Life at cellular level

Question 1

For a spontaneous reaction to occur, what must happen?

Answer 1

Energy must be released

and/or

Entropy must increase

(Free energy change, G, must be negative)

Question 2

For thermodynamically unfavourable reactions to occur in the body, what does the body do?

Answer 2

Reaction coupling with a catabolic reaction

Question 3

What is metabolism?

Answer 3

The chemical processes in a living organism by which food is used for tissue growth and/or energy production

Question 4

In terms of free energy, why is ATP used?

Answer 4

ATP hydrolysis releases free energy

Used to drive energetically unfavourable reactions

Stores free energy from exergonic reactions

(ATP hydrolysis is a catabolic process)

Question 5

NAD, FAD and NADP are commonly used in what type of reactions?

Answer 5

Redox

They are electron carriers

Question 6

In terms of entropy, why do lipids ‘clump together’ when in solution?

Answer 6

Increase entropy

• H2O molecules organise themselves around hydrophobic tails ∴ ordered
• When clumped together, total surface area of lipid decreases therefore area of ordered H2O is less therefore higher entropy

Question 7

What is an amphipathic molecule?

Answer 7

One with both hydrophobic and hydrophilic parts

Eg phospholipids

Question 8

Why are buffers so important to us?

Answer 8

Maintain homeostasis of pH

Enzymes and proteins structure reliant on pH

Question 9

What is the main buffer found in blood?

Answer 9

HCO3-

bicarbonate

Question 10

What is the first law of thermodynamics?

Answer 10

total energy of an isolated system is constant;

energy can be transformed from one form to another, but can be neither created nor destroyed

Question 11

What is the second law of thermodynamics?

Answer 11

the total entropy of an isolated system can never decrease over time

TE can be constant if:

• System is in steady state
• or is undergoing a reversible process

Question 12

Entropy of a system increases when…

Answer 12

Usable energy decreases

and un-usable energy increases

Question 13

Organisms carry out many chemical reactions in their cells, that grow and maintain order…

How is the 2nd law of thermodynamics still obeyed then?

Answer 13

Chemical reactions increase order

This decreases entropy

But generally, heat is generated and released into the surroundings and disorders it…

Thus TOTAL entropy increases, despite entropy being decreased/maintained in cells (as 2nd law states)

Question 14

What is anabolism?

Answer 14

the synthesis of complex molecules in living organisms from simpler ones together with the storage of energy; constructive metabolism

Question 15

What is dynamic steady state?

Answer 15

In the process of metabolising molecule X to intermediate Y then to product Z:

If the rate of X - Y and Y - Z is equal, then the concentration of Y remains constant

This is steady state, as all the shit remains constant, and is useful in the body as it means we can have a small amount of intermediates present, compared with the number of reactions that take place

Question 16

What is catabolism?

Answer 16

the set of metabolic pathways that breaks down molecules into smaller units that are either oxidized to release energy or used in other anabolic reactions (storage)

Question 17

Describe how anabolism and catabolism are interdependent.

Answer 17

Free energy flows between catabolic and anabolic pathways/reactions

Allowing them to occur

Question 18

ATP hydrolysis is used to supply energy to make ______ happen

Answer 18

Energetically unfavourable reactions

Question 19

What type of reaction is ATP often ‘made’ in?

catabolic or anabolic?

Answer 19

Catabolic
(Breakdown of complex to simple molecules)

Releases energy which is used to Phosphorylate ADP to make ATP which carries the energy to an anabolic reaction to allow it to happen (simply)

Question 20

Example

When PEP undergoes reactions to form pyruvate, what is the involvement of ADP/ATP?

Answer 20

ADP phosphorylated to ATP

PEP > Pyruvate is catabolic thus releases energy

Stored in ATP

Question 21

ATP hydrolysis is an ______ reaction

Answer 21

Exergonic

decrease in free energy

Question 22

What are the 5 chemical reaction types of life?

OGBIC

Answer 22

• Oxidation / reduction
• Group transfers
• Bond making / breaking
• Internal rearrangements
• Condensation and hydrolysis

Question 23

What type of chemical reaction is NAD+ and NADH involved with?

Answer 23

Redox

Question 24

What is the difference between substrate level and oxidative phosphorylation?

Answer 24

Substrate-level phosphorylation is directly phosphorylating ADP with a phosphate and energy provided from a coupled reaction

Oxidative phosphorylation is when ATP is generated from the oxidation of NADH and FADH2 and the subsequent transfer of electrons and pumping of protons (electron transport chain)

(If you don’t know what oxidative p. is, dont worry, its in terminal respiration lectures)

Question 25

Describe the structure and role of the nucleus.

Answer 25

``` Nuclear envelope - double membrane Nuclear pores Nucleolus Chromatin Nucleoplasm ``` Stores DNA and coordinates cellular activity

Question 26

Highlight the structure and function of the endoplasmic reticulum

Answer 26

SER and RER - Interconnected membrane tubes - Synthesis, storage and transport of biomolecules RER - protein synthesis at ribosomes attached to surface SER - Fatty acids, steroids, lipids (phospholipids made here and steroid hormones made from cholesterol)

Question 27

What is the structure and function of mitochondria?

Answer 27

``` Double membrane Cristae Mitochondrial matrix (enzymes, ribosomes, granules etc) Small amount of own DNA Cristae ``` ATP synthesis - aerobic respiration (oxidative phosphorylation)

Question 28

Describe what the Golgi is/does...

Answer 28

Series of hollow sacs (cisternae) Surrounded by/produces vesicles Receives and modifies proteins Then packages them into vesicles for transport

Question 29

Describe the different types of vesicles found in cells...

Answer 29

Secretory and storage Secretory - contain proteins to be released from the cell via exocytosis Storage - Store stuff

Question 30

Describe what lysosomes and peroxisomes are.

Answer 30

Lysosomes - type of storage vesicle. Breaks down unwanted stuff in the cell using powerful enzymes Peroxisomes - also a type of storage vesicle. Smaller than lysosomes. Involved with break-down of long chain fatty acids (in lipid metabolism lectures)

Question 31

What are cilia and flagella? How are they similar/different?

Answer 31

Cilia - hair like structures on some cells in the body such as the cells lining the airways - sweep secretions and particles across the cells - made of microtubules - single cilia are sensors Flagella - also made of microtubules but are longer than cilia - free-floating cells (eg sperm) - wave like movements used for propulsion of cell Cells with cilia are fixed and move other stuff, whereas cells with flagella use them for their own movement

Question 32

What is the cell cytoskeleton?

Answer 32

Flexible scaffolding that spans across the cytoplasm of cells Made of: - actin filaments - intermediate filaments - microtubules

Question 33

What are the main roles of the cell cytoskeleton?

Answer 33

Cell shape Hold position of organelles - organisation Intracellular transport - acts a bit like a railway network Connects to extracellular protein fibres - incorporating the cells into tissues Movement of cells - eg it is used when WBC's squeeze out of blood vessels to fight infection

Question 34

What is the general rule about solubility in water and in lipids and charge?

Answer 34

Polar/charged = soluble in water Un-charged/un-polar = soluble in fat

Question 35

What does amphipathic mean, and what is an example of an amphipathic molecule?

Answer 35

Molecule having both hydrophilic and hydrophobic parts phospholipids

Question 36

Define what pH is.

Answer 36

Negative logarithmic scale of proton concentration in a liquid, showing how acidic or alkaline a substance is

Question 37

What is the equation for pH?

Answer 37

-log10[H+] | log10 = log to the base 10

Question 38

What is the difference between a weak acid and a strong acid?

Answer 38

Strong - fully dissociates in solution | Weak - only partially dissociates

Question 39

What is the ionic product of water, and what is it useful for finding?

Answer 39

1 x 10^-14 Used to find the pH of an alkaline substance [H+] = (1 x 10^-14) / [OH-]

Question 40

What is a buffer and why are they fundamental to human life?

Answer 40

Solution that resists changes in pH when small additions of acid or alkali are made Needed in our blood especially in order to maintain homeostasis Our blood must be a specific pH otherwise we would die, pH affects protein shape and function, for example