A molecule that can pass though the cell membrane.

Transcription

1 Cell Membrane All cells and most organelles are surrounded by a protective barrier known as the cell membrane, aka the plasma membrane. Section of a cell membrane It is mostly made of phospholipids (fats). 1. WHat is another name for a cell membrane? 2. What is a cell membrabe mostly made of? 3. Draw a phospholipid. 4. How many layers of phospjolipids do you see? 5. What other srtuctures can be found in a cell membrane besides phospholipids? HOMEOSTASIS Cell membrane The cell membrane help maintain homeostasis (stable internal balance) by regulating what enters and leaves the cell. The cell membrane keeps the cell in BALANCE. A molecule that can pass though the cell membrane. 1. The box represents a cell surrounded by a cell membrane. This cell is NOT in balance, which may lead to a state of disease. What would the cell membrane have to do to maintain cell s homeostasis? 2. What would the cell look like AFTER it gained its balance back?...draw the cell.

2 Selectively Permeable The cell membrane is selectively permeable meaning it picks and chooses what can pass through, while blocking other substances. It is called a Gatekeeper. Glucose Oxygen Cell Membrane 1. Why is the cell membrane called a Gatekeeper? 2. What molecules in the picture can pass DIRECTLY through the plasma membrane? 3. What molecules are NOT allowed to move across the cell membrane?... Why? Simple Diffusion The movement of substances directly through the plasma membrane from the area of their HIGH concentration to the area of their LOW concentration WITHOUT of use of energy (ATP). Molecules move across the membrane WITH the concentration gradient (from High to Low). 1. Describe how the molecules in the picture move by simple diffusion. 2. Does this type of transport require energy?

3 OSMOSIS The diffusion of WATER molecules through a selectively permeable membrane from region with a LOT of water molecules to a region with FEWER (less) water molecules. 1. Examine the picture of the cell. The red Structures are water molecules. Where is MORE Water, inside or outside the cell? 2. Based on what you know about the movement of water, which direction will water move in order for the cell to maintain homeostasis? Why? Facilitated Diffusion The glucose molecules cannot diffuse across the membrane directly between phospholipds because they are too big. These molecules need a facilitator, a carrier protein. Glucose molecules 1. Why is the facilitated diffusion called facilitated? 2. What is the role of the CARRIER PROTEIN? 3. Examine the picture. How do molecules move across the membrane, from the area of their HIGH to the area of their LOW concentration OR Low to High? Protein Carrier

4 Passive Transport 1. Why is the passive transport called PASSIVE? HIG LOW 2. Examine the picture of the diffusion. Why is diffusion considered a PASSIVE transport? Active Transport 1. Why the active transport called ACTIVE? HIGH LOW 2. Examine the picture on the right. Why does this picture represent active transport?

5 Concentration The amount of SOLUTE (ex. Salt) dissolved in a given amount of SOLVENT (Ex. Water). The more solute in a solution the more concentrated it is. The less solute in a solution the less concentrated it is and it is said to be DILUTE. 1. Which of the two pictures show a concentrated A B solution? How do you know? 2. Which one shows a dilute solution? How do you know? 3. What do the red dots represent? Concentration Gradient Gradient describes a continuously changing difference between neighboring regions. If you are to use only ONE word to describe the word gradient, what word would that be?

6 Solute A substance is being dissolved in a solvent. Example of a solute: Salt 1. Examine the picture. What kind of solute is being dissolved in a beaker? 2. What does pure water represent? 3. What is the result of dissolving a solute in a solvent? Solvent A substance that does the dissolving. Example of a solvent: Water 1. Examine the picture of the beaker with a sugar solution. What ingredients were used to make this solution? 2. What is the solvent in this solution? 3. What is the solute?

7 Solution A solution is a homogeneous mixture. It consists of two parts: SOLUTE + SOLVENT. The solute is dispersed uniformly throughout the solvent. 1. What is a solution made of? 2. What type of mixture is a solution? 3. What kind of solution is made in the picture? 4. What is the solute used? Solvent? Dynamic Equilibrium Cells want equilibrium!... The equilibrium is reached when molecules spread out EVENLY on both sides of a cell membrane. Note: Molecules continue to move BACK and FORTH across a cell membrane, but the concentrations do not change. The picture above represents a cell placed in water. What would the picture look like when the equilibrium is reached? Draw the final picture.

8 Moving WITH (or down) a concertation gradient The transport of substances from the area of HIGH to the area of LOW concentration without the expenditure of energy (ATP) 1. How many molecules do you see inside the cell? 2. How many molecules do you see outside the cell? 3. Where do molecules move, INTO the cell or OUT the cell?...why? 4. How would you describe this movement of molecules across the membrane, with the flow or against the flow? 5. Is the energy required? Inside the cell Outside the cell Moving AGAINST (or up) a concertation gradient The transport of substances from the area of LOW to the area of HIGH concentration WITH the expenditure of energy (ATP). 1. How many molecules do you see inside the cell? 2. How many molecules do you see outside the cell? 3. Where do molecules move, INTO the cell or OUT the cell? 4. Do molecules move across the membrane WITH or AGAINST the flow? Inside the cell 5. Does this movement require energy?. Why? against Outside the cell

9 PERMEATE Cell membrane 1. Examine the picture and describe the meaning of the word PERMEATE in your own words. 2. What substances are permeable to the cell membrane (yellow or red)? 3. What substances are impermeable to the cell membrane (yellow or red)?