Biology 1B - Cellular Biology Flashcards
(124 cards)
1
Q
what chemical bonds are important for life
A
ionic - exchanging of electrons
covalent - sharing of electrons
hydrogen bonds - weaker interactions
2
Q
what is a membrane
A
phospholipid polymers of fatty acids, glycerol, phosphate and a terminal amine or alcohol group
3
Q
phospholipids are amphipathic molecules, what does this mean
A
it means in water they spontaneously form monolayers and bilayers
4
Q
what are important cellular functions of membranes
A
to compartmentalise metabolic activities
to protect cellular components
to provide a scaffold for signalling
as a medium for cellular energy generation
this is due to immiscibility of water and membranes
5
Q
how do membranes generate biological energy
A
ion (charge) gradients across membranes
6
Q
how can voltage across cell membranes be measured
A
using microelectrodes implanted in cells
7
Q
name some places membranes are found in eukaryotic cells
A
chloroplasts
Golgi apparatus
mitochondria
vacuole
nucleus
endoplasmic reticulum
8
Q
what are organelles
A
membrane delimited compartments in eukaryotic cells
9
Q
what is the importance of membrane transport
A
protect metabolic reactions within the cell against the environment
communicate and exchange materials between the cell and environment
transport proteins allow for controlled interaction of cell with environment
10
Q
describe membrane permeability
A
high permeability for small hydrophobic molecules and gases
limited permeability for water and hydrophilic molecules
very low permeability for ions ad large solutes
11
Q
what do transport proteins do
A
create hydrophilic passage
create a filter
provide possibility for energy coupling
provide possibility for regulation
12
Q
what is facilitated diffusion
A
transport proteins increase permeability of substances that already can move through membrane
13
Q
what two forces drive the movement of molecules across membranes
A
chemical gradient - concentration gradient
electrical gradient - charge gradient (only for charged molecules)
14
Q
what are positive and negative ions
A
cations - positive
anions - negative
15
Q
what is the charge inside a membrane
A
negative
16
Q
what is the electrochemical gradient
A
the net driving force for movement of a molecule resulting from combination of chemical and electrical gradients
17
Q
what are the transport proteins for active transport
A
pumps
co transport systems
18
Q
what are the transport proteins for passive transport
A
channels
carriers
19
Q
what are pumps (transport protein)
A
- active transport
- use energy coupling - use ATPases, transport is coupled to the hydrolysis of ATP
- conformational change occurs during transport
- pumps establish electrochemical gradients used to drive transport of other molecules (co transport systems, channels and carriers)
20
Q
describe how the sodium potassium pump works
A
1) transporter binds 3Na+ from the inside of the cell
2) phosphorylation occurs and conformation changes
3) now open side exposed to outside of cell, looses affinity for sodium
4) transporter releases 3Na+ to outside and binds to 2K+
5) dephosphorylation occurs and conformation changes
6) releases 2K+ to inside
21
Q
what are co transport systems
A
- active transport
- co-transporters couple the downward movement of one ion (driver) to the uphill movement of another solute (substrate)
22
Q
what are the two types of cotransport systems
A
symport - driver ion and substrate move in same direction (piggyback principle)
antiport - driver ion and substrate move in opposite directions (revolving door principle)
23
Q
what are channels
A
transporter proteins for passive transport
provides an aqueous pore for the passage of ions
24
Q
what are carriers
A
transport proteins for passive transport
undergoes conformational change that exposes ion binding sites to different sides of the membrane
25
how to ion channels exert tight control of the passage
they are selective and have higher permeability for certain ions
they are gated, meaning they can open and close in response to certain stimuli
26
how can ion channels be measured
using the patch clamp method
uses suction pipette and current amplifier to observe the current when channel is open and closed
27
what are stem cells
unspecialised cells that can reproduce indefinitely and differentiate into one or more specialised cell types
can self renewal or differentiate
adult and embryonic
28
what is meant by totipotent stem cells
(embryonic) generate all tissues of embryo and extra-embryonic tissues such as placenta
29
what are pluripotent stem cells
(embryonic) generate all three germ layers but not extra embryonic tissues
E.g.. embryonic stem cells
30
what are multipotent stem cells
(adult) able to differentiate into multi-lineages but not all germ layers
E.g. mesenchymal stem cells
31
what are unipotent stem cells
(adult) ability to differentiate along one lineage
e.g. most adult stem cells
32
what are the three germ layers
ectoderm - forms exoskeleton, top layer
mesoderm - develops into organs, middle layer
endoderm - forms the inner lining of organs, bottom layer
33
how are stem cells isolated from tissues
adult tissues and organs : biopsy, bone marrow
umbilical cord blood: at birth
foetal tissues and organs: after pregnancy termination
34
describe reproductive cloning (stomatic cell nuclear transplantation)
remove nucleus form egg or Oocyte to create an enucleated cell
replace it with nucleus of differentiated cell
if nucleus from donor maintains full genetic potential, leads to development of the recipients cell into all tissues/ organs of an organism (clone)
35
what are examples of nuclear transplantation in research
1) john Gurdon (1970s) experiment using Xenopus Leavis tadpoles
nucleus from differentiated frog cell transplanted into egg, found nucleus from differentiated frog cell can direct development of tadpole
however, efficiency decreases as donor cell becomes more differentiates, paved the way for stem cell technology
2) dolly the sheep
first example of mammalian reproductive cloning
cloned lamb from adult sheep by nuclear transplantation
one of several hundred failed attempts
confirmed chromosomal DNA identical to nucleus donor
developed conditions and cells weren't as healthy
36
what are challenges of mammalian reproductive cloning
- small percentage of cloned embryos develop normally to birth
- cloned animals don't always look/behave the same
- health of clone can be poor
37
describe human embryonic stem cells
derived from inner cell mas of blastocyst
self renew and expand indefinitely in culture
pluripotent
38
what is therapeutic cloning
the application of stomatic cell nuclear transplantation to produce patient specific cell lines isolated from an embryo
designed to replace injured/diseased tissues
not intended for in utero transfer
39
what are applications of embryonic stem cells
basic research
drug testing
toxicology
drug discovery
therapy
40
what are some ethical objections to human embryonic stem cells
- very early stage, when is it a life?
- range of policies for use of hESC across the world
- sometimes based on religious belief
41
what is a risk of using embryonic stem cells
teratomas
an often benign tumour containing tissues from more than one germ layer arising totipotent cells
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what are clinical concerns of use of hESC
mainly mixed differentiation, need to refine methods
teratoma potential
small experimental scale
animal products used in culture, infection and immune risks
43
what are hematopoietic stem cells used for?
multipotent
used for bone marrow transplants
transplanted into patients who need their blood system replaced such as people with leukaemia, sickle cell anaemia and immune deficiencies
44
what are autologous and allogenic stem cell transplants
autologous - stem cells taken from an individual transplanted back into that individual
allogenic - stem cells derived from one individual transplanted into a different individual
45
what are induced pluripotent stem cells (iPs cells)
reprograming differentiated cells to act like embryonic stem cells
46
what are 2 major potential uses of induced pluripotent stem cells for treatment
1) cell therapy - patients own cells reprogramed into iPs cells, replace non-functional tissues e.g. insulin producing cells
2) research and drug discovery:
reprogramed to become iPS cells - provide cellular model of the disease to understand the disease and develop treatments
47
what is a research potential of iPS cells
creating ALS neurons from stem cells to treat Amyotrophic lateral sclerosis
48
what is a therapeutic potential of iPS cells
to treat type 1 diabetes
reprograming iPS cells to differentiate into pancreatic beta cells which produce insulin
49
what are advantages of induced pluripotent stem cells
can make person specific cell lines
no embryos damaged - ethical alternative
50
what are problems with induced pluripotent stem cells
genetically modified
potential oncogenesis or damage to host genome
differentiation, e.g. teratomas
51
what is a stomatic cell
any body cell that does not produce gametes (egg or sperm)
52
what is a germ cell
a diploid reproductive cell that gives rise to a gamete
53
how does so much DNA (1m) for into sperm nucleus
and what does methylation affect
proteins called histones help with folding
DNA is wrapped around the histones, then folded and coiled
methylation affects how tightly coiled the DNA is and effectively switches genes off
54
how are phenotypes created
from complex interactions of genes
55
how are genes passed onto the next generation
through reproductive cells called gametes (sperm and egg)
56
how many chromosomes do humans have
23
57
what are the stages of the cell cycle
1) interphase - preparation phase, has 3 sub phases:
G1 - cell grows and produces proteins
S phase - DNA replication occurs, ensuring each daughter cell gets a full set of genetic material
G2 - cell prepares for mitosis
prophase - chromosomes condense, spindle fibres form and nuclear envelope breaks down
metaphase - chromosomes align at the centre of the cell
anaphase - sister chromatids are pulled apart to opposite ends of the cell
telophase - the nuclear envelope reforms, chromosomes start to decondense
cytokinesis - the cytoplasm splits, creating two identical daughter cells
58
what is the difference between a chromosome and chromatid
chromosome - consists of double stranded DNA
chromatid - identical halves of a duplicated chromosome
59
what are autosomes
sets of chromosomes that don't determine sex (22 pairs)
60
what are homologous chromosomes
two chromosomes in a pair that are the same length and carry alleles of the same genes
includes one chromosome from each parent
61
what is a karyotype
ordered display of pairs of chromosomes in a cell
62
what are non homologous chromosomes
chromosomes that do not belong to the same pair
contain different genes an do not pair during mitosis
63
when does mitosis occur
before cytokinesis after G2 in the cell cycle
64
what is meiosis
cell division producing gametes each possessing the haploid number of chromosomes and haploid content of DNA (4 daughter cells)
65
why is meiosis necessary
to allow offspring to be produced with half of their genetic information from their mother and father
66
describe meiosis
- occurs after s phase in cycle after DNA replication
- two sets of divisions occur:
meiosis I - homologous chromosomes separate, two haploid daughter cells are formed each containing duplicated chromosomes (reductional division)
meiosis II - sister chromatids separate, 4 haploid daughter cells are formed, each with a haploid set of replicated chromosomes
67
what is a key difference between mitosis and meiosis
mitosis conserves number of chromosome sets producing genetically identical cells
meiosis reduces number of chromosomes producing genetically different cells
68
what are some unique events in meiosis
1) at metaphase plate, there are paired homologous chromosomes instead of individual replicated chromosomes
2) it is homologous chromosomes instead of sister chromatids that separate
3) synapsis and crossing over: homologous chromosomes physically connect and share genetic information
69
what contributes to genetic variation/ diversity
mutations
independent assortment of chromosomes
crossing over
random fertilisation
70
how do mutations contribute to genetic diversity
mutations create different versions of genes called alleles
reshuffling of alleles during meiosis and reproduction produce genetic variation
71
what is independent assortment of chromosomes
equal chance of chromosomes from each parent lining up at metaphase I
homologous chromosomes originate randomly at metaphase I
72
what is crossing over
results in recombinant chromosomes that contain genes from each parent
begins very early in prophase as homologous chromosomes pair up gene by gene
73
how does fertilisation create genetic diversity
any egg can fuse with any sperm
74
what is a chiasma and centromere
chiasma = place where chromosomes cross over
centromere = centre of chromosome
75
what is epigenetics
the study of the chemical modification of specific genes or gene associated proteins of an organism
76
what is an epigenetic tag
methylation - influences the level of transcription that can occur of particular genes
77
what is bioenergetics
how cells produce and release energy
relates to capture, storage and conversion of energy
78
what is the first law of thermodynamics
no energy can be lost or gained within the universe, energy can only be converted from one state to another
79
what is the second law of thermodynamics
every energy transfer increases the entropy of the universe
80
what are the two types of energy
potential energy
kinetic energy
81
what do organisms require in terms of energy
constant energy input
82
what happens to organisms energy
looses some of its energy to the environment and fixes some of its energy irreversibly
83
what is cellular reparation
metabolic process with which an organism obtains energy by oxidising nutrients and releasing waste products
84
how do organisms obtain nutrients
by eating organic molecules
85
what is metabolism
totality of organisms chemical reactions
86
what is anabolism
use of energy to build complex molecules from smaller molecules
(requires energy)
87
what is an example of an anabolic reaction
protein synthesis
88
what is catabolism
release of energy through breaking down molecules
89
what is an example of a catabolic reaction
glycolysis
90
what is an exergonic reaction
a reaction where energy is released
the reactants have larger free energy than the products
energetically favourable
91
what is an endergonic reaction
a reaction that energy is required for
the reactants have lower free energy than the products
not energetically favourable
92
when can a reaction occur spontaneously
if G is negative in Gibbs free energy
(exergonic reaction)
93
what regulates metabolism
enzymes
94
what makes up metabolic pathways
a group of enzyme catalysed reaction
95
how do enzymes catalyse reactions
by lowering the activation energy
96
how are enzymes regulated
by gene expression and protein modification (e.g. phosphorylation)
97
how are enzymes often inhibited
by the end product
(negative feedback)
98
what are the three components of ATP
phosphate groups
ribose
adenine
99
when does ATP release energy
when the outermost inorganic phosphate (Pi) is cleaved off and yields adenine-diphosphate (ADP)
100
why is energy stored in the outermost Pi
because the negative charges in the molecule repel each other
101
what are two ways ATP can be formed
substrate level phosphorylation (transfer of phosphate group) e.g. glycolysis, citric acid cycle
oxidative phosphorylation (chemiosmosis, electron transport chain)
102
what is chemiosmosis
movement of ions down their electrochemical gradient across a semipermeable membrane
103
describe oxidative phosphorylation
high conc. of hydrogen in intermembrane space and low conc. inside cell
this is established by the electron transport chain
energy stored in a transmembrane proton(H+) gradient
ATP synthase harvests energy and rotates as particles move from high -> low concentration (chemiosmosis)
104
what is another energy source
redox potential and electron transport chain
105
how is energy produced via redox reactions (reduction and oxidation)
sugars (weakly electronegative) undergo oxidation, and electrons are relocated to oxygen (strongly electronegative) which is reduced
this releases energy
106
what is used as electron currency
NADH
many molecules of NADH are produced during the breakdown of food
107
what is the role of NADH in the electron transport chain
NAD+ captures electrons from redox reactions in the form of NADH and delivers them to the electron transport chain
108
what are the three stages in cellular respiration
glycolysis
citric acid cycle/kerbs cycle
oxidative phosphorylation (electron transport chain/chemiosmosis)
109
what is the purpose of glycolysis
to convert 1glucose molecule (6 carbon molecule) to 2pyruvate through two phases
110
what are the two phases of glycolysis
energy investment phase :
2 ATP used
energy payoff phase:
4 ATP formed
111
what is the net gain from glycolysis
2 pyruvate + 2H2O
2 ATP
2 NADH + 2H+
112
where does glycolysis occur
in cytosol
113
does glycolysis require O2
no
occurs under anaerobic conditions
114
where does the citric acid/ kerbs cycle occur
in the mitochondria
115
does the citric acid cycle require oxygen
yes
aerobic conditions
116
what is the "link reaction" and what are the three steps
preparing pyruvate for the citric acid cycle
1)2 pyruvate molecule looses one carbon each atom released as CO2, creating 2 Acetyl
2) NAD+ is reduced to NADH
3)2 Acetyl is attached to Coenzyme A forming 2 Acetyl CoA
117
where does the link reaction occur
in mitochondrial matrix
118
when does the link reaction not proceed
when there is no oxygen present
119
what happens during the citric acid cycle
acetyl-CoA combines with oxaloacetate to form citrate
citrate undergoes several transformations, cycle runs twice producing:
2 ATP
6 NADH and 2 FADH (for electron transport chain)
120
where does the electron transport chain occur
inner mitochondrial membrane
121
does ETC require oxygen
yes
122
what is the purpose of electron transport chain
Electrons from NADH and FADH₂ are transferred through the chain, releasing energy to pump protons into the intermembrane space. This creates a proton gradient that drives ATP synthesis via ATP synthase.
produces alt of ATP ( around 26-28ATP)
123
describe fermentation in eukaryotes
occurs after glycolysis when there is not enough energy for ETC to occur
produces 2ATP per glucose
produces build up of lactate
124
