Biological Membranes Flashcards
Describe the ‘Fluid Mosaic’ structure of cell membranes
- Phospholipids form bilayer
- Fluid bilayer
- Cholesterol, proteins are scattered throughout membrane
What is the purpose of a cell membrane?
- To control the entry and exit of substances into the cell
- Act as barrier to environment
Why aren’t water-soluble substances allowed through the phospholipid bilayer?
The centre of the bilayer in hydrophobic
What part of a phospholipid is located within the bilayer?
Hydrophobic tail
What is the role of cholesterol is a cell membrane?
- Provides membrane stability by binding to phospholipid tails, increasing density of membrane
Name 2 types of protein involved in transporting substances through the cell membrane
- Channel proteins
- Carrier proteins
How do glycolipids and glycoproteins stabilise a membrane?
- Formation of Hydrogen bonds with water
What is the function of glycolipids and glycoproteins in a membrane?
To act as receptors
Describe how one cell communicates with another
- One cell releases hormone
- Hormone travels in blood
- Hormone binds to receptor on target cell
Are receptors specific to messenger molecules?
Yes
Explain how warmer temperatures affects a membrane’s permeability
- Phospholipids have more kinetic energy
- Phospholipids move more
- Reducing membrane’s packing
What occurs when temperature is increasing that prevents a membrane’s ability to work?
- Bilayer melts
- Channel and carrier proteins deform
Explain how the solvent affects permeability of a membrane
- Some solvents dissolve lipids
- Damages membrane’s structure
How does increasing the concentration of a solvent affect permeability?
Increases permeability
Define the term ‘diffusion’
The random, natural, net movement of particles along a concentration gradient
What type of molecules can diffuse through cell membranes?
Small, non-polar molecules
Give 4 factors that affect the rate of diffusion
- Concentration Gradient
- Temperature
- Surface Area
- Distance
What component of cell membranes does facilitated diffusion use?
Channel and carrier proteins
Describe the process of facilitated diffusion
- Large molecule attaches to carrier protein
- Carrier protein changes shape
- Molecules released on opposite side of membrane
How do channel proteins work?
- Form pores in the cell membrane
- Allowing charged particles through
Explain the process of ‘active transport’
- Energy from ATP
- Used to move molecules and ions – Against a concentration gradient
- Carrier proteins used
Explain the process of endocytosis
- Cell surrounds substance with a section of plasma membrane
- Membrane pinches off to form a vesicle
Give an example of a cell that uses endocytosis
Phagocytes
What is required for endocytosis and exocytosis?
Energy from ATP
