How do we fuel our body?

Question 1

What is the Plasma Membrane?

Answer 1

• Boundary of cell – encloses and supports cell contents.

- Separates intracellular vs. extracellular materials.

Question 2

What is the Fluid Mosaic Model?

Answer 2

-Attaches cells to other cells and to the surrounding matrix.
-Cells communicate with their environment through their cell membrane.
-Determines what can move into and out of the cell (selectively permeable).
o Intra- and extracellular environment is different
-Difference in charge across membrane – membrane potential
-Structure – fluid mosaic model

Question 3

What is the lipid bilayer made of?

Answer 3

• Phospholipids

- Cholesterol

Question 4

What are proteins in the Fluid Mosaic Model?

Answer 4

• Inserted in the lipid bilayer
• Peripheral or integral
• Many are involved in transporting molecules across the cell membrane, e.g. channel proteins, carrier proteins, ATP powered pumps.

Question 5

What are channel proteins?

Answer 5

-Form a tiny channel through the plasma membrane
-Molecules of certain size, shape and charge can pass through
-Non-gated ion channels
oAlways open
-Gated ion channels
oOpened or closed by certain stimuli

Question 6

What are carrier proteins?

Answer 6

-Also called transporters
-Integral proteins move ions from one side of membrane to the other
o Specific binding sites
o Protein changes shape to transport ions or molecules
o Resumes original shape after transport
o Uniporters, symporters, antiporters

Question 7

What is ATP-Powered transport?

Answer 7

• Requires energy in the form of ATP.
• Transports substances AGAINST their concentration gradient, so the cell can accumulate substances.
• Example we learn is the sodium potassium pump.

Question 8

What is a Solute?

Answer 8

• Dissolved substance in a solution

- e.g. glucose, sucrose, ions (Na+, K+, Cl-)

Question 9

What is Solvent?

Answer 9

• Liquid that holds solutes

- Generally, water

Question 10

What is Solution?

Answer 10

-Mixture formed when solute dissolved in solvent

Question 11

What is Diffusion?

Answer 11

• Molecules move from an area of higher concentration to an area of lower concentration.
• Continues until the molecules have evenly distributed themselves throughout the solution.

Question 12

What is Diffusion through the cell membrane?

Answer 12

1. Certain specific nonlipid soluble molecules or irons diffuse through membrane channels
2. Other non-lipid soluble molecules, for which membrane channels are not present, can’t enter the cell
3. Lipid soluble molecules diffuse directly though the plasma membrane

Question 13

What is Filtered Diffusion?

Answer 13

• Move large, water soluble molecules or electrically charged molecules across the plasma membrane.
• Amino acids and glucose in, manufactured proteins out
• Passive

Question 14

What is Osmosis?

Answer 14

-Osmosis is the diffusion of water across a selectively permeable membrane, e.g. the plasma membrane

Question 15

What

Answer 15

• A selectively permeable membrane lets water to pass through, but any solutes dissolved in the water
• If the beaker contains distilled water (water with no solutes), water molecules will move back and forth across the membrane at the same rate
• The water level stays the same on both sides of the membrane

Question 16

What is the Effect of a Semi-Permeable Membrane?

Answer 16

1. Solute added to one side of beaker. It is too big to cross through the pores in the membrane
2. Solute distributes itself evenly in one half of the beaker
3. Water moves from area of low solute concentration to high solute concentration.
4. Water level on the RHS of the beaker drops and on the LHS of the beaker increases.
5. Water is moving down its concentration gradient

Question 17

What is the effect of the concentration of the solution?

Answer 17

• From these two examples we can see that the concentration of the solute determines how much water moves across the membrane
• The more concentrated a solution is, the more that solution will “pull” water towards it.
• A dilute or weak solution with a small number of solutes will only have a weak “pull” on water.
• A concentrated solution with a large number of solutes will have a strong “pull” on water.

Question 18

What is Osmolarity?

Answer 18

• This “pull” on water created by solutes is termed the solution’s Osmotic pressure or Osmolarity
• Osmolarity is measured in Osmoles/L or mOsmoles/L.
• Generally, in the body fluids we are working with solutions which are fairly dilute and so we use the unit mOsmoles/L.
• As we have seen, the osmolarity of a solution is directly related to the concentration of the solution.
• A weak solution will have a low osmolarity value
• A more concentrated solution will have a higher osmolarity value.
• A solution that has an osmolarity of 100mOsmol/L will have a smaller “pull” on water than a solution which has an osmolarity of 300mOsmol/L.

Question 19

What is Osmolarity in relation to Body Cells?

Answer 19

-Body fluids have many dissolved solutes
-Body fluids can be divided into
o intracellular
o extracellular (intercellular & intravascular)
-The osmolarity of the intracellular fluid of a normal cell under normal conditions is approximately 290mOsmol/L

Question 20

What is an Isotonic Solution?

Answer 20

• When a cell is placed in a solution that has the same osmolarity as the inside of the cell, the solution is called isotonic
• Water will move between the intracellular and extracellular fluid at equal rates (no net movement of water) and the cell is happy.

Question 21

What is a Hypertonic Solution?

Answer 21

• Let’s place a cell in a solution that has a higher osmolarity that inside the cell
• The solution with the higher osmolarity contains a greater concentration of solutes
• The solution is hypertonic
• It exerts a stronger “pull” on water
• Water is literally pulled out of the cell
• The cell loses water and shrinks

Question 22

What is a Hypotonic Solution?

Answer 22

• Let’s place a cell in a solution that has a lower osmolarity that inside the cell
• A solution with a lower osmolarity contains a lower concentration of solutes
• The solution is hypotonic
• In this case the cell exerts a stronger “pull” on water
• Water is literally pulled into the cell
• The cell takes in water – swell – burst!

Question 23

What is Metabolism?

Answer 23

-Total of all chemical processes that occur in body
-Metabolism includes
o Catabolism
-Energy-releasing process
-Where large molecules broken down to smaller molecules
o Anabolism
-Energy-requiring process
-Where small molecules joined to form larger molecules

Question 24

What is Catabolism?

Answer 24

-A large reactant is broken down to form smaller products
o Chemical bonds broken; energy released.
o Energy in carbohydrates, lipids, proteins is used to produce energy which drives anabolic reactions, e.g. active cell membrane transport, muscle contraction, protein synthesis.

Question 25

What is Anabolism?

Answer 25

-Two or more reactants chemically combine to form a new and larger product
o Chemical bonds made; energy stored in the bonds
o Responsible for growth, maintenance and repair
o Produce chemicals characteristic of life: carbohydrates, proteins, lipids, and nucleic acids.

Question 26

What is Energy (Kinetic & Potential)?

Answer 26

-The capacity to do work!
-Potential energy
o Stored energy that could do work but isn’t
-Kinetic energy
o Energy that is actually doing work and moving matter
-Conservation of energy means
o Total energy of the universe is constant, can’t be created or destroyed
o But energy can be converted from one type to another
-Our focus is chemical energy (& heat energy)

Question 27

What is Chemical Energy & ATP and the equation?

Answer 27

-Energy is stored in chemical bonds
-Breaking chemical bonds releases energy
-This energy can then do WORK
-There is a large amount of energy stored in the chemical bonds of nutrients
-When nutrients (e.g. glucose) are broken down, energy is released
-This energy is used to combine adenosine diphosphate (ADP) with an inorganic phosphate molecule (Pi) to make adenosine triphosphate (ATP)
-ATP stores the energy releases from breaking the chemical bonds
ADP + Pi + energy → ATP
-Some energy released from breaking a chemical bond is not captured and stored as ATP but is lost as heat
-Heat is used to maintain body temperature

Question 28

What is ATP & Potential Energy and the equation?

Answer 28

-ATP is the cell’s preferred way to store energy
-The small amount of energy stored in each molecule of ATP is easier for the cell to access that the larger amount stored in nutrient molecules
-When the cell needs energy, it breaks down ATP to ADP ATP ADP + Pi + energy
-This energy can be used by the cell to make new proteins, repair a damaged cell membrane, drive active transport across a membrane
-The two equations we are interested in are:
o ADP + Pi + energy ATP
o ATP ADP + Pi + energy

Question 29

What is Cellular Respiration and its stages?

Answer 29

-Cellular respiration is the process that breaks chemical bonds in food to produce energy which is stored as ATP
-Three main stages
1. Glycolysis
o Cytoplasm
2. Citric acid cycle
o Mitochondrial matrix
3. Electron transport change/oxidative phosphorylation
o Inner mitochondrial membrane

Question 30

What is Glycolysis?

Answer 30

-Occurs in the cytoplasm
-Breaks down 1 glucose molecule (6 carbon sugar) into 2 pyruvate molecules (3 carbons)
-Uses 2 ATPs in the early stages
-Produces 4 ATP by the end = net production of 2 ATP
-Produces 2 NADH molecules ◦ these are used in oxidative phosphorylation to produce more ATP
-Is anaerobic - does not require O2
-If oxygen is available pyruvate moves into the 2nd stage – the citric acid cycle
-If oxygen is not available, pyruvate gets converted to lactic acid
1 glucose → 2 pyruvate + 2 ATP + 2 NADH

Question 31

What is the Citric Acid Cycle?

Answer 31

-Matrix of the mitochondria
-Acetyl Coenzyme A formation
-Before the citric acid cycle begins:
o Pyruvate (3C) is converted to acetyl CoA (2C), producing 1 NADH and 1 CO2
o Each glucose we started with produces 2 pyruvates
o For each glucose molecule, we have: 2 Acetyl CoA + 2 NADH + 2 CO2
-Acetyl CoA enters the citric acid cycle, and is transferred to a 4 C molecule to make a 6-carbon molecule (citrate)
-The citrate then goes through a series of chemical reactions and loses two C groups as 2 C02 to end up back as a 4 C molecule ready to go through another cycle
-Every turn of the cycle produces 1 ATP + 3 NADH + 1 FADH2 + 2 C02
-The cycle turns twice for every glucose that enters glycolysis 1 glucose 2 pyruvate 2 Acetyl CoA 2 ATP + 6 NADH + 2 FADH2 + 4 C02

Question 32

What are NADH & FADH?

Answer 32

-Electron carrier molecules
o NAD+ = nicotinamide adenine dinucleotide
o FAD + = flavin adenine dinucleotide
-These molecules collect the electrons that are produced when chemical reactions occur during glycolysis and the citric acid cycle.
E.g. NAD+ + 2 e- + 2H+ → NADH + H+
-They transport these electrons to the electron transport chain in the inner mitochondrial membrane, donate the electrons to the membrane carriers, and oxidative phosphorylation occurs to generate ATP.

Question 33

What is Oxidative Phosphorylation?

Answer 33

• Most of the energy produced by cellular respiration is by oxidative phosphorylation
• NADH and FADH2 produced by glycolysis and the citric acid cycle pass through the electron transport chain (ETC) in the inner membrane of the mitochondria
• The ETC is a series of electron donors and receptors. NADH and FADH2 donate their electrons to the first acceptor in the chain, releasing H+ in the process.
• Acceptor molecule 1 then passes the electrons on to the next molecules in the chain and so on.
• Oxygen is the final electron acceptor & water is produced
• The movement of electrons from molecule to molecule in the membrane releases energy, this energy is used to generate a proton (H+ ion) gradient across the membrane.
• The protons then flow back across the membrane through a special channel. This flow of H+ is used by ATP synthase to produce ATP.
• Oxidative phosphorylation produces between 32 – 34 ATP.

Question 34

What are Amino Acids & Lipids?

Answer 34

-Fatty acids
o Undergo beta oxidation to form acetyl CoA
o Acetyl CoA can enter citric acid cycle to generate ATP, NADH and FADH2
-Amino acids
o Can be converted into intermediate compounds of CHO digestion e.g. keto acid, pyruvate, acetyl CoA