Chapter 4 Flashcards
The Energy of Life
Energy
The ability to do work, to move matter
-Kinetic and potential energy
Kinetic Energy
The energy of motion
(ex. extended spring, energy is released as kinetic energy and it’s transferred to ball)
Potential Energy
Stored energy that is available to do work
(ex. compressed spring has high potential energy
How are chemical bonds potential energy?
-molecules like glucose and triglycerides store energy in their bonds
-to release this energy, the cell breaks the bonds
-if the cell can’t capture the energy being released, it will be lost as heat
What is the total amount of energy?
The sum of the energy’s 2 forms
Calorie
The energy required to raise the temperature of 1 gram of water by 1 degree Celsius under standard conditions
Energy content of food is usually measured in what?
Kilocalories (kcal) which = 1,000 calories
-1 food Calorie (with a capital C) is actually a kilocalorie
Thermodynamics
The study of energy transformations
What are the 2 most important energy transformations?
-photosynthesis
-cellular respiration
In photosynthesis, plants and microbes use kinetic to gain potential energy how?
They use carbon dioxide, water, and kinetic energy in their chemical bonds. These molecules contain potential energy
Cellular respiration potential energy to kinetic energy how?
Energy-rich glucose molecules change back to carbon dioxide and water, liberating the energy necessary for life. Cells translate some of the potential energy in glucose into kinetic energy of molecular motion and use that kinetic energy to do work
First Law of Thermodynamics
-energy is converted form one form to another
-energy changes from within its biological system
-energy can never be created or destroyed, just converted
-the total amount of energy in the universe never changes
Why can’t cells use energy directly from sunlight?
The energy must first be captured, stored, and converted before it’s able to be used for cellular work
Why are energy transformations inefficient?
-energy will be lost at each step
-heat energy is disordered, which means it can’t be used or converted back to a useful form of energy
Entropy
A measure of disorder/randomness
-intact lightbulb= highly ordered
-smashed lightbulb= highly disordered
Second Law of Thermodynamics
Heat energy is constantly being lost into the universe, and heat energy is disordered, the entropy of the universe is always increasing
Why would a cell die if it’s too cold?
The colder the object feels, the slower the movement of atoms and molecules. They won’t be fast enough for the necessary functions of life
Electron transport chain
Membrane-bound molecular complex that shuttles electrons to slowly extract their energy
-participates in redox reactions
-accepts electrons and passes it onto the next
-small amounts of energy is lost at each step
Each redox reaction links an exergonic process with an endergonic process
The oxidation half is exergonic, since electrons are removed from the electron donor. Electron donor has more potential energy before it’s oxidized than it does after the reaction is complete. The reduction half is endergonic. The acceptor molecule has gained the energy rich electrons, so it ends up with more potential energy than it had before the reaction started
Metabolism
The sum of all the chemical reactions in cells
How can chemical reactions rearrange atoms?
-building complex molecules out of simple parts, like monomers, to form new chemical bonds
-breaking complex molecules into smaller parts, like monomers, which breaks apart chemical bonds
Endergonic reactions
Reactions that form bonds to build molecules, require energy input
-ex. photosynthesis, muscle contraction, building a barn out of boards and nails
Exergonic reactions
Reactions that break bonds to release energy stored in the bonds
-still requires a small amount of energy to start, but releases more energy than puts in
-ex. cellular respiration, old building collapsing into dust, steel, and chunks of concrete (this releases energy in the form of sound and heat)
Oxidation reactions
Release energy
-oxidation is the loss of 1 or more electrons from an atom or molecule
-energy released by the oxidized molecule is stored int eh electrons
Reduction reactions
Require energy
-reduction is the gain of 1 or more electrons by an atom or molecule, which requires energy
-the reduced molecule gains the energy stored in the electrons
Redox reactions cellular respiration and photosynthesis
-both use a small amount of energy at each step
-photosynthesis and cellular respiration both use electron transport chain
-as energy is released, cells store it and use it in other reactions
Oxidation-reduction reactions (redox reactions)
A chemical reaction in which 1 reactant is oxidized, and the other is reduced
-transfer energized electrons from one reactant to another
Coupled reactions
2 simultaneous reactions, one of which provides energy that drives the other
Phosphorylation
One molecule transfers its phosphate group to another molecule
Jobs that require energy in ATP
-transporting substances across membranes
-muscle contractions
-moving chromosomes during cell division
-synthesizing large molecules that make up cells
How can cells build up their pool of ATP?
By cellular respiration
How fast does a typical human cell turn over its entire supply
Every minute or so
-a typical human cell uses the equivalent of 2 billion ATP molecules a minute, just to stay alive
Why can’t a cell produce all its ATP at once?
The high energy bonds of ATP make it to unstable for long term storage. The cell must constantly produce ATP use the energy in glucose, fats, glycogen, and other molecules
ATP
Adenosine Triphosphate- a nucleotide that temporarily stores energy in the form that cells can use
-cells rely on the potential energy stored in ATP to power chemical reactions
-nitrogen base containing adenine, the 5-carbon sugar ribose, and 3 phosphate groups
-sometimes referred to as energy currency
How does ATP release stored energy?
Removing the endmost phosphate group by hydrolysis releases the potential energy stored in ATP. The cell then uses that energy to do work
How is ATP formed during cellular respiration?
Cellular respiration is a series of chemical reactions that release energy from sugar, producing ATP form ADP
-energy from exergonic reactions fuel ATP production (energy bar)
-ATP hydrolysis releases energy that fuels endergonic reactions (bike riding)
How does an ATP energized molecule make it more likely to bond with other molecules?
Glucose “activated” by a phosphate group. ATP donates phosphate group to glucose. Activated glucose then reacts with a short polysaccharide to build a longer polysaccharide
How can ATP change the shape of a targeted molecule?
ATP donates a phosphate group to protein, which changes shape. The new shape allows the ions to move across the membrane
Which organelles produce the most ATP?
Mitochondrion
What type of cells contains the most mitochondria?
The most energy hungry cells, like muscle and brain
How is ATP used to power cells activities?
It “spends” ATP by removing its endmost phosphate group,
The products of this exergonic hydrolysis are ADP (Adenosine Diphosphate) which only has 2 phosphate groups attached to ribose, a free phosphate group, and a burst of energy that the cell will use to do work
What are the specialized sacs of enzymes?
Mitochondria, chloroplasts, lysosomes, and peroxisomes
Why are enzymes important to biochemical reactions?
They speed up chemical reactions
-they are among the most important of all biological molecules
-chemical reactions in cells must occur very quickly to sustain life
-most enzymes are proteins, some are made of RNA
How are enzymes reusable?
It’s a protein that acts as a catalyst. It speeds up a chemical reaction without being consumed
Each enzyme fits the shape of a substrate
Substrate molecules bind to an enzymes active site, where the chemical reactions occur.
-the substrate is what the enzyme acts on
Active site of an enzyme
Region of an enzymes to which substrates bind to
How do enzymes alter substrates to form products?
They bind together, creating a chemical reaction, the product molecules are released. The enzyme will retain its original form
How can enzymes speed up a variety of reactions?
Not all enzymes break a single substrate into 2 products. Some enzymes combine 2 substrates into 1 product
Activation energy
The energy required to start a reaction
What to enzymes do to activation energy?
It lowers the activation energy. Without an enzyme, activation energy is high.
-when an enzyme binds to a substrate, activation energy is lowered
Enzyme cofactors
-some enzymes require cofactors that help catalyze reactions
-they participate in the reactions to increase enzyme activity
-inorganic: metal ions like zinc, copper, and iron
-organic: vitamins like vitamin C
How can cells control their biochemical reactions?
Through enzyme inhibition, which lower the activity of enzymes
-competitive and noncompetitive
Through negative feedback and positive feedback
Noncompetitive enzyme inhibitors
They change the shape of the active site
-cells can produce molecules that bind to an enzyme outside of its active site to alter the shape of the active site and prevent the substrate and enzyme from binding together
Competitive enzyme inhibitors
They block the access to the active site, it binds to the active site, blocking the normal substrates
How do inhibitors shut down reactions?
Inhibitors are the product of the reaction that the enzyme catalyzes
-once there is enough product in the cell, it would take too much energy to produce more of that product
Negative feedback
AKA: feedback inhibition
A process in which the product of the reaction slows the production of more product
-the product of enzyme 4 inhibits the production for enzyme 1 (it goes slower)
Positive feedback
The product of a reaction stimulates its own production
-enzyme 4 product stimulates the activity of enzyme 1 (it goes faster)
What factors can affect enzyme activity?
-if temperature is too high or too low
-if salt concentration is too high or too low
-if pH is too high or too low
Selective permeability
Property that enables a membrane to admit some substances and exclude others
Simple Diffusion
Substance moves across membrane without assistance from transport proteins
-carbon dioxide, oxygen, lipids and small, nonpolar molecules move freely across a membrane
Osmosis
Water diffuses across a selectively permeable membrane
Facilitated diffusion
Substance moves across membrane with assistance from transport proteins
-doesn’t require energy, requires membrane proteins
-down a concentration gradient
-produces ATP
Concentration gradient
Difference in solute concentrations between 2 adjacent regions
Passive transport
Movement of a solute across a membrane with direct expenditure of energy
DIffusion
Movement of a substance from a region where it’s highly concentrated to an area where it’s less concentrated
-dissipation of concentration gradient and the loss of potential energy
-doesn’t require energy input
Solutes can enter and exit a cell membrane depending on what?
-concentration gradient
-the chemical nature of the substance (polarity, size and charge)
Passive transport
Down a concentration gradient, doesn’t require energy input
-simple diffusion, osmosis, and facilitated diffusion
Active transport
Against a concentration gradient, often referred to as pump
-Requires energy
-membrane proteins use cellular energy to transport substances across a cell membranes
-ex. sodium- potassium pump in neuron and muscle cell
Different ways of crossing a cell membrane
-passive transport
-active transport
-or in vesicles, by endocytosis or exocytosis
Isotonic
Condition in which a solute concentration is the same on both sides of a selectively permeable membrane
-water moves equally in and out of cells
Hypotonic
A solution in which the solute concentration is lower than the other side of a selectively permeable membrane
-Water rushes into cell from outside, membrane may burst
-higher salt concentration in a cell, lower salt outside
Hypertonic
A solution in which the solute concentration is higher than the other side of a selectively permeable membrane
-water rushes out of cell, loses water, shrivels, may die
-lower salt concentration inside cell, higher salt outside
Turgor pressure
The force of water pressing against the cell wall
How do plants use osmosis to control the water concentration in plant cells?
-plants usually keep the solute concentration inside their cells lower than the outside, so that water enters the cell
-hypertonic surroundings result in loss of water, shrinking the large essential vacuoles. This causes the cell to lose turgor pressure, which causes the plant to wilt
How does facilitated diffusion produce ATP?
Hydrogen ions move across a membrane and down the concentration gradient through a transport protein. The protein uses potential energy in the concentration gradient to produce ATP
Steps of sodium potassium pump
1.) ATP binds to transport protein along with 3 Na+ from cytoplasm
2.) ATP transfers phosphate into protein, which changes shape, moving Na+ across membrane
3.) 2 K+ from outside of cell binds to protein, causing phosphate to release
4.) release of phosphate changes the shape of the proteins, moving K+ into the cytoplasm
Exocytosis definition and steps
Cells form vesicles to secrete large polar molecules such as proteins out of cells. Substances can eb moved against or down their concentration gradient this way
1.) vesicle surrounds the particles to be exported
2.) vesicle moves to the cell membrane
3.) vesicle merges with the membrane, releasing particles to the outside
Endocytosis definition and steps
Cells form vesicles as they engulf and large molecules the bring them into the cell. Substances can be moved against or down their concentration gradient this way
1.) a small portion of the cell membrane buds inwards, entrapping particles
2.) a vesicle forms, which brings the particles into cell
3.) vesicle surrounds the imported particles
-pinocytosis and phagocytosis
Phagocytosis
A form of endocytosis in which the cell engulfs a large particle
Pinocytosis
A form of endocytosis in which the cell engulfs a liquid containing small particles
How are electrical fish energy efficient?
The fish raise and lower their electrical output by regulating membrane transport in their cells
How do fish neurons make electricity?
-membrane proteins called sodium channels move Na+ ions across the cell membrane and into neuron cells
-neurons are activated by the Na+ influx
-the electrical organ produces electrical fields
Exocytosis brings sodium channels into membrane (fish)
-when there are lots of sodium channels in a neuron cell membrane, lots of Na+ ions enter the cell
-neurons are activated by the Na+ influx
-the electrical organs produce high electrical fields
Endocytosis removes sodium channels from the membrane (fish)
-when there are few sodium channels in a neuron cell membrane, less Na+ ions can enter the cell
-neurons activate less
-electrical organs produce low electrical fields
