BABS1201 Flashcards
1
Q
What features between eukaryotic and prokaryotic cells are shared?
A
- plasma membrane
- bilayer of phospholipids
- prokaryotes have no membrane-bound organelles - cytoplasm
- everything within the cell’s membrane excluding the nucleus - cytosol
- jelly-like fluid in the cytoplasm
- transport molecules around the cell - DNA
- prokaryotes have a single chromosomes in the nucleoid (no membrane)
- eukaryotes: chromosomes contained within the nucleus - ribosomes
- make proteins
2
Q
What are some organelles in eukaryotes?
A
- chloroplasts
- mitochondria
- contains many proteins such as RNA
3
Q
What is contained in animal cells?
A
- chromosomal DNA
- packed with proteins in the nucleus called chromatin - nuclear envelope - double membrane enclosing the nucleus (no cell wall)
- nuclei regions
- where rRNA are synthesised for ribosomes
4
Q
What are peroxisomes?
A
- specialised metabolic compartments
- single membrane
- contain enzymes that transfer hydrogen atoms to molecular oxygen
5
Q
What is an endoplasmic reticulum in the endomembrane system (ER)?
A
- network of membranes through which proteins and other molecules move
6
Q
What is a lysosome in a endomembrane system?
A
- contain enzymes
- digestive system of cells (breaks down lipids, carbs, proteins)
7
Q
What is a vacuole in a endomembrane system?
A
- sequester waste, maintain water balance
8
Q
What is the cytoskeleton in the endomembrane system?
A
- a network of changing fibers
- provides support and motility
9
Q
What do the different filaments inside the cytoskeleton do?
A
- microtubules
- hollow tubes
- provides ‘tracks’ for organelles
- provides motility (flagella) - microfilaments (or actin filaments)
- provide cell shape and provide ‘pulling’ forces
(think, muscle contraction) - intermediate filaments
- diverse group of filaments, present only in some animals
- anchors the nucleus
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)
11
Q
What is rough ER?
A
- has ribosomes on its surface
- membrane factory, adds phospholipids and protein to the membrane
12
Q
What are the parts of the endomembrane system?
A
- endoplasmic reticulum
- smooth ER
- rough ER
- vacuoles
- golgi apparatus
- cytoskeleton
- lysosomes
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
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)
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
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)
16
Q
What are the different structures of proteins?
A
- Primary
- Amino acids are linked by peptide bonds to form polypeptide chains - Secondary
- Parts of polypeptide chains can fold into regular shapes - Tertiary (3D)
- Fully folded protein - Quaternary structure
- Polypeptide chains can assemble into multi-sub-unit structures
17
Q
What is the structure of a single strand of DNA?
A
- joined by phosphodiester bonds
- sugar-phosphate backbone
18
Q
What are the types of RNA and their functions?
A
Different types:
- mRNA (messenger)
- carries protein information - tRNA (transfer)
- brings amino acids to ribosome for protein production
19
Q
What components are important in maintaining cell integrity?
A
Cell integrity is largely defined by the integrity of its membrane
- Phospholipid bilayer
- a permeability barrier to most molecules
- ionised, polar and large molecules will NOT cross unless a specific protein transporter is present - 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 - Red blood cells
- deliver oxygen
20
Q
What are membranes in the fluid mosaic model composed of?
A
- lipids (phospholipids and cholesterol), 0-25%
- proteins (peripheral and integral)
- carbohydrates (glycolipids and glycoproteins for recognition)
21
Q
What are some components of the fluid mosaic model?
A
- integral membrane protein - permanently embedded in the cell membrne
- peripheral proteins - attached to surface of membrane at different times
1 and 2 are important for the attachment of other proteins
- 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 - cytoskeleton
- cholesterol
- 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
- 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 - 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
What are carriers in facilitated diffusion?
- alternates between two shapes
- moves the solutes across the membrane during the shape change
- carriers have specificity
25
What is cotransport (in plants and higher animals) in active transport?
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
What is membrane potential?
- 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
How is an electrochemical gradient created by membrane potential?
- 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
What is endocytosis?
- cells that take up molecules by forming vesicles from the plasma membrane
- three types:
1. phagocytosis
2. pinocytosis
3. receptor-mediated cytosis
29
What is pinocytosis?
"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
What is phagocytosis?
"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
What is receptor-mediated endocytosis?
- when receptor proteins on the cell surface recognise and bind to specific molecules
- vesicles are formed
- highly selective, specific uptake process
32
What is catabolism?
- reactions that release energy by breaking down complex molecules into smaller molecules
33
What is anabolism?
- reactions that consume energy by building large complex molecules from smaller molecules
34
What is ATP? What does it do?
- adenosine triphosphate (ATP)
- the currency used by cells
Formula
ATP + H2O --> ADP + Pi
- it carries out chemical, physical and transport work
35
What are the three macronutrients in food? How is it broken up?
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
What does the utilisation of macronutrients require?
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
What are the three stages of carbohydrate catabolism?
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
What are cofactors?
- non-protein components, also called coezymes
- in redox reactions: NAD+, NADP, FADH, FADH2
39
What is an allosteric regulator?
- a substance that binds to a site on an enzyme
- may either inhibit or stimulate enzyme activity
40
What is feedback inhibition?
- the regulation of metabolic processes
- occurs when the end product interferes with the enzyme that helped produce it
41
What does the catabolism of glucose involve? (aerobic respiration)
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
What are the two parts of glycolysis?
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
Describe chemiosmosis in oxidative phosphorylation
- 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
Fermentation vs. aerobic respiration?
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
What are the parts of a chloroplast? (just draw a diagram)
- 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
What is the light reaction in photosynthesis?
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
Outline PSII in the light dependent reaction
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
Outline PSI in the light dependent cycle
- contain chlorophyll pigments
- P700, pair of chlorophyll
- reaction centre
PSI reaction:
1. photon excites chlorophyll
2. energy state is passed to P700 and then into the reaction centre
3. 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
4. electrons then enter another electron transport chain to reduce NADP to NADPH
5. 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
What is the photon gradient?
- 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
Outline the Calvin cycle (light-independent reaction)
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
Which bonds do carbohydrates, lipids, nucleic acids and proteins have?
carbohydrate - glycosidic bonds
nucleic acids - phosphodiester bonds
proteins - peptide bonds
lipids - ester bonds
