Topic 1 Flashcards
1
Q
Difussion
A
- the spreading out of particles in liquids and gases
- occurs because particles are in random motion
- more particles move from an area of higher concentration to an area of loewr cocnentration
- therefore, movement down the concentration gradient
- passive process (energy not consumed)
2
Q
Active transport
A
- moving against the concentration gradient (ie. moving from an area of low concentration to an area of high concentration)
- energy (ATP) and pump proteins are required
3
Q
Electron microscopes
A
- much higher resolution than light microscopes
- reveal the ultrastructure of cells
- needed to see viruses with diameter of 0.1 micrometres
4
Q
Hypotonic
A
- has a lower osmolarity
- water moves by omosis out of the hypotonic solution
5
Q
List 4 methods by which particles can move across membranes
A
simple diffusion, facilitated diffusion, osmosis, active transport
6
Q
Mitosis
A
- the division of the nucleus into two genetically identical daughter nuclei
7
Q
Isotonic
A
- has the same osmolarity
- therefore, water does not move by osmosis
8
Q
Define mutagen
A
agents that cause gene mutations
9
Q
Recognition features and function of chloroplast
A
- surrounded by double membrane
- variable in shape, but usually spherical or ovoid
- contains sacs of thylakoids, which are flattened sacs of membrane
- produces glucose/other organic compounds by photosynthesis
- starch grains may be present inside the chloroplasts if they have been photosynthesizing rapidly
10
Q
Prophase
A
- the chromosomes become shorter and fatter by coiling
- to become short enough, they have to coil repeatedly (supercoiling)
- the nucleolus breaks down
- microtubules grow from structures called microtubule organizing centres (MTOC) to form a spindle-shaped array that links the poles of the cell
- at the end of this phase, the nuclear membrane breaks down
11
Q
What is the role of cholesterol in membranes?
A
- disrupts the regular packing of the hydrocarbon tails of phospholipids, so prevents them from crystallizing and behaving as a solid
- however, it also restricts molecular motion and therefore the fluidity of the memrane
- it also reduces the permeability to hydrophilic particles such as sodium ions and hydrogen ions
- due to its shape, cholesterol can help membranes to curve into a concave shape, which helps in the formation of vesicles during endocytosis
12
Q
Osmosis
A
- water is able to move in and out of most cells freely
- the net movement of water molecules is called osmosis
- osmosis is caused by differences in the concentrations of substances dissolved in water
- water moves from areas of low solute concentration to areas of high solute concentration
- passive process
13
Q
Differentiate between a benign tumour and a malignant tumour
A
- benign tumours are ones in which the cells adhere to each other and do not invade nearby tissues or move to other parts of the body; they are unlikley to cause much harm
- malignant tumours can become detached and move elsewhere in the body and develop into secondary tumours; they are likely to be life-threatening
14
Q
Explain the development of primary and secondary tumours with reference to: mutagens, oncogenes, and metastasis
A
- mutagens cause gene mutations in oncogenes
- mutation in oncogenes results in uncontrolled cell division
- uncontrolled cell division forms a tumour
- tumour cell divides repeatedly to form a primary tumour
- metastasis is the movement of cells from a primary tumour to set up secondary tumours in other parts of the body
15
Q
Evaluate the hypothesis that smoking causes cancer.
A
- there is a positive correlation between smoking cigarettes and death by cancer
- the more cigarettes smoked per day, the higher the death rate due to cancer
- the result of the survey shows increases in death rate due to cancers of the mouth, lungs, larynx, pharynx; since these are the body parts that come into contact with the smoke from the cigaratte, this supports the hypothesis that smoking causes cancer
- however, there is also an increase in death rate due to cancers of the esophagus, stomach, kidney, bladder, pancreas and cervix
- correlation does not equal causation; just because there is a found correlation between smoking and cancer does not mean that one causes the other
- however, it has been found that several substances in cigarette smoke are carcinogens, making it likely that smoking causes cancer
16
Q
What are three components of animal cell membranes?
A
phospholipids, proteins, cholesterol
17
Q
Why do phospholipids form bilayers in water?
A
- phospholipids form bilayers in water due to the amphipathic properties of phospholipid molecules
- phosphate group is hydrophilic
- hydrocarbon tails are hydrophobic
- when mixed with water, the phosphate heads are attacted to the water by the hydrocarbon tails are attracted to each other
- thus, the phospholipids form double layers called phospholipid bilayers
18
Q
Define metastasis
A
- movement of cells from a primary tumour to set up secondary tumours in other parts of the body
19
Q
What common features do cells share?
A
- every living cell is surrounded by a membrane, which separates the cell contents from everything else outside
- cells contain genetic material which stores all of the instructions needed for the cell’s activities
- many of these activities are chemical reactions, catalysed by enzymes produced inside the cell
- cells have their own energy release system that powers all of the cell’s activities
20
Q
What is the purpose/function of sodium-potassium pumps and potassium channels?
A
- The axons of nerve cells transmit electrical impulses by translocating ions to create a voltage difference across the membrane
- At rest, the sodium-potassium pump expels sodium ions from the nerve cell, while potassium ions are accumulated within
- When the neuron fires, these ions swap locations via facilitated diffusion via sodium and potassium channels
21
Q
Telophase
A
- chromatids have reached poles and are now called chromosomes
- at each pole, the chromosomes are pulled into a tight group near the MTOC and a nuclear membrane reforms around them
- the chromosomes uncoil and a nucleolus is formed
- by this stage, the cell is usually already dividing and the two daughter cells enter interphase again
22
Q
Recognition features and function of free ribosomes
A
- appear as dark granules in the cytoplasm and are not surrounded by a membrane
- have the same size as ribosomes attached to the rER (80S)
- synthesize protein, releasing it to work in the cytoplasm, as enzymes or in other ways
- constructed in a region of the nucleus called the nucleolus
23
Q
What are the two main types of endocytosis?
A
Phagocytosis – The process by which solid substances are ingested (usually to be transported to the lysosome)
Pinocytosis – The process by which liquids / dissolved substances are ingested (allows faster entry than via protein channels)
24
Q
Define oncogenes
A
- genes that can become cancer-causing after mutating
- normal cell oncogenes control cell cycle and cell division
25
Q
What were the problems with the Davson-Danielli model?
A
- Freeze-etched electron micrographs
- rapid freezing of cells and then fracturing them
- fracture occurs along lines of weakness, including the centre of membranes
- globular structures scattered through free-etched images of the centre of membranes were interpreted as transmembrane proteins - Structure of membrane proteins
- proteins extracted from membranes were found to be varied in size and globular in shape (unlike the type of structural proteiin that would form continuous layers) - Fluorescent antibody tagging
- red/green fluorescent markers were attached to antibodies that bind to membrane proteins
- memrane proteins of some cells were tagged with red markers and others with green markers
- the cells were fused together and within 40 minutes, the red/green were mixed together showing that membrane proteins are free to move within the membrane rather than being fixed in a peripheral layer
26
Q
Endocytosis
A
- a process by which large substances (or bulk amounts of smaller substances) enter the cell without crossing the membrane
- results in the formation of a vesicle containing the materials that were outside of the cell
- this process is also used by some types of white blood cells in order to ingulf pathogens and kill them
- it is possible because of the fluidity of membranes
27
Q
Hypertonic
A
- has a higher osmolarity
- water moves by osmosis to the hypertonic solution
28
Q
Cytokinesis
A
- refers to the process of cell division
- occurs after mitosis
- different in plant and animal cells
29
Q
How do prokaryotes divide?
A
- binary fission
- used for asexual reproduction
- circular chromosome is replicated and the two copies of the chromosome move to opposite ends of the cell
- division of the cytoplasm
- each of the daughter cells contains one copy of the chromosome so they are genetically identical
30
Q
Explain algae as an atypical example of a cell which questions the cell theory
A
- algae are organisms that feed themselves by photosynthesis and store their genes inside nuclei
- many algae consist of one microscopic cell
- giant algae can grow to a length as much as 100mm despite only having one nucleus
31
Q
Simple difussion
A
- movement of particles across the membrane, down the concentration gradient
- involves particles passing between phospholipids in the membrane
- can only occur if the phospholipid bilayer is permeable to the particles
- non-polar particles (ie. oxygen) can diffuse into the cell esaily/passively if there is a higher concentration outside the cell than inside it
32
Q
Metaphase
A
- microtubules continue to grow and attach to the centromeres on each chromosome
- the two attachment points on opposite sides of each centromere allow the chromatids of a chromosome to attach to microtubules from different poles
- the microtubules are all put under tension to test whether the attachment is correct
- this happens by shortening of the microtubules at the centromere
- if attachment is correct, the chromosomes remain on the equator of the cell
33
Q
Explain how sodium-potassium pumps work
A
- sodium-potassium pump is an integral protein that exchanges 3 sodium ions (moves out of cell) with two potassium ions (moves into cell) against the concentration gradient
- thus, the process of ion exchange is active transport and requires energy
- the following occurs:
1. Three sodium ions bind to intracellular sites on the sodium-potassium pump
2 .A phosphate group is transferred to the pump via the hydrolysis of ATP
3. The pump undergoes a conformational change, translocating sodium across the membrane
4. The conformational change exposes two potassium binding sites on the extracellular surface of the pump
5. The phosphate group is released which causes the pump to return to its original conformation
6. This translocates the potassium across the membrane, completing the ion exchange
34
Q
Stem cell
A
- can divide again and again to produce copious quantities of new cells; good for the growth of tissues or the replacement of cells that have been lost/damaged
- not fully differentiated; can differentiate in different ways to produce different cell types
- essential in embryonic development for the above reasons
35
Q
Cytokinesis in animal cells
A
- plasma membrane is pulled inwards around the equator of the cell to form a cleavage furrow
- this is accomplished using a ring of contractile proteins, actin and myosin
- when the cleavage furrow reaches the centre, the cell is pinched apart into two daughter cells
36
Q
Cell differentiation
A
- specialized tissues can develop by cell differentiation in multicellular organisms
- different cells perform different functions
- often a group of cells specialize in the same way to perform the same function (tissue)
- the development of cells in different ways to carry out specific functions is called differentiation
- involves the expression of some genes and not others in a cell’s genome (cells have all genes needed to specialize in every possible way but only expresses certain ones)
- stem cells turn into specialised cells by signal cues
37
Q
Limitations on cell size
A
- surface area to volume ratio is important in the limitation of cell size
- large numbers of chemical reactions take place in the cytoplasm of the cells (metabolism)
- the rate of the reactions (metabolic rate) is proportional to the volume of the cell
- substances used for the reactions must be absorbed by the cell and the waste products must be removed; the rate at which substances cross this membrane depends on its surface area
- surface area:volume ratio is also important for heat production and loss
38
Q
Outline the seven functions of life
A
- Nutrition: obtaining food, to provide energy and the materials needed for growth
- Metabolism: chemical reactions inside the cell, including cell respiration to release energy
- Growth: an irreversible increase in size
- Response: the ability to react to changes in the environment
- Excretion: getting rid of the waste products of metabolism
- Homeostasis: keeping conditions inside the organism within tolerable limits
- Reproduction: producing offspring either sexually or asexually
Note: Unicellular organisms must carry out all functions of life in the one cell
39
Q
Outline the three sources of stem cells and the ethics of using them
A
- embryos –> embryonic stem cells
- almost unlimited growth potential/can differentiate into any type of cell
- less chance of genetic damage due to accumulation of mutations than with adult stem cells
- more risk of becoming tumour cells than with adult stem cells
- likely to be genetically different from an adult patient receiving the tissue
- ethical controversy because removal of cells from the embyro is likely to kill it - umbilical cord –> cord blood stem cells
- easily obtained/stored
- fully compatible with the adult individual that it comes from; no rejection issues
- limited capacity to differentiate into different cell types (naturally develops into blood cells)
- limited quantities of stem cells from one baby’s cord
- ethical because umbilical cord is discarded whether or not stem cells are taken from it. - bone marrow –> adult stem cells
- difficult to obtain; very few and buried deep in tissues
- limited capacity to differentiate/less growth potential than embryonic stem cells
- less chance of malignant tumours developing
- fully compatible with the individual it comes from; no rejection issues
- ethical because removal of stem cells does not kill the adult it comes from
