Life at cellular level Flashcards
Mainly A level chemistry and biology so Ive missed tons out
For a spontaneous reaction to occur, what must happen?
Energy must be released
and/or
Entropy must increase
(Free energy change, G, must be negative)
For thermodynamically unfavourable reactions to occur in the body, what does the body do?
Reaction coupling with a catabolic reaction
What is metabolism?
The chemical processes in a living organism by which food is used for tissue growth and/or energy production
In terms of free energy, why is ATP used?
ATP hydrolysis releases free energy
Used to drive energetically unfavourable reactions
Stores free energy from exergonic reactions
(ATP hydrolysis is a catabolic process)
NAD, FAD and NADP are commonly used in what type of reactions?
Redox
They are electron carriers
In terms of entropy, why do lipids ‘clump together’ when in solution?
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
What is an amphipathic molecule?
One with both hydrophobic and hydrophilic parts
Eg phospholipids
Why are buffers so important to us?
Maintain homeostasis of pH
Enzymes and proteins structure reliant on pH
What is the main buffer found in blood?
HCO3-
bicarbonate
What is the first law of thermodynamics?
total energy of an isolated system is constant;
energy can be transformed from one form to another, but can be neither created nor destroyed
What is the second law of thermodynamics?
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
Entropy of a system increases when…
Usable energy decreases
and un-usable energy increases
Organisms carry out many chemical reactions in their cells, that grow and maintain order…
How is the 2nd law of thermodynamics still obeyed then?
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)
What is anabolism?
the synthesis of complex molecules in living organisms from simpler ones together with the storage of energy; constructive metabolism
What is dynamic steady state?
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
What is catabolism?
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)
Describe how anabolism and catabolism are interdependent.
Free energy flows between catabolic and anabolic pathways/reactions
Allowing them to occur
ATP hydrolysis is used to supply energy to make ______ happen
Energetically unfavourable reactions
What type of reaction is ATP often ‘made’ in?
catabolic or anabolic?
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)
Example
When PEP undergoes reactions to form pyruvate, what is the involvement of ADP/ATP?
ADP phosphorylated to ATP
PEP > Pyruvate is catabolic thus releases energy
Stored in ATP
ATP hydrolysis is an ______ reaction
Exergonic
decrease in free energy
What are the 5 chemical reaction types of life?
OGBIC
- Oxidation / reduction
- Group transfers
- Bond making / breaking
- Internal rearrangements
- Condensation and hydrolysis
What type of chemical reaction is NAD+ and NADH involved with?
Redox
What is the difference between substrate level and oxidative phosphorylation?
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)
Describe the structure and role of the nucleus.
Nuclear envelope - double membrane Nuclear pores Nucleolus Chromatin Nucleoplasm
Stores DNA and coordinates cellular activity
Highlight the structure and function of the endoplasmic reticulum
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)
What is the structure and function of mitochondria?
Double membrane Cristae Mitochondrial matrix (enzymes, ribosomes, granules etc) Small amount of own DNA Cristae
ATP synthesis - aerobic respiration (oxidative phosphorylation)
Describe what the Golgi is/does…
Series of hollow sacs (cisternae)
Surrounded by/produces vesicles
Receives and modifies proteins
Then packages them into vesicles for transport
Describe the different types of vesicles found in cells…
Secretory and storage
Secretory - contain proteins to be released from the cell via exocytosis
Storage - Store stuff
Describe what lysosomes and peroxisomes are.
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)
What are cilia and flagella? How are they similar/different?
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
What is the cell cytoskeleton?
Flexible scaffolding that spans across the cytoplasm of cells
Made of:
- actin filaments
- intermediate filaments
- microtubules
What are the main roles of the cell cytoskeleton?
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
What is the general rule about solubility in water and in lipids and charge?
Polar/charged = soluble in water
Un-charged/un-polar = soluble in fat
What does amphipathic mean, and what is an example of an amphipathic molecule?
Molecule having both hydrophilic and hydrophobic parts
phospholipids
Define what pH is.
Negative logarithmic scale of proton concentration in a liquid, showing how acidic or alkaline a substance is
What is the equation for pH?
-log10[H+]
log10 = log to the base 10
What is the difference between a weak acid and a strong acid?
Strong - fully dissociates in solution
Weak - only partially dissociates
What is the ionic product of water, and what is it useful for finding?
1 x 10^-14
Used to find the pH of an alkaline substance
[H+] = (1 x 10^-14) / [OH-]
What is a buffer and why are they fundamental to human life?
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
