2.4 membranes Essay

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IB Biology 12 Study Guide
2.4 Membranes

2.4.1 Draw and label a diagram to show the structure of membranes.

2.4.2 Explain how the hydrophobic and hydrophilic properties of phospholipids help to maintain the structure of cell membranes.

The hydrophobic and hydrophilic properties of phospholipids cause them to align in a bilayers where the hydrophilic phosphate heads will be attracted to the water inside and outside of the cell and the hydrophobic fatty acids are in the center of the membrane. This bilayer allows the membrane to be very stable yet also flexible, enabling the cell to change shape easily.

2.4.3 List the functions of membrane proteins.

hormone binding sites enzymic action; catalyze (accelerate) many chemical reactions cell adhesion cell to cell communication channels for passive transport pumps for active transport

2.4.4 Define diffusion and osmosis.

Diffusion is the passive movement of particles from a region of high concentration to a region of low concentration.

Osmosis is the passive movement, which occurs along a concentration gradient, of water molecules, across a partially permeable membrane.
2.4.5 Explain passive transport across membranes by simple diffusion and facilitated diffusion.

Simple Diffusion Chemicals which are permeable to the phospholipid bilayer, such as oxygen, move from an area of high concentration through the plasma membrane to an area of lower concentration, resulting in even distribution throughout the system.
Facilitated Diffusion This form of diffusion involves specific carrier proteins which are capable of combining with substances to aid their movement. The carrier changes shape to accomplish this task but does not require ATP energy. However, the rate of diffusion does level off when equal saturation is accomplished.

2.4.6 Explain the role of protein pumps and ATP in active transport across membranes.

During active transport, substances are moved against the concentration gradient. The cell membrane has protein pumps embedded which are used to move substances through the membrane, with the help of ATP. Each protein pump only transports certain substances so the cell can control what comes in and what goes out.

2.4.7 Explain how vesicles are used to transport materials within a cell between the rough endoplasmic reticulum, Golgi
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