30 Questions
Which of the following factors can affect the permeability of cell membranes?
Temperature and pH
What is the role of intrinsic proteins in the plasma membrane?
Serving as channels or carrier proteins for transporting molecules
What is the purpose of using plant cells containing a colored pigment, like beetroot, in membrane permeability experiments?
To measure membrane permeability by observing pigment leakage
What is the suggested method for preparing beetroot samples for a membrane permeability experiment?
Rinse each piece to remove released pigment, ensuring samples are similar in size
In investigating the effect of temperature on membrane permeability, what range of temperatures can be used in the experiment with plant cells?
0 to 70°C
What is the primary function of extrinsic proteins found on the surface of the plasma membrane?
Functioning as enzymes to catalyze reactions
What is the main reason the fluid mosaic model is called 'fluid'?
Due to the constant movement of phospholipids
What role do glycoproteins play in the plasma membrane?
Act as recognition sites and antigens
How do glycolipids contribute to the plasma membrane's function?
By increasing membrane stability with hydrogen bonds
What is the primary function of phospholipids in the plasma membrane?
Form a barrier to lipid-soluble molecules
Why is cholesterol important in the plasma membrane?
To push phospholipids closer together
Which component of the plasma membrane acts as 'flags' for cell identification?
Glycolipids
What is the purpose of using a colorimeter in this experiment?
To measure how much light is absorbed by each liquid
What happens to membrane permeability at temperatures below freezing?
Increases as proteins in the membrane unfold and become deformed
Why does membrane permeability increase rapidly above 45°C?
As proteins in the membrane become denatured and start to unravel
What effect does an increase in temperature have on membrane fluidity?
Increases fluidity
How does permeability change between 0°C and 45°C?
Membranes are partially permeable
What effect do ice crystals have on membrane permeability?
Increase permeability by puncturing the membrane
What happens to a potato placed in a solution of higher water potential?
It gains mass
What is the result when a potato is placed in a solution of lower water potential?
It loses mass
What does it mean when there is no change in mass after placing a potato in a solution?
The solution is isotonic
What does active transport involve?
Moving molecules from low to high concentration with carrier proteins
What is the purpose of preparing serial dilutions of sucrose solution in the method described?
To determine the concentration of sucrose that results in no change in mass of potato pieces
In the method described, what does the percentage change in mass of the potato pieces indicate?
The osmotic effect of different sucrose concentrations on the potatoes
What is the purpose of adding stain like eosin to the specimen?
To create contrast and enable visualizing organelles
What is the role of the cover slip when preparing a specimen on a microscope slide?
To protect the specimen and prevent air bubbles
Why is homogenisation important in cell fractionation?
To release organelles by breaking apart the plasma membrane
What does cell fractionation aim to achieve?
Separating organelles based on density
Why is it essential to start with the lowest-powered objective lens when viewing specimens under a microscope?
To increase magnification gradually for better focus
What is the purpose of spinning the cell solution at high speeds in cell fractionation?
To separate organelles based on density
Learn about the fluid mosaic model used to describe the arrangement of molecules in the cell membrane, with phospholipids in constant motion and proteins scattered like tiles. Understand how this model represents the structure of the plasma membrane based on current evidence.
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