Unit 1: Transport Across Cell Membranes Booklet Key Points Flashcards
What denatures proteins?
Ph and high temperatures
What destroys phospholipids?
Alcohol
What is the cell membrane composed of?
Proteins and phospholipids
How do you know that the cell membrane contains proteins and phospholipids?
From an experiment to investigate the nature of the cell membrane using discs of cabbage by submerging them in acid, alcohol or boiling, I now know that the cell membrane contains proteins and phospholipids as the dye from the cabbage bled into the substances with high heat, acid or alcohol in them. This shows that they dye escaped the cell due to these conditions
What is the function of the cell membrane?
To control what enters and exits the cell.
What do the two main parts of a cell membrane do?
The phospholipids make the membrane fluid and able to move. The protein part are found within the membrane and on each surface
What do some proteins have that allows substances into and out of the cell?
Some proteins have a channel running through them. This allows certain substances to pass into and out of the cell.
What is the membrane described as being?
Selectively permeable
What substances can pass through the membrane?
Amino acids, fatty acids, glucose, cells
What substances cannot pass through the membrane?
Starch, proteins, fats
Explain diffusion
The molecules of liquids and gases move about freely all the time. If a substance is introduced, the molecules of this substance will move from a region of high concentration to a region of lower concentration until the concentration in all areas is equal. This process occurs passively with no energy input. The name given to this movement of molecules is diffusion.
What does the concentration gradient mean?
The concentration gradient means that the concentration of a particular substance is greater on one side than on the other
What is the relationship between the concentration gradient and rate of reaction?
The greater the difference in concentration, the faster the overall movement will be.
What is the difference between required substances and harmful substance during diffusion?
Substances required by a cell move into the cell from a higher concentration outside the cell to a lower concentration inside the cell.
Harmful substances leave the cell by diffusion from a higher concentration inside the cell to a lower concentration outside the cell.
Why is diffusion important to cells?
The gain from raw materials (oxygen and glucose) for respiration.
They remove harmful waste products (carbon dioxide)
What is the definition of diffusion?
Diffusion is the movement of the molecules of a substance down a concentration gradient from a region of higher concentration to a region of lower concentration until the concentration becomes equal.
What is the definition of osmosis?
Osmosis is the movement of water from a higher water concentration to a lower water concentration across a selectively permeable membrane.
What should you do when answering a question on osmosis?
It is important to convert the concentration of the solute to the concentration of water. That way it is easier to identify which side has the highest water concentration. Think of pure water as being 100% or 100mM or 100M or 100mol l-1 and subtract the solute value. This gives you a comparison of the water concentration.
How does osmosis affect plant cells?
If water moves into a normal cell, it becomes turgid.
If water moves out of a normal cell, it becomes plasmolysed.
How does osmosis affect animal cells?
If water moves into a normal cell, the cell will burst because it doesn’t have a cell wall.
If water moves out of a normal cell, the cell will shrink.
How are the cells affected by osmosis?
When animal cells are placed in a solution with a higher water concentration, the water moves in by osmosis and the cells burst. When animal cells are placed in a solution with lower water concentration, the water moves out by osmosis and the cells shrink. The animal cells burst because they don’t have a cell wall. When plant cells are placed in a solution with a higher water concentration, the water moves in by osmosis and the cells become turgid. The cells do not burst because they have a cell wall. When plant cells are placed in a solution with a lower water concentration, the water moves out by osmosis and the cells become plasmolysed.
What are factors affecting the rate of active transport which are needed to produce ATP from aerobic respiration?
Oxygen concentration
Glucose concentration
Temperature
What is active transport?
Active transport is when a substance moves across a cell membrane against a concentration gradient from a lower concentration to a higher concentration. This process requires energy to transport the substances from a lower concentration to a higher concentration. Substances cross the membrane through a protein molecule
