Work in Cells, Metabolic Pathways, Energy and ATP

Question 1

What are the 3 types of work of cells?

Answer 1

Movement/mechanical, membrane transport and chemical synthesis

Question 2

What is the name of the small organelles that are used to move things to specific locations in the cell?

Answer 2

Vesicles

Question 3

What is the function of cytoplasmic streaming?

Answer 3

For big cells to mix things around for equal concentrations, such as organelles, nutrients and biomolecules

Question 4

What are the names of the three motor proteins that power movement

Answer 4

Kinesin, Dynein, Myosin

Question 5

What are the names of the cytoskeletal tracks and which motor proteins use them?

Answer 5

Microtubules, for Kinesin and Dynein; Microfilaments (or actin filaments) for Myosin

Question 6

How do entire cells move (cell motility)?

Answer 6

Their actin cytoskeleton “pushes” the front end of the cell forward and also “pulls” the back of the cell forward

Question 7

Why is membrane transport important?

Answer 7

For maintaining osmotic balance and for nutrient uptake, excretion of waste, nerve signalling and muscle contraction

Question 8

Explain the function of the sodium pump (sodium/potassium ATPase) and which cells these are important for

Answer 8

The sodium pump maintains sodium and potassium at different concentrations across the cell membrane. It is particularly important in nerve cells and brain cells for nerve impulses

Question 9

Explain the function of the calcium pump (calcium ATPase) and which cells these are important for

Answer 9

The calcium pump keeps the calcium levels in the cells low by moving it out. It is particularly important in muscle cells, which can respond to sudden increases in calcium and contract

Question 10

Explain metabolic pathways

Answer 10

A series of chemical reactions that occur within a cell, that start with a substrate and finish with a product/reactant

Question 11

How are metabolic reactions typically controlled?

Answer 11

By enzymes, which are usually specific. They catalyse reactions.

Question 12

Explain metabolic disequilibrium and why its important

Answer 12

In cells the reactions don’t come to equilibrium - instead of the product being converted back to the reactant, it keeps going down the metabolic pathway by reactions. The free energy changes in these reactions allows cells to do work. If there was equilibrium and no free energy changes the cells would not be able to do work.

Question 13

Explain catabolic pathways

Answer 13

Complex molecules are broken into simpler ones. This is spontaneous and releases energy.

Question 14

Explain anabolic pathways

Answer 14

Complex molecules are built from simple ones. This is non-spontaneous and requires energy.

Question 18

What are the three main ways that metabolism is regulated via enzymes?

Answer 18

Allosterically, covalently and genetically

Question 18

Explain energy coupling

Answer 18

The energy released in catabolic pathways can be used for anabolic pathways. The energy released from catabolic pathways is converted into useful energy carriers such as ATP, NADH and NADPH

Question 19

Explain metabolic regulation and why it is important

Answer 19

Cells are able to control their metabolism by regulating enzymes. This ensures that they have the materials and energy to do work and hence be alive.

Question 20

What is the difference between kinetic and potential energy?

Answer 20

Kinetic energy relates to anything that moves, such as light, electrical or heat. Potential energy is related to structure or location such as chemical energy or proton gradient across a membrane

Question 21

How is the free energy change of a glucose oxidation reaction (ΔG) calculated? Is this an exergonic or endergonic reaction and what does that mean?

Answer 21

By subtracting G(glucose) from G(carbon dioxide and water). This is an exergonic reaction meaning energy is released and it is spontaneous.

Question 22

What is the difference between an exergonic and an endergonic reaction?

Answer 22

In exergonic reactions energy is released and it is spontaneous (indicated by negative ΔG value), whereas endergonic reactions require energy and they are non-spontaneous (indicated by positive ΔG value)

Question 23

ATP (adenosine triphosphate) is a nucleotide composed of what?

Answer 23

Adenine base, ribose sugar and 3 phosphates

Question 24

Explain ATP hydrolysis

Answer 24

The reaction of ATP and water yields inorganic phosphate (Pi) and ADP and releases energy

Question 25

What is the main difference between ATP and ADP

Answer 25

ATP has 3 phosphates whereas ADP has 2 (diphosphate), and ADP is more stable than ATP

Question 26

Is having higher free energy more stable or unstable? What does this mean in terms of the 2nd law of thermodynamics?

Answer 26

Higher free energy is more unstable. Due to the 2nd law of thermodynamics there is a tendency to move to a more stable state, i.e. a state of lower free energy.

Question 27

Why can organisms be ordered yet still increase the disorder of the universe?

Answer 27

There is always energy released/lost to the universe as things like heat during reactions. Reactions are never perfect, including energy coupling.

Question 28

Around how much ATP is made in your body per day?

Answer 28

About the same amount as your weight, for example someone who weighs 85kg would produce around 85kg of ATP per day.

Question 29

How is ATP made?

Answer 29

An inorganic phosphate (Pi) is added to ADP

Question 30

Can cells use heat energy to do work? Why/why not?

Answer 30

No they cannot use heat energy to do work. Heat energy makes things move around more, but because it is not specific it cannot be used for work