Module 4 - Cell function Flashcards
(90 cards)
1
Q
Cell theory
A
- cells are the basic unit of life
- all organisms are composed of cells
- cells are the smallest living thing
- cells arise only from pre-existing cells by division
2
Q
Factors that affect diffusion rate
A
- cell size
- SA available
- temperature
- concentration gradient
- distance
3
Q
SA:V ratio in small vs big cells
A
- small cells have higher SA:V ratio
- organisms made of many small cells have advantage over organism with fewer, larger cells
- as cell size increases, volume increases more rapidly than SA
4
Q
Structural similarities between prokaryotic and eukaryotic cells
A
- nucleoid/nucleus where DNA located
- cytoplasm
- ribosomes
- plasma membrane
5
Q
Prokaryotic cell features
A
- simplest organisms
- lack membrane bound nucleus
- DNA present in nucleoid
- cell wall outside plasma membrane
- contain ribosomes for protein synthesis
- flagellum for motility
- pili to sense temperature changes
6
Q
Bacteria cell wall
A
- most encased by strong cell wall
- composed of peptidoglycan, carb matrix cross-linked by short peptides
- protect cell, maintain shape, prevent excessive uptake/loss of water
- susceptibility of bacteria to antibiotics depends on cell wall structure
7
Q
Eukaryotic cell features
A
- contain membrane-bound nucleus
- more complex
- compartmentalization - endomembrane system + membrane bound organelles
- cytoskeleton for support and structure + to keep organelles in fixed locations
8
Q
Difference between animal and plant cells
A
plant cells have cell wall, chloroplasts and vacuoles
9
Q
Nucleus
A
- stores genetic information
- nuclear envelope with two phospholipid bilayers
- genes present in chromosomes
10
Q
Ribosomes
A
- large and small subunit
- cell’s protein synthesis machinery
- found in all cell types
- may be free in cytoplasm or associated with internal membranes
11
Q
Rough endoplasmic reticulum
A
- attachment of ribosomes to membrane
- synthesis of proteins to be secreted
- sent to lysosomes or plasma membrane via transport vesicles
12
Q
Smooth endoplasmic reticulum
A
- relatively few bound ribosomes
- synthesis of carbs, lipids and hormones
- store calcium detoxification
13
Q
Golgi apparatus
A
- flattened stacks of interconnected membranes
- packaging and distribution of molecules synthesized at one location and used at another within cell or outside of cell
- cis (near nucleus) and trans (near plasma membrane) face
14
Q
Protein transport through endomembrane system
A
- ER synthesizes protein
- transport to cis face of Golgi apparatus by transport vesicle
- protein modified and packaged into secretory vesicle for transport
- travel to plasma membrane releasing contents to ECF
15
Q
Lysosomes
A
- membrane bound digestive vesicles
- arise from Golgi apparatus
- contain enzymes that catalyze breakdown of macromolecules
- recycle old organelles or foreign matter
16
Q
Peroxisomes
A
- enzyme-bearing, membrane-enclosed vesicles
- contain enzymes involved in oxidation of fatty acids
- hydrogen peroxide produced as by-product and rendered harmless by catalase
17
Q
Vacuoles
A
- membrane-bound (tonoplast) structures typically found in plants
- central vacuole in plants
- contractile vacuoles in some fungi and animal cells
- storage in plants - waste, toxins, metals
18
Q
Mitochondria
A
- all types of eukaryotic cells
- bound by membranes: outer membrane, intermembrane space, inner membrane
- folds of inner membrane = cristae
- ATP and energy synthesis machinery
- own DNA
19
Q
Chloroplasts
A
- two membranes
- chlorophyll pigments for photosynthesis
- thylakoids = membranous sacs within inner membrane
- grana = stacks of thylakoids
- own DNA
20
Q
Endosymbiosis theory
A
- present-day eukaryotic organelles evolved by symbiosis between two free-living cells
- mitochondria and chloroplasts have similarities to prokaryotic cells
- chloroplasts = cyanobacterium, mitochondria = proteobacterium
21
Q
Eukaryotic cell walls
A
- plants, fungi and some protists
- plant + protist walls made of cellulose and hemicellulose
- fungal cell walls made of chitin
22
Q
Plasmodesmata
A
- specialized openings in cell walls in plants
- cytoplasm of adjoining cells connected
- communication and transport of molecules between cells
23
Q
Membrane structure
A
- phospholipid bilayer: polar hydrophilic heads on outside of membrane, nonpolar, hydrophobic, carbon chain tails on inside of membrane
- transmembrane proteins: allows water and nutrients to pass through channels as membrane impermeable
24
Q
Membrane protein functions
A
- transporters
- enzymes
- cell-surface receptors
- cell-surface identity markers
- cell-to-cell adhesion proteins
- attachments to cytoskeleton
25
First law of thermodynamics
- energy cannot be created or destroyed only changed from one form to another
- total amount of energy in universe remains constant
26
Energy
capacity to do work
27
States of energy
- kinetic = energy of motion
- potential = stored energy
28
Forms of energy
mechanical, heat, sound, electrical, light, radioactivity
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Energy flow
- sun provides energy for most living systems
- energy flows into biological world from Sun
- photosynthetic organisms absorb this energy and convert small molecules into complex molecules
- stored as potential energy in chemical bonds
- energy stored in chemical bonds used for cellular processes, break down bonds and release stored energy
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Redox reactions
- reduction oxidation, paired reactions
- oxidation = loses e-
- reduction = gains e-
- reduced form has higher level of energy
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Second law of thermodynamics
- energy cannot be transformed from one form to another with 100% efficiency
- lost as heat
- some energy always unavailable = entropy
- energy transformations proceed spontaneously to convert matter from less stable to more stable forms, downhill
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Entropy
- energy unavailable to do work
- less entropy = high available energy
- high entropy = low available energy
- less stable = less entropy
- more stable = high entropy
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Gibbs Free Energy
- energy available to perform work
- G = H - TS
- H = enthalpy, total energy
- T = absolute temperature
- S = entropy, unavailable energy
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Endergonic
- positive G
- products have more energy than reactants
- not spontaneous, requires input of energy
- uphill
- more activation energy required
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Exergonic
- negative G
- products have less energy than reactants
- energy lost as heat
- spontaneous
- downhill
- less activation energy required
36
Activation energy
minimum amount of energy required by reactants to start reaction
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ATP
- adenosine triphosphate
- primary energy currency used by cells
- cells store and release energy in bonds of ATP
38
ATP hydrolysis
ATP --> ADP + Pi + energy
- energy released used for other reactions
- releases one phosphate group = releases energy
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ATP composition
- ribose
- adenine
- chain of 3 phosphates, energy stored in phosphate bonds
- highest amount of energy, largest number phosphates
40
ATP cycle
- ATP drives endergonic reactions
- formation of ATP from ADP + AMP = endergonic
- hydrolysis of ATP = exergonic
- not suitable for long term energy storage as phosphate bonds too unstable
- fats + carbs better for storage
41
Autotrophs
able to produce own organic molecules through photosynthesis e.g. plants, algae
42
Heterotrophs
live on organic compounds produced by other organisms e.g. animals, fungi
43
Cellular respiration
- breaking down compounds to release ATP
- exergonic
- oxidation of organic compounds to extract energy from chemical bonds
- series of reactions
44
Aerobic respiration final e- acceptor
oxygen, reduced to H2O
45
Anaerobic respiration final e- acceptor
inorganic molecule e.g. CO2
46
Fermentation final e- acceptor
organic molecule e.g. organic acid
47
Aerobic respiration equation
C6H12O6 + 6O2 --> 6CO2 + 6H2O + energy
48
Electron carriers
- soluble, membrane-bound, move within membrane
- all carriers reversibly oxidized and reduced
- some carry both e- and protons
- NAD+ acquires two e- and a proton to become NADH
49
Oxidation of glucose stages
1. glycolysis - converts glucose into 2x pyruvate in cytoplasm
2. pyruvate oxidation - oxidized to acetyl-CoA and enters citric acid cycle
3. citric acid cycle
4. electron transport chain and chemiosmosis - inner membrane of mitochondria
50
Glycolysis
- converts 1 glucose (6C) to 2 pyruvate (3C)
- 10 step biochemical pathway
- occurs in cytoplasm
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Steps of glycolysis
1. priming reaction, -2 ATP
2. cleavage, 0 ATP
3. oxidation and ATP formation: 4 ATP + 2NADH
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Net energy production of glycolysis
2 ATP and 2 NADH
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Pyruvate fate without oxygen
- pyruvate reduced in order to oxidize NADH back to NAD+
- does not enter citric acid cycle
- regeneration of NAD+ forms lactate in animals and ethanol in plants
- fermentation/anaerobic respiration
54
Pyruvate oxidation
- mitochondria
- 3C pyruvate oxidized to 2C acetyl coenzyme A
- oxidation through decarboxylation by multi-enzyme complex
- net energy production: 2NADH
55
Citric acid cycle
- matrix of mitochondria
- acetyl-CoA enters citric acid cycle and reacts with oxaloacetate to form citrate
1. acetyl-CoA (2C) + oxaloacetate (4C) --> citrate (6C)
2. citrate rearrangement and decarboxylation
3. regeneration of oxaloacetate
- cycle occurs 2x as 2 acetyl-CoA
56
Citric acid cycle net energy production
- 6 NADH
- 2 FADH2
- 2 ATP
- total ATP yield = 2 ATP + (6 x 2.5) ATP + (2 x 1.5) ATP = 20 ATP
57
Electron transport chain
- series of membrane-bound e- carriers made of proteins
- embedded in inner mitochondrial membrane
- e- from NADH + FADH2 transferred to complexes of ETC, become oxidized
- each complex operates as proton pump, driving protons to intermembrane space
- e- move from one protein complex to other
58
ATP synthase
- uses H+ to make ATP
- accumulation of protons in intermembrane space drives protons into matrix via diffusion
- most protons re-enter through ATP synthase
- uses electrochemical gradient to make ATP from ADP + Pi
- chemiosmosis
- carried out by tiny rotary motor driven by proton gradient
59
Theoretical yield of respiration
- glycolysis = 5 ATP
- pyruvate oxidation = 5 ATP
- citric acid cycle = 20 ATP
- 30 ATP per glucose for eukaryotes
- 32 ATP per glucose for bacteria
60
Photosynthesis equation
6CO2 + 12H2O + light --> C6H12O2 + 6H2O + 6O2
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Types of photosynthesis
- oxygenic - cyanobacteria, algae, all land plants
- anoxygenic - some bacteria
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Leaf structure
- mesophyll: contain chloroplasts, palisade mesophyll, spongy mesophyll
- epidermis
63
Chloroplast structure
- outer and inner membrane
- intermembrane space
- thylakoid - disc-like structure
- granum - stack of thylakoids
- stroma - semi-liquid fluid surrounding thylakoids
- stroma lamella - connect grana
- contains photosynthetic pigments clustered into photosystems
64
Stages of photosynthesis
- light dependent reaction:
- thylakoid membrane
- H2O broken down and O2 released
- capture energy from sunlight
- make ATP and NADPH
- light independent reaction:
- stroma
- use ATP and NADPH to synthesize glucose from CO2
- Calvin cycle
65
Photon
particle of light, acts as discrete bundle of energy
- short wavelength = high energy
- long wavelength = low energy
66
Absorption spectrum
- which specific wavelength of light molecule can absorb
- different for each pigment
- visible range only
67
Pigment absorption
- molecules that absorb light energy in visible range
- 400-740 nm
- carotenoids = 440 and 470 nm
- chlorophyll a = 430 and 675 nm
- chlorophyll b = 450 and 625 nm
68
Types of photosynthetic pigments in plants
- chlorophyll a
- chlorophyll b
- carotenoids
69
Chlorophyll a
- main pigment in plants
- only pigment that can act directly to convert light energy to chemical energy
- absorbs violet-blue and red light
70
Chlorophyll b
accessory pigment absorbing wavelengths that chlorophyll a does not absorb
71
Chlorophyll structure
- porphyrin head and hydrocarbon tail
1. porphyrin ring = complex ring structure with alternating double and single bonds, magnesium ion at center of ring
2. photons excite electrons in ring
3. electrons shuttled away from ring
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Carotenoids
- accessory pigment
- carbon rings linked to chains with alternating single and double bonds
- can absorb photons with wide range of energies
- scavenge free radicals, protective role
73
Photosystem structure
1. antenna complex
2. reaction center
74
Antenna complex
- hundreds of chlorophyll b pigments
- capture photons from sunlight and channels them to reaction center
- consists of web of chlorophyll molecules linked together and held tightly in thylakoid membrane by matrix of proteins
75
Reaction center
- transmembrane protein-pigment complex
- 1 or more chlorophyll a molecule
- chlorophyll absorbs photon of light, electron excited to higher energy level
- passes excited electron out of photosystem to electron acceptor
- water = electron donor, gives e- to chlorophyll
76
Light dependent reaction steps
1. primary photon event - photon captured by pigment
2. charge separation - energy transferred to reaction center, excited electron transferred to electron acceptor molecule
3. electron transport - e- move through carries to reduce NADP+ to NADPH
4. chemiosmosis - produces ATP
77
Photosystem I
- P700
- accepts electron from plastocyanin
- transfers electrons ultimately to NADP+ to produce NADPH
- electrons lost from photosystem I replaced by electrons from photosystem II
78
How do photosystems work together
- carry out noncyclic transfer of electrons used to generate ATP and NADPH
- used in series
- photosystems replenished with e- obtained from splitting H2O
- b6-f complex/cytochrome connects photosystems
79
Photosystem II
- P680
- oxidizes water to O2 to replace electrons transferred to photosystem I
- passes e- to plastocyanin which passes it to photosystem I
- proton pump embedded in thylakoid membrane
80
Chemiosmosis
- electrochemical gradient used to synthesize ATP
- chloroplasts have ATP synthase enzymes in thylakoid membrane
- allow protons back into stroma
81
Calvin cycle
- build glucose using ATP and NADPH
- occurs in stroma
- doesn't need light
- from each cycle, one glucose synthesized
- C3 photosynthesis
- key step is attachment of CO2 to RuBP to form PGA
- uses Rubisco
82
Phases of Calvin cycle
1. carbon fixation - RuBP + CO2 --> PGA (3C)
2. reduction - PGA reduced to G3P
3. regeneration of RuBP using G3P
83
Output of Calvin cycle
- glucose not direct product
- G3P used to form glucose
- produces starch (storage) and sucrose (transport)
- every 6 molecules of CO2 entering cycle, 12 G3P formed, 2 leave cycle to form 1 molecule of glucose and 10 used to make 6 molecules of RuBP
84
Energy cycle
- photosynthesis uses products of respiration as starting substrates
- respiration uses products of photosynthesis as starting substrates
85
Rubisco's enzymatic activities
- carboxylation - addition of CO2 to RuBP, favored under normal conditions
- photorespiration - oxidation of RuBP by addition of O2, favored when stomata closed in hot conditions, creates low CO2 and high O2
- CO2 and O2 compete for active site on RuBP
86
C3 plants
- occurs in mesophyll cells
- plants that fix carbon using only C3 photosynthesis (Calvin cycle)
- dicot plants
87
C4 plants
- corn, sugarcane, grasses
- initially fix carbon using PEP carboxylase in mesophyll cells
- produces oxaloacetate (4C)
- converted to malate and transported into bundle-sheath cells
- malate decarboxylated to produce pyruvate and CO2
- carbon fixation using Rubisco via Calvin cycle
- energy cost - requires additional 12 ATP
- advantageous in hot climates to avoid photorespiration
87
C4 and CAM photosynthesis
- occurs in bundle sheath cell
- add CO2 to PEP to form 4C molecule
- use PEP carboxylase enzyme
- CAM = temporal solution to photorespiration
88
CAM plants
- many succulent plants
- stomata open during night and close during day
- fix CO2 using PEP carboxylase during night and store in vacuole
- during day, CO2 formed from malate and fixed into Calvin cycle
89
C4 vs CAM plants
- both use C3 and C4 pathways
- C4 - two pathways occur in different cells, mesophyll and bundle-sheath
- CAM - C4 pathway at night, C3 pathway during day
