4-5 Flashcards
(62 cards)
1
Q
Nucleic Acid vs Protein
A
- Nucleic acids are polynucleotides, joined by phosphodiester bonds
- Proteins are polypeptides, joined by peptide bonds
2
Q
Hersey and Chase Experiment
A
- Discovered that DNA is genetic material
- Labelled DNA with 32P
- Labelled protein with 35S
- Bacterophages infected E.coli bacteria
- After infection, they seperated the phage protein coats from bacterial cells
- 32P was found inside bacteria while 35S remained outside
3
Q
Watson and Crick
A
- Discovered the structure of DNA
4
Q
Nucleotide Structure
A
- Phosphate group
- Nitrogenous Base
- Pentose (5 Carbon sugars, which is deoxyribose or ribose)
Docs
5
Q
Purines and Pyrimidines
A
- Purines (2 carbon nitrogen ring) = Adenine and guanine
- Pyridine (1 carbon nitrogen ring) = Thymine and cytosine
6
Q
DNA
A
- Contains thymine instead of uracil
- Sugar is deoxyribose
- Double stranded
7
Q
RNA
A
- Contains uracil instead of thymine
- Sugar is ribose
- Single stranded
8
Q
Hydrogen Bonding between Base Pairs
A
- Hydrogen bond occurs when there is hydrogen atom attached to oxygen or nitrogen
- Two hydrogen bonds between A and T
- Three hydrogen bonds between G and C
9
Q
Nucleic Acid Formation
A
- mRNA interacts with ribosomes to ensure a specific protein is translated
- tRNA ensures a specific amino acid is incorporated into a protein
10
Q
Phospholipid Bilayer
A
- Phospholipids are amphipathic
- Hydrophillic head and hydrophobic tail
11
Q
Membrane Proteins
A
- Amphipathic with hydrophillic portions protuding out the membrane
12
Q
Fluid Mosaic Model
A
- Explains how molecules are spatially arranged in membrane
13
Q
Sidedness
A
- Asymmetrical distribution of proteins, CHO and lipids on its two sides
- Lipids can move around and flip around
- Proteins are fixed where they are
14
Q
Membrane Composition
A
- Lipids
- Phospholipids and cholesterol (0-25%)
- Cold temperature = Lipid more bunched up = Harder to move around
- Hot temperature = Lipid more loose = Easier to move around
- Proteins
- Peripheral and integral
- CHO
- Glycolipids and glycoproteins
15
Q
Cell Integrity
A
- Phospholipid bilayer is permeable to most molecules
- Hydrophobic molecules will dissolve in hydrophobic core and diffuse across membrane
- Oxygen, carbon dioxide and water cross membrane via simple diffusion
- Ionised, polar and large molecules can only cross via protein transporters
16
Q
Cell Integrity 2
A
- RBC withstand mechanical forces while being squeezed through capillaries
17
Q
Diffusion vs Osmosis
A
- Diffusion is the movement of molecules ffrom high concentration to low concetration
- Osmosis is the movement of water from low solute concetration to high solute concentration
18
Q
Tenacity
A
- Animal cells have no cell wall so they require an isotonic environment
- Plant cells require a hypotonic environment
19
Q
Passive Transport
A
- Movement of substances without energy
20
Q
Active Transport
A
- Movement of substances against their concentration gradient
21
Q
Vesicular Transport
A
- Movement via vehicles (endocytosis and exocytosis)
22
Q
Facilitate Diffusion
A
- Movement of molecules across membrane via protein channels or carriers
23
Q
FACILITATED DIFFUSION: Protein Channels
A
- Provide specific corridor for specific molecule
- Gated Channels are when channels may be opened or closed, depending on a stimulus
- E.G. Voltage-gated sodium channel
24
Q
FACILITATED DIFFUSION: Protein Carriers
A
- They bind to specific molecules on one side, change shape, and release the molecule on the other side
- Slower than channel proteins because carriers must bind and release molecules
- The rate of transport increases with concentration but eventually reaches a maximum (Vmax) when all carriers are occupied
25
Concentration Gradient
- Potassium is greater inside the cell
- Sodium is greater outside the cell
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ACTIVE TRANSPORT: Proton Pumps
- Transports H+ ions against concentration gradient
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ACTIVE TRANSPORT: Cotransport (plants)
- Movement of one molecule down its gradient drives the movement of another molecule against its gradient
28
Membrane Potential
1. 3 sodium ions bind to pump
2. Sodium is released out of cell and new protein shape in proton pump
3. 2 potassium binds to pump in new protein shape
4. Potassium is released into cell
29
Exocytosis
- Vesicles leaving the cell
1. Constitutive - Always releasing vesicle without signal
2. Regulated - Release triggered by signals
3. Lysosomal - Lysosomes fuse with plasma membrane to release waste
30
Endocytosis
- Vesicles entering the cell
1. Pinocytosis - Fluids and dissolved small molecules
2. Phagocytosis - Bigger molecules
3. Receptor-mediated endocytosis - Highly specific
- Receptor proteins on the plasma membrane recognise specific molecules and triggers endocytosis
31
Catabolism
- Release energy by breaking down complex molecules into smaller molecules
32
Anabolism
- Energy by building complex molecules from smaller molecules
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What is ATP used for
- Chemical work (E.G. Synthesis of polymers)
- Transport work (E.G. Active transport)
- Mechanical work (E.G. Muscles)
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Three Macronutrients
- Carbohydrates broken down into sugars
- Proteins broken down into amino acids
- Fats broken down into fatty acids
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Utilisation of Macronutrients
1. Digestion
2. Uptake by intestinal cells
3. Transport around the body
4. Uptake by cells
5. Catabolism / Storage inside cells
36
Activation Energy
- Certain amount of energy needed to “push the reactants uphill” before the downhill reaction can proceed
37
Influences on Enzyme Activity
- pH
- Temperature
- Cofactors
- Inhibitors
38
Cofactors
- Non protein components for catalysis
- Inorganic Cofactors such as iron required by hemoglobin to bind oxygen
- Organic Cofactors such as vitamins
39
Allosteric Regulation
- Inhibit or activate enzyme activity
- Binding a molecule at a site other than the enzyme's active site
40
Feedback Inhibition
1. The initial substrate binds to Enzyme 1, starting a series of reactions
2. This binds with more enzymes (1-5)
3. Finally, the pathway produces isoleucine, the end product.
4. When enough isoleucine has been made, it binds to an allosteric site on Enzyme 1 (not the active site)
5. This changes the shape of Enzyme 1, inactivating it
41
Fermentation
- Partial degradation of sugars without the need for oxygen
- In RBC, fermentation converts glucose to lactic acid
- Produces 2 ATP per glucose molecule
42
Aerobic Respiration
- Complete breakdown of sugars with oxygen
- Produces carbon dioxide and water
- Produces 30-32 ATP per glucose molecule
43
Oxidation and Reduction
- Chemical reactions involving electron transfer
- Oxidation loses electrons and Reduction gains electrons
44
Step 1: Glycolysis
- Occur in cytosol
- Glucose (6 carbon) is broken down into 2 pyruvate (3 carbon molecule)
- ATP is produced via substrate-level phosphorylation
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Stage 1: Energy Investment Phase
- Add phosphates to glucose (costs 2 ATP)
- Change shape and split it into two smaller molecules
- Both small molecules become G3P
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Stage 2: Energy Payoff Phase
- NADH is produced from G3P
- End result: 2 Pyruvate, 2 NADH, and 2 Net ATP
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Step 2: Pyruvate Oxidation to acetyl CoA
- 2 Pyruvate is transported to mitochondria
- Pyruvate is converted to Acetyl CoA, producing NADH and CO2
- Redox Reaction transfers a pair of electron to NAD+ resulting in NADH
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Step 3: Citric Acid Cycle
- Still in mitochondria
- Acetyl CoA produces 3 NADH, 1 FADH₂, 1 ATP, and 2 CO₂ per cycle
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Step 4: Oxidative Phosphorylation
- Electron transport chain and chemiosis
- Electrons from NADH and FADH₂ pass through ETC, creating a proton gradient
- ATP Synthase uses this gradient to produce ATP
- Produces around 26-28 ATP per glucose molecule
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Chemiosmosis
- Process by which ATP is synthesised using the energy stored in a proton gradient across a membrane
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Proton Gradient
- Created by pumping protons (H⁺) into the intermembrane space during the electron transport chain
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Fermentation
- Anaerobic process
- Produces 2 ATP per glucose through glycolysis
- Converts pyruvate to lactate (in animals) or ethanol and CO₂ (in plant)
- Advantages: Quick energy and no oxygen needed
- Disadvantages: Low ATP yield and lactate can cause muscle fatigue
53
Aerobic Respiration
- Requires oxygen
- Produces 30-32 ATP per glucose
- Involves glycolysis, TCA cycle, and oxidative phosphorylation
- Advantages: High ATP yield
- Disadvantages: Slower than fermentation and requires oxygen
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54
Step 1: Light Reactions
- Occurs in thylakoid membranes
- To convert light to chemical energy (ATP and NADPH)
1. Water splitting produces protons, electrons and oxygen
2. Chlorophyll absorbs light energy
3. Electrons move through the ETC, creating proton gradient
4. ATP is produced via chemiosmosis using ATP synthase
5. Electrons reduce NADP+ to NADPH
55
Step 2: Calvin Cycle
- Occurs in stroma of chloroplast
- Does not require light
- To fix Co2 into organic molecules to produce glucose
1. CO2 combined with RuBP to from a 3-carbon molecule
2. ATP and NADPH are used to reduce 3-phosphoglycerate to G3P
3. Some G3P is used to regenerate RuBP for cycle to continue
56
Photosystem II
- Absorbs light at 680 nm
- Splits H20 and release O2, protons and electrons
- Electrons move through the ETC, creating proton gradient
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Photosystem I
- Absorbs light at 700 nm
- Receives electrons from PS II via ETC
- Produces NADPH by transferring electrons to NADP+
58
Phases 1 of Calvin Cycle: Carbon Fixation
- CO2 combined with RuBP to form 3-phosphoglycerate
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Phase 2 of Calvin Cycle: Reduction
- 3-phosphoglycerate is converted to G3P
Uses ATP and NAD
- Some G3P exist the cycle to form glucose
60
Phase 3 of Calvin Cycle: Regeneration of RuBP
- Remaining D3P is used to regenerate RuBP
- Requires ATP
61
Photosynthesis vs Oxidative Phosphorylation
- Photosynthesis stores energy in glucose, while oxidative phosphorylation releases energy from glucose
- Photosynthesis reduces carbon (CO₂ to glucose), while respiration oxidizes carbon (glucose to CO₂)
