4.1) Structure of the cell surface membrane Flashcards
What is the primary structure of the cell-surface membrane?
Phospholipid bilayer
The phospholipid bilayer consists of hydrophilic phosphate heads and hydrophobic hydrocarbon tails.
What is the function of the cell-surface membrane?
Controls movement of substances in and out of the cell
It establishes different conditions inside and outside the cell.
Describe the fluid-mosaic model of cell membrane structure.
A model that describes the cell membrane as a mosaic of diverse protein molecules floating in or on the fluid lipid bilayer.
What are the characteristics of phospholipids in the cell-surface membrane?
- Hydrophilic heads point outward
- Hydrophobic tails point inward
- Form a bilayer structure
What role do phospholipids play in the cell membrane?
- Allow lipid-soluble substances to enter and leave the cell
- Prevent water-soluble substances from entering and leaving the cell
- Make the membrane flexible and self-sealing
How are proteins embedded in the cell-surface membrane?
- Some proteins are on the surface of the bilayer
- Others span the bilayer completely
What are the functions of proteins in the cell membrane?
- Provide structural support
- Act as channels for water-soluble substances
- Allow active transport through carrier proteins
- Serve as surface receptors
- Help cells adhere together
What is the function of cholesterol in the cell-surface membrane?
- Adds strength to the membrane
- Prevents loss of water and dissolved ions
- Reduces lateral movement of phospholipids
What are glycolipids and their function in the membrane?
- Made of carbohydrate and lipid
- Act as recognition sites
- Help maintain membrane stability
- Assist in cell attachment
What are glycoproteins and their role in the cell membrane?
- Carbohydrate chains attached to extrinsic proteins
- Act as cell-surface receptors for hormones and neurotransmitters
- Help cells to recognize one another
True or False: All plasma membranes have the same phospholipid bilayer structure.
True
The differences in properties arise from the various substances contained within.
Fill in the blank: The hydrophilic heads of phospholipids are attracted to _______.
[water]
Fill in the blank: Cholesterol molecules in the membrane help to _______ the movement of phospholipids.
[reduce]
What is the significance of the carbohydrate portion of glycolipids?
Acts as a cell-surface receptor for specific chemicals
Example: The human ABO blood system operates through glycolipids.
What do carrier proteins do in the cell membrane?
Bind to ions or molecules and change shape to transport them across the membrane.
What is the role of surface receptors in the cell membrane?
Identify cells and react to specific molecules, such as hormones.
What is the overall function of the cell-surface membrane?
Controls the movement of substances in and out of the cell.
Which end of the phospholipid molecule lies towards the inside of the cell-surface membrane?
Hydrophobic tails.
What type of molecule is likely to pass through the cell-surface membrane if it is soluble in lipids?
Lipid-soluble molecules.
What type of molecule is likely to pass through the cell-surface membrane if it is a mineral ion?
Channel proteins.
Suggest two properties that a drug should possess to enter a cell rapidly.
- Lipid-soluble
- Small size.
True or False: Most molecules can freely diffuse across the cell-surface membrane.
False.
List three reasons why many molecules do not freely diffuse across the cell-surface membrane.
- Too large to pass through channels
- Charged and repelled by protein channels
- Polar and have difficulty passing through non-polar hydrophobic tails.
What does the fluid-mosaic model describe?
The arrangement and structure of the cell-surface membrane.
Why is the cell-surface membrane described as ‘fluid’?
Phospholipid molecules can move relative to one another.
Why is the cell-surface membrane described as ‘mosaic’?
Proteins embedded in the phospholipid bilayer vary in shape, size, and pattern.
What role does cholesterol play in the cell-surface membrane?
Adds strength.
What is the function of glycoproteins in the cell-surface membrane?
Acts as recognition sites for chemicals like hormones.
Fill in the blank: The cell-surface membrane provides an internal transport system, such as the _______.
[endoplasmic reticulum].
What is the function of lysosomes in the cell?
Isolate enzymes that might damage the cell.
What is the significance of ribosomes on the rough endoplasmic reticulum?
Protein synthesis.
What are the hydrophilic heads of phospholipids?
The part of the phospholipid that interacts with water.
