2.3.1: Transport Across Membranes - Phospholipids and Membrane Structure

Flashcards made from this slideshow: https://docs.google.com/presentation/d/1iH8N7JguBMza9oPIu4MahkWu2Rosq7wLRoh-j1AWu2o/edit#slide=id.g30956a8a0d6_0_2850

Describe the structure of a triglyceride (include equation)

Describe the structure of a triglyceride (include equation)

• Glycerol head and 3 fatty acids joined by an ester bond

Glycerol + 3 fatty acids → triglyceride + 3 water

What are the main functions of a cell surface membrane?

• it is partially permeable so it controls what enters and leaves the cell

• It separates the cell contents from the external environment

What else do membranes do?

• Separate cell components from cytoplasm

• Involved in cell recognition

• Hold some of the components in some metabolic pathways in place

Describe the structure of a phospholipid

Head:

• polar

• hydrophillic

• contains a phosphate group

Tails:

• non-polar

• hydrophobic

• only two tails instead of 3 like there would be on a triglyceride

Differences between polar and non polar

Polar:

• charged

• hydrophillic

• water-soluble

• e.g. H₂O, glucose/amino acids, H⁺/Na⁺/Cl^-

Non-polar:

• uncharged

• hydrophobic

• lipid-soluble

• e.g. O₂, CO₂

Label this diagram

A - Phospholipid

B - Proteins

C - Cholesterol

D - Glycolipid

E - Glycoprotein

F - Channel protein

G - Receptor protein

H - Carrier protein

I - Phospholipid bilayer

What is the sturcture of cholesterol?

Occur within phospholipid bilayer of cell-surface membrane.

Very hydrophobic (prevent loss of water and dissolved ions)

What is the function of cholesterol?

• Reduce lateral movement of other molecules including phospholipids

• Make membranes less fluid at high temperatures

• Prevent leakage of water and dissolved ions from cell

What is the structure of glycoproteins?

Carbohydrate chains are attached to many extrinsic proteins on the outer surface of the cell membrane.

What is the function of glycoproteins?

• Act as recognition sites

• Help cells to attach to one another and so form tissues

• Allows cells to recignise one another (e.g. lymphocytes can recognise an organism’s own cells)

What is the function of a glycolipid?

• Made up of a carbohydrate covalently bonded with a lipid

Carbohydrate portion extends from the phospholipid bilayer into the watery environment outside the cell

What is the function of a glycolipid?

• act as recognition sites

• help to maintain the stability of the membrane

• help cells to attach to one another and form tissues

What s the structure of the cell surface/plasma membrane?

• Composed a phopholipid bilayer embedded in which are cholesterol and proteins

• (NB the membranes in a cell are flexible and can break and reform)

What is the function of a cell surface/plasma membrane?

• Controls passage of molecules in and out of cell

• Involved in cell signalling

• Involved in cell recognition

• Involved in cell adhesion (animal cells)

What is the structure of channel proteins?

Embedded in the membrane and covers the entire membrane (this is important because the channel must transport ions and molecules in and out of the cell)

What is the function of channel proteins?

Form water-filled tubes to allow water-soluble ions to diffuse across

What is the structure of a phospholipid?

• Hydrophillic heads pf both phospholipid bilayers point to the outside of the cell membrane

• Hydrophobic tails point inwards, repelled by water