Cell Respiration

플레이하며 배우기

이 문제들을 풀어 에너지를 얻은 뒤 낚시하고 탐험하세요. 계정이 필요 없어요.

교육자를 위해: Cell Respiration(Biology, SL)을(를) 위한 바로 쓸 수 있는 수업 슬라이드, 복습 노트 — 수업에 사용하거나, 학습자들이 실시간 게임으로 즐기는 인터랙티브 클래스 활동으로 진행하세요.

수업 노트

ATP: The Universal Energy Currency

ATP (adenosine triphosphate) is a small, soluble molecule that provides a short-term store of chemical energy for cells.
It is described as a universal energy currency because it is used in all organisms and can be reused countless times for different reactions.
ATP links energy-requiring and energy-yielding reactions in cells.
Its solubility and small size allow it to move easily within cells and organisms by facilitated diffusion.
ATP is a phosphorylated nucleotide made of ribose sugar, an adenine base, and three phosphate groups.
ATP is relatively stable at cellular pH and only breaks down when the enzyme ATPase is present, preventing wasted energy.
Hydrolysis of ATP releases a useful, not too large, quantity of energy, reducing waste while giving the cell control over which processes occur.

Uses of energy from respiration

ATP Hydrolysis and Synthesis

When ATP is hydrolysed, it forms ADP (adenosine diphosphate) and a phosphate ion (π), releasing free energy.
Removal of one phosphate from ATP releases approximately 30.5 kJ mol⁻¹, forming ADP; removal of a second releases another 30.5 kJ mol⁻¹, forming AMP.
Removal of the third phosphate from AMP releases 14.2 kJ mol⁻¹, forming adenosine.
ATP is re-synthesised when ADP combines with an inorganic phosphate (π) group; this is an energy-requiring reaction.
ATP synthesis is a condensation reaction because water is released as a waste product.
Humans use more than 50 kg of ATP per day but have only about 200 g in the body at any time, so ATP must be made continuously as needed.
ATP is not stored in living organisms because it is very reactive; glucose and fatty acids act as short-term energy stores, while glycogen, starch and triglycerides are long-term stores.

Uses of ATP in Cells

ATP provides energy for anabolic reactions that synthesise larger molecules from smaller ones.
ATP fuels active transport, moving molecules across the cell membrane against their concentration gradient.
ATP enables movement of the entire cell and movement of cell components such as chromosomes within the cell.
ATP is used for muscle contraction and for fuelling active transport.
ATP provides energy for moving molecules around the cell.
In warm-blooded animals, ATP helps generate heat to maintain body temperature.

Cell Respiration: Definition and Purpose

Cell respiration is the controlled release of energy from organic compounds to produce ATP.
It is a series of chemical reactions that happens in every cell and is a catabolic process.
Glucose is the main respiratory fuel used in cells; lipids and proteins can also be used but must undergo several changes first.
Glucose can enter glycolysis directly, making it easier to oxidise than lipids and proteins.
Proteins are primarily structural molecules, so they are used as respiratory fuel only when glucose and lipids are not available.
Energy is released in small, enzyme-controlled steps rather than one uncontrolled step, which would cause cell damage and tissue death.
To make ATP, a phosphate group is linked to ADP, using energy from the breakdown of organic molecules.

Balanced equation for aerobic respiration

Aerobic Respiration

Aerobic respiration is the breakdown of a respiratory substrate to produce ATP using oxygen.
The substrate is completely oxidised, releasing a large amount of energy.
Glucose is broken down fully into carbon dioxide and water.
Aerobic respiration yields approximately 36 ATP molecules per glucose molecule.
CO₂ is a waste product that must be excreted, except in plants where it is used for photosynthesis.
Water is a by-product and contributes to the organism's water needs; some desert animals survive on very little drinking water because of this.
In eukaryotes, most reactions of aerobic respiration take place in the mitochondria.

Balanced equation for aerobic respiration

Anaerobic Respiration

Anaerobic respiration takes place in the absence of oxygen and breaks down a respiratory substrate, producing less ATP.
Glucose is only partially oxidised, so only a small part of its chemical energy is released and transferred to ATP.
The only ATP-producing reaction that continues is the first stage of respiration, yielding around 2 ATP molecules per glucose molecule.
Around 36 ATP molecules that would be produced aerobically are not produced anaerobically.
Anaerobic respiration occurs in the cytoplasm and does not involve the mitochondria.
Different organisms produce different products: plants and yeasts produce ethanol and CO₂, while animals produce lactate.
Anaerobic respiration gives a short discharge of energy when oxygen runs out, which is better than zero ATP.

Anaerobic respiration in muscle

Comparing Aerobic and Anaerobic Respiration in Humans

Oxidation of glucose: complete in aerobic respiration, incomplete in anaerobic respiration.
Oxygen required: yes for aerobic, no for anaerobic.
Relative ATP yield: high (∼36 molecules) in aerobic, low (2 molecules) in anaerobic.
Products: CO₂ and H₂O in aerobic respiration; lactate in anaerobic respiration.
Location of reactions: cytoplasm and mitochondria in aerobic respiration; cytoplasm only in anaerobic respiration.

Factors Affecting the Rate of Cell Respiration

Metabolic activity of the cell: muscle cells have a higher rate of respiration than adipose cells due to higher energy needs.
Size of the organism: smaller organisms have a higher surface area : volume ratio and a higher rate of respiration to compensate for greater heat loss.
Oxygen supply: when oxygen availability is low, cells respire anaerobically.
Supply of respiratory substrates: glucose availability is particularly important; lower substrate supply means a lower rate of respiration.
Temperature: the rate increases up to the optimum temperature of the enzymes, then drops as enzymes denature.
pH: CO₂ released during respiration decreases pH, which may denature enzymes involved in respiration.

Rate of respiration and temperature

Respirometers and Measuring Respiration Rate

Respirometers measure and investigate the rate of oxygen consumption during respiration in organisms.
Experiments usually use live organisms such as seeds or invertebrates; use of animals should be minimised when seeds can provide excellent data.
Common features include a sealed container with live organisms and air, an alkaline solution (e.g. potassium hydroxide) to absorb CO₂, and a capillary tube against a graduated scale (a manometer).
Organisms respire aerobically and absorb oxygen; the CO₂ they release is absorbed by the alkali, reducing air pressure inside the sealed chamber.
The manometer fluid moves towards the organisms because of the pressure drop inside the chamber.
The respirometer must be kept in very temperature-controlled conditions (e.g. a thermostatically controlled water bath) because slight temperature fluctuations affect air pressure.
Repeat readings should be carried out for each set of conditions to identify and eliminate anomalies and give a reliable mean.
Oxygen sensors and CO₂ monitors can measure concentrations in real-time without exposing subjects to hazards such as strong alkalis, and dataloggers can record data over time for later analysis.

Calculating the Rate of Respiration

The volume of oxygen consumed (mm³ min⁻¹) can be calculated using the radius of the lumen of the capillary tube r (mm) and the distance moved by the manometer fluid h (mm) in a minute using the formula: πr²h.
First calculate the cross-sectional area of the capillary tube using πr².
Then calculate the volume of oxygen taken up by multiplying the cross-sectional area by the distance moved by the liquid.
Finally, calculate the average rate of oxygen consumption per minute by dividing the volume by the time in minutes.
The volume of oxygen consumed can then be used to determine the average rate of respiration per unit time.

슬라이드

Step through every slide for this topic — plus flashcards and revision notes — with a free account.

가입 — 무료 로그인

연습 문제

무료 미리 보기 — 64개 중 8개 문제. 가입하면 전부 볼 수 있어요.

1.ATP is described as a universal energy currency. What is the best explanation for this description?
Easy
- AIt is used in all organisms and can be used for different reactions and reused many times.
- BIt is stored in large amounts in every cell for long-term energy supply.
- CIt is only found in animals and used for muscle contraction.
- DIt is an enzyme that speeds up all energy-releasing reactions.
2.Which of the following correctly describes the structure of ATP?
Easy
- AA phosphorylated nucleotide made of ribose sugar, adenine base, and three phosphate groups.
- BA nucleotide made of deoxyribose sugar, adenine base, and three phosphate groups.
- CA molecule made of ribose sugar, adenine base, and two phosphate groups.
- DA protein made of three amino acids and a phosphate group.
3.When ATP is hydrolysed, it is converted to ADP and a phosphate ion. Which of the following best describes the energy change during this process?
Medium
- AEnergy is released and can be used for processes within a cell.
- BEnergy is taken in from the surroundings to break the bond.
- CEnergy is released only if oxygen is present.
- DEnergy is stored as heat and cannot be used by the cell.
4.Which of the following is NOT a feature that makes ATP suitable as an immediate energy source for cells?
Medium
- AIt is a very stable molecule that can be stored for long periods.
- BIt releases a small but sufficient quantity of energy.
- CIt can be hydrolysed quickly and easily by a single enzyme.
- DIt is soluble and can move easily within cells.
5.Which of the following are uses of ATP in the human body? (Select all that apply.)
Medium
- AActive transport of molecules across cell membranes
- BMuscle contraction
- CAnabolic reactions to synthesise macromolecules
- DLong-term storage of energy in adipose tissue
- EMovement of chromosomes within the cell
6.Which of the following statements about aerobic and anaerobic respiration in humans are correct? (Select all that apply.)
Medium
- AAerobic respiration completely oxidises glucose, while anaerobic respiration partially oxidises it.
- BAerobic respiration produces approximately 36 ATP molecules per glucose, while anaerobic respiration produces 2 ATP molecules per glucose.
- CAnaerobic respiration in humans produces lactate, while aerobic respiration produces carbon dioxide and water.
- DAerobic respiration takes place only in the cytoplasm, while anaerobic respiration takes place in the mitochondria.
- EAnaerobic respiration requires oxygen, while aerobic respiration does not.
7.ATP is a very reactive molecule and is not stored in large amounts in living organisms.
Easy
True or false?
8.Anaerobic respiration in plants and yeasts produces lactate.
Easy
True or false?

더 많은 문제

9.The hydrolysis of ATP is a reversible reaction, meaning ATP can be reformed from ADP and phosphate.
Easy
True or false?
10.Match each term with its correct description.
Medium
- ATP
- ADP
- Aerobic respiration
- Anaerobic respiration
- Molecule made of ribose, adenine, and three phosphate groups
- Molecule formed when ATP loses one phosphate group
- Breakdown of glucose using oxygen to produce a large yield of ATP
- Breakdown of glucose without oxygen to produce a small yield of ATP
11.Place the following steps of ATP hydrolysis in the correct order.
Medium
- ATP reacts with water
- A phosphate group is removed
- ADP and inorganic phosphate are produced
- Energy is released for cellular processes
12.Which of the following are features of ATP that make it suitable as an immediate energy source for cells? (Select all that apply.)
Medium
- AIt releases a small but sufficient quantity of energy when hydrolysed
- BIt is a large insoluble molecule that is stored in the liver
- CIt is relatively stable at cellular pH unless ATPase is present
- DIt can be recycled, as the breakdown of ATP is reversible
- EIt can only be synthesised when oxygen is absent
13.Which of the following statements about the products of anaerobic respiration are correct? (Select all that apply.)
Medium
- AAnimals produce lactate
- BPlants and yeasts produce ethanol and carbon dioxide
- CAll organisms produce carbon dioxide and water
- DGlucose is completely oxidised in anaerobic respiration
- EAnaerobic respiration yields about 2 ATP molecules per glucose
14.Match each component of ATP with its correct description.
Medium
- Ribose
- Adenine
- Three phosphate groups
- ADP
- A sugar that forms part of the ATP molecule
- A nitrogenous base
- The groups removed during hydrolysis to release energy
- The molecule formed when ATP loses one phosphate group
15.Match each feature of ATP with the benefit it provides to cells.
Medium
- Soluble and small
- Hydrolysis is quick and easy
- Can form phosphorylated intermediates
- Exists as a stable molecule
- Can transport energy to different areas of the cell
- Allows cells to respond to a sudden increase in energy demand
- Can make metabolites more reactive and lower activation energy
- Does not break down unless ATPase is present, so energy is not wasted
16.Place the following stages in the correct order to show how a respirometer measures oxygen consumption by germinating seeds.
Medium
- The alkali absorbs carbon dioxide released by the seeds
- The seeds respire aerobically and take in oxygen from the air
- The pressure inside the sealed container falls
- The manometer fluid moves towards the organisms
17.Place the following events in the correct order to show the ATP/ADP cycle in a cell.
Medium
- ATP is hydrolysed to ADP and phosphate
- Energy is released for cell processes
- ADP and phosphate are recombined during respiration
- ATP is re-synthesised
18.The reactions of anaerobic respiration occur in the cytoplasm of cells and do not involve the mitochondria.
Easy
True or false?
19.In aerobic respiration, glucose is completely oxidised to carbon dioxide and water, releasing a large yield of ATP.
Easy
True or false?
20.A respirometer contains germinating seeds and potassium hydroxide solution. Which change explains why the manometer fluid moves towards the seeds?
Medium
- AOxygen is absorbed by the potassium hydroxide
- BCarbon dioxide released by the seeds is absorbed, lowering the pressure
- CThe seeds release carbon dioxide, which increases the pressure
- DThe temperature of the water bath falls, increasing the pressure
21.A respirometer's capillary tube has an internal radius of 0.15 mm. The manometer fluid moves 23 mm in 25 minutes. Using π = 3.141, what is the average rate of oxygen uptake?
Medium
- A0.065 mm³ min⁻¹
- B1.625 mm³ min⁻¹
- C0.0707 mm³ min⁻¹
- D2.60 mm³ min⁻¹
22.Which of the following statements about anaerobic respiration in plants and yeasts are correct? (Select all that apply.)
Medium
- AIt produces ethanol.
- BIt produces lactate.
- CIt produces carbon dioxide.
- DIt occurs in the mitochondria.
- EIt yields approximately 2 ATP molecules per glucose molecule.
23.A respirometer is set up with germinating seeds. After equilibration, the manometer fluid moves 15 mm in 10 minutes. The capillary tube has an internal radius of 0.20 mm. Using π = 3.141, what is the average rate of oxygen consumption?
Medium
- A0.188 mm³ min⁻¹
- B0.019 mm³ min⁻¹
- C1.88 mm³ min⁻¹
- D0.094 mm³ min⁻¹
24.Predict, with a reason, whether the coloured liquid in the U-tube would move towards tube 1 or tube 2 during the experiment.
Medium
- ATowards tube 1, because oxygen is consumed and carbon dioxide is absorbed, reducing pressure.
- BTowards tube 2, because carbon dioxide is produced and oxygen is absorbed, reducing pressure.
- CTowards tube 1, because carbon dioxide is produced, increasing pressure.
- DTowards tube 2, because oxygen is consumed, increasing pressure.
25.A respirometer's capillary tube has an internal diameter of 0.30 mm. The manometer fluid moves 2.3 cm in 25 minutes. Using π = 3.141, what is the average rate of oxygen consumption?
Hard
- A0.065 mm³ min⁻¹
- B0.65 mm³ min⁻¹
- C0.0065 mm³ min⁻¹
- D0.13 mm³ min⁻¹
26.In anaerobic respiration, glucose is completely oxidised to carbon dioxide and water.
Easy
True or false?
27.Match each feature of a respirometer with its purpose.
Medium
- Alkaline solution
- Capillary tube with scale
- Thermostatically controlled water bath
- Control tube with inert material
- Absorbs carbon dioxide
- Measures the distance moved by the manometer fluid
- Maintains constant temperature
- Compensates for changes in atmospheric pressure
28.Place the following steps in the correct order to show how a respirometer measures oxygen consumption by germinating seeds.
Medium
- Seeds respire aerobically, using oxygen and releasing carbon dioxide.
- Potassium hydroxide absorbs the carbon dioxide released.
- Pressure inside the sealed chamber decreases.
- Manometer fluid moves towards the seeds.
29.In a respirometer, the manometer fluid moves towards the organisms. Which statement best explains why this happens?
Medium
- AOxygen is taken up and carbon dioxide is absorbed, so the volume of gas in the chamber decreases, lowering the pressure.
- BCarbon dioxide is taken up and oxygen is absorbed, so the volume of gas in the chamber decreases, lowering the pressure.
- COxygen is released and carbon dioxide is absorbed, so the volume of gas in the chamber increases, raising the pressure.
- DThe alkaline solution absorbs oxygen, so the pressure inside the chamber falls.
30.Which of the following is the correct reason for adding soda-lime (an alkali) to a respirometer?
Medium
- ATo absorb carbon dioxide released by the respiring organisms.
- BTo absorb oxygen from the air inside the chamber.
- CTo release carbon dioxide so that pressure changes can be measured.
- DTo release oxygen so that the organisms can keep respiring.
31.A respirometer has a capillary tube of internal diameter 1.0 mm. The water droplet moves 2.0 cm in 24 hours. Using π = 3.14, what is the volume of gas taken up per hour? (Volume = πr²l, where l is the distance moved.)
Medium
- A6.54 × 10⁻⁴ cm³ hour⁻¹
- B1.57 × 10⁻² cm³ hour⁻¹
- C1.57 × 10⁻³ cm³ hour⁻¹
- D6.54 × 10⁻³ cm³ hour⁻¹
32.In a respirometer experiment using germinating seeds, which of the following are valid reasons for keeping the temperature constant? (Select all that apply.)
Hard
- ATemperature fluctuations change the air pressure inside the chamber.
- BTemperature affects the activity of enzymes involved in respiration.
- CTemperature changes affect the solubility of carbon dioxide in the alkaline solution.
- DTemperature fluctuations cause the manometer fluid to expand or contract.
- ETemperature changes alter the volume of the seeds.
33.In a respirometer, the carbon dioxide released by the organisms is absorbed by an alkaline solution, so the decrease in gas volume is due to oxygen consumption.
Easy
True or false?
34.Match each component of a respirometer with its function.
Medium
- Alkaline solution (e.g., potassium hydroxide)
- Capillary tube with graduated scale
- Thermostatically controlled water bath
- Control tube with inert material
- Absorbs carbon dioxide released during respiration
- Measures the distance moved by the manometer fluid
- Maintains a constant temperature
- Compensates for changes in atmospheric pressure
35.Place the following steps in the correct order to show how a respirometer is used to measure the rate of oxygen consumption by germinating seeds.
Medium
- Set up the respirometer with germinating seeds and an alkaline solution.
- Allow the apparatus to equilibrate.
- Record the starting position of the manometer fluid.
- Record the position of the manometer fluid after a set time.
- Calculate the volume of oxygen consumed using πr²h.
36.Which molecule is the main respiratory substrate used in cells?
Easy
- AGlucose
- BProtein
- CFatty acid
- DAmino acid
37.Respiration is a catabolic process.
Easy
True or false?
38.Which part of the ATP molecule is the base?
Easy
- AAdenine
- BRibose
- CPhosphate
- DAdenosine
39.Which of the following are products of anaerobic respiration in plants and yeasts? (Select all that apply.)
Medium
- AEthanol
- BCarbon dioxide
- CLactate
- DOxygen
- EWater
40.Match each term with its correct definition.
Medium
- Cell respiration
- Aerobic respiration
- Anaerobic respiration
- Controlled release of energy from organic compounds to produce ATP
- Breaking down a respiratory substrate to produce ATP using oxygen
- Breaking down a respiratory substrate to produce ATP without oxygen
41.Complete the sentence about the synthesis of ATP.
Easy
ATP is formed when ADP is combined with an inorganic phosphate group in a ____ reaction, and ____ is released as a waste product.
42.A respirometer was set up with germinating seeds. After equilibration, the liquid in the capillary moved 2.3 cm in 25 minutes. The capillary tube had an internal diameter of 0.30 mm. Calculate the average rate of oxygen uptake in mm³ min⁻¹. Use π = 3.141. Give your answer to 3 decimal places.
Medium
43.Name the enzyme that catalyses the hydrolysis of ATP.
Easy
44.State the word equation for aerobic respiration.
Medium
45.A respirometer's capillary tube has an internal radius of 0.10 mm. The manometer fluid moves 30 mm in 20 minutes. Using π = 3.141, calculate the average rate of oxygen uptake in mm³ min⁻¹.
Medium
46.A respirometer's capillary tube has an internal radius of 0.25 mm. The manometer fluid moves 40 mm in 20 minutes. Using π = 3.141, calculate the average rate of oxygen consumption in mm³ min⁻¹. Give your answer to 3 significant figures.
Medium
47.The mass of the seeds was 1.8 g. Using the table, calculate the rate of oxygen consumption in cm³ g⁻¹ hour⁻¹. Use the total volume change from 0 to 12 minutes.
Medium
48.Complete the sentence about the effect of temperature on respiration.
Medium
As temperature increases up to the optimum, the rate of respiration ____ because enzyme activity increases; above the optimum, the rate ____ because enzymes denature.
49.Name the solution used in a respirometer to absorb carbon dioxide.
Medium
50.A respirometer's capillary tube has an internal diameter of 0.40 mm. The manometer fluid moves 36 mm in 30 minutes. Using π = 3.141, calculate the average rate of oxygen consumption in mm³ min⁻¹. Give your answer to 3 decimal places.
Medium
51.The removal of the first phosphate group from ATP releases approximately how much energy? Give your answer in kJ mol⁻¹.
Medium
52.In an athlete, 124.4 dm³ of oxygen consumed in cell respiration produced 17.25 kg of ATP. Calculate the mass of ATP produced per dm³ of oxygen, in kg dm⁻³. Give your answer to 3 significant figures.
Hard
53.Explain why it is necessary for the human body to synthesise such large amounts of ATP each day.
Hard
54.Compare and contrast aerobic respiration and anaerobic respiration.
Medium
55.A respirometer was set up to measure oxygen consumption of germinating seeds. Explain why an alkaline solution such as potassium hydroxide is added to the respirometer.
Hard
56.Explain how temperature influences the rate of ATP production in respiration.
Hard
57.Explain why it is important to keep the temperature constant in a respirometer experiment.
Hard
58.A respirometer was set up with germinating seeds. After equilibration, the liquid in the capillary moved 2.3 cm in 25 minutes. The capillary tube had an internal diameter of 0.30 mm. Calculate the average rate of oxygen uptake in mm³ min⁻¹. Use π = 3.141. Give your answer to 3 decimal places.
Medium
- A1.065 mm³ min⁻¹
- B-0.935 mm³ min⁻¹
- C2.065 mm³ min⁻¹
- D0.065 mm³ min⁻¹
59.A respirometer's capillary tube has an internal radius of 0.10 mm. The manometer fluid moves 30 mm in 20 minutes. Using π = 3.141, calculate the average rate of oxygen uptake in mm³ min⁻¹.
Medium
- A2.047 mm³ min⁻¹
- B-0.953 mm³ min⁻¹
- C0.047 mm³ min⁻¹
- D1.047 mm³ min⁻¹
60.A respirometer's capillary tube has an internal radius of 0.25 mm. The manometer fluid moves 40 mm in 20 minutes. Using π = 3.141, calculate the average rate of oxygen consumption in mm³ min⁻¹. Give your answer to 3 significant figures.
Medium
- A2.393 mm³ min⁻¹
- B0.393 mm³ min⁻¹
- C-0.607 mm³ min⁻¹
- D1.393 mm³ min⁻¹
61.The mass of the seeds was 1.8 g. Using the table, calculate the rate of oxygen consumption in cm³ g⁻¹ hour⁻¹. Use the total volume change from 0 to 12 minutes.
Medium
- A2.32 cm³ g⁻¹ hour⁻¹
- B0.32 cm³ g⁻¹ hour⁻¹
- C1.32 cm³ g⁻¹ hour⁻¹
- D-0.68 cm³ g⁻¹ hour⁻¹
62.A respirometer's capillary tube has an internal diameter of 0.40 mm. The manometer fluid moves 36 mm in 30 minutes. Using π = 3.141, calculate the average rate of oxygen consumption in mm³ min⁻¹. Give your answer to 3 decimal places.
Medium
- A0.151 mm³ min⁻¹
- B-0.849 mm³ min⁻¹
- C2.151 mm³ min⁻¹
- D1.151 mm³ min⁻¹
63.The removal of the first phosphate group from ATP releases approximately how much energy? Give your answer in kJ mol⁻¹.
Medium
- A36.7 kJ mol⁻¹
- B30.5 kJ mol⁻¹
- C27.4 kJ mol⁻¹
- D33.6 kJ mol⁻¹
64.In an athlete, 124.4 dm³ of oxygen consumed in cell respiration produced 17.25 kg of ATP. Calculate the mass of ATP produced per dm³ of oxygen, in kg dm⁻³. Give your answer to 3 significant figures.
Hard
- A2.139 kg dm⁻³
- B-0.861 kg dm⁻³
- C1.139 kg dm⁻³
- D0.139 kg dm⁻³

Unlock all 64 questions & more

무료 계정을 만들어 이 주제의 모든 문제, 슬라이드, 플래시카드, 복습 노트를 확인하세요.

가입 — 무료 로그인

기출 문제

이 주제의 기출 문제 연습이 곧 나와요.

곧 출시