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BABS1201 Flashcards

1
Q

What features between eukaryotic and prokaryotic cells are shared?

A
  1. plasma membrane
    - bilayer of phospholipids
    - prokaryotes have no membrane-bound organelles
  2. cytoplasm
    - everything within the cell’s membrane excluding the nucleus
  3. cytosol
    - jelly-like fluid in the cytoplasm
    - transport molecules around the cell
  4. DNA
    - prokaryotes have a single chromosomes in the nucleoid (no membrane)
    - eukaryotes: chromosomes contained within the nucleus
  5. ribosomes
    - make proteins
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2
Q

What are some organelles in eukaryotes?

A
  1. chloroplasts
  2. mitochondria
    - contains many proteins such as RNA
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3
Q

What is contained in animal cells?

A
  1. chromosomal DNA
    - packed with proteins in the nucleus called chromatin
  2. nuclear envelope - double membrane enclosing the nucleus (no cell wall)
  3. nuclei regions
    - where rRNA are synthesised for ribosomes
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4
Q

What are peroxisomes?

A
  • specialised metabolic compartments
  • single membrane
  • contain enzymes that transfer hydrogen atoms to molecular oxygen
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5
Q

What is an endoplasmic reticulum in the endomembrane system (ER)?

A
  • network of membranes through which proteins and other molecules move
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6
Q

What is a lysosome in a endomembrane system?

A
  • contain enzymes
  • digestive system of cells (breaks down lipids, carbs, proteins)
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7
Q

What is a vacuole in a endomembrane system?

A
  • sequester waste, maintain water balance
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8
Q

What is the cytoskeleton in the endomembrane system?

A
  • a network of changing fibers
  • provides support and motility
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9
Q

What do the different filaments inside the cytoskeleton do?

A
  1. microtubules
    - hollow tubes
    - provides ‘tracks’ for organelles
    - provides motility (flagella)
  2. microfilaments (or actin filaments)
    - provide cell shape and provide ‘pulling’ forces
    (think, muscle contraction)
  3. intermediate filaments
    - diverse group of filaments, present only in some animals
    - anchors the nucleus
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10
Q

What is smooth ER in the endomembrane system?

A
  • has an outer surface that lacks ribosomes (plays a diverse role in metabolic processes)
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11
Q

What is rough ER?

A
  • has ribosomes on its surface
  • membrane factory, adds phospholipids and protein to the membrane
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12
Q

What are the parts of the endomembrane system?

A
  • endoplasmic reticulum
  • smooth ER
  • rough ER
  • vacuoles
  • golgi apparatus
  • cytoskeleton
  • lysosomes
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13
Q

What is the golgi apparatus?

A
  • consists of cisternae
  • warehouse for proteins
  • proteins are modified, stored and transported
  • new vesicles are formed here and leave to new sites
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14
Q

What are the macromolecules of life and name their monomers?

A
  • Carbohydrates (monosaccharides, which are simple sugars)
  • Lipids (fatty acids)
  • Proteins (amino acids)
  • Nucleic acids (nucleotides with nitrogenous bases G, A, T, C or U)
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14
Q

Describe the process of synthesising and breaking down of polymers. How are peptide bonds formed?

A
  • Synthesis: dehydration to form a new covalent bond
  • Breakdown: hydrolysis to split a covalent bond
  • enzymes catalyse both

Formation of polypeptides:
- dehydration reaction between the carboxyl group of one amino acid and the amino acid group of the next

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15
Q

What is the structure of an amino acid?

A
  • central alpha carbon attached to
  • amino group (NH3+)
  • carboxyl group (COO-)
  • hydrogen atom (H)
  • variable side chain (“R”)
    (be able to identify)
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16
Q

What are the different structures of proteins?

A
  1. Primary
    - Amino acids are linked by peptide bonds to form polypeptide chains
  2. Secondary
    - Parts of polypeptide chains can fold into regular shapes
  3. Tertiary (3D)
    - Fully folded protein
  4. Quaternary structure
    - Polypeptide chains can assemble into multi-sub-unit structures
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17
Q

What is the structure of a single strand of DNA?

A
  • joined by phosphodiester bonds
  • sugar-phosphate backbone
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18
Q

What are the types of RNA and their functions?

A

Different types:

  1. mRNA (messenger)
    - carries protein information
  2. tRNA (transfer)
    - brings amino acids to ribosome for protein production
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19
Q

What components are important in maintaining cell integrity?

A

Cell integrity is largely defined by the integrity of its membrane

  1. Phospholipid bilayer
    - a permeability barrier to most molecules
    - ionised, polar and large molecules will NOT cross unless a specific protein transporter is present
  2. Membrane proteins
    - maintains mechanical flexibility and durability of cells
    - sustain mechanical forces as the proteins of the membrane skeleton are responsible for the deformability, flexibility and durability
  3. Red blood cells
    - deliver oxygen
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20
Q

What are membranes in the fluid mosaic model composed of?

A
  1. lipids (phospholipids and cholesterol), 0-25%
  2. proteins (peripheral and integral)
  3. carbohydrates (glycolipids and glycoproteins for recognition)
21
Q

What are some components of the fluid mosaic model?

A
  1. integral membrane protein - permanently embedded in the cell membrne
  2. peripheral proteins - attached to surface of membrane at different times

1 and 2 are important for the attachment of other proteins

  1. carbohydrates (CHO)
    - can be attached to protein (to form glycoproteins), or to lipids to form glycolipids
    - allows cells to be recognised by other cells and proteins
  2. cytoskeleton
  3. cholesterol
  4. phospholipid bilayer
22
Q

Types of transport

A

Passive/simple diffusion
- only for non-ionic, non-polar and small molecules
- no energy required
- concentration gradient
- not specific

Facilitated diffusion:
- transport aided by proteins/channels/a carrier
- no energy required
- concentration gradient
- specific

Active transport:
- requires membrane protein
- requires energy
- ATP hydrolysis
- specific

Co-transport
- coupling of molecules
- no energy

23
Q

What are channels in facilitated diffusion?

A
  1. channels
    - provide a corridor for specific molecules or ions to cross the membrane
    - allows the cell to take up and retain the molecules it needs and exclude what is unwanted
  2. gated channels
    - require another type of molecule to be bound to a specific site before they function
    - can be opened or closed in response to a stimulus such as binding a specific molecule
24
Q

What are carriers in facilitated diffusion?

A
  • alternates between two shapes
  • moves the solutes across the membrane during the shape change
  • carriers have specificity
25
Q

What is cotransport (in plants and higher animals) in active transport?

A

In plants:
- a proton pump gives active H+ transport
- return of H+ to the cytosol down a concentration gradient drives the uptake of sucrose
- indirect active transport of sucrose

In higher animals:
- macromolecules are hydrolysed to monomers by enzymes in the digestive tract and the monomers (e.g. amino acids & glucose) are taken up by cells lining the small intestine using a variety of both passive and active transport proteins

26
Q

What is membrane potential?

A
  • the voltage difference across a membrane
  • cytoplasm is negative compared to extracellular fluid (-50mV to -200mV)
  • favours passive transport of cations into the cell and anions out of the cell
  • drive other processes such as the opening of voltage-gated channels
27
Q

How is an electrochemical gradient created by membrane potential?

A
  • diffusion of ions is affected by both an electrical force (membrane potential) and a chemical force (ion concentration)
  • this acts as an energy source that affects the trafficking of all charged molecules across the membrane
28
Q

What is endocytosis?

A
  • cells that take up molecules by forming vesicles from the plasma membrane
  • three types:
    1. phagocytosis
    2. pinocytosis
    3. receptor-mediated cytosis
29
Q

What is pinocytosis?

A

“cellular drinking”

  • new vesicles are formed by random invaginations of the plasma membrane
  • any and all solutes are taken into the cell
  • no specificity
30
Q

What is phagocytosis?

A

“cellular eating”

  • a cell engulfs a particle by wrapping around it and packaging it into a large vesicle/vacuole
  • used by macrophages in higher animals to destroy bacteria - involves recognition of what is “foreign”
31
Q

What is receptor-mediated endocytosis?

A
  • when receptor proteins on the cell surface recognise and bind to specific molecules
  • vesicles are formed
  • highly selective, specific uptake process
32
Q

What is catabolism?

A
  • reactions that release energy by breaking down complex molecules into smaller molecules
33
Q

What is anabolism?

A
  • reactions that consume energy by building large complex molecules from smaller molecules
34
Q

What is ATP? What does it do?

A
  • adenosine triphosphate (ATP)
  • the currency used by cells

Formula
ATP + H2O –> ADP + Pi

  • it carries out chemical, physical and transport work
35
Q

What are the three macronutrients in food? How is it broken up?

A

Macronutrients
- carbohydrates (sugars)
- proteins (amino acid)
- fats (fatty acids)

Breaking up
- food is broken down to CO2 and H2O during catabolism, providing ATP (from ADP + Pi)

  • the energy released from ATP (when hydrolysed back to ADP + Pi) is used to power functions
36
Q

What does the utilisation of macronutrients require?

A
  1. digestion (polymer to monomer)
  2. uptake by intestinal epithelial cells
  3. transport around the body
  4. uptake by cells of different tissues
  5. catabolism/storage inside cells
37
Q

What are the three stages of carbohydrate catabolism?

A

Stage I.
- digestion

Stage II.
- breakdown of the smaller molecules from stage I into acetyl CoA

Stage III.
- citric acid cycle and oxidative phosphorylation produce ATP by oxidation of the acetyl group from acetyl CoA

38
Q

What are cofactors?

A
  • non-protein components, also called coezymes
  • in redox reactions: NAD+, NADP, FADH, FADH2
39
Q

What is an allosteric regulator?

A
  • a substance that binds to a site on an enzyme
  • may either inhibit or stimulate enzyme activity
40
Q

What is feedback inhibition?

A
  • the regulation of metabolic processes
  • occurs when the end product interferes with the enzyme that helped produce it
41
Q

What does the catabolism of glucose involve? (aerobic respiration)

A
  1. GLYCOLYSIS
    - glycolysis breaks down glucose into 2 pyruvate (cytosol)
    - 6 carbon into two 2 carbon molecules
    - produces 2 ATP
  2. PYRUVATE OXIDATION
    - pyruvate molecules are oxidised to acetyl CoA (2 carbon molecule) by dehydrogenase enzymes
    - this redox reaction transfers a pair of electrons to NAD+ resulting in 2 NADH
    (occurs in mitochondria matrix)
  3. CITRIC ACID CYCLE (two cycles from oxidation of glucose because two molecules)
    - 2 acetyl CoA enter the citric acid cycle and is broken down into CO2
    - 2 ATP
    - 6 NADH is produced
    - 2 FADH2
    - 6 CO2
  4. OXIDATIVE PHOSPHORYLATION
    (electron transport chain)
    - reduced molecules NADH and FADH2 are oxidised
    - protein gradient drives ATP production
    - ultimately, the electrons are transferred to molecular oxygen, reduced to water

TOTAL ATP PRODUCTION
- 32 ATP are produced through the oxidation of a glucose molecule
- can also be 30 ATP because NADH produced in the cytosol as a product of glycolysis can be worth less than those produced in the mitochondrial matrix
- NADH powers ATP production

42
Q

What are the two parts of glycolysis?

A

glycolysis - “sugar splitting”

Stage I.
- energy investment
6 carbon molecules are split into two 3 carbon molecules
- 2 ATP gets hydrolysed into 2 ADP + 2 inorganic phosphates (Pi)

Stage II.
- pyruvate production (3C)
- provides an energy payoff (4 ATP)

  • in total, 2 ATP are produced per glucose molecule
  • 2 NADH are formed by the oxidation of glucose
43
Q

Describe chemiosmosis in oxidative phosphorylation

A
  • the proton gradient across the inner mitochondrial membrane drives the synthesis of ATP
  • protons re-enter the matrix via ATP synthase
  • this generates a electron transport chain that drives ATP synthesis from ADP + Pi (inorganic phosphate) in complex V
44
Q

Fermentation vs. aerobic respiration?

A

In fermentation (cytosol)
- an alternative process when there is a shortage of oxygen
- ATP produced by substrate-level phosphorylation
- ATP produced rapidly
- 2 ATP produced per glucose molecule
- NADH reoxidised in a reaction involving the final electron acceptor eg. pyruvate → lactate

In aerobic respiration (mitochondria)
- ATP mainly produced by oxidative phosphorylation
- 32 ATP (slower process, ATP gets transferred to other areas) per glucose molecule
- NADH re-oxidised in the electron transport chain

45
Q

What are the parts of a chloroplast? (just draw a diagram)

A
  • outer and inner membrane, separated by an intermembrane space
  • interior is a dense fluid/gel-like substance called the stroma
  • within the stroma are membranous sacs called thylakoids
  • inside the thylakoids is the thylakoid space
  • stacks of thylakoids are called grana
  • chlorophyll is located in the thylakoid membranes-
46
Q

What is the light reaction in photosynthesis?

A
  1. In the thylakoid, water is split, producing protons (H+), electrons and O2
  2. Light is absorbed by the chlorophyll pigment, powering the transfer of the electrons and H+ to NADP+
    - ATP is produced
47
Q

Outline PSII in the light dependent reaction

A

In the thylakoid! H2O becomes O2

PSII (PS = photosystem)
- membrane
- have a reaction centre

P680
- a pair of chlorophyll in the PSII

Process:
- photon excites chlorophyll,
- energy state is passed to P680 and then into the reaction centre
- a pair of electrons is transferred into the reaction centre
- P680 becomes P680+ (strongest biological oxidising agent known)
- H2O enters into the reaction centre and replaces lost electrons in P680+ to turn it back into P680
- the electron transport chain continues into PSI

48
Q

Outline PSI in the light dependent cycle

A
  • contain chlorophyll pigments
  • P700, pair of chlorophyll
  • reaction centre

PSI reaction:
1. photon excites chlorophyll

  1. energy state is passed to P700 and then into the reaction centre
  2. a pair of electrons is transferred into the reaction centre
    - P700 becomes P700+
    - electrons from PI replace lost electrons in P700+, turning it into P700 again
  3. electrons then enter another electron transport chain to reduce NADP to NADPH
  4. through the electron transport chain, ADP + Pi is converted to ATP from the flow of protons from the thylakoid space into the stroma (ATP synthase)
49
Q

What is the photon gradient?

A
  • protons are released into the thylakoid space, creating a proton gradient
  • the oxygen atoms from the splitting of water readily form O2, and the electron is transferred to P680
  • ATP synthase is then able to utilised this gradient to produce ATP
50
Q

Outline the Calvin cycle (light-independent reaction)

A
  1. Carbon fixation
    - 6 CO2 + 6 RuBP =
    12 molecules of 3-phosphoglycerate (3PG)
    - RuBisCO (enzyme),
  2. Reduction
    - 12 ATP becomes 12 ADP + a phosphate group
    - intermediate from ATP reduction:
    1-3-bisphosphate reduction
    - 12 G3P is created from the above
    - NADPH is reduced to NADP + H+
    - 2 molecules of G3P goes on to create glucose
    - 10 molecules of G3P are recycled to make 6 molecules of RuBP
  3. Regeneration
    - in order to remake the CO2 receptor
    - 5 RuBP + 10 G3P are used to make 6 RuBP

Net gain is 1 G3P from 3 CO2 molecules

51
Q

Which bonds do carbohydrates, lipids, nucleic acids and proteins have?

A

carbohydrate - glycosidic bonds

nucleic acids - phosphodiester bonds

proteins - peptide bonds

lipids - ester bonds

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