are major drug targets )

1. integral Protein - integrated throughout the entire membrane and really tough to remove. Passive transport. Integral membrane proteins enable ions and large polar molecules to pass through the membrane by passive or active transport. a. channel protein - allows outside extracellular to pass through the cell by its concentration gradient; it doesn't require energy or ATP. They can also do the reverse. Ex. if we have too much sodium and we need to get rid of it, channel proteins pump it out. No energy is needed/ATP. They go with the concentration gradient (down a concentration gradient) b. Carrier Protein - carries substances into the cell. So, if there is a molecule outside the cell and we need that molecule, the carrier protein will protect this substance so that it can enter the cell safely. It can also do this in reverse. Unlike Channel Proteins, Carrier Proteins can go against the concentration gradient. Sometimes use energy/ATP 2. peripheral proteins - its on the outside of the cell membrane and really easy to remove. Ex. hormone protein ***the difference is that Integral Proteins are stuck inside the cell membrane and as a result it is very difficult to remove. Peripheral Proteins attach and remove themselves from their cell membrane or from other proteins, such as the hormone; it goes in, makes something happen and leaves. They can also exist inside the cell. 3. Lipid bound protein - so rare and difficult to find. Why? because proteins are preset to interact with the environment and lipid bound are stuck on the interior. Cant interact with inside or outside of cell. 4. Glyoprotein - can exist on any of these. Chain of sugars attached to a any protein. Glyco means sugar. ITs sugar plus protein. Function is signaling; it allows a cell to recognize another cell.

phospholipid bilayer

A phospholipid is a lipid made of glycerol, two fatty acid tails, and a phosphate-linked head group. The bilayer is a thin polar membrane made of two layers of lipid molecules. These membranes are flat sheets that form a continuous barrier around all cells.

Explain the mechanism by which substances move across membranes against a concentration gradient.

Active transport allows a cell to maintain concentrations of small molecules that are different from the concentrations of its surroundings. For example, an animal cell has a higher concentration of potassium ions (K+) and a lower concentration of sodium ions (Na+) than the solution outside the cell. The generation of nerve signals depends on these concentration differences, and the sodium-potassium pump helps cells maintain these steep gradients by shuttling Na+ and K+ across the membrane.

describe how large substances can be imported into or exported from a cell by being wrapped into a membrane

As illustrated in Figure 5.19A, a cell uses the process of exocytosis (from the Greek exo, outside, and kytos, cell) to export bulky materials. In the first step of this process, a membrane-enclosed vesicle filled with macromolecules (purple) moves to the plasma membrane. Once there, the vesicle fuses with the plasma membrane, and the vesicle's contents spill out of the cell. When we weep, for instance, cells in our tear glands use exocytosis to export a salty solution containing proteins. In another example, certain cells in the pancreas manufacture the hormone insulin and secrete it into the bloodstream by exocytosis. In endocytosis (endo, inside), a cell takes in macromolecules or other particles by forming vesicles or vacuoles from its plasma membrane. Figure 5.19C shows three kinds of endocytosis. The left micrograph shows an amoeba taking in a food particle, an example of phagocytosis, or "cellular eating." The amoeba engulfs its prey by wrapping extensions, called pseudopodia, around it and packaging it within a vacuole. As Module 4.10 described, the vacuole then fuses with a lysosome, and the lysosome's hydrolytic enzymes digest the contentsThe center micrograph shows pinocytosis, or "cellular drinking." The cell is taking droplets of fluid from its surroundings into tiny vesicles (arrows). Pinocytosis is not specific; it takes in any and all solutes dissolved in the droplets. In contrast to pinocytosis, a third type of endocytosis, called receptor-mediated endocytosis, is highly specific. The micrograph on the right shows one stage of the process. The plasma membrane has indented to form a pit. The pit is lined with receptor proteins that have picked up particular molecules from the surroundings. The pit will pinch closed to form a vesicle that will carry the molecules into the cytoplasm.

Explain the forces behind the passive diffusion across membranes

Because a cell does not perform work when molecules diffuse across its membrane, the diffusion of a substance across a biological membrane is called passive transport. Passive transport is extremely important to all cells. In our lungs, for example, passive transport down concentration gradients is the sole means by which oxygen (O2), essential for metabolism, enters red blood cells and carbon dioxide (CO2), a metabolic waste, passes out of them.

distinguish between passive transport and active transport

Both use ion channels to move ions across the cell membrane, in or out of the cell. Differences: Passive Transport (or Diffusion) moves ions from high concentration to low, using no metabolic energy. Active Transport moves ions from low concentration to high, using metabolic energy in the form of ATP.

Passive transport

Diffusion - Requires no energy to move molecules down their concentration gradient (from high to low concentration). require membrane transport proteins. Channel proteins

why do molecules passively move down concentration gradients?

Facilitated diffusion. ... A concentration gradient exists for these molecules, so they have the potential to diffuse into (or out of) the cell by moving down it. However, because they are charged or polar, they can't cross the phospholipid part of the membrane without help.

Describe the importance of osmosis to all cells

Osmosis is the diffusion of water across a membrane from a solution of lower solute concentration to one of higher solute concentration (5.16). Osmosis causes cells to shrink in a hypertonic solution and swell in a hypotonic solution. In isotonic solutions, animal cells are normal but plant cells are limp. The control of water balance is called osmoregulation (5.17)

Describe an amoeba feeding by phagocytosis

Recognition. Engulfment. Digestion. Expulsion Phagocytosis, process by which certain living cells called phagocytes ingest or engulf other cells or particles. The phagocyte may be a free-living one-celled organism, such as an amoeba, or one of the body cells, such as a white blood cell.

Active transport

Requires energy and carrier proteins to move molecules down or against their concentration gradient. require membrane transport proteins

Osmosis

The diffusion of water across a selectively permeable membrane

Predict the direction of water movement based upon differences in solute concentration

The direction of water movement based on differences on solute concentrations depends on how the water diffuses down its own concentration.

what causes diffusion and why is it a spontaneous event?

The main cause of diffusion is the continuous movement (or kinetic energy) of atoms in matter. Why is it spontaneous? since one solute is independent of the concentration gradients of other solutes and because it involves a passive transport process, which implies that energy is not expended when substances diffuse down their concentration gradient.

phospholipids bilayer

The phospholipid bilayer consists of two layers of phospholipids, with a hydrophobic, or water-hating, interior and a hydrophilic, or water-loving, exterior. The hydrophilic (polar) head group and hydrophobic tails (fatty acid chains) are depicted in the single phospholipid molecule.

describe the fluid properties of the cell membrane

The plasma membrane is a fluid combination of phospholipids, cholesterol, and proteins. Carbohydrates attached to lipids (glycolipids) ...and to... proteins (glycoproteins) extend from the outward-facing surface of the membrane.

Describe the essential structure and function of the cell membrane

The primary function of the "plasma membrane" is to protect the cell from its surroundings. It is selectively permeable! In all cells is composed of a phospholipid bilayer with embedded proteins, the plasma membrane is selectively permeable to ions and organic molecules and regulates the movement of substances in and out of cells. Bipolar nature of the molecule is the key to how the membranes work. Each phospholipid molecule has a hydrophilic head region (phopho portion) and a hydrophobic tail region (lipid portion). What gives a membrane its shape? It is the way the phospholipids arrange themselves.

hypertonic

a solution that contains a higher concentration of solutes (remember when someone is hyper, they seem to have MORE energy).

hypotonic

a solution that contains a lower concentration of solutes (remember hypo rhymes with low)

Isotonic

a solution that contains an equal concentration of solute and solvent

channel proteins (transport Proteins)

act as a channel for water soluble molecules to pass by facilitated diffusion. Passive transport

fluid mosaic model

describes the plasma membrane as a fluid combination of phospholipids, cholesterol, and proteins. Carbohydrates attached to lipids (glycolipids) and to proteins (glycoproteins) extend from the outward-facing surface of the membrane.

distinguish between exocytosis and endocytosis

important for the import/export of large molecules. Endocytosis is the process of capturing a substance or particle from outside the cell by engulfing it with the cell membrane, and bringing it into the cell. Via vesicles or vacuoles. Exocytosis the movement of materials out of the cytoplasm of a cell via membranous vesicles or vacuoles.

carrier proteins (pumps)

proteins that use ATP to actively transport molecules across a membrane from a lower concentration to a higher concentration. Passive and active transport.

solvent

the liquid that is doing the dissolving (usually a liquid, but can sometimes be a solid or gas)

diffusion

the movement of particles from an area of high concentration to an area of low concentration. This process allows molecules that are small and lipophilic (lipid-soluble), including most drugs, to easily enter and exit cells.

facilitated diffusion

uses integral membrane proteins to move polar or charged substances across the hydrophobic regions of the membrane polar and charged molecules, such as carbohydrates, amino acids, nucleosides, and ions.