cellular energetics Flashcards
(50 cards)
describe the first and second laws of thermodynamics and explain why they are important to cellular energetics
first law: conservation of energy (energy cannot be created or destroyed only converted to other forms)
cells convert energy from one form to another, this law ensures that cells must obtain energy from their environment and convert it efficiently
Second law: entropy increases: every energy transformation increases the entropy of the universe
the processes that cells use generate heat and waste
cells must continuously expend energy to maintain order and stay alive
define endergonic and exergonic reactions and describe ow they are linked in cellular energetics
exergonic: reactions that release energy, the products have less energy than the reactants
cellular respiration
endergonic: reactions that require an input of energy to occur, the products have more free energy than the reactants
photosynthesis
define the basic structure of ATP, understand how it stores and releases cellular energy, and the relationship of ATP to exergonic and endergonic reactions
ATP structures: adenine, ribose, three phosphate groups, the high energy bonds are between ribose and three phosphate groups
stores and releases energy: it is stored in the phosphate bonds particularly between the second and third ribose, when the bond is broken ATP becomes ADP and an inorganic phosphate
relation ship of ATP to exergonic and endergonic reactions: ATP serves as a bridge between energy releasing and energy consuming reacitons
describe oxidation and reduction reactions and explain their relationship to endergonic and exergonic reactions
oxidation: loss of electrons
reduction: gain of electrons
redux reactions always occur together if one molecule is oxidized, another is reduced
exergonic: if electrons are transferred from a high energy molecule to a lower energy acceptor
endergonic: if electrons move from a low energy donor to a high energy acceptor
Describe the process of diffusion and the factors that influence diffusion rates
Diffusion is the passive movement of molecules from a higher concentration area to a lower concentration area, driven by the molecules kinetic energy
the steeper the gradient the faster the diffusion
higher temperature speeds up diffusion
smaller molecules diffuse faster than larger ones
the more permeable the membrane the faster the diffusion
a larger surface area allows for more molecules to be diffused at once
the shorter the distance the faster the diffusion
in denser solvents diffusion is slower
Describe selective permeability and how it influences movement of materials across plasma membranes, including what types of molecules easily pass through the membrane and which cannot.
selective permeability means the plasma membrane controls what enters and exists the cell, allowing some substances to pass freely while blocking or regulating others.
made of a phospholipid bilayer
phospholipids have both hydrophobic and hydrophilic tails
small non polar molecules pass easier
small uncharged polar molecules can also pass easier but to a lesser extent
molecules that cannot pass: Larger molecules, ions and charged molecules, and most polar molecules
Describe facilitated diffusion and active transport, the difference between them, and when the cell might use each transport type.
facilitated diffusion: the passive movement of molecules across the membrane with the help of membrane proteins no energy required
high to low
active transport: movement of molecules against the concentration gradient using energy from ATP
low to high
Describe the process of osmosis and explain how solute concentration differences across a membrane influence osmotic movement.
osmosis: the passive movement of water against a selectively permeable membrane from a area of lower concentration to an area of higher concentration
continues until the equilibrium is reached
no energy required
involves only water
water moves to dilute the solute
Describe how facilitated diffusion and active transport differ from osmosis and diffusion.
diffusion and osmosis: are passive, and rely only on concentration gradients
Facilitated diffusion is passive but uses proteins while active transport is energy dependent
Define tonicity, hypertonic, isotonic, and hypotonic and explain water movement across a plasma membrane in response to tonicity.
Tonicity refers to the relative concentration of solutes outside a cell compared to inside a cell, it determines the direction of water movement across the plasma membrane by osmosis
isotonic means the concentration is the same outside the cell and inside the cell
hypertonic means the concentration is higher outside the cell
hypotonic means the concentration is higher inside the cell
Briefly explain endocytosis and exocytosis.
endocytosis is the process by which a cell takes in a large molecule or particles by engulfing them within its plasma membrane creating a vesticle
exocytosis is the process by which a cell releases large molecules by fusing a vesticle with the plasma membrane spilling the contents outside
Name the ultimate source of energy for most life on earth and explain the role of photosynthesis in converting this energy into a form that is useable by all form of life on earth.
sunlight
photosynthesis converts sunlight to chemical energy
Write the overall equation for photosynthesis and explain the role of each of the reactants (i.e., where it comes from and what it is used for) and products (i.e., how is it formed and where it goes) in the photosynthetic process.
6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6O₂
co2 comes from the air, h2o comes from the soil, and light from the sun
glucose is used for energy and o2 is released as a byproduct
Describe the basic structure of a chloroplast and the function of each of the following: chlorophyll, thylakoid, stroma and granum.
chloroplast: where photosynthesis occurs
chlorophyll: the green pigment that absorbs light
thylakoid: membrane sacs where light reactions occur
stroma: fluid area where the Calvin cycle occuts
granum: stack of thylakoid
Describe how the characteristics of light (wavelength and intensity) can influence photosynthesis, including a description of which wavelengths are used by photosynthetic organisms.
shorter wavelengths are best for photosynthesis
high light intensity=faster photosynthesis
Describe what happens during the light dependent reactions, including what goes in, what comes out, and where these reactions take place.
occurs in thylakoid membranes, uses water and light, produces ATP NADPH and oxygen, oxygen comes from splitting water
Describe the basic structure of a photosystem and explain its function in the light reactions.
photosystem is the proteins and pigments
absorbs light and transfer electrons during light reactions
Explain how an electron transport chain is used in the production of ATP and NADPH in photosynthesis.
moves electrons through proteins in the thylakoid membranes
creates ATP and NADPH using light energy
Describe what happens during the Calvin Cycle (aka Calvin-Benson Cycle), including what goes in, what comes out, and where these reactions take place.
Occurs in: stroma
Uses: CO₂, ATP, NADPH
Produces: glucose (C₆H₁₂O₆)
Does not need light directly
Explain the role of the Calvin Cycle in producing carbohydrates and describe the three main stages (see the figures in the Calvin Cycle section of today’s reading).
makes glucose from CO2
3 main stages: carbon fixation, reduction and regeneration of RuBP
Describe the role of ATP and NADPH in photosynthesis, including where they are produced, where they are used, and what they are used for. Use your understanding of this objective to explain how the light dependent reactions and Calvin cycle are coupled.
made in light dependent reactions
used in the Calvin cycle
provides energy and electrons to build glucose
Explain why the uptake of carbon dioxide and the release of oxygen can be used to measure rates of photosynthesis.
you can measure the rate of Co2 intake or o2 output
more co2 used or more o2 produced means faster photosynthesis
Write the overall equation for respiration and explain the role of each of the reactants (i.e. where it comes from and what it is used for) and products (i.e. how it is formed and where it goes) in the respiration process.
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP
glucose comes from food
oxygen comes from breathing
produces ATP, CO2 and H2O
Describe the role of NAD+, NADH, FAD, and FADH2 in respiration.
NAD⁺ and FAD: electron carriers
They pick up electrons and become NADH and FADH₂, which take electrons to the electron transport chain
