Cell Physiology Physiology = the study of the vital processes of an organism

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Caitlin Anthony
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Cell Physiology Physiology = the study of the vital processes of an organism 1) Homeostasis = a steady state that a tissue, organ, system or organism maintains by self-regulating adjustments =

1 Cell Physiology Physiology = the study of the vital processes of an organism 1) Homeostasis = a steady state that a tissue, organ, system or organism maintains by self-regulating adjustments = ability to adapt to a change and stay in a balanced state - ie) kidney will double in size if the other is removed goose bumps & shivering conserve body heat going into shock in an emergency - cells maintain homeostasis with their environment by means of the plasma membrane - the cell membrane is a differentially permeable or semi permeable membrane between the cell and its environment (or neighboring cell) = allows certain substances to cross into and leave the cell while other substances are prohibited - Factors Affecting the Selective Permeability of the Plasma Membrane: 1. Particle size 2. Particle solubility 3. Concentration inside or outside of the cell 4. Electrical charge of the Particle (ions move across the membrane slowly if same charge as cell membrane) 5. Plasma membrane structure 2) Structure of the Plasma Membrane (a.k.a. Fluid Mosaic Model)* = lipid bilayer embedded with proteins - the 2 layers are composed of mobile phospholipid molecules : phospholipids have a polar water soluble end (hydrophilic) and a non polar fat soluble end (hydrophobic) : the hydrophilic ends face the outer environment & the inner cell components -special protein molecules (glycoproteins) embedded in the lipid bilayers serve different functions: a. Markers = so cells can identify each other - explains transplant and transfusion rejection b. Receptors for chemical messages (hormones) c. Regulators of what enters or attaches to cells d. Transporters carrying specific materials into & out of the cell

2 FLUID MOSAIC MODEL OF THE PLASMA MEMBRANE

3) Transport of Substances - substances are moved through the cell membrane in a variety of ways: A) Passive Transport = movement of materials across a cell membrane without the cell using its own

Simple Diffusion = the random movement of substance from an area of high concentration to an area of low concentration - establish equilibrium (although motion is not stopped on the microscopic

3 3) Transport of Substances - substances are moved through the cell membrane in a variety of ways: A) Passive Transport = movement of materials across a cell membrane without the cell using its own energy (with the concentration gradient) - modes of passive transport: 1. Simple Diffusion = the random movement of substance from an area of high concentration to an area of low concentration - establish equilibrium (although motion is not stopped on the microscopic level) - used for small, non-polar molecules, ions and gases - factors affecting diffusion = concentration, temperature, & pressure 2. Osmosis - is the diffusion of water - as water molecules enter a cell, pressure occurs inside against the cell membrane - in plant cells this pressure is referred to as turgor pressure : gives plants their rigidity : when turgor pressure = osmotic pressure, equalibrium is reached - the type of solution the cell is in will affect osmosis:

a) Isotonic Solution : iso = same, tonic = strength : solute concentration (molecules dissolved in water) inside the cell equals the solute concentration outside the cell : is

pressure within the cell : the cell walls of plant cells allow them to withstand this pressure :animal cells lack cell walls so would swell and eventually burst (cytolysis)

4 a) Isotonic Solution : iso = same, tonic = strength : solute concentration (molecules dissolved in water) inside the cell equals the solute concentration outside the cell : is perfect for cells b) Hypotonic Solution : hypo = lower : solute concentration outside the cell is less than that found inside the cell : water flows inward causing increased pressure within the cell : the cell walls of plant cells allow them to withstand this pressure :animal cells lack cell walls so would swell and eventually burst (cytolysis) therefore they have water removing mechanisms - single celled organisms have contractile vacuoles (ie. Paramecium) - multicellular organisms have specialized organs (ie. Kidneys, lungs sweat glands)

5 c) Hypertonic Solution : hyper = higher : solute concentration outside the cell is greater than that found inside the cell : the organism loses water = cells shrink : causes plasmolysis (a.k.a. Reverse osmosis) - plants cell wilt (caused by lack of water, excess fertilizer) - animals cells dehydrate (caused by drinking salt water, swimming in high content salt water, treating a cut with salt solution)

3. Facilitated Diffusion - special channel protein molecules in the cell membrane speed up the movement of molecules already moving across the cell membrane = a fast

6 3. Facilitated Diffusion - special channel protein molecules in the cell membrane speed up the movement of molecules already moving across the cell membrane = a fast pass - very selective ie. Glucose diffuses into red blood cells 100 s of times faster than other sugars) What type of solution is each of the following cells in? A B C

B) Active Transport = movement of substances across the cell membrane requiring the cell to use its own energy - energy is needed to move molecules from an area of low concentration to an area of

Facilitated Transport = a protein pump - special protein carrier molecules in the cell membrane receive an energy boost from the cell which helps them transport molecules against the concentration

9 B) Active Transport = movement of substances across the cell membrane requiring the cell to use its own energy - energy is needed to move molecules from an area of low concentration to an area of high concentration (against the concentration gradient) - modes of active transport: 1. Facilitated Transport = a protein pump - special protein carrier molecules in the cell membrane receive an energy boost from the cell which helps them transport molecules against the concentration gradient* - some actively pump materials out of the cell as well - Energy used is in the form of ATP (Adinosine Triphosphate) 1 Protein Pump (specific to Na + based on shape) 2 NRG causes the pump to change its shape forcing the substance through (Na + ) 4 Release of the phosphate causes the pump to revert to original shape forcing Substance 2 (K + ) through 3 New shape of pump allows substance 2 (K + ) to enter

lysosomes - two forms of endocytosis: a) Phagocytosis : process through which cells engulf solid particles : ie.

10 2. Endocytosis - endo = into; cytosis = movement of substances within the cell by means of the cytoplasm - transport of large molecules (ie. lipids, proteins, amino acids) into the cell by engulfing (surrounding) the molecule with pseudopods until it has been enclosed within a vacuole - molecules are then digested by enzymes from the lysosomes - two forms of endocytosis: a) Phagocytosis : process through which cells engulf solid particles : ie. amoeba, white blood cells b) Pinocytosis : process through which cells engulf liquid droplets : ie. fat droplets are engulfed by cells in the small intestine 3. Exocytosis - exo = out of - large molecules (ie. wastes, excess water) are stored in vacuoles which move to and join with the cell membrane expelling their contents = opposite of endocytosis

12 4. Metabolism = all the chemical reactions that build up and tear down molecules within the cell - involves energy production and use within the cell - all organisms require energy in order to complete life processes ie. active transport, reproduction, movement, growth and repair, etc. - this energy is obtained on a cellular level A) Energy = the capacity for doing work or causing change - cannot be created or destroyed, only changed from 1 form to another = First Law of Thermodynamics : ie. heart attack victims receive electrical energy which is converted to mechanical energy - there are many forms of energy (light, heat, chemical, electrical, mechanical, etc.) however, ultimate energy source for all living organisms is the sun 1. Energy Storage and Transformation - energy storage and conversion processes are critical for sustaining life - ATP (adenosine triphosphate) is a compound that stores chemical energy in cells : energy is kept in these small packets so that it can be used quite readily = ie. keeping one hundred loonies for buying things instead of a single $20 bill Adenosine Phosphate Phosphate Phosphate : whenever energy is needed, the terminal (end) phosphate breaks off of ATP = a bit of energy is released and ADP (adenosine diphosphate) is left Adenosine Phosphate Phosphate NRG

13 : ADP can be used as an energy source (strip end phosphate AMP) but is not an efficient energy source (like using quarters to purchase goods). = is an energy carrier (picks up NRG released during oxidation-reduction reactions and uses it to attach a phosphate and form ATP again) ADP + P - P = CYCLIC ATP 2. Oxidation-Reduction Reactions = transfer of electrons from 1 atom/molecule to another to go from high energy (unstable) reactants to low energy (stable products) - energy is released in large amounts 3. Electron Transport Systems - rapid release of energy is not suited for cells : causes damage (cells = proteins; energy = heat) = NRG is released in a series of steps as particles are passed from 1 acceptor molecule to another - ie. like a hot potato Types of Metabolic Reactions = photosynthesis, respiration, and fermentation

14 B) Photosynthesis (pp. 97 fwd) General Formula: 6CO 2 + 6H 2 O + Solar NRG chlorophyll > C 6 H 12 O 6 + 6O 2 process through which solar energy is converted into chemical energy stored in the bonds of glucose molecules occurs in the chloroplast Involves 2 stages: o Light-Dependent Reactions o Light-Independent Reactions (Calvin Cycle) i) Light- Dependent Reactions Site: in the disk shaped thylakoids of the grana Purpose: Produce ATP & harvest H + ions to use in the Light Independent Reactions Involves: o Photolysis - process by which H 2 O is split into H + ions & O atoms by the sun o Phosphorylation - process of adding a phosphate to ADP creating ATP (requires energy) a) Photosystem II Inputs are light and water Photons of sunlight strike photosystem II (chlorophyll a) causing the release of 2 high energy electrons to the Primary Electron Acceptor These electrons pass down an Electron Transport Chain releasing energy to form ATP from ADP by phosphorylation b) Photosystem I Electrons at the base of the ETC in Photosystem II are reenergized by the sun and passed to the Secondary Electron Acceptor These electrons pass down a 2nd, shorter ETC releasing NRG to form more ATP At the same time, photolysis splits water into H + ions, an O atom & 2 electrons electrons = will replace the 2 e _ s lost by chlorophyll a H + ions = picked up by the carrier molecule NADP, forming NADPH, which will be used in the Light Independent Reactions Oxygen = given off as a byproduct in the form of O 2 gas

15 **All molecules of NADPH & ATP created in the Light Phase are used in the Calvin Cycle

16 ii) Light Independent Reactions (Calvin-Benson Cycle) Occurs in the gel between the grana called stroma Purpose: Build carbohydrate molecules using products of the light-dependent reactions Does not require solar energy as it uses the energy stored in the ATP molecules = occurs day and night 3 CO 2 molecules from the atmosphere enters the chloroplasts via stomates Energy from ATP is used to join each CO 2 to carrier molecule, Rubisco (RuBP) The Rubisco carriers force the 3 CO 2 to bond forming a 3 Carbon compound called Phosphoglyceric Acid (PGA). o The 3 RuBP are freed to pick up more CO 2 Energy from ATP is used to join the PGA molecules with H + ions donated by NADPH to form PGAL (Phosphoglyceraldehyde) Both ADP and NADP are recycled to the Light-Dependent Phase PGAL can be used as it is or molecules of PGAL can be combined to form more complex carbohydrates (ie. Glucose, sucrose, starch)

17 What gas is released in the Light Dependent Reactions? 1. Carbon dioxide 2. Oxygen 3. Water vapour 4. All of the above What is made in Photosystem I & II? 1. C 6 H 12 O 6 2. ATP 3. CO 2 4. All of the above What new gas enters the Calvin Cycle? 1. Carbon dioxide 2. Oxygen 3. Water vapour 4. All of the above What is produced by the Calvin Cycle? 1. Sugars 2. ATP and NADPH 3. O 2 4. All of the above

18 D. Cellular Respiration (pp. 107 fwd) The process by which mitochondria in the cells of all living organisms break down glucose to make ATP = convert the NRG stored in glucose to a form the cell can use Chemical equation for cellular respiration: C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O + ATP complementary to photosynthesis = products of photosynthesis used in cellular respiration Two types: Aerobic respiration: requires O 2 ; results in complete breakdown of glucose Anaerobic respiration: requires no O 2, incomplete decomposition of glucose i) Aerobic Respiration Involves 3 stages: Glycolysis, the Kreb s Cycle, & the Electron Transport System a) Glycolysis Site: occurs in the cytoplasm of the cell Purpose: Split sugar into 3 C molecules to be processed in the mitochondria does not require the presence of oxygen 1. A molecule of glucose is split into two 3 carbon molecules of PGAL using two molecules of ATP. 2. Each PGAL molecule is converted into Pyruvate by removing a H + ion & e - s. Energy is released in this process (creates 2 ATP per pyruvate). 3. The H + ions & e - s are picked up by the carrier molecule NAD which becomes NADH. 4. The pyruvate and NADH molecules are carried over to the next stages. Net Results: 1 C 6 H 12 O 6 produces: 2 pyruvate 2 NADH 4 ATP (-2 invested) = 2 ATP

19 b) Krebs Cycle (a.k.a. Citric Acid Cycle) Site: occurs in matrix (inner compartment ) of the mitochondrion in cell Purpose: break down pyruvate to harvest H + ions & e - s to put through the ETC requires oxygen Matrix Christae 1. To prepare pyruvate for entering the Krebs cycle, a carrier molecule, Coenzyme A, picks up each pyruvate and converts it into Acetyl CoA by removing a Carbon, Hydrogen and electrons. Carbon atoms are joined to Oxygen to form CO 2 while the H and e-`s are picked up by NAD creating NADH. For each acetyl CoA : 1 CO 2 is created (exhaled) 1 NADH **The 2 acetyl CoA molecules can now enter the Kreb Cycle. 2. The Krebs Cycle is like a big circular assembly line. Each acetyl CoA is picked up by a Citric Acid, a 4 Carbon carrier molecule which carries it through the cycle. 3. Each acetyl CoA is broken down by stripping off H + ions & e - s which are picked up by the carrier molecules NAD & FAD producing NADH & FADH 2. Carbon atoms are joined to Oxygen to form CO 2. = nothing is left of the original glucose molecule (taking apart Leggo) 4. The energy released from this process produces ATP. Net Results:(for each acetyl CoA) : 1 ATP : 3 NADH and 1 FADH 2 : 2 CO 2

20 c) Electron Transport System (a.k.a. Electron Transport Chain) Site: occurs in the cristae (inner folded membranes) of the mitochondrion Purpose: produce ATP via phosphorylation requires oxygen 1. 2 ATP are used to put the NADH and FADH 2 from Glycolysis and the Krebs Cycle into the Electron Transport System. 2. The NADH and FADH 2 are each stripped of H + ions & e - s. 4. These ions and electrons are sent to a series of carrier molecules (enzymes) which pass them from 1 enzyme to the next, releasing NRG to create ATP. = like a hot potato 5. The hydrogen ions and e- s join with oxygen to form H 2 O(g) which is exhaled. Each NADH produces 3 ATP, and each FADH 2 produces 2 ATP. Net Results: 6 H 2 O (exhaled) 10 NADH produce 30 ATP 2 FADH 2 produce 4 ATP 34 ATP (but 2 invested) = 32 ATP **Most of the ATP for aerobic respiration is produced in this stage

21 **ATP Totals for aerobic respiration: Glycolysis 2 ATP Citric Acid Cycle 2 ATP Electron Transport Chain 32 ATP 1 Glucose = ~36 ATP in all for aerobic respiration INPUT GLYCOLYSIS PREP FOR KREBS CYCLE KREBS CYCLE E - TRANSPORT CHAIN OUTPUT

22 ii) Anaerobic Respiration (a.k.a. Fermentation) Also called incomplete cellular respiration Does not require oxygen to make ATP Is Glycolysis but in the absence of O 2 pyruvate is converted into more stable products 2 types: a) Alcohol Fermentation o used by yeast o as there is no O 2 the pyruvate is rearranged forming ethanol & releasing CO 2 Net Results: 2 ATP CO 2 (make bread rise) Ethanol (produce beer, wine) b) Lactate Fermentation o used by anaerobic bacteria and muscles o lack of O 2 causes pyruvate to be converted to lactic acid & CO 2 is released. o bacteria (ie. milk turns sour) o muscle cells: a lack of sufficient oxygen during strenuous exercise causes lactic acid build up in muscles resulting in muscle cramps and fatigue Net Results: 2 ATP CO 2 Lactic Acid Comparing Aerobic and Anaerobic Respiration ATP production : Aerobic = 36 vs Anaerobic = 2 **Aerobic Respiration is more efficient due to the Electron Transport Chain = is where most ATP is formed - like complete combustion of fuel in a car

23 4. Metabolism = all the that build up and tear down molecules within the cell - involves and within the cell - all organisms require energy in order to complete life processes ie. active transport, reproduction, movement, growth and repair, etc. - this energy is obtained on a A) Energy = the capacity for doing work or causing change - cannot be only changed from 1 form to another = First Law of Thermodynamics : ie. heart attack victims receive which is converted to - there are many forms of energy (light, heat, chemical, electrical, mechanical, etc.) however, ultimate energy source for all living organisms is 1. Energy Storage and Transformation - energy processes are critical for sustaining life - ATP (adenosine triphosphate) is a compound that chemical energy in cells : energy is kept in these small packets so that it can be used quite readily = ie. Adenosine Phosphate Phosphate Phosphate : whenever energy is needed, the terminal (end) phosphate breaks off of ATP = a bit of energy is released and ADP (adenosine diphosphate) is left Adenosine Phosphate Phosphate NRG

24 : ADP can be used as an energy source (strip end phosphate AMP) but is not an efficient energy source = (picks up NRG released during reactions and uses it to attach a phosphate and form ATP again) ADP + P - P = CYCLIC ATP 2. Oxidation-Reduction Reactions = of electrons from 1 atom/molecule to another to go from (unstable) reactants to (stable products) - energy is released in 3. Electron Transport Systems - rapid release of energy is not suited for cells : causes damage (cells = proteins; energy = heat) = NRG is released in a as particles are passed from 1 acceptor molecule to another - ie. Types of Metabolic Reactions = photosynthesis, respiration, and fermentation

Involves 2 stages: o Light-Dependent Reactions o Light-Independent Reactions (Calvin Cycle) i) Light- Dependent Reactions Site: in the disk shaped thylakoids of the Purpose: Produce & harvest to use

25 B) Photosynthesis (pp. 97 fwd) General Formula: 6CO 2 + 6H 2 O + Solar NRG chlorophyll > C 6 H 12 O 6 + 6O 2 process through which is converted into stored in the bonds of glucose molecules occurs in the chloroplast Involves 2 stages: o Light-Dependent Reactions o Light-Independent Reactions (Calvin Cycle) i) Light- Dependent Reactions Site: in the disk shaped thylakoids of the Purpose: Produce & harvest to use in the Involves: o Photolysis - process by which is split into by the o Phosphorylation - process of adding a to creating (requires energy) c) Photosystem II Inputs are and Photons of sunlight strike photosystem II (chlorophyll a) causing the release of 2 high energy electrons to the Primary Electron Acceptor These electrons pass down an releasing energy to form ATP from ADP by phosphorylation d) Photosystem I Electrons at the base of the ETC in Photosystem II are by the and passed to the Secondary Electron Acceptor These electrons pass down a 2nd, shorter releasing NRG to form more ATP At the same time, photolysis splits into H + ions, an O atom & 2 electrons electrons = will replace the by chlorophyll a H + ions = picked up by the carrier molecule, forming which will be used in the Light Independent Reactions Oxygen = given off as a byproduct in the form of

26 **All molecules of NADPH & ATP created in the Light Phase are used in the Calvin Cycle

27 ii) Light Independent Reactions (Calvin-Benson Cycle) Occurs in the gel between the grana called stroma Purpose: Build molecules using products of the light-dependent reactions Does not require solar energy as it uses the energy stored in the molecules = occurs 3 CO 2 molecules from the atmosphere enters the chloroplasts via Energy from ATP is used to join each CO 2 to carrier molecule, The Rubisco carriers force the 3 CO 2 to bond forming a 3 Carbon compound called Phosphoglyceric Acid o The 3 RuBP are freed to pick up more CO 2 Energy from ATP is used to join the molecules with donated by NADPH to form (Phosphoglyceraldehyde) Both ADP and NADP are to the Light-Dependent Phase PGAL can be used as it is or molecules of PGAL can be combined to form more complex carbohydrates

29 D. Cellular Respiration (pp. 107 fwd) The process by which mitochondria in the cells of all living organisms break down glucose to make ATP = Chemical equation for cellular respiration: C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O + ATP complementary to photosynthesis = Two types: Aerobic respiration: requires results in complete breakdown of glucose Anaerobic respiration: requires incomplete decomposition of glucose i) Aerobic Respiration Involves 3 stages: Glycolysis, the Kreb s Cycle, & the Electron Transport System a) Glycolysis Site: occurs in the of the cell Purpose: Split sugar into 3 C molecules to be processed in the mitochondria does not require the presence of oxygen 1. A molecule of glucose is split into two 3 carbon molecules of using two molecules of ATP. 2. Each PGAL molecule is converted into by removing a H + ion & e - s. Energy is released in this process 3. The H + ions & e - s are picked up by the carrier molecule which becomes 4. The pyruvate and NADH molecules are carried over to the next stages. Net Results: 1 C 6 H 12 O 6 produces: pyruvate NADH ATP (-2 invested) = 2 ATP

b) Krebs Cycle (a.k.a. Citric Acid Cycle) Site: occurs in of the mitochondrion in cell Purpose: break down pyruvate to harvest H + ions & e - s to put through the ETC requires oxygen Matrix Christae 1.

30 b) Krebs Cycle (a.k.a. Citric Acid Cycle) Site: occurs in of the mitochondrion in cell Purpose: break down pyruvate to harvest H + ions & e - s to put through the ETC requires oxygen Matrix Christae 1. To prepare pyruvate for entering the Krebs cycle, a carrier molecule, picks up each pyruvate and converts it into by removing a Carbon, Hydrogen and electrons. Carbon atoms are joined to Oxygen to form while the H and e-`s are picked up by NAD creating For each acetyl CoA : CO 2 is created (exhaled) NADH **The 2 acetyl CoA molecules can now enter the Kreb Cycle. 2. The Krebs Cycle is like a big circular assembly line. Each acetyl CoA is picked up by a a 4 C carrier molecule which carries it through the cycle. 3. Each acetyl CoA is broken down by stripping off which are picked up by the carrier molecules NAD & FAD producing &. Carbon atoms are joined to Oxygen to form CO 2. = nothing is left of the original glucose molecule 4. The energy released from this process produces Net Results:(for each acetyl CoA) : ATP : NADH and FADH 2 : CO 2

c) Electron Transport System (a.k.a. Electron Transport Chain) Site: occurs in the (inner folded membranes) of the mitochondrion Purpose: produce ATP via requires 1.

31 c) Electron Transport System (a.k.a. Electron Transport Chain) Site: occurs in the (inner folded membranes) of the mitochondrion Purpose: produce ATP via requires 1. are used to put the NADH and FADH 2 from Glycolysis and the Krebs Cycle into the Electron Transport System. 2. The NADH and FADH 2 are each stripped of H + ions & e - s. 6. These ions and electrons are sent to a series of carrier molecules which pass them from 1 enzyme to the next, releasing to create = like a hot potato 7. The hydrogen ions and e- s join with oxygen to form which is exhaled. Each NADH produces and each FADH 2 produces Net Results: 6 H 2 O (exhaled) 10 NADH produce ATP 2 FADH 2 produce ATP ATP (but 2 invested) = **Most of the ATP for aerobic respiration is produced in this stage

32 **ATP Totals for aerobic respiration: Glycolysis 2 ATP Citric Acid Cycle 2 ATP Electron Transport Chain 32 ATP 1 Glucose = in all for aerobic respiration INPUT GLYCOLYSIS PREP FOR KREBS CYCLE KREBS CYCLE E - TRANSPORT CHAIN OUTPUT

33 ii) Anaerobic Respiration (a.k.a. Fermentation) Also called Does not require to make ATP Is Glycolysis but in the absence of O 2 pyruvate is converted into more stable products 2 types: a) Alcohol Fermentation o used by o as there is no O 2 the pyruvate is rearranged forming & releasing Net Results: 2 ATP CO 2 (make bread rise) Ethanol (produce beer, wine) b) Lactate Fermentation o used by o lack of O 2 causes pyruvate to be converted to & is released. o bacteria (ie. milk turns sour) o muscle cells: a lack of sufficient oxygen during strenuous exercise causes lactic acid build up in muscles resulting in muscle cramps and fatigue Net Results: 2 ATP CO 2 Lactic Acid Comparing Aerobic and Anaerobic Respiration ATP production : Aerobic = vs Anaerobic = **Aerobic Respiration is more efficient due to the = is where most ATP is formed - like complete

Releasing Food Energy

Releasing Food Energy All food is broken down by the body into small molecules through digestion. By the time food reaches your, bloodstream it has been broken down into nutrient rich molecules that can