Unit 13 - Phospholipid Bilayer

Unit 13 - Phospholipid Bilayer

What you need today:

• Pen and paper

• Take notes and write down any questions.

Questions from last week

Where is the cilia on the animal cell ?

• Cilia surround the outside of the cell

What is a centriole?

• Pairs of microtubule structures

• They controls the separation of the chromosome to form two new cells 

What makes it so that the ribosomes coat the rough ER and not the smooth ER?

• Because of the different roles they have

• Ribosomes are key to synthesis and packaging of proteins

Why does the cytoplasm allow waste products to dissolve into it?

• Waste products are also dissolved before they are taken in by vacuoles or sent out of the cell.

How do cell components affect fluid balance?

• Excellent question and we will cover this over the next few weeks

Today

Phospholipid Bilayer

Aims of today

• Cell Membranes (The Phospholipid Bilayer)

  •Structure

  •Function

  •Movement of materials

  •Protein channels 

Why are we talking about the phospholipid bilayer?

• The lipid bilayer acts as a barrier to the passage of molecules and ions into and out of the cell.

• However, an important function of the cell membrane is to allow selective passage of certain substances into and out of cells.

Poll

How are we feeling about the components of a cell?

• Good

• Ok

• Needs improvement

Cell Membranes

• Cells are bound by plasma membranes

• These act as a selective barrier (semipermeable) to substances entering and leaving the cell and interacts with both adjacent cells and the surrounding environment.

• Cell membrane are fluid and therefore damage can be repaired almost immediately 

Multiple Choice

What does semipermeable mean?

• Allowing certain substances to pass through it but not others

• Allowing all substances to pass through it.

Nuclear Membrane

• Nuclear membranes act as a selective barrier to substances entering and leaving the nucleus

• Defines the boundaries for genetic material within the nucleus 

Cell Membranes

• Membranes have the same bio chemical structure

• Composed of a double layer of phospholipid molecules, protein, cholesterol and sometimes sugars

• The double layer is often called a bilayer due to the arrangement of the molecules

Phospholipid Bilayer

• The heads are made from glycerol and a group of phosphorus and nitrogen atoms

• The tails are made from chains of fatty acids

• The head is electrically charged and often referred to as the “polar head”

• The fatty acid tails do not carry any charge

Phospholipid Bilayer

• Phospholipids contain a hydrophilic head and a hydrophobic tail

• The head is able to exist with water

• The tails like most fats do not like water

Open Ended

You have 2 minutes now to draw the head & the tail. Message 'Complete' in the answer box when done.

Water is everywhere!

• The Hydrophobic tails are trying to escape all the water.

• The Hydrophilic heads are trying to be in contact with the water.

Poll

What does Hydrophilic mean?

• Water loving

• Water hating

Phospholipid Bilayer

• Phospholipids are not bonded to each other, which makes the double layer fluid

• Hydrogen bonding of water holds the 2 layers together

• Cholesterol embedded in the membrane makes it stronger, more stable and less fluid

  (not part of the phospholipids, just next to them!)

• The Phospholipid Bilayer is both dynamic and flexible

Multiple Select

What is cholesterol's role in supporting the bilayer?

• Fluid

• More stable

• Weaker

• Stronger

Phospholipid Bilayer

• Also present are protein molecules on both the inner and outer surfaces

• Some pass all the way through the membrane and act as channels for substances moving in and out of cells or passing on messages

• Sometimes sugar chains attach (Glycolipids & Glycoproteins) and are also present with proteins to enable cells to stick together and form tissues 

Multiple Choice

What molecules help substances move in and out of cells?

• Glycolipids

• Glycoproteins

• Proteins

Tasks for you to complete

• Watch the video sent in the chat (0 to 4 minutes 38 seconds)

• Describe in your own words how the bilayer works include the following 

• •Polar Heads

  •Fatty acid tails

  •Hydrophobic & Hydrophilic Labels

  •Cholesterol

  •Protein Channels 

Resources to help

• https://www.khanacademy.org/science/high-school-biology/hs-cells/hs-the-cell-membrane/a/structure-of-the-plasma-membrane

• https://chem.libretexts.org/Courses/University_of_Kentucky/UK%3A_CHE_103_-_Chemistry_for_Allied_Health_(Soult)/Chapters/Chapter_14%3A_Biological_Molecules/14.3%3A_Phospholipids_in_Cell_Membranes#:~:text=Phospholipid%20bilayers%20are%20critical%20components,into%20and%20out%20of%20cells.

• https://www.khanacademy.org/test-prep/mcat/cells/cell-membrane-overview/a/fluid-mosaic-model-cell-membranes-article

Form submission

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