Notes : 2.1 - 2.4 Exchange Of Substances Flashcards
How does surface area to volume ratio affect transport of molecules?
The lower the surface area to volume ratio, the further distance molecules need to travel to reach all parts of the organism. Diffusion alone is not sufficient, so specialised gas exchange surfaces are required.
Name three features of an efficient gas exchange surface.-
- Large surface area, e.g. aveoli
- Thin/short distance, e.g. one cell thick wall of capillaries.
- Steep concentration gradient, maintained by blood supply or ventilation.
What is Fick’s law? Give the corresponding equation.
Fick’s law States that :
- The rate of diffusion is directly proportional to the surface area.
- The rate of diffusion is directly proportional to the concentration gradient.
- The rate of diffusion is directly proportional to the diffusion distance.
What is the structure and properties of a cell membrane?
• Phospholipid bilayer
• Membranous proteins e.g. transporters, receptors, enzymes.
• Controls movement of substances in and out of the cell.
label the lungs
How is the mammalian lung adapted for gas exchange?
- Alveoli provide a large surface area.
- **Steep concerntration gradient **is maintained through good blood supply and ventilation. This is beacusde there is a high con of oxygen in the aveolus, so oxygen will diffuse into the red blood cells and there is a high con of co2 in the red blood cells so it will diffuse into the aveolus.
- Only one cell thick capilary walls, providing a short diffusion distance.
- Extensive capilary network around aveoli provides large surface area.
What is meant by the fluid mosaic model?
Cell membranes are fluid, and have a mosaic-like arrangement of proteins.
How is the alveolus (one alveoli) adapted for gas exchange
- Epithelial cells are one cell thick.
- Short diffusion distance between the alveolar endothelium and the capillary endothelium.
Define passive transport and give examples of this.
The movement of particles down a concentration gradient (high to low), meaning no energy is required. Diffusion, facilitated diffusion, and osmosis are all passive.
What evidence led to development of the fluid-mosaic model?
• Phospholipids naturally form bilayers in water.
• Microscope images show proteins on membrane surface.
• Lipid-soluble substances pass more easily in and out of cells than water-soluble.
Blurt everything you know about cholesterol in the phospholipid bi-layer.
- It binds to the fatty acid tails.
- It makes pholispids less fluid by restricting the movement of phospholipids and proteins which prevents water and dissolved ions from leaving the cell.
Blurt everything you need to know about osmosis.
- Include definition
The movement of free water molecules from an area of high to low concentration, across a partially permeable membrane.
- Through Phospholipid bilayer.
- No energy required.
Blurt everything you need to know about diffusion.
- Include definition .
The movement of hydrophobic or small unchrage molecules from an area of high to low concentration.
- Through Phospholipid bilayer.
- No energy required.
Define facilitated diffusion.
The movement of hydrophilic molecules or ions from an area high to low concentration via the help of a carrier protein or channel protein.
- Through Phospholipid bilayer.
- No energy required.
Define active transport.
The movement of molecules against a concentration gradient (low to high), meaning energy in the form of ATP is required. Also uses carrier proteins.
How are large molecules moved across a cell membrane?
Large molecules are transported via endocytosis and exocytosis.
Endocytosis = cell
membrane forms a vesicle and engulfs the material, which enters the cytoplasm.
Exocytosis = vesicle fuses with cell
membrane to release contents from cell.
p.s they both involve energy from ATP.
Fully label the fluid mosaic model.
Blurt everything you know about glycoproteins.
these are proteins with sugar molecules attached.
- They act as recognition sites and antigens (antigens are like little ‘flags’ on the surface of our cells which allows our body to detect which cells are our own and which cells are foreign).
Blurt everything you know about Glycolipids
these are phospholipids with sugar molecules attached. They have a similar function to glycoproteins - they also act as recognition sites and antigens. They also increase membrane stability by forming hydrogen bonds with water molecules.
Blurt everything you know about intrinsic proteins
these are proteins which span both bilayers of the plasma membrane. They act as channels or carrier proteins to transport water-soluble molecules.
Blurt everything you know about extrinsics proteins
these are proteins which are found on the surface of the plasma membrane. They usually function as enzymes and catalyse chemical reactions inside the cell.
What are channel proteins ?
- Carrier proteins are involved in facilitated diffusion and active transport of molecules across the cell membrane.
Channel proteins are like tunnels in cell membranes.
They provide a direct pathway for specific molecules or ions to pass through the membrane.
These proteins are like gates that open and close in response to signals, allowing controlled movement of substances.
What are carrier proteins ?
Carrier proteins
They grab onto specific molecules on one side of the membrane, change shape, and then release the molecules on the other side.
These proteins are selective and transport molecules across the membrane one at a time.
