Cellular Transport and Processes Unit 4 Obj. 1.2.1, 4.2.1, 4.2.2

The Cell Membrane The gateway to the cell

Cell Membrane Flexible Allows unicellular organisms to move

Functions of the Cell Membrane Protection Regulates what comes in and out Allows cell recognition Anchoring sites for cytoskeleton Attachment sites for enzymes Binds cells together at junctions Contains cytoplasm

Structure and Components of Cell Membrane Phospholipid = phosphate head (hydrophilic) and lipid tails (hydrophobic) Bilayer = two layers Studded with proteins (peripheral = partially through and integral = all the way through) and carbohydrates

Phospholipids Contains two fatty acid chains that are non-polar (tail) and a polar head made of -PO4 (phosphate)

Selective Permeability Hydrophobic and hydrophilic Polar and non-polar Allows membrane to “choose” what comes across and maintain homeostasis Hydrophobic molecules (can dissolve in lipids) pass easily, hydrophilic molecules(can dissolve in water) do not

Semi-permeable membrane Hydrophobic molecules can pass through freely even if they are large Hydrophilic molecules can only pass through freely if they are very small and can “slip through the cracks” Examples: CO2, O2, H2O

Homeostasis Balanced internal condition of cells Also called equilibrium Maintained by plasma membrane controlling what enters and leaves the cell

Types of Transport

Simple Diffusion Requires no energy  passive transport Molecules have a natural kinetic energy Molecules move from an area of high concentration to an area of low concentration

Diffusion in Liquids

Diffusion Through a Membrane Solute moves down the concentration gradient  from high to low

Osmosis Diffusion of water across a membrane  water is so special, it gets its very own transport! Moves from high water potential to low water potential

Osmosis High water potential, Low solute concentration Low water potential, High solute concentration

Aquaporins Special channels for water to pass through during osmosis

Comparing Solutions Isotonic = when the concentration of two solutions is the same Hypotonic = when comparing two solutions, the solution with the lesser concentration of solutes Hypertonic = when comparing two solutions, the solution with the greater concentration of solutes

Cell in Isotonic Solution The Plasma Membrane 4/25/2017 Cell in Isotonic Solution 10% NaCL 90% H2O ENVIRONMENT CELL NO NET MOVEMENT 10% NaCL 90% H2O What is the direction of water movement? equilibrium The cell is at _______________. G. Podgorski, Biol. 1010

Cell in Hypotonic Solution The Plasma Membrane 4/25/2017 Cell in Hypotonic Solution 10% NaCL 90% H2O CELL 20% NaCL 80% H2O What is the direction of water movement? G. Podgorski, Biol. 1010

Cell in Hypertonic Solution The Plasma Membrane 4/25/2017 Cell in Hypertonic Solution 15% NaCL 85% H2O ENVIRONMENT CELL 5% NaCL 95% H2O What is the direction of water movement? G. Podgorski, Biol. 1010

Cells in Solutions

What can happen to a cell in different solutions? Cytolysis = the cell bursts from water rushing in and making it swell up, occurs in hypotonic solutions Plasmolysis = the cell shrivels up from water rushing out, occurs in hypertonic solutions isotonic hypotonic hypertonic

Cytolysis and Plasmolysis

Osmosis in Red Blood Cells The Plasma Membrane 4/25/2017 Osmosis in Red Blood Cells Isotonic Hypertonic Hypotonic G. Podgorski, Biol. 1010

isotonic hypotonic hypertonic hypertonic isotonic hypotonic The Plasma Membrane 4/25/2017 isotonic hypotonic hypertonic hypertonic isotonic hypotonic G. Podgorski, Biol. 1010

Facilitated Diffusion Does not require energy  passive transport Needs some help from transport proteins  they allow the molecules through Molecules move from high to low concentrations Channel proteins = embedded in the cell membrane and have pore for materials to cross Carrier proteins = can change shape to move material from one side to the other

Channel Proteins

Carrier Proteins

Active Transport Requires energy or ATP to occur Moves materials from low to high concentrations = against the concentration gradient

Other forms of cell transport Exocytosis = cell releases large amount of material Endocytosis = cell takes in a large amount of material by folding it in the cell membrane Pinocytosis = cell takes in liquid, “cell drinking” Phagocytosis = extensions of cytoplasm surround and engulf large particles and take them into the cell

Exocytosis

Exocytosis

Endocytosis

Pinocytosis

Pinocytosis

Phagocytosis

Photosynthesis

We need energy Energy is the ability to do work Most energy on earth comes from the sun Heterotrophs get energy by eating other organisms Autotrophs make their own food and energy  photosynthesis = when they use the sun (light energy) as their energy source

How do we store energy? Chemical bonds are formed = energy is stored Chemical bonds are broken = energy is released Adenosine triphosphate (ATP) = main source of energy for cells, provides power for almost all functions Contains adenine, ribose (5-carbon sugar), and 3 phosphate groups

How do we store energy? ATP = “charged” battery, stores energy Energy is released by breaking off the last phosphate group  Adenosine diphosphate (ADP) ADP = “dead” battery, energy has been released

How does photosynthesis work? Plants use the energy from the sun to convert water and carbon dioxide into oxygen and glucose (sugar) Joseph Priestly – discovered that plants make oxygen. He placed a lit candle under a jar and waited until it had consumed all the oxygen. He discovered that if he placed a sprig of mint in the jar and waited a few days, the candle could be lit again, indicating that the plant produced oxygen.

Photosynthesis equation 6CO2 + 6H2O light> C6H12O6 + 6O2 Carbon dioxide + water light> glucose + oxygen Carbon dioxide, water, and light must be present for photosynthesis to occur

What kind of light does photosynthesis need to occur? Sunlight is “white” light  a mixture of different wavelengths of light Pigment = light-absorbing molecule Chlorophyll = main pigment of plants, does not absorb green light very well  gets reflected back to our eyes

Inside a Chloroplast Thylakoids = small disc-shaped saclike photosynthetic membranes Grana = stacks of thylakoids Stroma = region outside thylakoid membranes

Electron Carriers Electrons gain a great deal of energy when they are excited by the sun  require special carriers NADP+ (nicotinamide adenine dinucleotide phosphate) = main electron carrier NADP+ holds 2 high energy electrons and additional hydrogen ion  becomes NADPH NADPH carries electrons to chemical reactions elsewhere in the cell

Two Parts of Photosynthesis 1. Light-dependent reaction = produces energy from solar power (photons) in the form of ATP and NADPH 2. Calvin Cycle or Light Independent Reaction Also called “carbon fixation” or “C3 Fixation” Uses energy (ATP and NADPH) from light reaction to make glucose

Factors affecting photosynthesis Temperature Availability of water Light intensity These factors are different in different areas of the world  plants develop special adaptations

Respiration

What is cellular respiration? Cellular respiration is the process that releases energy by breaking down glucose and other food molecules in the presence of oxygen. Two kinds of respiration: Aerobic respiration = occurs if oxygen is present Anaerobic respiration = occurs if oxygen is not present

Equation Cellular respiration: 6O2 + C6H12O6  6CO2 + 6H2O + Energy (ATP) Recall – Photosynthesis equation: 6CO2 + 6H2O light> 6O2 + C6H12O6

Process Cellular respiration happens in a series of steps Energy is released slowly, which allows the cell to trap more of it and store it in ATP

Process Step 1: Glycolysis One molecule of glucose (C6H12O6) is broken in half, producing two molecules of pyruvic acid (C3H6O3) Uses up 2 molecules of ATP  energy “investment” 4 molecules of ATP are produced  net gain of 2 ATP molecules Occurs in cytoplasm of cell Does not require oxygen  can be part of aerobic or anaerobic respiration Electron carrier = NAD+ (without electron pair)  NADH (with electron pair)

Process – Anaerobic respiration Step 2: Fermentation Occurs in cytoplasm of cells In plants, yeasts, etc. it is called “alcoholic fermentation” pyruvic acid + NADH  alcohol +CO2 + NAD+ In animal cells and some prokaryotes, it is called “lactic acid fermentation” pyruvic acid + NADH  lactic acid + NAD+ Lactic acid = burning sensation in muscles during exercise

Process – Aerobic respiration Step 2: Krebs cycle Occurs in mitochondria Pyruvic acid is broken down into carbon dioxide Produces 2 ATP

Process – Aerobic respiration Step 3: Electron transport chain Occurs in mitochondria Produces H2O and 34 ATP

Comparing aerobic and anaerobic respiration Produces 36 ATP Produces CO2 and H2O Occurs in mitochondria and cytoplasm Produces 2 ATP Can produce CO2, lactic acid, and/or alcohol Occurs in cytoplasm

Comparing photosynthesis and cellular respiration Function Energy capture Energy release Location Chloroplasts Mitochondria Reactants CO2 and H2O C6H12O6 and O2 Products Equation 6CO2 + 6H2O  C6H12O6 + 6O2 C6H12O6 + 6O2  6CO2 + 6H2O Energy Energy