Cellular Transport And the Cell Cycle Diffusion Diffusion is the movement of particles from a region of high concentration to an area of lower concentration At all temperatures above absolute zero, the individual atoms that constitute any substance are always in movement. The amount of this movement is what constitutes temperature itself. Diffusion Cont. Particles of a substance will move from a region of high concentration to a region of lower concentration. The difference in concentration of atoms is know as a concentration gradient As particles move in a given area, an equilibrium is reached where the space between the particles becomes fairly uniform. This equal distribution of atoms is called dynamic equilibrium Selective Permeability Membranes are selectively permeable, or semi-permeable which means that only some substances can pass through, but not others. Its kind of like a screen door.. Membrane Structure and Function Membrane Function Membranes organize the chemical activities of cells. The outer plasma membrane forms a boundary between a living cell and its surroundings Exhibits selective permeability Controls traffic of molecules in and out Membrane Function Internal membranes provide structural order for metabolism Form the cell's organelles Compartmentalize chemical reactions Fluid Mosaic Model of the PM A membrane is a mosaic Proteins and other molecules are embedded in a framework of phospholipids A membrane is fluid Most protein and phospholipid molecules can move laterally Membrane Structure Phospholipids are the major structural component of membranes. Phospholipid Membrane Structure All membranes are phospholipid bilayers with embedded proteins. Label the: Hydrophilic heads Hydrophobic tails Phospholipid Bilayer Plasma Membrane Made up of two layers of phospholipids Controls what moves into and out of the cell Selectively permeable Embedded in the bilayer are proteins Most of the membranes functions are accomplished by the embedded proteins. Integral proteins span the membrane Peripheral proteins are on one side or the other of the membrane Passive Transport Transport (diffusion) of particles across the membrane without the use of energy by the cell Particles move from a region of high concentration to a region of low concentration across the concentration gradient Passive transport by proteins Common method for moving sugars and amino acids across membranes Driven by a concentration gradient (substances on both sides of the membrane are trying to reach equal concentration) Facilitated Diffusion - Transport of materials across the plasma membrane with the aid of channel proteins Passive Transport Video Video What is Osmosis? Osmosis Diffusion of water across a selectively permeable membrane The plasma membrane does not limit the diffusion of water Water moves freely through proteins called aquaporins In a cell, water always tries to reach an equal concentration on both sides of the membrane What Controls Osmosis? Concentration gradient - Unequal distribution of particles Cells in an Isotonic Solution Isotonic Solution when the concentration of dissolved substances in the solution is the same as the concentration of dissolved substances inside of the cell Equal movement of water into and out of the cell, cell stays the same size Cells in a hypotonic solution Hypotonic solution when the concentration of dissolved substances is lower in the solution outside the cell than the concentration inside the cell Water is pulled into the cell, the cell swells and the internal pressure increases Cells in a hypertonic solution Hypertonic Solution where the concentration of dissolved substances outside the cell is higher than the concentration inside the cell. Water moves out of the cell, the cell shrinks, and internal pressure decreases Water moves into a cell placed in a ___________________ solution. A.Osmotic B.Hypertonic C.Isotonic D.Hypotonic Water moves out of a cell if it is placed in a _______________ solution A.Hypotonic B.Hypertonic C.Isotonic D.Passive A cell moves particles from a region of lesser concentration to a region of greater concentration by _________________. A.Facilitated Diffusion B.Passive Transport C.Osmosis D.Active Transport If a cell is placed in salt water, water leaves the cell by _____________. A.Osmosis B.Diffusion C.Active transport D.Phagocytosis After viewing the recipe above, explain the role of osmosis in making pickles. Be ready to share your answers! Active Transport Cells can move particles from a region of low concentration to a region of high concentration, but it takes ! Active Transport movement of materials through a membrane against the concentration gradient Active Transport Cont. Proteins in the cell membrane (Carrier proteins) bind with particles of the substance. When the right molecule binds to the right carrier protein, ATP allows the carrier protein to change shape so that the particle can be moved to the other side of the membrane Examples of Active transport Transport of Large Particles Some cells can take in large molecules, groups of molecules, or even whole cells Endocytosis process by which a cell engulfs a material and forms a vacuole inside of the cell Exocytosis expulsion or secretion of materials from the cell Used to get rid of waste, secrete hormones Both endocytosis and exocytosis require cellular energy (Active transport) Endocytosis and Exotytosis Use the play dough to model the processes of endocytosis and exocytosis. Be able to explain the process. When you have finished, wait for Mrs. Johnson to come and check your work and hear your explanation. Active Transport Video Video Release of waste or large cell products from inside to outside of cell _____________________. A.Endocytosis B.Exocytosis C.Osmosis D.Facilitated Diffusion Type of cell transport which requires energy from the cell. A.Osmosis B.Facilitated Diffusion C.Active Transport D.Passive Transport Active Transport is to carrier protein as _____________ is to channel protein. A.Osmosis B.Endocytosis C.Exocytosis D.Facilitated Diffusion When cell engulfs a large particle and forms a vacuole inside the cell _____________________. A.Endocytosis B.Exocytosis C.Osmosis D.Facilitated Diffusion Term for cell eating A.Osmosis B.Exocytosis C.Pinocytosis D.Phagocytosis Cells come in different sizes Red blood Cells = 8 m Some nerve cells can be up to 1mm in length The yolk of an Ostrich egg measures 8cm Most living cells are between 2 and 200 m Given the wide range of cell sizes, why cant most organisms be just one giant cell? What limits cell size? Diffusion Diffusion is fast and efficient over short distances but slow and inefficient over larger distances a mitochondrion at the center of a hypothetical cell with a diameter of 20 cm would have to wait months before receiving molecules entering the cell What limits cell size? cont. DNA The nucleus contains blueprints for the cells proteins (proteins are used throughout the cell by the organelles) There is a limit as to how quickly the DNA (blueprints) can be copied The cell cant survive unless there is enough DNA to support the protein needs of the cell Some large single celled organisms have developed more than 1 nucleus What limits cell size? Cont. Surface area to volume ratio As cell size increases, its volume increases faster than its surface area If cell size doubles, the cell would require eight times more nutrients and would have eight times more waste to excrete. The surface area would increase only by a factor of four. The plasma membrane would not have enough surface area for nutrients, waste and oxygen to diffuse through Surface area to volume ratio 1cm 2cm 4cm Surface area = 6cm 2 Volume = 1cm 3 Surface area = 24cm 2 Volume = 8cm 3 Surface area = ?? Volume = ?? Refer to PS lab 8.1 pg 209 Cell Size Video Video The structure most responsible for maintaining cell homeostasis is the ___________. A.Cytoplasm B.Mitochondria C.Cell Wall D.Plasma Membrane As a cell grows, its ___________ increases more than its ___________. A.Length, volume B.Width, surface area C.Volume, surface area D.None of these Which of the following explain why a cells size is limited? A.Volume increases faster than surface area B.Surface area increases faster than volume C.Homeostasis is disrupted by a cell that is too large D.Both a and c Limits to cell Size summary. -The cell membrane controls what moves in and out of the cellhomeostasis -The cell membrane represents the surface area of the cell -Small cells have a greater surface area to volume ratio than larger cellswhich is good. -If cells get too large: - they cant make enough protein to keep the cell running -diffusion is too slow so the cell wont be able to get what it needs (food and waste) -the surface area to volume ratio decreases, which decreases the ability of the plasma membrane to do its job for the cell (the cell cant get in enough food, oxygen or get rid of enough waste, CO2) -Many different types of cells have found ways to become large by developing adaptations that increase their SA to V ratio and amount of DNA Cell Reproduction Cell Reproduction (video clip) The cell theory states: all cells come from preexisting cells We know that all organisms grow and change Throughout our lives, worn-out tissues are repaired or replace by new cells All of this occurs through Cell Division The process by which new cells are produced from one cell Results in two cells that are identical to the parent cell What are Chromosomes? Chromosomes dark staining structures that contain genetic material (DNA) Made up of DNA and protein Chromatin long strands of DNA wrapped around protein (resembles a tangled plate of spaghetti) Before a cell can divide, the long strands of chromatin must be organized into a chromosome Chromosomes Video clip The Cell Cycle The sequence of growth and division of a cell 2 phases: Growth Division The Growth Phase: Interphase The majority of a cells life is spent growing and making more DNA, this period is called Interphase During interphase, cell grows in size and the chromosomes are duplicated G1 phase - rapid growth S phase DNA synthesis and replication G2 phase Centrioles replicate and cell prepares for division The Division Phase: Mitosis Cells undergo mitosis as they approach the maximum cell size at which the nucleus can provide blue-prints for proteins and the plasma membrane can efficiently transport nutrients and waste into and out of the cell 4 phases of Mitosis: Prophase Metaphase Anaphase Telophase The Cell Cycle Cell Cycle Summary -All cells have a life cycle where they grow carry out their functions then divide. Cell cycles vary from cell type to cell type. -There are two main phases of the cell cycle Interphase Growth Mitosis Division -During Interphase, the cell grows (G1), copies DNA (S). and gets ready to divide (G2) -As a result of Mitosis, two new cells are formed having properties like the parent cell because the DNA was replicated before division -The cells DNA is doubled during the synthesis (S) phase then reduced back to the original amount after mitosis (M) Mitosis: Prophase 1 st stage of mitosis (longest stage) Chromatin coils up into visible chromosomes Each duplicated chromosome is made of 2 sister chromatids held together by a centromere The nucleus begins to disappear Centrioles migrate to opposite ends of cell Spindle fibers become visible Mitosis: Metaphase 2 nd stage of mitosis (short stage) Chromosomes become attached to the spindle fibers by their centromeres Chromosomes line up on the midline Mitosis: Anaphase 3 rd stage of mitosis Sister chromatids are pulled apart the spindle fibers attached to the centromere and the centriole begin to shorten pulling the chromatids from each other Mitosis: Telophase 4 th stage of mitosis Chromatids reach the opposite poles of the cell Chromosomes unwind, spindle begins to break down, nucleolus reappears and nuclear envelop forms around each set of new chromosomes MitosisFreprod.html&size=35.1kB&name=modchromosome.jpg&p=chromosome+structure&type=jpeg&no=85&tt=573&ei=UTF-8 Mitosis animation Mitosis animation Division of Cytoplasm Cytokinesis division of cytoplasm between the two newly formed cells Different for plant and animal cells Life Cycle of a Cell and Cell Division Video clip Among the following, the term that includes the others is ___________. A.Interphase B.Nuclear division C.Mitosis D.Cell Cycle By the end of prophase, each of the following has occurred except ______________. A.Tighter coiling of the chromosomes B.Breaking down of the nuclear envelope C.Disappearing of the nucleolus D.Lining up of chromosomes in the cell The longest phase of the cell cycle is ________________. A.Prophase B.Interphase C.Metaphase D.Mitosis A chromatid is attached to a spindle fiber by the ________________. A.Nucleolus B.Deep furrow C.Centromere D.Centriole The sequence of growth and division of a cell makes up ______________ A.Mitosis B.The Cell Cycle C.Chromosomes D.Cytoplasmic Division Identify the stage of mitosis A.Anaphase B.Metaphase C.Prophase D.Telephase Identify the stage of mitosis A.Anaphase B.Metaphase C.Prophase D.Telephase Results of Mitosis So whats the point? Mitosis guarantees that the two new cells that are produced are genetically identical. The two new daughter cells will carry out the same cellular processes and functions as those of the parent cell and will grow and divide just as the parent cell did. Control of the Cell Cycle The full story of how the cell cycle is controlled is not fully understood Scientist do agree on some aspects of what causes cells to divide Enzymes Enzymes Control the Cell Cycle Different enzymes control different parts of the cell cycle Interphase growth (G1 phase) synthesis (S phase) getting ready (G2 phase) mitosis (prophase, metaphase, anaphase, telophase) Sometimes cells lose control of the cell cycle Can result from: Not enough enzyme Too much enzyme Production of enzymes at the wrong time Enzyme production is controlled by genes Cancer cells behave much differently than normal cells. spend very little time in interphase and go through mitosis uncontrollably. Approx. 1/10,000 of your cells are cancerous-the good news-your defense cells usually kill them fast. Cancer Uncontrolled cell division can result in cancer Cancer is a mistake in the cell cycle. Cancerous cells form tumors Tumors deprive normal cells of nutrients Cancer cells can enter the blood stream and spread throughout the body (metastasis) Video clip Causes of Cancer Genetic factors (Heredity) Viruses that cause damage to genes Environmental Factors that damage genes Cigarette smoke Air pollution Water pollution UV exposure Radiation Incidence of Cancer People of different countries develop different types of cancer Ex. Breast cancer is high in the U.S, Stomach cancer is high in China When people move from one country to another, cancer rates follow the pattern of the country in which they are currently living Cancer Prevention There is a clear link between a health lifestyle and incidence of cancer Diet Low fat, high fiber Fruits, vegetables, grains Vitamins & Minerals Caratenoids Vitamins A, C & E Calcium Exercise No tobacco use Cell Aging and Cancer Video clip Video clip Growth and Development in Multicellular Organisms Cells Tissues Organs Organ systems Organism Video clip No matter how complex the organism, the cell is still the basic unit of organization