Lecture 13 & 14 Cell metabolism and Bioenergetics Flashcards

Question

What is a Heterotroph?

Answer 1

Organism that obtains energy from the foods it consumes. Ingest organic carbon molecules to generate energy and building blocks for biosynthesis (e.g. ATP synthesis).

Answer 2

organisms which use energy from photons of light

Answer 3

Photoautotrophs use light energy to synthesise organic molecules from (inorganic) CO₂ = photosynthesis Energy absorbed by photoreceptors and transformed into chemical bond energy (e.g. green plants & photosynthetic bacteria)

Answer 4

Photoheterotrophs use light energy plus organic substrates to synthesise organic molecules (some bacteria)

Answer 5

Photosynthesis of glucose: 6 CO₂ + 6 H₂O + light energy → C₆H₁₂O₆ + 6 O₂

Answer 6

uses light energy to synthesise organic Molecules. But cannot use CO₂ as their sole carbon source. purple and green non-sulfur bacteria and heliobacteria Use organic compounds from the environment to satisfy their carbon requirements: carbohydrates, fatty acids and alcohols

Answer 7

organisms which use energy derived from chemical bonds

Answer 8

use chemical energy to synthesise organic molecules from CO₂ (bacteria or archaea living in hostile environments) Use ferrous iron hydrogen, hydrogen sulfide, elemental sulfur ammonia To generate the energy to synthesise organic molecules from CO₂

Answer 9

use chemical energy plus organic substrates (most animals e.g. Homo sapiens and some plants)

Answer 10

12H₂S + 6CO₂ → C₆H₁₂O₆ + 6H₂O + 12S e.g. Purple sulfur bacteria (Chromatiaceae bacteria) Hydrogen sulfide is oxidized to produce granules of elemental sulfur, which can be oxidized to form sulfuric acid. (blood lakes in texas)

Answer 11

Further subdivided on the type of reducing equivalent used to transfer energy

Answer 12

Inorganic compounds are used as electron donor. Litho = rock; troph = eating (Greek) Lithotrophs generally thrive in inhospitable regions such as the deep ocean and the Earth’s crust First organisms to have lived on this planet

Answer 13

Fe²⁺ (ferrous iron) → Fe³⁺ (ferric iron) + e^- NH₃ (ammonia) → NO₂ (nitrite) + e^- NO₂ (nitrite) → NO₃ (nitrate) + e^- S^₂₋ (sulfide) → S0 (sulfur) + e^-

Answer 14

Organic compounds are used as electron donors The freed energy is stored as potential energy in: * ATP * Carbohydrates * Lipids * Proteins The energy is used for life processes as moving, growth and reproduction

Answer 15

**Complete oxidation of glucose:** Glycolysis: produces ATP and NADH Citric Acid Cycle: produces NADH and FADH₂ Electron Transport Chain: produces ATP

Answer 16

Heterotrophs eat **autotrophs** and other **heterotrophs**

Answer 17

1. Energy requirement 2. Carbon requirement 3. Reducing equivalent

Answer 18

* The nature (and relevance) of bioenergetics (as relates to cell metabolism) * Laws of thermodynamics, entropy (degree of disorder) and enthalpy (total heat) * Fundamental differences between living versus abiotic systems

Answer 19

a branch of physics focused on the relationships between heat/temperature and energy/work (originally in abiotic systems)

Answer 20

a branch of biochemistry concerned with energy flow (applied thermodynamics) in living systems

Answer 21

energy remains within that system; can be neither added nor lost from “the system” to that system’s surroundings

Answer 22

energy can be added to or lost from “the system” to that system’s surroundings (the universe)

Answer 23

Law of conservation of energy

Answer 24

the total energy of a closed system remains constant – i.e. energy is conserved; it can not be created or destroyed, it can only change form Potential energy can become kinetic energy and vice versa

Answer 25

• In a “biological system” (cell/tissue/organ/organism): Energy out = energy in – energy stored Energy lost = energy in – energy stored Heat lost = energy in – energy harnessed

Answer 26

If energy in \> energy out, will store calories as **glycogen** or **adipose tissue**.

Answer 27

the sum of the entropies of all participating bodies in a closed system must increase (or remain constant) * Entropy commonly regarded as degree of disorder / chaos * Entropy = thermal energy unavailable to do work

Answer 28

Yes, * Universe tends towards disorder / chaos * Cells tend towards order! * Organisation sacrifices available energy (i.e. it increases entropy!)

Answer 29

• Organisation sacrifices available energy (i.e. it increases entropy!) (heat loss in both)

Answer 30

Provided by **chemical bond energy** in food **- Digestion**: Proteins, lipids, carbohydrates broken down into monomers (amino acids, sugars, fatty acids) **- Oxidation** of small organic molecules to build new proteins, lipids, carbohydrates

Answer 31

• Can assemble C-based molecular materials = **anabolism** Anabolic reactions require energy • Can disassemble C-based molecular materials = **catabolism** Catabolic reactions liberate energy

Answer 32

Enzymes **Lower** Activation Energy of Chemical Reactions in Metabolism

Answer 33

1. Oxidoreductase (redox reactions) 2. Transferase (transfering chemical group) 3. Hydrolase (ryhdrating or loss of water) 4. Lyase (breaks chemical bonds) 5. Isomerase (changes structure) 6. Ligase (can ligate molecules)

Answer 34

Even when ΔG is negative, need to invest energy (overcome activation energy EA ) for reaction to proceed

Answer 35

For most biochemical reactions, E_A is very **high.** High E_A **stops** reaction from occurring spontaneously (in absence of appropriate enzyme) Substrates / reactants lack sufficient E_A so exist in _metastable state_

Answer 36

* Substrate binds at active site which is specific (or selective or preferential) * Substrate has a recognised structure and/or consensus sequence * Two models of ES complex formation * Second reaction – conversion of the enzyme-substrate complex to an enzyme-product [EP] complex * In an enzyme protein, involves chemical interactions between substrate and amino-acid side chains in catalytic centre of active site

Answer 37

complementary fixed shapes to both E and S

Answer 38

E and/or S change conformation as complex forms (e.g. binding of D-glucose to glucokinase)

Answer 39

The energetically unfavourable reaction (X to Y) is driven by the energetically favourable reaction (C to D) The net free energy of the coupled reaction is less than 0 i.e. 𝚫G is overall negative

Answer 40

**non-protein, organic/inorganic molecule/ion essential for catalysis** • May be bound to the enzyme as a prosthetic group (e.g. Zn2+ ion bound to active site of carboxypeptidase) * Apoenzyme – incomplete and inactive * Holoenzyme = apoenzyme + cofactor * Cofactor is unaltered in the course of the reaction!

Answer 41

_small, organic molecule (usually a vitamin derivative) required for catalysis_ Examples: * **CoA** = coenzyme A = derivative of vitamin B5 (pantothenic acid) – fatty acyl esterification and transport * **Biotin** = coenzyme R = vitamin B7 – required by carboxylase enzymes

Answer 42

_organic molecule required for the main reaction which is changed in the course of that reaction_ E.g. Oxidation of a respiratory substrate leads to collateral reduction of a pyridine nucleotide co-substrate * NAD+ reduced to NADH * NADP+ reduced to NADPH * FAD reduced to FADH2

Answer 43

* Chemical bond energy i**s in food** * Catabolism (**breaking**) and anabolism (**making**) bonds can be coupled for energetically **favourable** reactions * Enzymes are **catalysts** that **lower** the activation energy of a reaction • Enzymes can use **cofactors, cosubstrates or coenzymes** to drive a reaction * Cofactors **do not** change, cosubstrates **do** change during the enzymatic reaction

Answer 44

Adenosine Trisphosphate (ATP)

Answer 45

- There are different bonds energies within the triphosphate, which determines where you would break the bond - Y-bond broken for release of energy to create ADP

Answer 46

ATP conversion to ADP drives energetically **unfavourable** reactions * ATP acts as an electron carrier 'Activated carrier - ready to release energy' * Provide readily transferable chemical groups (important to create amino acids - glutamine)

Answer 47

NADH, NADPH and GTP involves the transfer of a proton

Answer 48

Allows to harness energy at each point and creates new molcules for use in the body.

Answer 49

_GLYCOLYSIS_ * Oxidising sugars * Produces ATP without O₂(anerobic environment) * Occurs in most cells-principal source of energy in anaerobic systems * Uses 2x ATP to make 4x ATP (net gain 2x ATP)

Answer 50

Fermentation produces ATP in the **absence of oxygen** (e.g yeasts and skeletal muscle) • Two forms of fermentation reaction 1. Releases **lactate** 2. Releases **alcohol and CO₂** • Converts NADH back to NAD+ for glycolysis

Answer 51

*High ATP/ADP ratio needs to be maintained* Food energy is stored as: 1. Fatty acids (triacylglycerols in adipocytes) 2. Glycogen (branched polysaccharides as small granules in many cells) * Oxidation/gram fat – 2x more energy than glycogen * 6 fold difference in mass of energy stored in fat against glycogen. 1. Glycogen stores: energy for one day 2. Fat stores: energy for one month

Answer 52

* Only chloroplasts in plants can harness energy through photosynthesis * Energy needs to be stored and delivered to other cells in the plant * Two forms of storage: Glucose, & Starch and fat

Answer 53

Glycolosis produces 2 ATP Krebs Cycle produces 2 ATP ETC produces 34 ATP

Answer 54

_Glycolytic switch_: when a cell switches from **aerobic** to **anaerobic** metabolism * Glycolytic switch (Warburg effect) in cancer cells. * Glycolytic switch in T cells to induce cytokine secretion and inflammation * Diabetes is the impaired regulation of insulin resulting in abnormal metabolism of carbohydrates and elevated blood glucose levels.

Lecture 13 & 14 Cell metabolism and Bioenergetics Flashcards

(85 cards)