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SFM 2018 > Life at a Cellular level > Flashcards

Life at a Cellular level Flashcards

1
Q

Briefly describe life processes in terms of the Laws of Thermodynamics.

A
  • Energy can be converted from one form to another but never created nor destroyed. All energy transformations ultimately lead to more entropy in the universe. This is true for living organisms even though the processes create more order, the heat created is released into the universe, creating more entropy there.
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2
Q

What are the three quantities that a useful or free energy closed system can be defined by?

A

Enthalpy - H - Heat released to surrounds (this reflects number / kind of bonds formed and broken)

Entropy - S - Randomness / disorder

Absolute temperature - T

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3
Q

What is Gibbs free equation?

A
  • Gibbs free energy equation: ΔG = ΔH - TΔS
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4
Q

What is Gibbs free energy used to define?

A
  • Gibbs free energy is used to define the spontaneity of a reaction. Spontaneous reactions occur if a system gives up energy and/or becomes more random and increases in entropy.
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5
Q

What is a cell?

A

The cell is the functional unit of all living things.

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6
Q

Why are cells small?

A

Smaller cells = larger surface area to volume ratio. This allows for gas exchange to happen more easily, diffusion becomes easier.

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7
Q

What are stem cells?

A
  • Stem cells are cells that can differentiate into many cell type (multipotent) or all cell types of the body (pluripotent)
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8
Q

What is cell differentiation?

A

cells pass through a series of changes during development -> changes in gene expression is reflected in the alteration of cell structure and behavior.

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9
Q

What is cell fusion?

A

Cell fusion is where small number of cell types undergo a process of cell fusion as part of their normal differentiation.

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10
Q

How do cancer cells arise - in relation to differentiation?

A

Cancer cells divide without any control, they fail to coordinate with normal cells and fail to differentiate into specialised cells. Cancer cells displace and replace normal cells if not stopped.

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11
Q

What are the 4 forms of cellular transport mechanisms in a cell?

A
  • Passive diffusion
  • Facilitated diffusion
  • Endocytosis
  • Exocytosis
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12
Q

How does the Cell membrane structure allow for cellular transport?

A
  • Cell membrane (plasma membrane) are selective barriers that detect chemical messengers and signaling molecules from surrounding cells or other organs.
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13
Q

What is needed for passive diffusion to take place?

A
  • Concentration gradient needed

- Lipid soluble molecules that pass freely (non polar)

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14
Q

What is needed for facilitated diffusion to take place?

A
  • Concentration gradient needed

- Requires carrier molecules

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15
Q

Name the cell organelles

A

1) Mitochondria
2) Nucleus
3) Rough endoplasmic reticulum
4) Smooth endoplasmic reticulum
5) Lysosomes
6) Peroxisome
7) Cillia
8) Flagella

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16
Q

With gibbs free energy equation, what do neg G and pos G mean?

A

Negative G means energy is released (Catabolism), positive means energy is used (Anabolism).

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17
Q

Explain the structure of the Mitochondria (4)

A
  • outer membrane has pores
  • Inner membrane has cristae
  • Matrix contains binding sites for calcium and also most of the enzymes for oxidation of food molecules.
  • They have their own circular DNA, ribosomes (similar to bacterial ribosomes), The synthesis most of their own proteins and they self replicate.
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18
Q

Explain the structure of the Nucleus. (4)

A
  • Contains DNA nucleoprotein and some RNA
  • Nucleoli are sites of ribosomal RNA synthesis and ribosomal assembly
  • DNA tends to be one of two forms - heterochromatin or euchromatin
  • Nuclear membrane (envelope) contains a phospholipid bilayer, encloses the nucleus, contains pores and is closely associated with the endoplasmic reticulum.
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19
Q

Explain the structure of the Rough endoplasmic reticulum.

A

It is membrane bound, has ribosomes attached, protein modifications and transport coordinated by the RER and golgi apparatus.

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20
Q

What is the Smooth endoplasmic reticulum used for?

A

It is mainly used to break down compounds (e.g) drigs and glycogen) or synthesis compounds (e.g lipids) (mainly used for breakdown.

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21
Q

What are lysosomes used for?

A

They are used to seperate enzymes from the rest of the cell - used in autophagy (digestion of cells own materials) or digestion of engulfed particles (e.g bacteria)

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22
Q

Explain the cillia’s structure and use.

A

Short, usually many present, move with stiff power stoke and flexible recovery stroke.

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23
Q

What are the 6 main membrane functions?

A

1) Transport
2) Enzymatic activity
3) Receptors for signal transduction
4) Intercellular joining
5) Cell - cell recognition
6) Attachment to the cytoskeleton and extracellular matrix.

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24
Q

Explain how the cell membrane structure allows for transport.

A

protein spans the membrane which may provide a hydrophilic channel across the membrane that is selective for a particular solute – some transport proteins hydrolyze ATP as an energy source to actively pump substances across the membrane.

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25
Q

Explain how the cell membrane structure allows for enzymatic activity.

A

Proteins built into the membrane may be an enzyme with the active site exposed to substances in the adjacent solution - in some cases enzymes in membrane act as a team that catalyse sequential steps of a metabolic pathway.

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26
Q

Explain how the cell membrane structure allows for signal transduction.

A

membrane protein exposed to the outside of the cell may have a binding site with a specific shape that fits the shape of a chemical messenger such as a hormone. External signal may cause a conformational change in the protein that indicates a chain of chemical reactions in the cell

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27
Q

Explain how intercellular joining occurs.

A

Membrane proteins of adjacent cells may be hooked together in various kinds of intercellular junctions. Some membrane proteins (CAMs) of this group provide temporary binding sites that guide cell migration and other cell to cell interactions.

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28
Q

Explain how the cell membrane structure allows for cell-cell recognition.

A

Some glycoproteins serve as identification tags that are specifically recognized by other cells

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29
Q

How is the cell attached to the cytoskeleton and extracellular matrix?

A

Elements of the cytoskeleton and the extracellular matrix may be anchored to membrane proteins which help maintain cell shape and fix the location of certain membrane proteins. Others play a role in cell movement or bind adjacent cells together.

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30
Q

What are the 5 main roles of the cytoskeleton?

A

1) supports and maintains cell shape
2) Holds organelles in position
3) Moves organelles
4) Involved in cytoplasmic streaming
5) interacts with extracellular structures to hold cell in place.

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31
Q

What are the three types of filament in the cytoskeleton?

A

1) Microfilament – made up of strands of the protein actin, often interact with strands of other proteins
2) Intermediate filaments – made up of fibrous proteins organized into tough, rope like assemblages that stabilize a cell’s structure and help maintain its shape
3) Microtubules – long hollow cylinders made up of many molecules of the protein tubulin. Tubulin consists of two subunits, alpha-tubulin and beta-tubulin

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32
Q

What are the three types of cell membrane junctions?

A

1) Tight junctions
2) Desmosomes
3) Gap junctions

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33
Q

What is a tight junction?

A

create physical barrier for diffusion across layers of cells. It depends on calcium.

34
Q

What are adhesive junctions (cell adhesions):

A

adherens junctions - link actin filamints in two different cells

35
Q

What are gap junctions?

A

Channels linking two cell cytoplasm together

36
Q

Describe the difference between prokaryotic cell and eukaryotic cell (4 difference)

A
  • Prokaryotic cell: - Bacteria
    - Lack nuclear membrane
    - No mitochondria
    - No membrane bound structures
  • Eukaryotic cell: - Human cells
    - Multicellular animals and plants
    - Nucleus with membrane
    - Membrane bound structures
37
Q

Explain dynamic steady state in life

A

Life involves processes occuring in a dynamic steady state. In biological reaction pathways, products from on are used in the next pathway and so are unable to reach equilibrium. Food is supplied and waste is removed in a continuous state. This is called a ‘dynamic steady state’. It allows entropy produced to be used in the construction of higher order compounds.

38
Q

Define entropy

A

Entropy: entropy is a gauge of randomness or chaos within a closed system. As usable energy is irretrievably lost, disorganization, randomness and chaos increase.

39
Q

Define metabolism.

A

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

40
Q

Define catabolism.

A

The breakdown of complex molecules in living organisms to form simpler ones, together with the release of energy

41
Q

Define anabolism.

A

The synthesis of complex molecules in living organisms from simpler ones together with the storage of energy. (constructive metabolism).

42
Q

In general terms describe the structures of ATP and ADP.

A

ATP/ADP act as a free energy carrier, coupling anabolic and catabolic reactions using phosphate group transfers.

43
Q

In general terms describe the structure of NAPD/NAD and FAD.

A

NAPD/NAD and FAD are used in redox reactions as electron carrier.

44
Q

What is the difference in energy between creating and breaking down ATP.

A

Break down of ATP releases the same amount of energy as used to create an ATP molecule.

45
Q

Define the major elements used to construct human biomolecules.

A
  • H, C, N, O, Na, P, S, Cl, K, Ca, we need a relatively large intake of these in our daily diet. About 12 other trace elements are needed in very small amounts. (e.g Fe haemglobin)
  • 99% of you is H, O, N and C, C is the most versatile and can form stable bonds with H, O and N. It is believed the bonding versatility of C explains why it forms the basis of almost all biomolecules.
46
Q

State the importance of chemical functional groups.

A
  • Biochemical molecules are defined by functional groups of atoms that involved bonds between carbon and other groups of atoms
  • Polarity of C bonds is critical to functionality ( C-C and C-H stable as they share e’s equally, C-O and C-N or C-functional group are highly polar which alters C bond reactivity)
47
Q

What is the configuration of a molecules?

A
  • Configuration: this is the fixed arrangement of atoms in a molecule, molecules containing a C=C can be cis or trans
48
Q

What is the conformation of a molecule?

A
  • Conformation: The precise arrangement of atoms in a molecule. Bonds which can rotate allow many different conformations which are inter-convertible without breaking and re-forming covalent bonds. Interactions of groups around the C-C bond will dictate how freely the bond can rotate which will favour certain conformations in the molecules.
49
Q

What examnples of 5 chemical reactions occuring in living organisms.

A
  • Redox reactions: usually 2 electrons gained or lost, e.g glycolysis in muscles – glucose -> Pyruvate -> Lactate
  • Making and breaking C-C bonds: E.g Cleavage of glucose in glycolysis
  • Internal rearrangements : E.g Glucose-6-Phosphate -> Fructose-6-Phosphate in glycolysis
  • Group transfers: E.g Group transfers in glycolysis
  • Condensation and hydrolysis reactions: E.g Formation and breaking of nucleic acids and proteins by condensation and hydrolysis reactions
50
Q

Describe the GENERAL structure of a protein

A

Polymers of amino acids, monomers linked together by peptide bonds.

51
Q

Describe the general structure of nucleic acids.

A

Polymers of nucleotide monomers linked by 3’,5’ - phosphodiester bonds. There are 2 kinds of bases in nucleic acids, pyrimidines (flat single rings C T U) and purines (Flat double rings A G)

52
Q

Describe the general structure of polysaccharides.

A

Polymers of sugar monomers linked by glycosidic bonds

53
Q

Describe the general structure of lipids.

A

Usually contain one or more long-chain fatty acid. There are several classes of lipids.

54
Q

Describe the two classes of lipids

A

1 Triacylglycerides: also called triglycerides, they are non-poler storage lipids. Made up of 3 fatty acid chains linked to glycerol, this makes them polar.

55
Q

How are glucose polymers formed?

A

Glucose polymers are formed by condensation reactions between two glucose monomers.

56
Q

How is glycogen (starch) formed?

A

In glycogen(starch) one glucose monomer is linked to another which locks the additional glucose in cyclic form.

57
Q

What is a reducing end of a glucose polymer?

A

When lots of monomers link together all monomers of the chain are locked in the cyclic form except the end monomer which can remain linear – this end monomer therefore forms a ‘reducing end’.

58
Q

Describe D-glucose

A
  • It is termed as a reducing sugar.
  • Linear form (but not cyclic) has an aldehyde group, which can be oxidized. If this is oxidized then the other reactant would be reduced so glucose is termed a ‘reducing sugar’.
59
Q

Where can hydrogen bonds occur?

A
  • Hydrogen bonds can occur between any electronegative atom (usually O or N) and a H atom that is electropositive.
60
Q

what is the definition of hydrogen bonds.

A
  • Definition: a weak bond between two molecules resulting from an electrostatic attraction between a proton in one molecule and an electronegative atom in the other.
  • Hydrogen bonds are strongest when the 3 atoms involved lie in a straight line.
61
Q

What makes a molecule water soluble?

A
  • A water soluble (hydrophilic) molecule can form hydrogen bonds (E.g sugars, alcohols, aldehydes, ketones).
  • When these things dissolve water-water H-bonding and solute-solute H-bonding is replaced with more energetically favorable solute-water H-bonding.
  • Charged molecules are also water soluble, water forms ‘screens’ around each ion keeping the NaCl in solution once dissolved, this type of ‘screening’ also works for more complicated biomolecules.
62
Q

Define the term ‘amphipathic’ and give an example of an amiphipathic molecule

A

amphipathic molecules contain both hydrophobic and hydrophilic parts, phospholipids are an examples of an amphipathic molecule.

63
Q

Describe what is meant by the term ‘buffer’.

A

A buffer is a solution which resists changes in pH when acid or alkali is added to it. The acid and bases of buffer solutions are pairs, they are known as common conjugate acid-base pairs.

64
Q

Describe the fundamental properties of water.

A

Water is polar molecule, the O is more electronegative than H so it attracts electrons of the covalent bond towads it, this gives O and H partial charges which make it polar. The polarity of water allows for hydrogen bonding.

65
Q

Explain why water is fundamental to life. (5)

A
  • Evolution has been shaped by this one substance more than others because:
    1) It bathes our cells
    2) Dissolves and transports compounds
    3) Allows compounds to move within and between cells
    4) Participates in chemical reactions
    5) Dissipates heat
66
Q

Describe how water can act as a weak acid.

A
  • Water dissociates slightly with the Kw of water is Kw = 1 × 10-14 (mol/L)2
67
Q

Explain the role of the Golgi apparatus.

A

Role of the golgi apparatus is to process and bundle macromolecules like proteins and lipids as they are synthesised within the cell

68
Q

What is the most abundant substance in all living organisms?

A

Water is the most abundant substance in all living organisms - approx. 70% by mass

69
Q

Why has evolution been shaped by water more than any other substance? (5)

A

1) It bathes our cells
2) Dissolves and transports compounds
3) Allows compounds to move within and between cells
4) Participates in chemical reactions
5) Dissipates heat

70
Q

Where does the water in our bodies lie?

A

60% water in the cells (intracellular fluid (ICF) ) 25 litres

40% outside the cells (extracellular fluid ECF) 15 litres

71
Q

Describe the structure of a Chylomicron.

A

The phospholipid heads and outer edges of proteins are all hydrophilic (polar) therefore the heads of the phospholipids must be on the outer edges or the lipids can not be transported throughout the body.

72
Q

What is the use of a chylomicron?

A

Chylomicrons transport hydrophobic lipids in the blood.

73
Q

Describe the hydrophobic effect.

A

The hydrophobic effect is where non-polar (uncharged) molecules arrange themselves in water so as to minimize disruption of the hydrogen bonding among surrounding water molecules. This is the most energetically favorable arrangement of the molecules – it is considered to be the major driving force for the folding of globular proteins.

74
Q

Describe the fundamental properties of water? (2)

A
  • Water is a polar molecule, the O is more electronegative than H so it attracts electrons of the covalent bond towards it, this gives O and H partial charges which make it polar.
  • The polarity of water allows for hydrogen bonding.
75
Q

Explain why water is fundamental to life. (5)

A
  • Evolution has been shaped by this one substance more than others because:
    1) It bathes our cells
    2) Dissolves and transports compounds
    3) Allows compounds to move within and between cells
    4) Participates in chemical reactions
    5) Dissipates heat
76
Q

What are the normal blood measurements of pH, [HCO3-] and [CO2]?

A
  • pH = 7.4
  • [HCO3-] = 24.0 mM
  • [CO2] = 1.20 mM
77
Q

Give an example of a human buffer.

A
  • Blood HCO3- is a buffer, if we did not have the bicarbonate buffer system then the pH would fluctuate wildly as cellular products of acids (lactic acid, ketone bodies) would cause marked drops in blood pH.
78
Q

Why is it important to maintain a pH of 7.4 in patients?

A
  • It is important to maintain blood pH of around 7.4 – if patients have high acid levels they have their [HCO3-] and [CO2] monitored.
79
Q

How is the Henderson-Hasselbalch equation used in patients with high acid levels?

A

-Henderson-hasselbalch equation can be used to check how much buffering capacity remains in a patient with high acid levels (metabolic acidosis).

80
Q

State the Henderson-Hasselbalch equation.

A

pH = pKa + log [HCO3-]/[CO2]

81
Q

Describe how water can act as a weak acid.

A

Water dissociates slightly with the Kw of water is Kw = 1 × 10-14 (mol/L)2

SFM 2018 (6 decks)

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