Discover Biology: Chapter 4

Pinocytosis

"Cell drinking" the plasma membrane is not selective about what it brings in.

Phagocytosis

"Cell eating" : When a single white blood cell engulf an entire bacteria or yeast.

What are some examples of molecules that are too large to pass freely through the cell membrane?

- Sugars -amino acids - nucleotides

Diffusion Concepts - equilibrium? -What does heat do for equilibrium? - Difference between small and large substances (atoms and molecules )?

1. Equilibrium is when a substance is evenly distributed. No concentration difference. 2.Heat makes reaching equilibrium quicker because there is more ENERGY available

1.Signaling Molecules 2.Target Cells 3. Receptor proteins

1. Ions or small molecules, or larger proteins that are released 2. The target cell senses the released signaling cell usually through receptor proteins Most signaling molecules are short lived, though some lie for a few days

Concept Check: 1. Why cant ions such as NA+ move across the phospholipid bilayer unassisted? 2. Compare channel proteins and carrier proteins.

1. NA+ is hydrophilic, so it can't cross the hydrophobic bi-layer. 2. Channel proteins = open tunnel, does not require energy inpput Carrier proteins = revolving door, can be both active and passive ------- passive requires ATP or other energy source.

Concept Check 1. Compare osmosis and simple diffusion 2.Is your blood hypertonic, hypotonic or isotonic?

1. Osmosis is a special kind of simple diffusion. It refers specifically to the movement of water from a region of low solute to a region of higher solute concentration. 2. Blood is isotonic. Iso = equal

Concept Check: 1. What is meant by the selective permeability of biological membranes? 2. How is passive transport different from active transport in cell membranes?

1.Selective permeability refers to whether of not a substance can move through the phospholipid bilayer freely or not. 2. Passive transport happens spontaneously, as substances move down the concentration gradient. Active transport would be against the concentration gradient and woule require energy.

Concentration gradient

A difference in concentration between two regions. molecules may be unevenly distributed in a substance. kool aide mixed in water

Channel Proteins

Allow certain substances that are just the right size and just the right charge to move through the plasma membrane. They form a tunnel that spans the width of the plasma membrane! A calcium channel only allow calcium ions to flow across, and not potassium ions!

Anchoring junctions Tight Junctions Gap junctions

Anchoring junctions: Link cells together so they can collectively brace against forces that might rupture a single cell Tight Junctions: Light grout in bathroom tile ---- formed between adjacent cells to keep substances out Gap junction: allow direct connections between cells to exchange ions/signaling molecules ---- rapid communication between brain cells and heart muscles is very important

Transport Vesicle

Can move molecules around inside a cell, and also move molecules into and out of a cell through the plasma membrane

What is a hypotonic solution?

Cells gain water: A hypotonic solution is one in which more water flows into the cell than out of it. The external medium has a lower solute concentration Hyper = more, too many, too much Hypo = less, fewer, not enough Iso = equaly

Hypertonic solution

Cells lose water: total solute concentration outside exceeds total solute concentration inside

Exocytosis

Cells release substances into their surroundings. A transport vesicle fuses with the plasma membrane and then releases its cargo. (Inside of transport vesicle is called the LUMEN) - When we eat a sugary snack, the pancreas releases insulin via exocytosis, signaling other cells to take up the glucose released from the snack.

How is cystic fibrosis connected to channel proteins?

For people with cystic fibrosis, they are missing a specific channel protein that transports chloride ions across the membrane ---- so salt build up, causing health problems

What moves more easily through cell membranes, hydrophobic molecules or hydrophilic molecules?

Hydrophobic molecules move more easily through cell membranes because the mix more easily with the hydrophobic core of the phospholipid bi-layer.

Plasmodesmata

Like gap junctions, but in plants ---- allow for rapid flow of water, ions an molecules between plant cells.

Do substances such as sodium and potasium, with electrical charges, pass easily through cell membranes?

No, these substances are HYDROPHILIC, so they are repelled by the HYDROPHOBIC interior of the phospholipid bilayer. So, they would need transport proteins to get across

The sodium potassium pump

One of the most important active carrier protiens in our cells. There is a lot of sodium in our bloodstream, and little potassium. In our cells, the situation is reversed, with high potassium and low sodium. The sodium potassium pump maintains the right balance.

What is Osmosis? ( Is it an active or a passive process? What drives the process?

Osmosis is the diffusion of water across a selectively permeable membrane. (from a region of lower solute concentration to a region of higher solute concentration). - a type of diffusions - a passive process - concentration differences drive the process

Pond dwelling protist such as paramecium take up water by osmosis. The concentration of water molecules outside the pramecium is higher than it is inside, driving water into the cell. Why is the concentration higher inside?

Paremecium have load of other SOLUTES inside their cytosol, so there is less water in there ------ creates diffusion of water from area of high to low concentraiton.

Diffusion

Passive transport of a substance from a region of high concentration to a region of lower concentration. -Energy is required to move a substance from an area of low concentration to an area of high concentration. Example: Food coloring going into water. The food coloring, through a passive process, will move from areas of high concentration to areas of low concentration.

What is the difference between active carrier proteins and passive carrier proteins?

Passive= moving substances down a concentration gradient active carrier proteins (membrane pump)= moving against a gradient with the aid of ATP or other energy source GLUCOSE generally moves into a cell passivel. There is much more of it in the bloodstream than in the cytoplasm

signal transduction pathway

Plasma membrane receptors bind their signaling molecule at the cell surface and must then relay receipt of the molecule to the cytoplasm ---- signaling molecules may need to cross the membrane and enter the nucleus (hormones are generally hydrophobic, so the can cross the membrane)

Receptor mediated Endocytosis

Receptor proteins (in the plasma membrane) determine what will be incorportated into the transport vesicle that arise in a membrane - LDL cholesterol is taken in

Plasma Membrane

Separates the inside of the cell from the environment outside of it -Has a phospholipip bi-layer that has many proteins which serve different fuctions.

What is simple diffusion? What are some elements that can move freely into and out of cells through passive diffusion?

Simple diffusion is when substance move in and out of cells passively ----- particularly true of small molecules like oxygen and carbon dioxide.

how do carrier proteins get ions/amino acids/ sugars/nucleotides across the membrane?

The bind with them (into specific folds in the protein) on one side and then release them on the other side

Cytoplasm

The liquid inside a cell. The inside of a cell will be quite different than the outside.

Selective Permeability

The membrane must allow some molecules and ions to pass through and some most be kept out - some thing like oxygen molecules can pass freely in and out. - some things require a transport protein to get through the membrane

Endocytosis

The opposite of exocytosis

Passive transport Vs Active transport

This describes the movement of material across the cell membrane. Some material require an input of energy to get across the membrane (like pushing a ball up a hill). Some material passes freely (like pushing a ball down a hill).

Osmosis is described with reference to the concentration of solutes rather than the concentration of water molecules, which are the solvent. What is the difference between a solvent and a solute?

Water is called the universal solvent. Many things can dissolve in it. A solute is something that is dissolved in in a so solvent.

What is facilitated transport?

When membrane proteins move a substance across the membrane. Channel proteins and carrier proteins

aquaporins

allow water to move rapidly across the plasma membrane ---- a kind of transport protein

Isotonic solution

equal concentration inside and out

neurotransmitters

fast acting signaling molecules released by nerve cells

What substances need help moving across the plasma membrane?

ions, polar molecules, and larger molecules (sugars, amino acids) need help getting through

hormones

long lasting signaling molecules such as testosterone and estrogen that can act over long distances

Transport Proteins

provide pathways for material to leave or enter a cell