Biology 101 Unit 2 Exam Sapling
How do enzymes catalyze reactions?
- Enzymes bind with and change the conformation of substrates. - Lower the activation energy by binding with substrates - Enzymes UNABLE to change a molecules free energy - Enzymes are NOT consumed by reactions, can bind with another substrate and catalyze again - do NOT cause a release of energy
Enzyme vs Active Site vs Substrate
Enzyme - Biological catalyst - Protein containing an active site Active Site - specific enzyme location that binds with the substrate Substrate - is a substance that the enzyme acts upon - may be a lipid
How do chlorophyll pigments absorb energy from light?
A photon excites an electron in the chlorophyll to a higher energy state.
Which processes occur under which conditions?
Aerobic - Citric Acid Cycle - Electron Transport Chain Both - Glycolysis Anaerobic - Fermentation
Which of the following correctly contrasts anabolic and catabolic pathways?
Anabolic pathways are synthesis pathways, whereas catabolic pathways are degradation pathways.
Why does arsenic and limited oxygen result in fermentation?
Arsenic prevents acetyl-CoA formation, whereas limited oxygen disables the electron transport chain.
cellular respiration equation
C6H12O6 + 6O2 --> 6CO2 + 6H2O + ATP
Exergonic
Chemical reactions that release energy - Cellular respiration
_____ disrupts cellular respiration by destroying the proton gradient in the mitochondrion. _____ disrupts cellular respiration by stalling the conversion of pyruvate to acetyl CoA. _____ disrupts cellular respiration by stalling the electron transport chain.
DNP Arsenic Low oxygen
An enzyme catalyzes a reaction in a way that results in a lower activation energy. What is the significance of a lower activation energy?
It increases the rate of a cellular reaction. (Lower activation energy --> Increased rate of reaction)
a product that donates electrons to the electron transport chain
NADH
Does fermentation produce ATP?
No, ATP is produced after gylcolysis. The point of fermentation is to continue glycolysis to produce ATP.
Which of the following are produced during photosynthesis in plants?
Oxygen & Carbohydrates
Some molecules that leave the chloroplasts at the end of photosynthesis will be used in cellular respiration. Which molecules are these?
Sugars & Oxygen
Why does disrupting the Calvin cycle impact the light reactions of photosynthesis?
The Calvin cycle regenerates ADP & NADP - Calvin cycle uses, rather than regenerates, ATP
What is the primary role of water in photosynthesis?
The breakdown of water provides electrons and H ions for the light reactions.
Which statement below best explains why fermentation occurs in mammals?
When oxygen concentration is low, it replenishes NAD+ needed during glycolysis.
What is a cofactor?
compound that interacts with an enzyme and is required for the enzyme to function - Not all enzymes require cofactors
Which of the following describes how cofactors and coenzymes affect the function of enzymes?
- INCREASE catalytic function - Cofactors = INORGANIC non-protein molecules coenzymes = ORGANIC proteins
Which of the following describes a catabolic pathway?
- a pathway that breaks down molecules into smaller subunits - ENERGY RELEASED - Glycolysis converts one molecule of glucose to two molecules of pyruvate - A lipid molecule is broken down into fatty acid subunits
Which of the following describes an anabolic pathway?
- a pathway that generates molecules from smaller subunits - ENERGY ADDED - Photosynthesis generates storage carbohydrates from CO2 and H2O - A nucleic acid molecule is constructed from nucleotide subunits
Kilocalorie
- a unit of energy equal to 1,000 calories - most common way to measure the amount of energy in food
Which of the following best describes the overall role of enzymes in metabolism?
Enzymes increase the speed of reactions.
What does the citric acid cycle yield?
Per glucose molecule: - two ATP molecules - two FADH2 molecules - eight NADH molecules
Which statement describes the function of photosynthetic pigments in leaves?
They capture light energy and remove electrons from a donor.
BMI
a measure of body weight relative to height BMI = (weight/height) x 703
Complete Proteins
contain all 9 essential amino acids
Where does citric acid cycle occur?
eukaryotes: mitochondria prokaryotes: cytoplasm.
aerobic processes of the citric acid cycle and the electron transport chain take place in
mitochondria
Incomplete Proteins
proteins that lack one or more of the essential amino acids
Cellular respiration consumes glucose during glycolysis. What product of glycolysis can be subsequently modified to enter the citric acid cycle under aerobic conditions?
pyruvate - In the presence of oxygen, pyruvate (a product of glycosis) is modified to form the molecule acetyl-CoA, which can enter the citric acid cycle - During anaerobic conditions, the pyruvate produced by glycolysis will undergo fermentation to lactic acid and NAD instead of being converted to acetyl-CoA.
Why does disruption of oxidative phosphorylation also disrupt other cellular processes?
Oxidative phosphorylation generates ATP, which is required for many cellular processes.
Photosynthesis equation
6CO2 + 6H2O + light energy --> C6H12O6 + 6O2
the direct energy source for glycolysis
ATP
Metabolism
All of the biochemical reactions in an organism All conversions of matter and energy taking place in an organism
Both photosynthesis and cellular respiration are cellular processes that involve glucose. How do these two processes differently affect the metabolism of glucose?
Glucose is produced during photosynthesis to hold the energy gathered from light, whereas glucose is broken down during cellular respiration to release stored cellular energy.
Glycolysis
Glycolysis converts glucose into two molecules of pyruvic acid. Pyruvic acid can then be converted to a form that enters the citric acid cycle. The first part of glycolysis requires an "investment" of two ATP molecules, but the pathway later generates four ATP. Therefore, glycolysis produces a net gain of two ATP. Glycolysis also contributes to cellular respiration by generating NADH, a compound that carries electrons to the electron transport chain.
What is energy?
the ability of a system to perform work
What is heat?
the transfer of energy from a system with more thermal energy to a system with less thermal energy - heat is NOT a type of energy
Glycolysis is a step in the breakdown of glucose. Which of the following statements describe glycolysis?
- It breaks down glucose to two pyruvate molecules. - It is common to aerobic and anaerobic respiration. (Glycolysis is an anaerobic process, but also occurs under aerobic conditions; it does not use oxygen, and it occurs whether or not oxygen is available) - produces ATP, NADH, and pyruvate - 1 glucose --> 2 ATP (4 are generated but 2 are used at the start) & 2 NADH & 2 pyruvate/pyruvic acid - Takes place in cytoplasm of cell
How do enzymes lower the activation energy of a reaction?
- by holding two substrates in the correct orientation to each other - by forming a temporary bond between the active site and the substrate - by producing conditions within the active site conducive to the reaction
Vitamin D is the only fat soluble vitamin that
- can be synthesized by cells - essential for normal bone growth
What is a mineral?
- inorganic compound obtained in the diet that is required (in small amounts) for normal metabolism - calcium, phosphorus, sodium, and magnesium - MICRONUTRIENT
Photosynthesis
- is a cellular process that occurs in the chloroplasts of plant cells - cannot convert sunlight energy to sugars without the direct input of carbon dioxide - produces sugars for the plant using the energy from sunlight
Activation Energy
- is required to bring the reactant molecules to a transition state - amount of energy required to initiate a chemical reaction - the crest of the hill; difference between the transition state energy (highest point on a graph) and reactants
What is a vitamin?
- organic compound obtained in the diet that is required (in small amounts) for normal metabolism - CANNOT be synthesized by body, MUST be obtained through diet - function as enzyme cofactors, antioxidants, and hormone-like - MICRONUTRIENT
During the light-dependent reactions of photosynthesis, energy excites electrons in chlorophyll molecules, transforming the energy into chemical energy. 1) What provides the energy that excites the electrons in the chlorophyll molecules? 2) What is the source of the electrons that replace the excited electrons lost from chlorophyll?
1) Sunlight 2) H2O
All plants require ___ mineral nutrients
17
Endergonic
A chemical reaction that requires the input of energy in order to proceed. - Photosynthesis - Cells use (ATP), to provide energy to endergonic reactions.
Fat soluble vitamins are
A, D, E, K - soluble in fat, stored in body
a product that can be used directly for energy
ATP
Water soluble vitamins
B and C - soluble in water, not stored in body
Which of the following molecules are reactants in photosynthesis in plants?
Carbon Dioxide & Water
Electron Transport Chain
Compounds that enter the electron transport chain: - NADH - FADH2 - O2 - ADP Compounds produced by the electron transport chain: - NAD+ - FAD - H2O - ATP
Anaerobic respiration allows a cell to break down carbohydrates in the absence of oxygen. Identify how NAD is used by animal cells during anaerobic respiration.
During fermentation, NAD+ is generated from NADH and is used to continue glycolysis.
What does the law of conservation of energy state?
Energy can be transformed, but it cannot be either created or destroyed.
Some nutrients are considered essential nutrients because they either cannot be synthesized in the body or cannot be synthesized in sufficient quantities to maintain homeostasis. Essential nutrients must be consumed as part of a healthy and balanced diet. Which of the following choices are considered essential nutrients in the human diet?
Essential fatty acids Vitamins Minerals
Which steps of cellular respiration generate NADH or FADH2 as products, and which steps receive those molecules as inputs?
Generates NADH or FADH2 - Glycolosis - Citric Acid Cycle - Acetyl CoA Production Receives NADH or FADH2 Oxidative phosphorylation
a carbohydrate that enters glycolysis directly
Glucose
Explained
Light is the source of energy in photosynthesis and is required during the light-dependent reactions of photosynthesis. Light energy excites an electron on a chlorophyll molecule, allowing the electron to escape from the chlorophyll molecule. An electron from a water molecule (H2O) replaces the excited electron after the water molecule is separated into hydrogen and oxygen. The excited electron from chlorophyll is used during the rest of the light-dependent reactions to produce the energy carrier molecules, ATP and NADPH. These molecules transfer the energy captured from light to the next stage of photosynthesis, the light-independent reactions. Energy-rich carbohydrates are produced from carbon dioxide (CO2) molecules and the energy carrier molecules during the light-independent reactions. Carbon dioxide is not needed for the light-dependent reactions.
Macronutrients vs Micronutrients
Macronutrients - required in large amounts - main components of organic molecules - 9 of them - N, O, C, H, P, S, K, Ca, Mg - include proteins, fats, and carbohydrates Micronutrients - required in small amounts - mainly enzyme cofactors (non-protein helpers that are catalysts in enzyme reactions) - 8 of them - Cl, Mn, B, Fe, Cu, Zn, Ni. Mo
Why is cellular respiration referred to as an aerobic process?
Requires oxygen to occur - glucose can be broken down anaerobically, through a different pathway, the number of ATP molecules that are generated is significantly reduced
Saturated vs Unsaturated Fatty Acids
Saturated - Solid at room temp - Fatty acid tails straight - NO double bonds in the fatty acid carbon chains - Fatty acid tails pack tightly together - Produce inflexible membrane at low temps - Chocolate - Cheese Unsaturated - Liquid at room temp - Bent fatty acid tails - At least one double bond in the fatty acid tails - Maintain some space btwn adjacent phospholipids - Allow membrane to remain fluid & flexible at low temps - Vegetable Oil - Flaxseed Oil
Photosynthesis Process
Sunlight energy captured in the chloroplasts --> energy used to split water molecules, releasing oxygen --> protons from the water molecules then fuel the conversion of carbon dioxide into sugar molecules --> sugar molecules and their carbohydrate derivatives comprise the majority of a plant's biomass. Cellular respiration occurs in the mitochondria of the plant cell. During cellular respiration, sugar is broken down using reactions that require oxygen to provide cellular energy in the form of ATP. The plant also uptakes soil nutrients that cannot be synthesized from carbon dioxide and sunlight.
How does adenosine triphosphate (ATP) drive energy-required reactions in the cell?
The hydrolysis of ATP is coupled to a non-spontaneous reaction. - non-enzyme-catalyzed hydrolysis of ATP by water produces heat. However, this energy can not be coupled to another chemical reaction.
Where in citric acid cycle is CO2 produced?
The number of carbon atoms entering the cycle as acetyl-CoA will equal the number of carbon atoms that leave the cycle in CO2. Therefore, two CO2 molecules leave the cycle for each acetyl-CoA molecule that enters
Pyruvate is a product of glycolysis and is subsequently converted to acetyl-CoA. Acetyl-CoA is a substrate for the citric acid cycle (CAC). Exactly how many molecules of glucose must be oxidized in glycolysis to provide the input for four turns of the CAC?
Two 1 glucose --> 2 pyruvate --> 2 Acetyl-CoA
Chemical energy
energy inherent to an object based on its molecular composition
Essential Nutrients
nutrients necessary for normal body functioning that must be obtained from food - cannot be synthesized and required for certain metabolic processes - vitamins, dietary minerals, essential fatty acids and essential amino acids
DNP causes _____ to pass directly across the inner mitochondrial membrane instead of returning to the mitochondrial matrix through _____ proteins. Because of DNP's effect on the mitochondrion, less energy is captured in the form of _____ and more energy is instead wasted as heat.
protons ATP Synthase ATP
end product that is modified to enter citric acid cycle
pyruvic acid
What is kinetic energy?
the energy an object has due to its motion - heat is NOT a form of it - no system can spontaneously become more ordered, that requires an input of energy
In most plants, carbon is fixed through photosynthesis when the enzyme Rubisco attaches carbon dioxide molecules to RuBP. However, under high oxygen concentrations, Rubisco can also attach oxygen molecules to RuBP, initiating a process called photorespiration. Select all of the following statements that accurately describe photorespiration.
Photorespiration: - reduces the rate at which sugar is produced by the Calvin cycle. - is metabolically expensive. - releases CO2. - WASTEFUL PROCESS THAT USES ENERGY AND DECREASES PHOTOSYNTHETIC OUTPUT - takes place in stroma of chloroplast - common on hot, dry, sunny days
What is potential energy?
Potential energy is the energy that an object has based on its position or arrangement - can be increased by doing work on the object
CAC/Krebs
The CAC is used by aerobic organisms to generate NADH and FADH2, both of which can donate electrons to the electron transport chain.
Although the path of one glucose molecule through glycolysis generates a total of four ATP molecules, there is a net gain of only two ATP for each glucose molecule that enters the pathway. Why does the passage of one glucose molecule through glycolysis have a payoff of only two ATP molecules?
Two ATP molecules are used in the initial phase of glycolysis, reducing the net gain to two ATP.
Calorie
amount of energy necessary to increase the temperature of 1 g of water by 1 °C
In eukaryotic cells, each stage of cellular metabolism generates a different net amount of ATP. Which stage directly generates the greatest number of ATP molecules per metabolized glucose molecule?
electron transport chain and ATP synthase Per glucose molecule: - net yield of glycolysis: two ATP molecules - net yield of citric acid cycle: two ATP molecules - net yield of the electron transport chain and ATP synthase: 32 ATP molecules (potential for 34)
Thermal energy
energy produced by the movement of molecules within an object - object contains thermal energy but NOT heat
Certain nutrients that are important for a healthy and balanced diet are considered essential nutrients. Which of the following statements describes essential nutrients for the human body?
nutrients that the body cannot synthesize or does not produce in sufficient quantities
