Cell Biology

Cell Theory (3)
living organisms are made of one or more cells, cells are the smallest units of life, all cells come from pre-existing cells
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What are the exceptions to cell theory? (3)
Skeletal muscle, Giant Algea & Aseptate fungi
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Skeletal Muscle
(300 or more mm long) made of fibers that are much larger than normal cells & contain many nuclei
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Giant Algea
(as much as 100mm) consists of many small cells but only has one nucleus
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Aseptate Fungi
consists of hyphae (thread-like structures) have many nuclei in their long threads
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Name the functions of life (7)
Nutrition, Growth, Response, Excretion, Metabolism, Homeostasis, Reproduction
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What happens as a cell grows larger?
surface area to volume ration becomes smaller
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Advantages to being multicellular (2)
1) it can grow to a larger size 2) its cells can differentiate so that different cells do different jobs
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When do emergent properties arise?
when the interaction of individual component produce new functions
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Emergent Properties
new properties that emerge from the interaction of their cellular components (multicellular)
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Allele
one of the possible forms of a gene (eye colour: gene for eye colour is the same for both green and brown eyes BUT allele is different)
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Genome
An organisms entire set of genes
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Where can a multicellular organisms genome be found?
In every cell (though some genes may not be used or 'turned off'
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When is a cell 'committed'?
Once it is has gone down a pathway of development and becomes fixed and cannot change to a different pathway
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Stem cells
cells that have the capacity to divide and differentiate along different pathways
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Three examples of stem cells of Stem Cells
embryonic stem cells, adult stem cells (bone marrow skin, liver) & umbilical cord blood or placenta of newborn
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Advantages of using embryonic stem cells over adult stem cells
adult stem cells do not have the same capacity as embryonic stem cells to differentiate along different pathways
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Ethical issues of using stem cells therapeutically
.Newborns cannot consent for stem cells to be harvested from their umbilical cord, .If an embryo dies from the procedure it can be argued as immoral
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Counter-arguments to embryonic stem cell treatment
Early stage embryo's are just a ball of cells, .They lack a nervous system- feel no pain .left over embryo's from IVF> better used for stem cells than just killed
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examples of therapeutic stem cell use
Stargardt's muscular dystrophy & leukemia
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Stargardt's muscular dystrophy
genetic disease (kids 6-12) Mutation in eye, causes mem. protein used for active transport malfunction Vision becomes worse Experiment done- Embryonic stem cells injected into eye Cells attach to retina and stayed there for 4 months Eyesight improved
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Leukemia
Cancer- abnormal amount of white blood cells produce by bone marrow.
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Stem cell treatment of Leukemia (4)
Large needle inserted into large bone of donor, fluid removed from bone marrow. Stem cells extracted and froze. High doses of chemo (kill cancer cells) .Donors stem cells returned to body.Large needle inserted into large bone of donor, fluid removed
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1μm
0.001mm
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1nm
0.001μm
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Eukaryote
organisms whose cells contain a nucleus, associated with histone proteinsorganisms whose cells contain a nucleus, associated with histone proteins
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Prokaryote
organisms whose cells lack a nucleus, no membrane bound organelles and no associated histone proteins
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Binary Fission
process in which prokaryotic cells divide
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The process of Binary Fission
Bacterial chromosome is replicated. These move to opposite ends of the cell. wall and plasma pull inwards> two identical cell. binary fission can occur every 30 mins
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Eukaryotic cells with a single membrane (5)
Rough endoplasmic reticulum, Smooth endoplasmic reticulum, Golgi apparatus, Lysosomes, Vesicles and vacuoles
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Eukaryotic cells with a double membrane (3)
Nucleus, Mitochondrion, Chloroplast
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Name the main organelles of prokaryotes
Cytoplasm, Nucleoid (containing naked DNA), 70S Ribosomes, Pilli, Plasma membrane, Cell wall, Flagellum
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Lysosomes
enzymes that hydolosise big molecule
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Golgi apparatus
packages proteins into vesicles
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Rough and Smooth Endoplasmic Reticulum
transports and synthesises proteins
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Pro's and Con's to using adult stem cells
Pro's: fully compatible with adult stem cells, Con's: Difficult to obtain, Less potential than embryonic cells
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Pro's and Con's to using embryonic stem cells
Pro's: Less chance of genetic damage/ mutation, Con's: more potential for tumor formation, chance of regection
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The Davson-Danielli Model
(1930's) Model of membrane structure. There is a bilayer of phospholipids in the center of the membrane with layers of proteins on either side
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Reason for Davson-Danielli Model (3)
1)Chem. analysis of membrane showed they were composed of phospholipids and proteins 2) Evidence suggested there was a phospholipid bilayer 3)Experiments showed layers of protein could act as a barrier
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The Singer-Nicolson Model
(1950s-60s) evidence accumulated and falsified Davson-Danielli Model. Model currently used
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What did the Singer-Nicolson Model show to falsify the Davson-Danielli Model? (3)
1)Micrographs showed globular proteins were in the center of phospholipid bilayer 2)Analysis of mem. proteins showed some parts were hydrophobic 3)Fusion of cells w/ mem. proteins taged w/ coloured markers showed proteins can move in mem. colours mix
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Intergral proteins
embedded in the phospholipid bialyer
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Peripheral proteins
attached to outer surface of the phospholipid bialyer's membrane
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Glycoproteins
sugar units attached onto the outer surface of the phospholipid bialyer's membrane
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Phospholipids
basic components of all biological membranes
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Amphipathic molecule
Part of molecule is attracted to water (hydrophilic) ans part is not attracted to water (hydrophobic)
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What happens when phospholipids are mixed with water?
They naturally become arranged into bilayers, hydrophilic heads facing outwards.
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Cholesterone
restricts movement of phospholipid molecules (reduces fluidity and permeability of membrane)
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Diffusion
passive movement of particles from a region of high concentration to a region of low concentration
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Diffusion can occur across a membrane if...
there is a concentration gradient and the membrane is permeable to the particle
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Partly permeable membranes
allow some substances to diffuse through but not others
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Facilitated diffusion
the passive movement of molecules across the cell membrane via the aid of a membrane proteins (channel and carrier proteins)
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Simple diffusion
passive movement along a gradient, which will continue until molecules become evenly dispersed (equilibrium)
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Passive transport
the movement of material along a concentration gradient (high concentration ⇒ low concentration)
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Active transport
the movement of materials against a concentration gradient (low concentration ⇒ high concentration) using energy from ATP
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Describe sodium and potassium channel proteins in membranes
They are in the membranes of neurons that open and close, depending on the voltage across the membrane. They are voltage-gated membranes and are used to transmit nerve impulses
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Where in the nervous system are potassium channels contained?
The axons of neurons that are used during an action potential
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Channel proteins
only allow one type of substance to pass through the membrane (specific)
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Function of potassium channels in axons
Closed when the axon is polarized but open in response axon depolarization> allows K^+ ions to exit by facilitated diffusion (repolarizes axon). Only open for short time before globular sub-unit blocks the pore
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Osmosis
passive movement of water molecules from a region of lower solute concentration to a region of higher solute concentration across a partially permeable membrane
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What is the reason for Osmosis (water moving to regions with higher solute concentration)?
Attractions between solute particles and water molecules
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Osmolarity of a solution
the number of moles of solute particles per unit volume of solution (pure water has 0 osmolarity)
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Hypotonic
Solutions with a relatively higher osmolarity
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Hypertonic
Solutions with a relatively lower osmolarity
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Mass change
[final mass-initial mass/initial mass] x100
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What must be done before a tissue or organ transplant to prevent osmosis causing the tissue's cells to swell or shrink?
Isotonic saline is used in some procedures, Donor organs surrounded by isotonic slush when transported
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What are protein pumps in the membrane used for?
active transport
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Describe how substances are transported via protein pumps (4)
1) Particle enters pump from the side w/ lower concentration 2) Particle binds to a specific site. Other particle types cannot bind 3)ATP energy used to change shape of pump 4) Particle released onto side w/ higher concentration- pump returns to norm
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antiporter
type of transporter protein which allows two different molecules to pass across the cell membrane at the same time. The sodium-potassium pump is a antiporter
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How is the energy required for the sodium-potassium pump obtained?
by converting ATP to ADP and phosphate, so it is a ATPase (Na^+/K^+-ATPase)
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What does one ATP provide the sodium-potassium pump?
enough energy to pump 2 potassium ions in and 3 sodium ions out of the cell
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What are the concentration gradients generated by the sodium-potassium pump needed for?
the transmission of nerve impulses in axons
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ATP
Adenosine triphosphate- high-energy molecule found in every cell
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Endocytosis
The process by which large substances (or bulk amounts of smaller substances) enter the cell without crossing the membrane
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Exocytosis
The process by which large substances (or bulk amounts of small substances) exit the cell without crossing the membrane
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Spontaneous generation
Theory that life could appear in non-living material. Believed until the 19th century. Not currently possible
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What does the universality of the genetic code suggest?
that all life evolved from the same original cells
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Louis Pasteur
his experiment verified the principle that cells can only come from pre-existing cells (spontaneous generation of cells and organisms does not now occur on Earth)
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Symbiosis
two organisms living together
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The endosymbiotic theory
Eukaryotic cells evolved from early prokaryotes that were engulfed by phagocytosis> These stayed undigested as it contributed new functionality to the engulfing cell (photosynthesis) Over generations cell lost independent utility & became organelles
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What characteristics of mitochondria and chloroplasts are explained by the endosymbiotic theory? (4)
.Grow and divide like cells .They have naked loops of DNA, like prokaryotes .Synthesis own proteins w/ 70s ribosomes, like prokaryotes .Both doubled membraned
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How much DNA is stored in a human nucleus?
2 meters of DNA
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What do chromosomes do during mitosis?
condense by supercoiling (via condenstation)
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Sister chromatids
Two parts of the chromosomes (containing an identical DNA molecule)
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Centomere
the point which holds the sister chromatids together
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The phases of Mitosis (4)
Prophase, Metaphase, Anaphase, Telophase
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Cyclins
proteins used to ensure that tasks are performed at the correct time
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Serendipity
making 'happy' and unexpected discoveries by accident (i.e Tim Hunt's discovery of cyclin when studying protein synthesis in sea urchin eggs)
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Describe cyclin function
Binds to cyclin-dependant kinase enzymes- These become actives &attach to phosphate groups to other proteins in cell- This triggers other proteins activity & carry out tasks specific to one of the cell cycle phases
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Oncongenesis
formation of tumors
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Oncogenes
a gene that has the potential to cause cancer. Mutations have to occur in several oncogenes in the same cell for control to be lost
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Primary tumors
some benign (don't grow rapidly or spread) other malignant & spread to other parts of the body (becoming a secondary tumor
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Carcinogenic
cancer-causing
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Metastasis
the spread of cancer from one location (primary tumour) to another, forming a secondary tumour
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Mutagens
chemicals which increase the risk of tumor formation (ionizing radiation)
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Is there a correlation between smoking and cancer?
Yes; strong positive correlation
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