Cell Transport Biology 11
Jan 16, 2016
• 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
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• 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.
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Cell TransportCell 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??)
• 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.
PassiveTransport
• A solution that has the same concentration of solutes as the cell.
• Therefore there is no net movement of water molecules
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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.
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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.
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Cytolysis: The bursting or rupture of a cell.
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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 Channels Carrier 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 PumpActive 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.
• 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
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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