Topic 1: Cell theory Flashcards
(101 cards)
1
Q
What are the 3 parts of cell theory
A
- Living organisms are composed of cells
- Cells are the smallest units of life
- cells only arise from pre-existing cells
2
Q
What are the exceptations to cell theory
A
- Straited muscle cell
- Giant algae
- Aseptate Fungai Hyphae
3
Q
Striated muscle cell
A
- challenges the idea that cells always function as autonomous, independent units.
- fibres are enclosed inside a membrane, but these fibres are much larger than most cells (300mm) and are multi-nucleated
- the nucleus is surrounded by one single continuous membrane.
4
Q
Giant Algae
A
- challenges the idea that larger organisms are always made up of microscopic cells
- can grow up to 100mm in length, yet are unicellular
5
Q
Aseptate Fungai Hyphae
A
- challenges the idea that living structures are composed of discrete cells
- most fungi, hyphae are divided into cells by internal walls called ‘septa’.
however aseptate, do not have septa, therefore, they have long undivided sections of hypha which have a continuous cytoplasm, with no end wall or membrane and contain many nuclei.
6
Q
what are the functions of life
A
- Metabolism
- Response
- Homeostasis
- Growth
- Excretion
- Reproduction
-Nutrition
7
Q
Metabolism
A
The web of all enzyme-catalyzed reactions in a cell or organism
8
Q
response
A
Living things can respond to and interact with their environment
9
Q
Homeostasis
A
The maintenance and regulation of internet cell conditions
10
Q
Growth
A
Living things can grow or change in size/shape
11
Q
Excretion
A
The removal of metabolic waste
12
Q
Reproduction
A
Living things produce offspring either asexcally or sexually
13
Q
Nutrition
A
Feeding by either the synthesis of organic molecules or the absorption of organic matter
14
Q
Paramecium: functions of life
A
Metabolism - reactions in the cytoplasm catalysed by enzymes
Response - Reacts to Stimuli: reveres direction of movement when it touches a solid object
Homeostasis- Keep internal conditions within limits
Growth- Increase in size and dry mass by accumulating organic matter and minerals from its foods
Excretion- Expels waste products of metabolism: CO2 from respiration diffuse out of the cell
Reproduction- reproduces asexually or sexually
Nutrition- Feeds on smaller organism by ingesting and digesting them in vesicles.
15
Q
Chlamydomonas: functions of life
A
Metabolism- Reactions in the cytoplasm catalysed by enzymes
Response- Reacts to stimuli: senses where the brightest light is within its eyespot and swims towards it
Homeostasis- Keeps internal condition within its limits
Growth- Increases in size and dry mass due to photosynthesis and absorption of materials
Excretion- Expels waste products of metabolism: oxygen from photosynthesis diffuses out of the cell
Reproduction: either sexually or asexually
Nutrition- Produces its own food by photosynthesis using a chloroplast that occupies much of the cell
16
Q
Surface Area
A
Affects the rate at which particles can enter and exit the cell
17
Q
Volume
A
Affects the rate at which materials are made or used within the cell
18
Q
How can cells increase their surface area
A
- Changing their shape to be long and thing
- Having folds in the cell membrane
19
Q
Why do cells reproduce
A
- for growth in multicellular organisms
- for reproduction in single cell organisms
- to replace, dead or damaged cells
20
Q
Emergent Properties
A
Are properties of a group that are not possible when any of the individuals elements of a group act alone. Many cells form tissues and organs which become systems to perform an even wider range of functions.
21
Q
Stem Cells
A
Cells with the potential to develop into many different types of specialised cells within the body
22
Q
How are stem cells different from other body cells
A
- Self renewal: can continuous divide
- Potency: are undifferentiated and can differentiate in different ways to produce different cell types.
23
Q
Embryonic Stem Cells
A
cells from the embryo that are undifferentiated can become any type of cell. These are found in the inner cell mass of blastocysts
24
Q
Adult Stem Cells
A
Cells found in certain adult tissues that can become a limited number of types of cells. Adult tissues include the bone marrow or liver
25
Blastocysts
thin- walled hollowed structure in early embryonic development that contains a cluster of cells called the inner cell mass from which the embryo arises.
26
Stargardts Disease
A genetic disease that causes blindness in children,
affects a membrane proteins in the retina causing a photo receptor cells in the retina to become degenerative
27
Parkinson's Disease
A degenerative disorder of the central nervous system caused by the gradual loss of dopamine producing cells in the brain. Typically exhibiting tremors, rigidity, slowness of movement and postural instability. Treated by replacing dead nerve cells with living, dopamine producing cells.
28
Ethical Considerations of Stem Cells
In favour: the health and quality of life of patients suffering from otherwise incurable conditions may be greatly improved.
Against: Stem cell therapies depend on the source of the stem cells. the use of stem cells involve the creation and death of an embryo, to obtain embryonic stem cells.
29
Calculating Magnification
M= I/A, M= magnification, I=size of image, A=actual size of object.
30
Prokaryotic cell structure
unicellular organisms, small (between 1-10 micrometres)
31
Eurkayotic cell structure
Organelle are compartmentalized which allows for different chemical reactions to be separated from other organelles and allows for an increase in efficiency.
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advantages from being compartmentalised
- efficacy of metabolism: enzymes and substrates can become localized and much more concentrated.
-localised conditions: differ pH and other factors can be kept at optimal levels
- toxic/damaging substances: can be isolated
-number or organelles can be changed depending on the cells requirements.
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cytoplasm
internal fluid component of the cell where some chemical reactions may occur.
34
cell wall
found in: plants and prokaryotic cells
- maintains shape and prevents bursting (lysis)
- plant cells- made of cellulose, bacteria- made of peptidoglycan.
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cell membrane
controls the movement of materials in and out of the cell. made up of two layers of phospholipids with embedded proteins.
36
Pili
Hair like extensions that enable adherence to surface or mediate bacterial conjugation. Found in: {prokaryotic cells}
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Flagellum
mainly used for movement, found in Prokaryotes and Eukaryotes
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Nucleoid region
- Found of Prokaryotes.
- Region of the cytoplasm where the DNA is located
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Rough Endoplasmic Reticulum
Found in Eukaryotes, Folds and transports polypeptides into transport vesciles
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Smooth Endoplasmic Reticulum
Found in Eukaryotes. Synthesis and transport of lipids, sex hormones and storing calcuim ions, while transporting RER products to other parts of the cell.
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Golgi Appartus
made of flattened sacs called cisternae. Involved in collecting, packaging and transporting molecules. 'Final Modification and packaging of proteins into secretory vesicles.
42
Lysosome
Contains digestive enzymes for the destruction of unwanted cellular material, Enzymes are primarily used for digestion and removal of excess of worn-out organelles. food particles and engulfed viruses of bacteria
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ribosome
The site of proteins synthesis
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mitochondria
the site of aerobic cellular respiration.
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Permanent large Vacuole
Storage of cell sap, in plant cells
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Vacuole
to store material, like water, salt and proteins
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nucleus
contains DNA which controls cellular functions by coding for proteins. Also responsible for controlling activities, mitosis, replication and chromosomes.
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chloroplast
site of photosynthesis: captures energy from the sun and changes it into food for plants.
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Centrosome
Organelle within cytoplasm that divides and migrates to different poles of the cell during mitosis and is involved in the formation of the mitotic spindle, assembly of microtubules and regulation of cell cycle regression.
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plasmid
Autonomous circular DNA molecules that may be transferred between bacteria
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Binary Fission
Prokaryotes reproduce asexually using the process of binary fission.
1. Chromosome is replicated and each identical copy is moved to either end of the cell
2. the cell elongates. new cell wall forms and plasma membrane pinches in
3. cross walls dorm two separate cells and the two new cells separate.
52
Light microscope vs Electron microscope
Light = focuses visible light through a specimen
electron= uses beams of electrons to form highly magnified images
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plant VS animal cell
1. Cell wall vs no cell wall
2. Chloroplasts present vs No chloroplasts
3. Large central vacuole vs Vacuoles absent or small
4. Store excess glucose as starch vs Stores excess glucose as glycogen
5. No centrioles within the centrosome area vs Has centrioles within the centrosome area
6. Generally have a fixed regular shape vs Generally have an amorphous (flexible) shape
7. Do not have cholesterol in cell membrane vs Have cholesterol in membrane
54
Prokaryotic vs Eukaryotic
1. DNA in a loop form, with no proteins Vs. DNA wrapped around proteins
2. DNA free in the cytoplasm Vs. DNA enclosed within nucleus
3. No membrane-bound organelles Vs. Has membrane-bound organelles
4. 70s ribosomes VS. 80s ribosomes
5. Size less than 10μm Vs. Size more than 10μm
55
Light Microscope Vs Electron Microscope (table)
1. Light rays VS. Electron beams
2. x2000 VS. x500 000
3. Living or dead can be viewed VS. Has to be dead
4. Small & portable VS. Large
5. Easy to use VS. Time consuming to set up
6. Relatively cheap VS. Very expensive
56
Phospholipids
a lipid consisting of a glycerol, bound to two fatty acids and a phosphate group.
Made up of two parts
-1. hydrophilic phosphate head
-2. Hydrophobic fatty acid tail.
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Membrane proteins
integral proteins: Permanently embedded
Peripheral proteins: temporary embedded.
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Different functions of proteins
Junctions: connects cell together
Enzymes: Can act as enzymes
Transport: Responsible for facilitated diffusion and protein pumps
Recognition: for cells to identify each other
,Anchorage: Attachment points for the cytoskeleton
Transduction: receptor for hormones.
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cholesterol
controls membrane fluidity by making the phospholipids pack more tightly and regulates the fluidity and flexibility of the the membrane. The hydroxyl group makes the head polar and hydrophilic, being attracted to the phosphate heads and non-polar hydrophobic tails are attached to the tails of the phospholipids.
60
Fluid Mosiac model
created by Singer and Nicolson in 1972. cell membrane are represented according to a fluid mosaic model.
fluid: the cell membrane is described to be fluid because of its hydrophobic integral components such as lipids and membrane proteins that move laterally or sideways throughout the membrane.
Mosaic: cell membrane is composed of different kinds of macromolecules.
61
danielli and davson model
1935, Davson and danielli suggested a model that proposed the lipid bilayer was covered on both sides by a thin layer of protein.
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Falsification of the Davson and danielli model
electron microscope emerged, noticed inconsistencies:
- not all membrane were symmetrical
- membranes with different functions also have a different composition
- a protein layer is not likely because it is non-polar and doesn't interact well with water
Proof
freeze fracture electron micrographs : fracturing frozen cells allowed the outer phospholipids bilayer to be removed and micrographs showed globular proteins present on the upper surface of the inner phospholipid layer.
protein extraction: proteins extracted were globular and varied in size. parts of there surface were hydrophobic, suggesting they were imbedded within the bilayer and their hydrophobic regions could attract fatty acid tails.
63
Passive VS Active Transport
Passive :
Particles move from areas of higher concentration to areas of lower concentration (along a concentration gradient)
* Hence, passive transport does not require chemical energy as it is driven through by kinetic and natural energy
* There are four major types of passive transport: simple diffusion, facilitated diffusion, filtration and osmosis
Active:
* Particles move from areas of lower concentration to areas of higher concentration (against a concentration gradient)
* Hence, active transport requires energy through ATP and the assistance of a type of protein called a carrier protein
* There are three major types of active transport: rotein pumps, endocytosis, exocytosis
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Simple Diffusion
When molecules move between Phospholipids
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Facilitated Diffusion
When molecules move through proteins that change shape to allow only certain molecules to move through:
- Larger polar molecules, glucose and ions pass through channel proteins spanning the phospholipid bilayer.
- a channel protein forms a small hydrophilic pore through which hydrophilic substances can pass.
- channel proteins are specific for a single type of substances.
66
Osmosis
Type of facilitated diffusion.
the passive movement of water between a semi-permeable membrane. moves through a special protein channel called aquaporins.
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Osmolarity
a measure of solute concentration as defined by the number of osmoles of solute per litre of concentrations.
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Hypotonic
used to describe a solution has a lower concentration of solutes
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Isotonic
when the solutions on either side of the membrane is equal
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Hypertonic
a solution that has a higher concentration of solutes.
71
Sodium Potassium Pump
active transport pump that exchanged sodium ions for potassium ions:
1. 3 Na* ions located inside the cell bind to the carrier protein
2.A phosphate group is removed from ATP and binds to the carrier protein
3. the carrier protein changes shape and transport Na* ions outside of the cell
4. 2 K* located outside of the cell bind to the carrier protein.
5. the phosphate group is released, restoring the protein to its original shape.
6. The 2 K* ions released into the cell
72
Endocytosis
Active Transport
- The taking in of an external substances by an inward pouching of the plasma membrane, forming a vesicle.
73
Pinocytosis
intake of extracelluar fluid (endocytosis)
74
Phagocytosis
Intake of large particles (like Pathogens) (form of Endocytosis)
75
Exocytosis
The release of substances from a cell when a vesicle joins with the cell plasma membrane.
76
Falsification of Spontaneous Generation
Louis Pasteur's experiment disproved that 'living things can arise from non-living things':
1. Boil nutrient broth and place it in two flasks
2. One flasks had access to open air, other did not
3. A sample from each flask was incubated to check for the presence of live bacteria
* Only the one with the open neck grew bacterial cells. This supported Cell Theory #3: Cells only arise from pre-existing cells
77
Endosymbiotic Theory
- suggest that mitochondria and chloroplast were once prokaryotic cells and engulfed by another prokaryotic cell to create eukaryotic cells.
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Process of endosymbiotic theory
1. About 2 billion years ago, a host cell engulfed a prokaryotic cell (bacteria) capable of photosynthesis or cell respiration
2. The bacterial cell and prokaryote formed a symbiotic relationship
3. Over time, that bacteria cell underwent changes to eventually become a mitochondria
4. The same could be said for photosynthetic bacteria and chloroplasts
79
Evidence of Endosymbiotic Theory
1. They are about the same size as prokaryotes
2. Divide by binary fission, like prokaryotes
3. Have their own DNA in a circular loop, like prokaryotes
4. Have 70s ribosomes, like prokaryotes
5. Have a double membrane (from when they were engulfed)
6. Genes in the DNA of mitochondria and chloroplasts are more similar to prokaryotes than the cell in which they are found
80
Mitosis purpose
o Growth: Multicellular organisms increase their size by increasing their number of cells through mitosis
o Asexual Reproduction: Certain eukaryotic organisms may reproduce asexually by mitosis
o Tissue Repair: Damaged tissue can recover by replacing dead or damaged cells
o Embryonic development: A fertilized egg (zygote) will undergo mitosis and differentiation in order to become an embryo
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Interphase
consists of the cell parts f=of the cell cycle that don;t invlove cell division
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G1 phase
increase in cytoplasm volume, organelle production and protein synthesis (normal growth)
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S phase
DNA Replication
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G2 phase
increase in cytoplasm volume, double the amount or organelle and protein synthesis (prepare for cell division)
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G0 phase
Resting phase where the cell leaves the cell cycle and has stopped dividing. Cell carries out all normal functions without the need of dividing.
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Prophase
* DNA Supercoil: chromatin condenses and becomes sister chromatids, which are visible under the light microscope
* Nuclear membrane is broken down and disappeared
* Centrosomes move to the opposite poles of the cell
Spindle fibres: begin to form
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Metaphase
Chromatids line up in the equator
spindle fibres attach to the centromere of sister chromatids
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Anaphase
-contraction of the spindle fibres cause the separation of the sister chromatids
-chromatids are now considered chromosomes
-chromosomes move to opposite poles of the cell.
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Telophase
- Chromosomes uncoil to become chromatin
- Spindle fibres break down
- New nuclear membrane reforms at opposite poles.
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Cytokinesis
The splitting of the cell immediately following mitosis
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Cytokinesis in animal cells
* A cleavage furrow forms around the middle
* The ring contracts pinching the cell in two
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Cytokinesis in plant cells
* A cell plate forms in the middle
* The cell plate grows until the two cells separate
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Cyclins
* Cyclins are proteins that control the progression of cells through the cell cycle
* Cells cannot progress to the next stage of the cell cycle unless the specific cyclin reaches it threshold
* The cyclins bind to receptors and this complex must be present for the next part of the cell cycle to being
* This serves as a checkpoint, preventing cells from moving too quickly or from progressing at all
* Nerve cells (like others) lack the necessary cyclins, as they can’t reproduce
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Cancer
the disease that results when the primary tumor spreads to other parts of the body
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Metastasis
The spreading of cancerous cells through the body via the blood or other mechanisms
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Oncogenes
Genes that have to turn 'on' to start division and a turn 'off' when cell division is complete
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carinogens
agents that can cause cancer, such as viruses, X-ray, UV radiation
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Mutagens
Agents that can cause mutations in one's DNA which can lead to cancer.
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Primary Tumour
A mass of cells that are dividing at abnormally fast rates for no apartment reason
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When do primary tumours form
o Carcinogens or genetic mutations cause a change to the oncogene of a cell
o The malfunctioning oncogene causes the cell to continuously replicate
o The mass of defective cells forms a primary tumor
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Secondary tumours
the tumour that forms in other parts of the body after metastasis of the primary tumour
