Cell Transport Biology 11

Two parts of a Solution: –Solute A substance dissolved in another substance, usually in lesser amount. –Solvent A substance in which another substance is dissolved, forming a solution Biology 112

Cell membranes are selectively permeable. This means that some things can pas through while others cannot. Proteins embedded in the cell membrane are used as channels and pumps which allow substances through or not. Biology 113 Cell Transport

Diffusion Diffusion is the movement of molecules from an area of high concentration to an area of lower concentration.

Cell Transport There are three types of cell transport: –Simple Diffusion –Facilitated Diffusion –Active Transport

Passive Transport Passive Transport: Movement of materials across the cell membrane going with the concentration gradient (from a region of greater concentration to a region of lesser concentration). Simple Diffusion and Facilitated Diffusion are both examples of Passive Transport *Cell uses no energy to transport particles!

Simple Diffusion No transport protein used Movement with the concentration gradient (high to low) No additional cell energy required Examples: water, oxygen, carbon dioxide.

Homeostasis To maintain a stable, constant condition. To maintain equilibrium. The cell wants its internal environment to be the same as its external environment.

Concentration Gradient When there is a difference in concentrations: –High concentration means more particles –Low concentration means less particles –In diffusion, particles move from a high concentration to a low concentration to reach on EQUAL concentration (equilibrium) on each side.

Passive Transport Examples a) Osmosis – specific type of diffusion (can you remember the definition??)Osmosis b) Facilitated diffusion – Process by which molecules diffuse across a cell membrane with the aid of transport proteins. This is for particles that cannot dissolve into the lipid bi-layer or are too large to pass through.Facilitated diffusion

PassiveTransport

A solution that has the same concentration of solutes as the cell. Therefore there is no net movement of water molecules Biology 1112

Hypertonic The solution has higher concentration of solutes then the cell. Therefore there will be a net movement OUT of the cell.

A solution that has a lower concentration of solutes than the cell. There will be a net movement of water into the cell. Biology 1114 Hypotonic

Osmotic Pressure This is the pressure that water exerts on the hypertonic side of a selectively permeably membrane. It can be problematic for living cells because they can burst from over-inflation with water or shrivel up from loss of water.

Biology 1116 Cytolysis: The bursting or rupture of a cell.

Biology 1117

Facilitated Diffusion Transport protein used: carrier protein or channel protein Movement with the concentration gradient No additional cell energy required Passive Example: glucose molecules

Facilitated Diffusion Similar to simple diffusion in the sense that it is diffusion (across a membrane) from a high concentration to a lower concentration. However, this time the rate of diffusion is greatly accelerated by the action of membrane proteins that act as carrier molecules and aid in diffusion.

Facilitated Diffusion Protein ChannelsCarrier Proteins

Passive Transport Video

Active Transport Molecular Active Transport: Movement of materials across the cell membrane going against the concentration gradient (from a region of lesser concentration to a region of greater concentration). *Requires energy from cell!

Active Transport Transport protein used: Carrier Protein Movement AGAINST the concentration gradient (low to high) Additional cell energy required Active Example: Sodium Potassium Pump

Active Transport Molecular active transport involves protein pumps. Examples of active transport: –Cells in Gills of marine fish actively pump out salts. –Root cells of plants often take in large quantities of ions.

Active transport Video

Sodium Potassium Pump Active Transport

Bulk Membrane Transport Active transport (requires energy) Requires the creation of vacuoles and vesicles Two types: –Endocytosis –Exocytosis Animation

Endocytosis Endocytosis: The process by which the plasma membrane engulfs and takes in substances from a cell’s environment. *Common in unicellular organisms. 2 types: –i) Phagocytosis: Form of endocytosis in which large solid particles are taken into the cell. Example – WBC’s engulfing harmful bacteria –ii) Pinocytosis: Form of endocytosis in which small liquid droplets are taken into the cell. a.k.a. cell drinking

Endocytosis

Phagocytosis

Exocytosis Exocytosis: Cell products or wastes are enclosed in vesicles and released to outside of cell.Exocytosis: Process: –Golgi Apparatus “packages” the material into a vesicle and sends it to the cell membrane –The vesicle fuses with the membrane –The material is deposited outside the cell *Reverse process of endocytosis. Examples = secretion or elimination of waste

Energy and Life Photosynthesis and Respiration Biology 1133

What is energy? Energy is the capacity to do work. All living this require energy, but how do they get it? There are two ways to receive energy, –Produce it –Consume it

Photosynthesis The sun is the main source of energy for the earth. Autotrophs make their own food, and most are green plants. This is done through the process of Photosynthesis.

Photosynthesis We know photosynthesis requires energy from the sun, but the sun is not available 24 hours a day! Photosynthesis must occur in two phases: –Light dependent reactions Convert light energy into chemical energy (ATP and NADPH) –Light independent reactions Uses ATP and NADPH from the light dependent reactions to build glucose.

Role of Photosynthesis Plants use it to make food Animals get their food from plants, so therefore, from photosynthesis as well (consumers) Photosynthesis also produces oxygen which most living things need to respire and live.

The process of photosynthesis Light is trapped by chlorophyll and provides energy for photosynthesis Sunlight energy is used to split water in half (photolysis)

The process of photosynthesis Products from splitting water: –Protons  stored for later use –Electrons  Passed to chorophyll –Oxygen  can be used in respiration or release Light energized the electrons and turns them into high energy electrons. These are passed down an electron transport chain

Electron Transport Chain Is a series of proteins on the thylakoid membrane of chloroplasts. Electrons are passed from one protein to another, and energy is released which: –Helps join ADP and phosphate to form ATP –Allows hydrogen to join with NADP to form NADPH –Both forms of energy are used in light independent reactions.

Process of Photosynthesis Glucose is formed when the high energy electrons, protons from storage and carbon dioxide from air are combined. This is takes place in chloroplasts and is known as the Calvin Cycle. This is a part of the light independent reactions.

The Calvin Cycle 1. Grab: A five-carbon carbon catcher catches one molecule of carbon dioxide and forms a six-carbon molecule. 2. Split: the enzyme RuBisCO (with the energy of ATP and NADPH molecules) breaks the six-carbon molecule into two equal parts. NADP (nicotinamide adenine dinucleotide phosphate) is a coenzyme that carries electrical energy used in cellular processes.

The Calvin Cycle 3. Leave: A trio of three carbons leave and become sugar. The other trio moves on to the next step. 4. Switch: Using ATP and NADPH, the three carbon molecule is changed into a five carbon molecule. 5. The cycle starts over again

Photosynthesis Once sugars are created through the calvin cycle, mitochondria can now use it for cellular respiration. The mitochondria uses glucose, or sugars, to create ATP which is a usable energy for the cell. This not only occurs in plant cells, but in our own cells as well. By consuming other plants and animals, our body uses the sugars ( carbohydrates) that we eat into usable energy by mitochondra.

Review Questions What is the primary function of photosynthesis? Name two molecules that are produced during the light dependent reactions of photosynthesis and serve as temporary sites for energy storage. In eukaryotic cells, photosynthesis occurs in organelles named? True or False The Calvin cycle (= light-independent reactions) can occur in a plant that is in dark room so long as the materials carbon dioxide, ATP, and NADP-H are present.

Cellular Respiration Process by which mitochondria break down food molecules to produce ATP in plants and animals. Nutrients + Oxygen  Water + ATP + CO2

Cellular respiration Changes organic chemical energy (glucose) into inorganic chemical energy (ATP) Three stages of cellular respiration –Glycolosis Anaerobic ( does not require oxygen) –Krebs Cycle Aerobic ( requires oxygen) –Electron Transport Chain Aerobic (requires oxygen)

Glycolysis Breaks down glucose into two molecules of pyruvic acid Uses enzymes and takes place in the cytoplasm of the cell Produces –2 pyruvic acid molecules – used in next step of cellular respiration –2 ATP molecules –energy for the cell –2 NADH – electron carrier

Before the next step of cellular respiration, the pyruvic acid molecules formed in the glycolysis must go into the mitochondria. The next two aerobic reactions will then form: Pyruvic acid  CO2 + Water + ATP

Krebs Cycle Is a series of chemical reactions used by all aerobic organisms to generate energy. Provides the hydrogen and electrons needed for the electron transport chain, which happens in the mitochondria.

Krebs Cycle The following is formed during the Krebs Cycle: –2 Molecules of CO2 are released –2 Molecules of ATP are formed –3 molecules of NAD+ are combined with hydrogen ( NAD+  NADH) –1 molecule of FAD+ combines with hydrogen ( FAD+  FADH)

Electron Transport Chain Following the Krebs cycle, the electron transport chain uses the electron carriers (NADH and FADH2) to pass electrons down a protein chain and slowly releases energy that is used to form ATP and water molecules. This transfers the most energy.

Equation

Summary Photosynthesis- Converts solar energy into chemical energy Cellular Respiration – Converts chemical energy into usable energy Therefore living things deal with three types of energy! –Solar energy –Chemical energy (sugars / lipids) –Usable energy (A.T.P.)

Review Questions What are the three main processes of Cellular Respiration? What is produced during glycolysis? Name two electron carriers. Compare and contrast: –Anaerobic and aerobic –Photosynthesis and Cellular respiration