Phospholipids

Cell Membrane

Gateway to the cell

Multiple Choice

Plasma membranes are made of these molecules. (Check your notes from Tuesday)

• Hydrolipids

• Ionlipids

• Oxylipids

• Phospholipids

Phospholipids

• Membrane is made of phospholipds

• The head of the phospholipid likes water

• The tail of the phospholipid hates water

• When placed in a liquid they form a lipid bilayer

• The heads face the water and the tails face one another

Multiple Choice

What forms when phospholipids are placed in liquid?

• Phospholipid Monolayer

• Phospholipid Dilayer

• Phospholipid Bilayer

• Phospholipid Quadlayer

Proteins

In addition to the lipids there are proteins within the cell membrane. These proteins serve several functions. Receptor proteins enable a cell to sense its surroundings and communicate with other cells. Transport proteins aid in the movement of substances in and out of the cell.

Multiple Choice

What are the functions of the proteins found in the cell membrane?

• Transport and Communication

• Protection and support

• Photosynthesis and Cellular Respiration

• Protein Synthesis

Carbohydrates

Another piece of the cell membrane is carbohydrates.  Carbohydrates form cellular markers or ID tags that allow cells to recognize each other.  In humans, immune cells can tell the difference between body cells and foreign cells they should attack.

Multiple Choice

What is the function of a carbohydrate in the cell membrane?

• Transport

• Cellular Recognition

• Communication

• Defence

Cholesterol

In the cell membrane cholesterol helps keep the cell membrane fluid. It will also reduce the permeability of the membrane by increasing the packing of the phospholipids.

Multiple Choice

Most of the time you hear it is best to lower cholesterol. Why does the body need some cholesterol?

• To regulate the permeability of the cell membrane.

• To control passage of materials in and out of the cell

• So cells can recognize one another.

• So cells can talk to one another

Homeostasis

• A balanced internal environment or condition

• All cells must maintain homeostasis

• Also called equilibrium

• Maintained by the plasma membrane controlling what enters and leaves the cell

The importance of Homeostasis

• Many chemical reactions necessary for life only happen within a narrow range of conditions

• Photosynthesis occurs best between 50 - 68 degrees

• Cellular respiration cannot occur if the body temperature gets too high

• Proteins fall apart if the temperature gets too high and they slow down if the temperature gets too low

Multiple Choice

Why is it important for all cells to maintain homeostasis?

• Photosynthesis can only happen between 98-100 degrees

• Necessary reactions happen within a narrow range of conditions

• Necessary reactions happen within a broad range of conditions

• Cellular respiration does not happen in all cells

Multiple Choice

Based on this graph and the fact that proteins fail to function if the temperature is too high or too low what type of molecule is an enzyme?

• Protein

• Phospholipid

• Lipid

The membrane is selectively permeable

• Permeable = allowing substances to pass through

• The cell membrane allows the passage of some molecules or ions and inhibits, or prevents, the passage of others.

Multiple Choice

Why would the cell want to select what enters and/or leaves?

• Don't let organelles or cytoplasm out

• Don't let toxins or waste products in

• Don't let organelles out and don't let toxins in

• Keep everything out

• Keep everything in

Multiple Choice

Why is it important for the membrane to be able to move like a fluid?

• Allows molecules to move to where they are needed within the membrane

• Allows single celled organisms to move

• Enables the membrane to easily repair itself

• All of these

The fluid mosaic model

The cell membrane is said to be a fluid mosaic.  Fluid = individual phospholipids and proteins can move side-to-side within the layer, like a liquid.  Mosaic = the pattern produced by the scattered protein molecules looks like a mosaic when viewed from above.

Solubility

• The ability of a substance to dissolve in a solvent (usually a liquid)

• Materials that are soluble in lipids (fat) can easily pass through the cell membrane

• Oxygen, Carbon Dioxide, and water can easily pass through the membrane.

• 
  

Multiple Choice

Which of the following processes requires carbon dioxide and water?

• Photosynthesis

• Cellular Respiration

Multiple Choice

What does Photosynthesis produce?

• Oxygen

• Glucose

• ATP

• Oxygen and Glucose

• Glucose and ATP

Photosynthesis Reminder:

Oxygen is produced during the Light Reactions when water is split for the Electron Transport Chain. Even in the dark photosynthesis can continue though! Glucose is produced in the Calvin Cycle which does not require light energy to happen.

Multiple Choice

How would photosynthesis be impacted if a plant were kept in the dark?

• No impact

• No O2 production, Glucose still produced

• No Glucose production, O2 would still be produced

• Photosynthesis would stop

Multiple Choice

Which cellular process requires oxygen and glucose?

• Photosynthesis

• Cellular Respiration

Multiple Choice

What does cellular respiration produce?

• Water

• Carbon Dioxide

• ATP

• All of these

Multiple Choice

Which reaction in cellular respiration produces the most ATP?

• Glycolysis

• Krebs Cycle

• Electron Transport Chain

• All of these

Insoluble molecules

• Ions (charged molecules) and large molecules (such as Glucose) can't move through the membrane on their own.

• These substances must pass through the membrane via a transport protein

• 
  

Multiple Choice

Glucose is a large carbohydrate that must pass through the membranes of several organelles. Which organelle produces glucose?

• Mitochondria

• Nucleus

• Endoplasmic Reticulum

• Chloroplast

Multiple Choice

Where within the cell is glucose broken down into pyruvate?

• The cytoplasm

• The mitochondria

• The golgi

• The chloroplast

Cellular Respiration Reminder:

Glycolysis, which breaks down Glucose, is anaerobic. It can happen without oxygen being present.

Multiple Choice

How much ATP can be produced through anaerobic respiration (Glycolysis)?

• 2

• 4

• 1

• 6

Multiple Choice

After glycolysis where do the pyruvate go for the Krebs Cycle?

• The cytoplasm

• The mitochondria

• The golgi

• The chloroplast

Cellular Respiration Reminder:

The Krebs Cycle, and the Electron Transport Chain, do require oxygen to occur. They are aerobic.

Multiple Choice

What processes occur in a cell performing cellular respiration without oxygen?

• Glycolysis and Fermentation

• Fermentation and Krebs Cycle

• Glycolysis and Krebs Cycle

• Krebs Cycle and ETC

An intro to cell transport:

• In order to maintain homeostasis cells must transport material in and out all the time

• Passive transport requires no energy from the cell. Materials simply flow across the membrane via simple or facilitated diffusion.

• Facilitated diffusion requires a protein. Simple diffusion happens through the phospholipids.

• Active transport requires the cell to use energy and pump materials across the membrane. Requires a protein.

Multiple Choice

What molecule does the cell use for energy to perform active transport?

• Glucose

• ATP

• Carbon Dioxide

• Oxygen

Multiple Choice

Molecules that can simply diffuse through the membrane pass through which structure?

• Proteins

• Carbohydrates

• Phospholipids

• Cholesterols

Multiple Choice

Molecules that move via facilitated diffusion or active transport must pass through which structure?

• Proteins

• Carbohydrates

• Phospholipids

• Cholesterols