Passive transport processes: Diffusion Diffusion is the movement of ions or molecules from regions of high to low concentration; down a concentration gradient. Diffusion and the plasma membrane The plasma membrane is semipermeable which means it will allow certain substances to go in and out but not others. Moecules that pass through the phospholipid bilayer easily: Hydrophobic molecules: 02 and N2 Non-polar: Benzene Small uncharged polar molecules: H20, Urea, glycerol and CO2 Molecules that don’t pass through the phospholipid bilayer easily: Large uncharged molecules: Glucose Polar molecules: Sucrose Ions (charged): H+, Na+, HCO3, K+Ca2+, Cl- and Mg2+ Therefore the three characteristics of a molecule that determine their permeability through the membrane are: 1. Polarity- Hydrophobic vs Hydrophilic 2. Charge- Charged vs Uncharged 3.
| | | A) | cytoskeleton | | | B) | fluid mosaic model | | | C) | impermeable membrane | | | D) | genetic material | | | | | | Feedback: Phospholipids in the plasma membrane create a fluid environment in which other molecules can float, allowing selective permeability. This is known as the fluid mosaic model. | | 13 CORRECT | | What effect has eukaryotic evolution had on cells? | | | A) | more simplified structures | | | B) | greater adaptability
Lipid-soluble material moves through the membrane via the phospholipids; so they allow lipid-soluble substances to enter and leave the cell, prevent water-soluble substances entering and leaving the cell. Different kinds of membranes can contain phospholipids with different fatty acids, which affect the strength and flexibility of the membrane, and animal cell membranes. They also contain cholesterol which links the fatty acids together which stabilises and strengthens the membrane. The proteins in the membrane either sit on one of the layers (extrinsic proteins) or proteins that span the bilayer from one side to another (intrinsic proteins). The extrinsic proteins on the outside surface of the membrane either give support to the membrane or in conjunction with the glycolipids act as receptors for molecules such as hormones
Carrier Mediated Transport Carrier Mediated Transport is the movement of substances across the plasma membrane by protein carrier molecules, this transport is used when molecules can’t cross membrane or cross very slowly. These are examples of important molecules that require carrier mediated transport, water, glucose, amino acids, vitamins, phosphate, multivalent cations. There are three mechanism of carrier mediated transport, one is facilitated diffusion, two is second is primary active transport and three is secondary active transport. Facilitated diffusion is also known as facilitated transport. This is a form of passive transport across a membrane in which a transporter protein facilitates the movement of an impermeable membrane or ion across the plasma membrane down its concentration gradient.
The protein molecule is able to float in the membrane – part of it is embedded in the membrane, part of it sticks into the cytoplasm, and part of it sticks out into the aqueous environment of the cell. What do you suspect about its structure, including its amino acid sequence, to make it behave as it does? * Examine the diagram of the cell membrane below. Is the diagram a “good” illustration of the fluid mosaic model of the cell membrane? What aspects of cell membrane structure are accurately illustrated by it?
3. Cell junctions are important because they are the point of contact between the plasma membranes of tissue cels. 4. The surface of epithelial cell that would face the lumen of an internal organ is the apical surface. 5.
CHAPTER 5: MICROIAL METABOLISM PRE-TEST 1: Which of the following types of transport involves the expenditure of energy and special membrane proteins? ACTIVE TRANSPORT 2: Which of the following molecules serves as the short-term recyclable energy supply for a cell? ATP 3: Which of the following is a waxy lipid found predominantly in the cell walls of Mycobacterium? MYCOLIC ACID 4: Catabolic reactions are chemical reactions that BREAK LARGE MOLECULES APART 5: Denaturation is typically a problem with which of the following? PROTEINS 6: A difference in the concentration of a chemical on both sides of a membrane leads to which of the following phenomena?
Kirstie Javier AP Biology Period 4 November 14, 2011 Proteins Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. Some types of chemical bonds/ interactions are disulfide bonds, hydrogen bonds, ionic bonds, and hydrophobic interactions. Disulfide bonds form when two cytosine molecules join together to form a bond between their two sulfur atoms. Such bonds cross-link polypeptide chains or parts of chains. Because they are nonpolar covalent bonds, they are very strong bonds and not easily broken.
The energy for this process is supplied by the hydrolysis of ATP using the enzyme ATPase and a specific protein channel in the membrane. Active transport is the movement of substances from where they are less concentrated to where they are more concentrated. It is undertaken by carrier proteins in cell membranes, which move specific molecules or ions against the concentration gradient using energy supplied by ATP. Cells have many adaptations to allow them to facilitate active transport; they may have carrier proteins in the cell surface membrane designed to transport particular molecules or ions or possess many mitochondria to supply the required ATP. Active transport requires energy in the form of ATP and protein carriers to move the molecules across the membrane.
The Effect of Diffusion and Osmosis on Hypertonic and Hypotonic Solutions. Introduction: In order to maintain homeostasis, a cell must be able to transport materials back and forth across the membrane due to the fact that cell membranes are selectively permeable. Selectively permeable means that some substances can pass through the membrane while others cannot, like glucose, proteins and carbohydrates. Both solutes and solvents may cross the cell membrane. Solutes meaning: the substance that is being dissolved, while solvents meaning: substance being dissolved into, much like diffusion.