life at the cellular level Flashcards

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1
Q

Describe the features of prokaryotic cells vs eukaryotic cells.

A

Prokaryotic cells: no nuclear membrane, no mitochondria and no membrane bound organelles. Eukaryotic cells: multicellular animals and plants, membrane bound organelles and nucleus.

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2
Q

What does facilitated diffusion require?

A

Carrier molecules.

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3
Q

What are the 4 types of junctions in cells?

A

1) Tight/occulding junctions - prevent extracellular constituents getting inside the cell. 2) Adhesive - link actin filaments of 2 different cells. 3) Desmosomes: link keratin filaments in 2 different cells. 4) Gap: channels linking 2 cell cytoplasms together for communication eg. heart muscle.

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4
Q

What is the difference between pancrine and endocrine?

A

Pancrine: target cell is close to signalling cell. Endocrine: effects can be further away

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5
Q

What type of DNA do mitochondria have?

A

Their own circular DNA. They self-replicate, have their own ribosomes and make most of their own proteins.

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6
Q

What is the difference between heterochromatin and euchromatin?

A

Heterochromatin stains darker as it is tightly packaged and is in cells that are less active. Euchromatin is in cells that are active in transcription and stains lighter.

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7
Q

What is the function of the smooth ER?

A

To break down compounds like drugs and glycogen or to synthesise compounds like lipids.

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8
Q

What are the 3 molecules that make up the cytoskeleton?

A

Microfilaments (smallest, make up strands of actin), intermediate filaments (fibrous) and microtubules (long strands of alpha and beta tubulin).

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9
Q

What is 99% of us made of and why?

A

H, N, O and C as they form the strongest bonds. C is the most versatile and forms the basis of all biomolecules.

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10
Q

Define conformation and configuration.

A

Conformation: the arrangement of atoms in a molecule that can move without breaking H bonds. Configuration: fixed arrangement of atoms in a molecule.

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11
Q

Give an example of alterations to cis and trans conformation.

A

Rhodopsin in the retina is made from retinal and opsin. Retinal is in cis conformation and light converts it to trans.

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12
Q

Are biological molecules in L or D conformation?

A

All are in L.

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13
Q

What are the 5 chemical reactions of life?

A

1) Redox: H transfered in glycolysis and NAD+ becomes NADH. 2) Making/breaking C-C bonds: cleavage of glucose in glycolysis to release some of its potential energy. 3) Internal rearrangements: G6P –> F6P. 4) Group transfers: F6P to F6bP. 5) Condensation and hydrolysis: molecules are joined by condensation and broken by hydrolysis. Condensation reactions make water and hydrolysis reactions use water to split compounds.

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14
Q

How many bonds are in A-T vs C-G?

A

A-T has 2 bonds and C-G has 3 bonds.

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15
Q

Describe the structure of glucose polymers.

A

Formed by condensation reactions between glucose monomers. Lots of monomers liked together? Locked in cyclic form except the end monomer which remains linear and forms a reducing end.

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16
Q

What is the first law of thermodynamics?

A

Energy can be converted from 1 form to another, but the total energy in the universe remains constant.

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17
Q

What is the second law of thermodynamics?

A

All energy changes ultimately lead to more disorder in the universe –> increase entropy.

18
Q

What does Gibbs free energy tell us?

A

How spontaneous a reaction is in a closed system. G = H- TS.

19
Q

When would a spontaneous reaction occur?

A

If delta G is negative.

20
Q

Why are some reactions coupled?

A

So that thermodynamically unfavourable reactions can occur. For example, glycolysis is overall delta G negative.

21
Q

Intermediates in reaction pathways are often said to be in?

A

Dynamic steady state. The intermediate molecule does not change in concentration even through it is being made and degraded.

22
Q

Define metabolism.

A

The chemical process in a living organism whereby food is used for tissue growth or reproduction.

23
Q

What does free energy flow in pathways depend on?

A

ATP hydrolysis and ADP condensation, ATP allows anabolic, thermodynamically unfavourable reactions to proceed through coupling of catabolic, thermodynamincally favourable reactions.

24
Q

What is the difference between a nucleotide and a nucleoside?

A

Nucleoside = Sugar + Base. Nucleotide = Sugar + Base + Phosphate.

25
Q

Describe the bonding in water.

A

Water is polar as O is more electronegative that H.

26
Q

What is a hydrogen bond?

A

A bond between any electronegative atom (O or N usually) and a H atom that is electropositive. These molecules are polar and soluble in water.

27
Q

What is the difference in water solubility between charged and uncharged molecules?

A

Charged molecules are water soluble. Un-charged molecules are hydrophobic.

28
Q

What is a liposome?

A

Water on the inside and outside.

29
Q

How are hydrophobic lipids transported through the blood?

A

In a chylomicron.

30
Q

pH + pOH = ?

A
  1. 1 pH unit is a 10-fold increase/decrease in concentration of H ions.
31
Q

What is the difference between a stong and weak acid?

A

Strong acids fully dissociate in water. Weak acids only partially dissociate.

32
Q

What is a conjugate acid-base pair?

A

Acids are proton donors and bases are proton acceptors. A proton donor and a proton acceptor make up a conjugate acid-base pair.

33
Q

What is the dissociation constant?

A

The tendency for an acid to lose its proton and form its conjugate base.

34
Q

What happens when you make a solution of weak acid in pure water then add NaOH to change the pH?

A

Acetic acid ionises slightly. NaOH dissociates completely. The OH binds to the H of acetic acid to form water. As more NaOH is added, more HAc ionises to Ac. At the midpoint, 50% of NaOH is added. 50% of HAc is dissociated to give HAc and Ac. Here, pH = pKa. Beyond the midpoint, HAc continues to be used up until all of the original acid is ionised to Ac.

35
Q

What is pKa?

A

The pH value at which there are equal concentrations of the acid and conjugate base.

36
Q

When does full titration occur?

A

When all of the original HAc is ionised to Ac.

37
Q

What is a buffer?

A

A buffer solution is one which resists changes in pH when small quantities of an acid or an alkali are added to it. Buffering range is when lots of OH is added without a big change in pH.

38
Q

What is the Henderson-Hasselbalch equation used for?

A

Relates acid dissociation to buffering ability of weak acid/conjugate base. Use when you are trying to work out the amount of weak acid or conjugate base you have in a given biological system.

39
Q

What do buffers do in the body?

A

Mop up protons or dissociate if a solution is too alkaline. They maintain balance.

40
Q

Which 2 buffer systems are important in the body?

A

In cells - phosphate buffer system. In plasma - bicarbonate buffer system.