Springfield Central High School Unit 4 (Part 2) Lesson 4 Introduction to Cell Functions Overview of Cell Functions and Cellular Transport Springfield Central High School

Massachusetts Frameworks for Cell Form Unit Central Concepts: Cells have specific structures and functions that make them distinctive. Processes in a cell can be classified broadly as growth, maintenance, and reproduction. 2.4   Identify the reactants, products, and basic purposes of photosynthesis and cellular respiration. Explain the interrelated nature of photosynthesis and cellular respiration in the cells of photosynthetic organisms. 2.6   Describe the cell cycle and the process of mitosis.  Explain the role of mitosis in the formation of new cells, and its importance in maintaining chromosome number during asexual reproduction. 2.7   Describe how the process of meiosis results in the formation of haploid cells.  Explain the importance of this process in sexual reproduction, and how gametes form diploid zygotes in the process of fertilization.

Questions to Ponder What is the function of cell wall? What is the function of cytoskeleton? What is the function chloroplasts? What is the function of mitochondria? Which organelle contains digestive enzymes to break down organic molecules? Which organelles produces lipids? What is the function of the rough endoplasmic reticulum? What is the function of the smooth endoplasmic reticulum?

Cell Function: The main ideas and what we need to learn about cell function. Cellular Transport: How things get in and out of cells Osmosis is the diffusion of water through a selectively permeable membrane. Passive transport moved a substance with the concentration gradient and requires no energy from the cell. Active transport moves material against the concentration gradient and requires energy to overcome the opposite flow of materials that are moving with the concentration gradient. Large particles may enter the cell by a process known as endocytosis and leave by exocytosis.

Cell Function: The main ideas and what we need to learn about cell function. (Cont.) Cell growth and reproduction: Cell size is limited by the diffusion rate of materials into and out of the cell. Cell size is also limited by the amount of DNA available to the program the cell’s metabolism. Cell size is also limited by the cell’s surface to volume ratio. Cells grow many instead of growing large Cell Cycle, Nuclear Cell Division and Cytokinesis Interphase: a period of growth and metabolism. Mitosis has four phases: Prophase Metaphase Anaphase Telophase Meiosis produces gametes, (sex cells) Gametes have half the number of chromosomes as other cells in an organism.

Mitosis and Meiosis Mitosis turns one nucleus into two so that as the cell divides both new cells have the same chromosomes, (DNA). Meiosis turns a nucleus into four nuclei each with half the number of chromosomes as the original nucleus. The cells made with these reduced chromosome nuclei are the sex cells of sexually reproducing organisms.

Cellular Transport: How things get in and out of cells. Cells need to get water, oxygen and nutrients into them, while cells also need to get waste out of them. Things going in or out of the cell need to pass the cell barrier, the plasma membrane. There are 4 basic ways things pass through the plasma membrane, two require energy from the cell two do not require energy from the cell: No Energy Required (Passive transport) Osmosis Facilitated diffusion Energy Required (Active Transport) Carrier proteins Endocytosis and exocytosis

Cell Transport: Plasma Membrane The plasma membrane is made of the molecule phospholipids Phospholipids have a lipid (fatty acid) end that is hydrophobic, (hates water) and a phosphate group end that is hydrophilic, (loves water). The fatty acids always move away from water while the phosphate ends always move toward water. Since cells are filled with water and surrounded by water the phospholipids make two layers ( a bilayer)

Cell Transport: Plasma Membrane, (cont) When phospholipids are dropped in water they form a sphere that is filled with and surrounded by water. The water in the sphere is trapped and somewhat isolated from the water outside the membrane bilayer. This is the beginning of a cell. The cell can control the environment inside the sphere with a controlled use of chemistry and energy. The questions now arise: How can the cell control access to and maintain a stable environment inside the sphere? How do nutrients and other cell needs get into the cell? How do cell wastes get out of the cell?

Cell Transport: Osmosis and Diffusion Diffusion is the movement of particles from an area of higher concentration to an area of lower concentration. Osmosis is the diffusion of water across a selectively permeable membrane. Osmosis is a special case of diffusion In a cell, water always tries for an equal concentration on both sides of the plasma membrane. Water will go where water is low. Understanding Water Concentration Here we see 3 beakers: one has pure water, the second has tap water and the third has salt water. All three beakers are filled to the 100mL line, but each has a different amount of water and therefore a different water concentration, (concentration = molecules/volume). Which beakers have the highest and lowest water concentrations? Explain your choices. What is in the pure water? What is in the salt water?

Cell Transport: Osmosis and Diffusion (cont) Cells have H2O in them and H2O around them. Therefore, are only 3 condition in which a cell can be found: Hypotonic If the H2O concentration is lower in the cell than outside the cell, H2O will move into the cell. Hypo means under Hypotonic solution has less (or “under”) dissolved things in the H2O around the cell than the H2O is in the cell. A cell in a hypotonic solution will take in H2O. Water moves into a cell that is in a hypotonic solution. Hypertonic Hyper means over Hypertonic solution has more (or “over”) dissolved things in the H2O around the cell than does the H2O that is in the cell. A cell in a hypertonic solution will lose H2O Water moves out of a cell in a hypertonic solution. Isotonic If the H2O concentration is equal on both sides of the cell membrane, H2O will neither move in nor out of the cell. Iso means equal Isotonic solution has an equal amount of dissolved things in the H2O that surrounds as the H2O in the cell. A cell in an isotonic solution doesn’t take in or give off any H2O. Water does not move in or out of a cell in an isotonic solution

Cell Transport: Osmosis and Diffusion (cont) Passive transport Passive transport is the movement of particles across a cell membrane by diffusion or osmosis; the cell uses no energy to move particles across the membrane. Water, lipids, and lipid soluble substances can pass the plasma membrane. Protein channels: Particles that are not water, lipids, or lipid soluble and are too big to pass through the phospholipid bilayer can use diffusion to pass through protein channels. Passive transport of materials across the plasma membrane with the aid of protein channels is called facilitated diffusion. Sugars and amino acids often need facilitated diffusion to enter cells. Facilitated diffusion like all diffusion relies on a concentration gradient. The cell spends no energy using diffusion.

Cell Transport: Carrier Proteins and Active Transport Active transport is an energy requiring type of cellular transportation. It transports materials across the cell membrane against a concentration gradient. Sometimes the cell wants more of something it already has plenty of. In these cases the cell must spend energy to go against the concentration gradient. The energy must be spent to counteract the movement with the concentration gradient. Active transport uses carrier proteins. Carrier proteins have a specific shape to capture a specific molecule or ion. When the molecule is captured the cell uses energy to change the carrier protein’s shape, which allows the molecule to enter the cell.

Cell Transport: Transport of Large Particles Endocytosis and Exocytosis Endocytosis : Sometimes cells take in large molecules our groups of molecules that are too large for protein tunnels or carriers. In these cases the plasma membrane engulfs (or grows around) the particle that the cell wants to take in. This is called endocytosis. Exocytosis Likewise when the cell wants to expel a large molecule the plasma membrane grows around the particle that the cell wants to get rid of. This is exocytosis.

Questions to Ponder from Lesson 1  What is passive transport into cells? What is active transport in cells? What are osmosis and diffusion? What are endocytosis and exocytosis? What is mitosis? What is the cell cycle? What is meiosis? What is the cell membrane and how is it formed? What are the three conditions that a cell can find itself in? What happens to the cell in each of these conditions? Why do animal cells burst easily but plant cells do not?? 15