Cellular Transport and The Cell Cycle Hook: raison activity Chapter 8

Osmosis Diffusion of water In a cell, water always moves to reach an equal concentration on both sides of the membrane. *In order for diffusion to occur, there must be a concentration gradient (uneven distribution of particles)*

Isotonic Solution Occurs when the concentration of dissolved substances in a solution IS THE SAME AS the concentration of dissolved substances inside a cell. Occurs when the concentration of water in the solution IS THE SAME AS the concentration of water inside the cell. *Osmosis still occurs. Movement of water into the cell equals the amount of water moving out of the cell.*

Hypotonic Solution Happens when there is more water outside of the cell. Happens when the concentration of dissolved substances outside the cell is less than inside the cell. Water moves into the cell Pressure inside cell increases Plant cells do not burst in hypotonic solutions

Hypertonic Solutions Happens when there is more water inside the cell. Happens when the concentration of dissolved substances outside the cell is more than inside the cell. Water moves out of the cell Pressure inside cell decreases Cells shrivel

Osmosis Demo  Try This! Procedure: Label beaker 1 “Water” and beaker 2 “Salt” Place 100 mL of water into each. Place 3 tablespoons of salt into the salt beaker and stir until it is dissolved. Measure and record the mass of each potato piece. Record the texture of each. Place one potato piece in each beaker. Cover the beakers with plastic wrap and allow them to sit undisturbed for 2 days. On the second day, remove the potato cubes and blot them dry on the outside. Record their masses. Analysis: Describe what happened to the mass of each cube before soaking. Describe what happened to each cube after soaking. Explain the changes you observed in terms of osmosis.

Passive Transport Molecules, like water, that are able to freely pass through the membrane without the cell using any energy use “passive transport”. There are 2 types of passive transport: Diffusion/Osmosis Facilitated Diffusion TEAM POINTS: research the problem with channel proteins due to cystic fibrosis (Cl – transport)

Facilitated Diffusion Transport proteins help substances move across the plasma membrane. Facilitated diffusion occurs when materials need a transport protein (aka. channel proteins) in order to diffuse across the concentration gradient (from high concentration to low concentration until equal). Requires no energy input by the cell. Carrier proteins are a type of transport protein that change shape to allow a substance through the membrane.

Active Transport A cell can move particles from a region of lower concentration to a region of higher concentration. Requires energy from the cell Requires a transport protein, called a carrier protein because it has a shape that fits a specific molecule.

Transport of Large Particles Endocytosis: Occurs when a cell engulfs a large molecule, groups of molecules or whole cells. Once engulfed and enclosed by a portion of the plasma membrane, that portion of the plasma membrane breaks away. Results in a vesicle with its contents move inside the cell.  REQUIRES ENERGY!

Exocytosis: Occurs when the cell expulses/secretes a material. Used to expel waste REQUIRES ENERGY!

Try This! Compare and contrast active and passive transport across the cell membrane. Fill in the following table: Type of Transport Transport Protein Used? Direction of Movement Requires Energy Input from cell? Classification of Transport (Passive/ Active) Simple Diffusion Facilitated Diffusion Active Transport FOLDABLE ACTIVITY

Cell Growth & Reproduction Factors affecting cell size: Diffusion DNA (replication can only happen so fast) Surface area-to-volume ratio Try Problem-Solving Lab 8.1

Cell Division Useful to replace damaged cells and for growth & development. Before cell division occurs, chromatin condenses into chromosomes.

Chromosomes For most of a cell’s lifetime, chromosomes exist as chromatin (DNA wrapped around histones, forming nucleosomes) Non-reproductive cells have 46 chromosomes each in their nucleus (23 pairs, 1 pair from each parent) Reproductive cells (ova & spermatozoa) only have 23 chromosomes, or 1 from each pair)

The Cell Cycle See Mitosis Worksheet There are 3 stages to the cell cycle: Interphase Majority of the cell’s life is in this stage G1 Stage: Cell grows in size and carries on metabolism (protein production is high) S stage: Chromosomes are duplicated in preparation for cell division G2 Stage: Cell continues to grow (centrioles, mitochondria and other organelles replicate) and cell prepares for division

2. Mitosis -Process by which 2 daughter cells are formed (each with 46 chromosomes, or 23 pairs) -Mitosis can be divided into sub-stages: a. Prophase b. Metaphase c. Anaphase d. Telophase **See Worksheet for details** 3. Cytokinesis Process of cell dividing in 2 Animals: plasma membrane pinches along the equator Plants: Cell plate is laid down across the equator. A cell membrane forms around each cell. New cell walls form on each side of the cell plate.

Results of Mitosis -Results in genetic continuity (daughter cells are identical to mother cell and will carry out the same cellular processes and functions as those of the parent cell) -In multicellular organisms, mitosis results in a group of cells that work together as tissue.

Control of the Cell Cycle Cancer results from uncontrolled cell division. Proteins (cyclins) and enzymes control the cell cycle. Protein and enzyme production are directed by genes (segment of a DNA strand) found in chromosomes.

Cancer: A mistake in the cell cycle Occurs when there is a mutation in a gene responsible for producing substances that are involved in controlling the cell cycle. Cancerous cells form masses (tumors) that deprive normal cells of nutrients. Metastasis: When cancer cells enter the circulatory system and spread throughout the body. Most common types of cancer: lung, colon, breast and prostate cancers

Causes of Cancer There are both genetic and environmental factors: -Cigarette smoke -Air and water pollution -Exposure to UV rays -Viral Infections Each of these factors are known to damage the genes that control the cell cycle. Breast cancer rates are high in the USA and low in Japan, Stomach cancer is high in japan and rare in the USA

Cancer Prevention There is a clear link between lifestyle and the incidence of cancer. Factors that reduce the risk of developing cancer: Diets low in fat and high in fiber Vitamins and minerals (vitamin A, C and E). Daily exercise Not using/exposing yourself to tobacco Reduce stress levels Get enough sleep