Cell Transport Processes - Biology Notes PDF

DIFFUSION IN CELLS Concentration Gradient: Different concentrations on each side of cell membrane = diffusion possible Concentration gradient determines direction of movement of water or solutes Diffusion = passive transport NO energy (ATP) required. ...

DIFFUSION IN CELLS Concentration Gradient: Different concentrations on each side of cell membrane = diffusion possible Concentration gradient determines direction of movement of water or solutes Diffusion = passive transport NO energy (ATP) required.  OSMOSIS Concentration gradient but molecules can’t get through the water will move instead. This is the process of osmosis high water concentration (low solute) to an area of low water concentration (high solute)  DIRECTION OF H2O MOVEMENT Hypertonic solution = higher solute concentration Hypertonic solutions gain water. Hypotonic solution = lower solute concentration. Hypotonic solutions lose water. Isotonic solution are solutions with equal solute concentrations.  FACILITATED DIFFUSION - The movement is in response to the concentration gradient but needs help from a protein facilitator. - Facilitated diffusion is a form of passive transport How facilitated diffusion works  FACILITATED DIFFUSION (2) 1. Channel proteins create channels through which small water-soluble molecules can move in response to a concentration gradient.  FACILITATED DIFFUSION (3) 2. Carrier proteins can attach to molecules not able to diffuse, resulting in carrier protein shape change to move molecule The protein then returns to its original shape  ACTIVE TRANSPORT Against concentration gradient, requires energy input. Cell may need certain concentration gradients for certain processes.  ACTIVE TRANSPORT(2) Energy needed for active transport is produced in the mitochondria, through cellular respiration from adenosine triphosphate (ATP).  ENDOCYTOSIS AND EXOCYTOSIS Some molecules still too large to get through Last option: use vesicles – sacs that surround the large particle and contain it. Both endo and exo require energy (ATP) from the mitochondrion  ENDOCYTOSIS Endocytosis (think enter) The cell membrane forms a pocket around the cell and engulfs it.  EXOCYTOSIS Exocytosis “Think Exit” Reverse order or endocytosis to rid of wastes. A vesicle surrounds the particle, moves to the cell membrane, fuses with it and ruptures, releasing the contents outside the cell.  CELL SIZE Rate of materials entering or leaving cell is limited by surface area of the cell membrane. The larger the surface area, the more materials can move in or out of the cell.  CELL SIZE Larger cells need more materials to “feed” on and more waste products to eliminate. More difficult for materials, especially oxygen, to get deep into the cell where it is needed. An increase in volume = more difficult for cell survival.  VOLUME CALCULATION For a cube or rectangular prism Volume = length x width x height  SURFACE AREA CALCULATION Review of grade 9 math Area = length (1) x width (w) For a cube: SA = 6 x the area of one face For a rectangular prism: SA = the areas of all the sides added together  SURFACE AREA TO VOLUME RATIO Tells us the amount of surface area per unit of volume (cm2/cm3) Greater ratio = more readily materials can enter/leave the cell. - Increased side length of a cube = SA to V ratio decreases - Graph Curve = volume increases at a much greater rate than the surface area. Why would this be a problem for a very large cell?  SA TO VOLUME RATIOS: PART 2 Skinny or flat have greater surface area for a given amount of volume.  SPECIALIZED CELL SHAPE TO INCREASE SURFACE AREA Examples: Microvilli and Villi of small intestine absorb nutrients from digested food. Root hairs of plants absorb nutrients and water.  All cells get to point where SA is inadequate to V In order to be larger than this an organism must become multicellular. The cell divides.  MAXIMIZING POTENTIAL Individual cells need to have the greatest possible surface area to volume ratio because: 1. Smaller distances for molecules to travel 2. Lots of opportunities for transport (passive and active) of substances to occur.  UNICELLULAR Made up of only a single cell Single celled organisms are NOT simple A single celled organism can do most things that we need trillions of cells to do Euglena – a single celled green algae MULTICELLULAR Made up of two or more cells Have specialized cells. Variety of cells with unique functions to support life. Coordination of all cells for survival of organism.  ADVANTAGES OF BEING MULTICELLULAR - Division of Labor: can perform tasks more effectively and efficiently - Size: In multicellular organisms, internal transport systems allow efficient exchange of materials. These transport systems permit the organism to grow to a larger size. - Interdependence of Cells: If one cell of a multicellular organism dies, it does not kill the entire organism.  ORGANIZATION Molecules: groups of atoms Organelles: organic molecules with specific functions Cells: groups of organelles with specific functions Tissues: groups of cells with specific functions. Ex. muscles, nerves, connective tissue Organs: groups of tissues with specific functions. Ex. heart Organ systems: groups of organs with specific functions Ex. circulatory system Organisms: groups of organ systems carrying out specific functions Know this Organization!  TWO TYPES OF PLANTS 1. Herbaceous - plants with little wood in their stems. Survive for one growing season 2. Woody – cork and bark  PLANT SYSTEMS 1. Shoot System (everything above ground) Functions: Photosynthesis Transport of nutrients/water Reproduction Storage  PLANT SYSTEMS (2) 2. Root System (everything underground) Functions: Anchorage Absorption of water and minerals Transport of food and water  PLANT TISSUES Meristems Growth region of the plant Cells divide by mitosis Two different meristem regions: one to produce shoot tissue and one to produce root tissue  DERMAL TISSUE The outermost layer of cells Usually one cell-layer thick Functions: 1. Involved in gas exchange 2. Secretes a waxy cuticle. Prevents dehydration. 3. Protection from disease.  GROUND TISSUE Bulk of the plant, beneath the epidermis Functions Loosely packed to allow flow of gases Provides strength and support in the stem Food and water storage in roots Location of photosynthesis in leaves  VASCULAR TISSUE Common to both the shoot and root system Thick-walled cells made of cellulose and lignin Function Responsible for transport of materials in plant  VASCULAR TISSUE (2) Xylem – non-living Function Water and minerals travel through from roots to the leaves to be used in photosynthesis  VASCULAR TISSUE (3) Phloem - living Function Transport's sucrose and sugars around the plant for metabolism. Cellulose synthesis and storage Composition Made of sieve tube cells (no nuclei) Controlled by companion cells (with nuclei)  SPECIALIZATION IN PLANT CELLS Cells become differentiated as they develop. This differentiation allows for cells to become specialized with specific tasks. Special Cells  SPECIALIZATION IN PLANT CELLS (2) Root Hairs Cells of the root system produce tiny hair like projections called root hairs. Function in providing more surface area for the absorption of water SPECIALIZATION IN PLANT CELLS (3) Dermal cells Produce a waxy cuticle to protect the cell from water loss  SPECIALIZATION IN PLANT CELLS (4) Guard Cells - Form tiny pores called stomata that allow for gas exchange. - Contain chloroplasts  PHOTOSYNTHESIS Photosynthesis = light and synthesis = putting together Word Equation: Water + carbon dioxide -- (chlorophyll and light) -- 🡪 glucose + oxygen Reactants Products Chemical Equation 6H2O (l) + 6CO2 (g) -- (chlorophyll and light) --🡪 C6H12O6 (aq) + 6O2 (g) Reactants Products  CELLULAR RESPIRATION The reverse chemical process of photosynthesis. Cytoplasm and Mitochondria. Word Equation: Glucose + oxygen 🡪 carbon dioxide + water + energy Reactants Products Chemical Equation: C6H12O6 (aq) + 6O2 (g) 🡪 6CO2 (g) + 6H2O (l) + energy Reactants Products - Photosynthesis: only happens in plants (different parts in the day and night) - Cellular Respiration: happens in plants and animals (all of the time) Gas Production Day: Photosynthesis (plants): produces glucose and O2 Cellular respiration (plants and animals): producing CO2 and H2O Rate of cellular respiration in plants is lower than animals so less O2 needed and less CO2 produced Result (Day): more O2 released, light is required Gas Production At Night: - Only cellular respiration occurring using glucose, and producing H2O and CO2 - Result: CO2 released, glucose is required.  THE LEAF TISSUES AND GAS EXCHANGE - Air can enter cells in leaves by passive diffusion - Leaves have specialized cells to: 1. Maximize gas exchange 2. Provide needed reactants 3. Remove the products of leaf reactions Stomata = tiny pores controlled by guard cells on either side. Guard cells have two different functions: 1. To allow materials in and out when necessary 2. Protect against H2O loss  GUARD CELLS SWELL TO OPEN THE STOMA How it occurs: Light strikes guard cells -> accumulation of potassium ions by active transport (ATP needed) Photosynthesis in these cells = ATP for active transport  Hypertonic guard cells so water enters by osmosis Guard cells swell Outer walls are thinner than the inner walls so the cell under pressure bulges outward.  No more light = active transport of K+ ions stops and K+ diffuses out Photosynthesis also stops (no ATP) Cells become hypotonic to surrounding cells  H20 leaves guard cells by osmosis Guard cells become limp Stoma close  STOMA WILL ALSO CLOSE IF: Excessive water loss – guard cells will lose turgidity There is a lack of CO2 for photosynthesis  WHY IS WATER LOSS AN IMPORTANT ISSUE FOR PLANTS? H2O is continually being lost due to evaporation When water is scarce guard cells close the stomata to preserve as much water as possible Transpiration = H2O vapor leaving plant through stomata  ENVIRONMENT AND STOMATA In hot dry climates with low humidity, plants have fewer stomata In very humid areas plants have more stomata CO2 low, stomata will maximally open  POSITIONING OF STOMATA AND ENVIRONMENT Normally on underside of leaves On upright leaves e.g. grasses, cattails; on both surfaces of the leaves On floating leaves – on the upper surface On submerged leaves – no stomata upright leaves floating leaves submerged leaves OTHER AREAS OF GAS EXCHANGE Gas exchange can also take place through openings called lenticels in woody stems  GROUND TISSUE Mesophyll Specialized ground tissues between the lower and upper epidermis There are two types of mesophyll tissues  PALISADE TISSUE CELLS Below the upper epidermis Long, rigid, rectangular cells that are tightly packed together Arranged so many cells are exposed to the sun's rays  SPONGY MESOPHYLL TISSUE Loosely packed, irregularly shaped Less rigid Allow for gas exchange by diffusion throughout the leaf - Diffusion is very efficient in plants because of the air present in the spongy mesophyll of the leaf and stem - Air diffuses through the stomata and into the air spaces in the leaf  VASCULAR BUNDLE Functions: - provides the leaf with water needed for transpiration - Contained in ribs called leaf veins - Xylem: transports H2O from roots to leaves - Phloem: transports sugars from photosynthesis from leaves to roots  GAS EXCHANGE IN PLANTS Plants have NO specialized organs for gas exchange. It occurs by diffusion. Gas exchange occurs through stomata and air spaces Cytoplasmic Streaming is a mechanism that circulates materials within the cell. Consider Water is required in the leaves for photosynthesis Water gets into the plant roots from soil Question How does water get from the roots to the leaves? What forces cause water to move against the force of gravity? Type Your Answers into the Google Jamboard!  COHESION The tendency of molecules of the same kind to stick together This is caused by the polar nature of water. The slightly positive end of one molecule attracts the slightly negative of another. Result = molecules tend to hold together  ADHESION Tendency of unlike molecules to stick together  ROOT PRESSURE Xylem pressure Dissolved minerals in cells and the roots from active transport produce higher solute concentrations inside cell H2O drawn in by osmosis creating a pressure that forces fluid up the xylem *Tall plants have other factors as well  TENSION OR TRANSPIRATION PULL Created by evaporation of H2O As one H2O molecule evaporates, it creates a pull on the adjacent H2O molecule. Along with cohesion and adhesion, transpiration pull is enough to move H2O in xylem from roots to leaves and then out of the xylem into the ground tissue.  Rate of transpiration is temperature dependent: Hotter = more H2O loss Colder = less H2O loss Most of the H2O is lost to transpiration. The rest is used in the process of photosynthesis.  TONICITY Plasmolysis = shrinking of cytoplasm and plasma membrane away from the cell wall hypertonic environment (H2O loss). Turgid = firm due to H2O entering (hypotonic environment). Turgidity important H2O can pass in and out of vacuole with no net increase in volume Pressure in the cells helps hold up green parts of plant to sunlight. Plants benefit in hypotonic environments  SUGAR TRANSPORT IN PLANTS Sugar transported in phloem tissue Sugar source is leaves. The sugar sink is places where sugars used/stored. Phloem is made up of sieve tube cells which depend on companion to move sugars into/out of sieve tube cells. Phloem in the leaves Companion cells actively transport sugar molecules from the sites of photosynthesis Phloem becomes loaded H2O moves into cells by osmosis and then into sieve cells Increased pressure pushes, H2O and sugars through phloem to rest of plant Sugars move into other cells and are used for life processes.  CONTROL SYSTEMS Plants respond to certain stimuli A stimulus is a signal that can cause a reaction Plants can grow: Toward nutrients Away from poor growth conditions Tropism = plant’s response to an external stimulus  TROPISMS Response toward a stimulus is positive Response away from a stimulus is negative  PHOTOTROPISM Photo = light tropism = movement in response Plant growth in response to light Stems and leaves grow towards light 🡪 positively phototropic Roots will grow away from light 🡪 negatively phototrophic  GRAVITROPISM Plant growth in response to gravity Roots tend to grow toward gravity 🡪 positively gravitropic Stems grow away from gravity 🡪 negatively gravitropic  THERMOTROPISM Plants respond to changes in temperature When a plant is warmed, it will continue to grow where it is warm  CHEMOTROPISM Plants grow towards areas with high concentrations of nutrients Roots detect chemicals and branches sent out towards the source (positive) If unwanted chemicals to close, some plants will send roots out in the opposite direction (negative)  HYDROTROPISM Plants can grow towards soils with higher water concentrations Desert plant root systems grow great distances to find H2O (positive) Swamp plant roots grow up and out to find areas with little H2O (negative)  LIGHT EXPOSURE All plants respond to seasonal amounts of sunlight  THIGMOTROPISM A plant’s response to physical contact Positive thigmotropism: response towards stimulus. E.g. action of Venus fly trap Negative thigmostropism: response away from stimulus E.G a roots response to a stone in the soil  MECHANISM OF RESPONSE Plants produce hormones (auxins) Asymmetric growth of cells on either side of the root or stem Results in movement toward or away from a stimulus.