The Cell (Plasma) Membrane The cell membrane is made up of three organic parts: lipids, proteins, and carbohydrates. It has many parts but is still very flexible: a fluid mosaic model.
The Cell (Plasma) Membrane Made of a phospholipid bilayer - a double layer of lipids
The Cell (Plasma) Membrane Proteins serve as channels or pumps - “doors” that things can pass through
Transport proteins provide larger openings in the plasma membrane through which particles can pass…
The Cell (Plasma) Membrane Carbohydrates act like chemical “ID tags” - how cells recognize one another
Why is the cell membrane so important? The membrane provides structure and controls what enters and leaves the cell.
Why is the cell membrane so important? The cell membrane is said to be semipermeable, or selectively permeable, because some substances can pass through easily while others cannot. It regulates homeostasis between the solutions on each side of the membrane.
Solutions, Solutes, and Concentration A solution is a mixture of two or more substances. Solutes are the substances dissolved in a solution. Example: In a solution of Kool-aid, our solutes are Kool-aid mix and sugar.
Solutions, Solutes, and Concentration Concentration refers to the amount of solutes dissolved in a solution. One packet of Kool-aid mix dissolved in a glass of water is more concentrated, while one packet of Kool-aid mix dissolved in a gallon of water is less concentrated.
Passive Cell Transport In passive transport, no energy is required. There are three kinds of passive transport: Diffusion Osmosis Facilitated diffusion
Passive Cell Transport In passive transport, no energy is required. There are three kinds of passive transport: Diffusion Osmosis Facilitated diffusion
Passive Cell Transport: Diffusion Diffusion is the movement of molecules from areas of to concentration. HIGH LOW
Passive Cell Transport: Diffusion If a substance CAN cross the membrane, it tends to move towards the area where it is LESS concentrated until the two areas reach EQUILIBRIUM (equal concentrations). Think of people filling up a movie theater
Passive Cell Transport: Osmosis Osmosis is the diffusion of WATER through a semi-permeable membrane. Water also moves from areas of HIGH to LOW concentrations (think of a waterfall). If a solute is too large to diffuse, water molecules will diffuse instead until the two solutions reach equilibrium.
Osmosis: movement (diffusion) of water / solvent
Passive Cell Transport: Facilitated Diffusion Facilitated diffusion occurs when protein “doors” in the cell membrane help larger molecules move across the membrane. Still passive transport because solutes move from high to low concentration gradients.
Passive, aided diffusion A form of passive transport using transport proteins Passive, aided diffusion
Passive Transport When molecules move with the concentration gradient, it means molecules move from HIGH to LOW concentrations. This does not require energy (ATP). Think of a waterfall. Is it easy or hard for water to flow down a waterfall? Does it take a lot of energy?
Types of Solutions Hypertonic- concentration of solute outside of cell is greater than inside of cell, water flows out, cell shrivels
Types of Solutions Hypotonic- concentration of solute inside cell is greater than outside of cell, water flows in, cell swells
Types of Solutions Isotonic- concentration of solution is the same inside and outside of cell, water flows equally in and out, cell remains same size
A: Hypertonic
B: Hypotonic
C: Isotonic
Active Cell Transport In active transport, energy IS required.
Active Cell Transport Protein pumps within the membrane “pump” molecules and solutes such as calcium, sodium, and potassium across membranes. Changes in the shape of the protein allow molecules to move in specific directions.
Active Cell Transport Endocytosis is the process of creating “pockets” in the membrane which are then pinched off and taken inside the cell. Exocytosis is opposite process --- vacuoles within the cell merge with the cell membrane and deposit their contents outside of the cell.
Active Cell Transport When cells move molecules against the concentration gradient, it means molecules move from LOW to HIGH concentrations. This does require energy (ATP). Think of paddling upstream, or trying to go up a waterfall.
Active Cell Transport A lot of the energy used our cells is devoted to active transport – we need certain concentrations of molecules in order for specific parts of our bodies to function. For example, unequal concentrations of Na+ and K+ ions help our nerve cells function.
Active Cell Transport Therefore, both passive and active transport help us maintain homeostasis.
Chemical Energy and ATP A T P (adenosine triphosphate) is the main chemical compound in cells that stores and releases energy
How does it work? ADP is ATP with one less phosphate Energy is stored in the bond between the three phosphates ATP must lose a phosphate to become ADP
How does it work? When the phosphate bond is broken, energy is released Like breaking a glow stick or a hot/cold pack
How does it work? *[ATP] breaks down to [ADP + Phosphate] and releases energy to carry out life processes
Why do we need ATP? ATP is “energy currency” in the cell When ATP breaks down into ADP, it provides energy for cellular processes: Making proteins Energy for photosynthesis Active transport
Why do we need ATP? Our cells store a limited amount of ATP only enough for a short period of activity cells regenerate ATP from ADP as needed ***like recharging and using a cell phone