Unit 1: Cell Biology Flashcards
1
Q
When did multicellular life first appear?
A
550 million years ago
2
Q
How did multicellular life evolve?
Multicellular life evolution
give steps
A
- Unicellular cells worked together
- As organisms increased in cell number + size, distance between cells and environment increased as well, so they couldn’t rely on direct exchanges of materials with the environment and they couldn’t get rid of waste at an adequate speed
- started evolving to cell differentiation, making specialized cells which were grouped together, making tissue
3
Q
What did the first multicellular organism evolve from?
A
Unicellular cells
4
Q
What is a cell?
A
The smallest unit that can perform the functions of life
5
Q
Who was Robert Hooke?
A
Robert Hooke was the man to coin the term ‘cell’ in 1600s after seeing plant cells in cork tissue under a microscope. He called it a cell because he was reminded of the cells monks used for meditation.
6
Q
Where did the term ‘cell’ come from?
A
Robert Hooke used word ‘cell’ in 1600s after seeing plant cells in cork tissue under a microscope because he was reminded of cells monks used for meditation
7
Q
How did Cell Theory come about?
A
- Robert Hooke used word ‘cell’ in 1600s after seeing plant cells in cork tissue under a microscope because he was reminded of cells monks used for meditation
- no clear rules were later there for cells vs non-cells so we needed to define cells
- in 1838 cell theory came about based on work by Theodor Schwann, Matthias Schleiden, and Rudolph Virchow
8
Q
Which 3 scientists produced work to form the cell theory?
A
Theodor Schwann, Matthias Schleiden, and Rudolph Virchow
9
Q
What year did cell theory come about?
A
1838
10
Q
Why was there a need for cell theory?
A
There were no clear rule for cells vs non-cells so we needed to define cells
11
Q
What are the rules of cell theory?
A
- all living organisms are composed of cells
- cells are the smallest unit of life
- cells come from pre-existing cells (omni cellulae e cellula)
12
Q
What three cells are exceptions to cell theory and why?
A
- The striated muscle cells: multiple nuclei/are multinucleated, and each cell is 30 mm long. typical cell has one nucleus and is smaller
- Acetabularia: from 0.5 to 10 cm long, longer than typical cell
- Aseptate fungal hyphae: many nuclei, no septa, and shared cytoplasm. essentially combined cells
13
Q
What are striated muscle cells and why are they atypical?
Unit 1 Knowledge
A
Striated muscle tissues are made of sarcomeres which show a striped/striated pattern under the microscope. The striated cells have multiple nuclei/are multinucleated. Each muscle fibre cell is also 30 mm long, which is larger than the typical cell.
14
Q
What are Acetabularia and why are they atypical?
A
Acetabularia is a giant single-celled green algae, from 0.5 to 10 cm. It has 3 parts: rhizoid (root-like), stalk, and a top umbrella that might fuse into a cap
15
Q
What are Aceptate Fungal Hyphae and why are they atypical?
A
Aseptate fungal hyphae are hyphae (long threads) with many nuclei, no septa (dividing cell walls), and share a cytoplasm. Cells are all basically combined here
16
Q
What is a μm
A
Micrometer
17
Q
Convert 1 μm to nm
A
1 μm = 1000 nm
18
Q
Convert 1 mm to μm
A
1 mm = 1000 μm
19
Q
Draw the size of drawing, magnification, actual size pyramid
A
https://file.notion.so/f/f/e52fcf8a-d6ea-4a2d-a3c3-d8bce0c54560/644e46ca-d3b2-48d8-981f-99deec143e4b/Untitled.png?id=63dc7163-9d86-4ea3-a284-be2a3b3aaee6&table=block&spaceId=e52fcf8a-d6ea-4a2d-a3c3-d8bce0c54560&expirationTimestamp=1713398400000&signature=jsbDaZnFO-TSV4Hra5QYK6JoeswcfOyyu2Sxl-fVy_0&downloadName=Untitled.png
20
Q
What are the functions of life?
A
Metabolism, response, homeostasis, growth, reproduction, excretion, nutrition
MR H GREN
21
Q
Define metabolism as a function of life
A
Metabolism is life-supporting chemical reactions that take place in cells
22
Q
Define response as a function of life
A
Response to stimulus is a reaction to changes in the external environment
23
Q
Define homeostasis as a function of life
A
Homeostasis is the maintenance of an internal environment
24
Q
Define growth as a function of life
A
Growth is an increase in shape/size over an organisms lifespan
25
Define reproduction as a function of life
Reproduction is the production of offspring either sexually or asexually
26
Why is a virus non-living?
Virus' can not reproduce or metabolize
27
Define excretion as a function of life
Excretion is the removal of waste products
28
Define nutrition as a function of life
Nutrition is the intake of nutrients
29
What is a paramecium?
| Definition, size, environment, eating habits, structure
Definition: Genus of unicellular protozoa
Size: Less than 0.25 mm in length
Environment: Widespread in aquatic environments, particularly stagnant ponds
Eating Habits: heterotrophs, feeding on food particles
Structure: Have cilia to move. Cilia are hair-like things that cover the entire cell and beat rhythmically to move the cell in a certain direction.
30
How does paramecium showcase the functions of life?
Metabolism: catalyzed by enzymes and occur in cytoplasm.
Response: beating cilia helps to propel paramecium towards desired environments. The wave action of the cilia moves the paramecium in response to changes in the environment.
Homeostasis: osmoregulation. The contractile vacuole fill up with water and expel through the plasma membrane to manage the water content.
Growth: After consuming and assimilating biomass from food, it get’s larger until it divides
Reproduction: sexual + asexual (more common). Binary fission when too big. The nucleus can divide to support mitosis, so reproduction is often asexual.
Excretion: digested nutrients go to the cytoplasm and the vacuole is shrinked. Vacuole goes to the anal pore, and ruptures, expelling the waste outside of the cell. The entry and exit of substances is thus controlled by the plasma membrane.
Nutrition: engulfs food through endocytosis. soluble products are absorbed into the cytoplasm. Eats microorganisms.
31
What is a chlamydomonas
| Definition, size, environment, eating habits, structure
Definition: Genus of unicellular green algae (chlorophyta)
Size: 10-30 micrometers in diameter
Environment: In soil, water, oceans, and snow on mountain tops
Eating habits: Autotrophs
Structure: Cell wall, chloroplast, 'eye' that detects light, 2 flagella which are like whips which it uses to swim
32
How do chlamydomonas showcase the 7 functions of life?
Metabolism: catalyzed by enzymes and occur in cytoplasm.
Growth: increases through production of organic molecules during photosynthesis + mineral absorption. Increase until they divide.
Response: Wave action of the cilia moves the algae in response to changes in the environment. It also uses eye spot to sense light changes and moves to brighter areas.
Homeostasis: osmoregulation. The contractile vacuole fill up with water and expel through the plasma membrane to manage the water content.
Nutrition: Photosynthesis happens in the chloroplasts to provide nutrition
Reproduction: sexual or asexual when it’s big enough, through mitosis.
Excretion: The plasma membrane controls the entry and exit of substances, including the diffusion out of waste oxygen.
33
Why is the surface area to volume ratio important?
- Cell growth is limited by their surface area: volume ratio
- volume grows more than SA in a cell when a cell grows
- if difference is too big, not enough molecules can come in, and not enough waste + heat can get out
- larger SA:Volume ratio means more efficiency
- Diffusion pathways are shorter
- concentration gradients are easier to generate
34
Why does the brain have folds?
folds in brain increase surface area and let more tissue fit in a smaller place. Folding helps fit the growing cortex (cortex is associated with intelligence), and lets nerve signals travel a significantly smaller distance
35
What is Lissencephaly?
Lissencephaly is where cortex doesn’t fold right and so children don’t develop much after 3-5 months, and most die by age 10
36
Why does the small intestine have folds?
| Add: What they're called
- small intestine has folds that increase SA coming in contact with food. These folds are called villi.
- Nutrients are absorbed in the body by villi
- cells making up villi have microvilli, increasing SA even more
37
What is Celiac disease?
Celiac disease is where the immune system destroys the villi as a response to gluten in the diet, and the person can suffer from malnutrition as a byproduct
38
How did multicellular organisms evolve?
1. grew since they were no longer limited
2. specialized through differentiation
3. Started showing emergent properties
39
What is differentiation?
process where cells develop to have more distinct structure + function
40
What are emergent properties?
The interaction between different parts allows the organism to do more than the sum of the cells. the whole is greater than the sum of its parts.
41
How does differentiation happen?
- genome is the complete set of genes, chromosomes, or genetic material present
- cellular differentiation is the process of an unspecialized stem cell changing to carry out a specific function in the body differentiation occurs due to expression of different genes
- emergent properties tell us that the whole is more than the sum of its parts
- human genome has around 21,000 genes. all are present in each cell, but not all are active in each cell type.. we have 220 distinct highly specialised cell types. all these specialised cells and the organs constructed from them have developed as a result of differentiation.
- at early stage of fertilized egg, some cells divide and develop differently. Until this stage, the cells in an embryo are pluripotent embryonic stem cells that can divide into any type of body cell.
- once a cell differentiates, there’s no reversing it naturally
- all diploid cells of an organism share an identical genome. each cell has all the genetic instructions, but not all genes are expressed in all cells. In totipotent embryonic stem cells, the entire genome is active. Newly formed cells get signals which deactivate genes. The fewer active genes, the more specialised.
42
What are stem cells?
Unspecialized cells that differentiate along different pathways. They retain the capacity to divide indefinitely and differentiate into specialized cell types, if provided with the right stimulus.
43
What are the types of stem cells and what can they do?
- Totipotent stem cells can differentiate into any type of cell and can give rise to a complete organism
- pluripotent stem cells can differentiate into all body cells but can’t give rise to a whole organism
- Multipotent stem cells can differentiate into a few closely related types of body cell
- Unipotent stem cells can differentiate into their associated cell type
44
What is stargardt's disease?
| Definition, frequency, appearance time, cause, effect
* Stargardt’s disease is of the eye. It’s inherited from juvenile macular degeneration which affects only a small part of the retina and causes progressive loss of central vision
* affects 1 in 80,000 ~ 100,000
* appears in late childhood to early adulthood
* caused by passed down recessive genetic mutation in gene ABCA4 which causes a transport protein on photoreceptor cells to malfunction, causing the cells to malfunction and then degenerate
* production of a dysfunctional protein that cannot perform energy transport.causes progressive and eventually total loss of central vision.
45
How can stem cells be used to treat Stargardt's disease?
Patients get retinal cells from human embryonic stem cells, which are injected in the retina. They become functional. Central vision improves as a result of more functional retinal cells. This treatment is still in at the stage of limited clinical trials but will likely be used in the future.
46
What is leukemia?
| Definition, effects
- Leukemia is a cancer of blood or bone marrow which results in abnormally high levels of poor-functioning white blood cells
- patients have higher risk of developing infection, anemia, and bleeding
47
How can stem cells be used to treat leukemia?
| Include risks/benefits
- one of the first conditions to be treated with stem cells
- treated by harvesting hematopoietic stem cells (HSCs) which are multipotent stem cells that can be taken from bone marrow, peripheral blood or umbilical cord blood
- patient later goes through chemotherapy and radiotherapy to destroy the diseased white blood cells
- then HSCs are implanted back into the bone marrow where they form healthy white blood cells
- use of own HSCs means far less risk of immune rejection than with traditional bone marrow transplant
48
Why is harvesting stem cells from embryos controversial?
- arguments for:
- cells can be used in cell therapy
- transplants can easily be attained without any harm
- the embryo is unlikely to feel pain as cells are harvested at an early stage
- look at diagram
- stem cells can be made without need for fertilisation and destruction of ‘natural’ human embryos
- arguments against:
- involves creation and destruction of human embryos
- embryonic stem cells are capable of continued division and might develop into cancerous cells and cause tumors
- excess embryos are killed
- alternative technology might do this
- religion and god
- potential for cloning
49
What are the main differences between eukaryotic and prokaryotic cells?
Size: Eukaryotic are between 10 and 100 micrometers in diameter, prokaryotic are between 0.1 to 0.5
Compartmentalization: Eukaryotes have complex memberane-bound organelles (compartmentalization) and prokaryotes don't
50
What did Carl Woese do and what allowed him to?
Light microscope was invented in early nineteenth century and made study of tissues and cell structure possible. Detailed structure was unraveled once the electron microscope was invented in the early 1930s. Originally cells were categorized as prokaryotes and eukaryotes. Carl Woese classified them into 3 groups: bacteria (prokaryotic), eukaryota, and archae (prokaryotic)
51
What are the three life gruops?
bacteria (prokaryotes), eukaryota, and archae (prokaryotic)
52
What are prokaryotes and their structure?
Definition: Earliest cell type from 3.5 billion years ago. Have bacteria + archae.
Cellular structure:
- cell wall encloses cell, protects it, helps maintain shape, and prevents cell from bursting in hypotonic media
- cytoplasm - fills cell and is site of all metabolic reaction
- pili (sing. pilus) - protein filaments on cell wall that help in adhesion and transferring DNA between 2 cells
- flagella (sing. flagellum) - longer than pili, and responsible for ability to move through their whip-like movements
- 70S ribosomes are the sites of protein synthesis
- Nucleoid region includes naked DNA (DNA without proteins known as histones) and controls the cell activities and reproduction
- plasmids are small circles of DNA which carry few genes that often give antibiotic resistance and are used in making genetically modified bacteria
- Ribosomes in prokaryotic cells (70S) are smaller than eukaryotic cells (80S). 70S and 80S refer to the RNA subunits sedimentation rate.
53
Draw a diagram of a prokaryotic cell
https://file.notion.so/f/f/e52fcf8a-d6ea-4a2d-a3c3-d8bce0c54560/2c734f30-ee64-4be4-a9f8-b33915e6ccde/Untitled.png?id=97034f9f-10b5-4930-a98d-9e5eff3211c7&table=block&spaceId=e52fcf8a-d6ea-4a2d-a3c3-d8bce0c54560&expirationTimestamp=1713398400000&signature=8YA5nmDX7yKB4mYLlwkM3fI1QgSME7AgspzsPmG3A-8&downloadName=Untitled.png
54
Define and outline binary fission
Definition: Method of semi-conservative reproduction for prokaryotic cells.
Process:
- chromosome is replicated semi-conservatively, starting at the point of origin
- starting with the point of origin, 2 copies of DNA move to opposite sides of the cell
- cell elongates
- plasma membrane grows inward and pinches off, forming 2 separate genetically identical cells
55
What is a eukaryotic cell?
- complex cell
- genetic material is isolated from the cytoplasm by being held in a membrane-bound nucleus
- represent the Eukaryota domain and include Protocista, Fungi, Plantae, and Animalia
56
How do eukaryotes benefit from compartmentalization?
| define it too
Definition: formation of compartments in the cell by membrane-bound organelles. All Eukaryotes have it
Advantages:
* more efficient metabolism since enzymes and substrates are enclosed and more concentrated within organelles
* internal conditions like pH can be differentiated to have different enzymes have their optimal conditions
* toxic or damaging substances can be better isolated
* can flexibly change positions and numbers of organelles in the cell
57
Draw an animal cell
https://file.notion.so/f/f/e52fcf8a-d6ea-4a2d-a3c3-d8bce0c54560/0c768d65-0784-4a84-967e-aab2a5f9154e/Untitled.png?id=aa66fbc4-0d6d-4d24-8852-01da6feaa201&table=block&spaceId=e52fcf8a-d6ea-4a2d-a3c3-d8bce0c54560&expirationTimestamp=1713398400000&signature=WQmxO8s2B8C5rF_hVViSaDTX7cx6IvSFBgsVqUKFlgk&downloadName=Untitled.png
58
Draw a plant cell
https://file.notion.so/f/f/e52fcf8a-d6ea-4a2d-a3c3-d8bce0c54560/1fb97123-9a98-4b91-912d-0e1096088f21/Untitled.png?id=0a1f3b00-c85e-4ac4-b68b-e820a60fd995&table=block&spaceId=e52fcf8a-d6ea-4a2d-a3c3-d8bce0c54560&expirationTimestamp=1713398400000&signature=bN-q5GfK8tZa8CWo3Ev2zGOfj9898EOrYnA3hLW7rD4&downloadName=Untitled.png
59
Outline the structure of a eukaryotic cell
| Organelles + Their functions
Plasma membrane - controls exports and imports. protective barrier around the cell. semi-permeable. made of phospholipid bilayer, proteins, carbohydrates.
Cytoplasm - fills cell and holds organelles. contains enzymes which catalyse various reactions like glycolysis that occur within the cytoplasm. Transport in cytoplasm can take place through cyclosis.
Mitochondria - site of cellular respiration where ATP (Adenosine triphosphate) is generated. Powerhouse of the cell
80S ribosomes - sites of protein synthesis. free ribosomes produce proteins used within the cell. bound ribosomes line the outer membrane of the rough ER.
Nucleus - controls all the activities as well as reproduction in unicellular organisms. contains genetic information that controls all cell activities. this information is stored on chromosomes.
Nuclear membrane - porous double membrane which separates the nucleus from the cytoplasm
Nucleolus - dense body in the centre of the nucleus involved in production of ribosomes
DNA/chromatin/chromosome - genetic material that contains instructions for what proteins to make
Smooth endoplasmic reticulum - produces and stores lipids, including steroids. Transports materials.
Rough endoplasmic reticulum- Tubes and canals with ribosomes attached. transports protein produced by ribosomes on its surface to the Golgi apparatus. these proteins are usually used outside the cell.
Golgi apparatus - Stacks of membranes. Receives proteins from the endoplasmic reticulum. Modifies, sorts, and repackages them into vesicles for delivery throughout the cell via golgi vesicles. The vesicles can also perform exocytosis
Vesicle - small sac which transports and releases substances made by the cell by fusing together with the cell membrane
Lysosomes(not in plant cells) - contain hydrolytic enzymes and are important to destructing microbes engulfed by white blood cells, as well as the destruction of old cellular organelles
Centrioles(not in plant cells) - important in nuclear division by helping establish microtubules
Vacuoles - membrane-bound organelles that store nutrients and wastes. help cell’s osmotic balance and storage of substances. can also have hydrolytic substances similar to lysosomes. In plant cells, there’s a central vacuole which stores water for the cell.
Cell walls(not in animal cells) - protect cell, maintaining shape and preventing it from bursting in hypotonic media. rigid frame aroun the cell membrane which provides strength, protection, and support.
Chloroplast (not in animal cells) - double-membrane-bound organelles containing pigments (mainly chlorophyll) and are responsible for photosynthesis.
60
Draw an exocrine gland cell
https://file.notion.so/f/f/e52fcf8a-d6ea-4a2d-a3c3-d8bce0c54560/a821c7b0-8cf1-433e-b45e-87aa0ca2f596/Untitled.png?id=394ece59-adfc-4c54-9c1c-2d555fa91129&table=block&spaceId=e52fcf8a-d6ea-4a2d-a3c3-d8bce0c54560&expirationTimestamp=1713398400000&signature=W_jaLYwSjNVAi19j4bB-UW3YlUL4bJfGiPWUIr0zQ-w&downloadName=Untitled.png
61
What is an exocrine gland cell?
Location: Pancreas
Function: Secretes enzyme into a duct. The ones in the pancreas secrete digestive enzymes via the pancreatic duct into the small intestine where they aid digestion of food. Exocrine cells have well-developed networks of rough ER for protein synthesis, and the golgi apparatus that makes vesicles with these. vesicles merge with plasma membrane to release content into small intestine
62
Draw a palisade mesophyll cell
https://file.notion.so/f/f/e52fcf8a-d6ea-4a2d-a3c3-d8bce0c54560/ed62acd9-288b-484a-a085-27bac01e2613/Untitled.png?id=e4297b90-6dc0-40c2-9c25-6b87c3386752&table=block&spaceId=e52fcf8a-d6ea-4a2d-a3c3-d8bce0c54560&expirationTimestamp=1713398400000&signature=a4dd2eETS6XZoGk61mEg3auhX9wEfU3C65VSxcGuSuU&downloadName=Untitled.png
63
What is a palisade mesophyll cell?
- site of photosynthesis as there’s lots of chloroplasts
- contains greatest number of chloroplasts per cell in plants
- positioned right under upper epidermis, meaning it’s exposed to the highest amount of light
- main function is to photosynthesis
64
Outline the characteristics of a membrane
- think of a membrane as big soap bubbles
- membranes are fluid, flexible, and dynamic
- are fluid due to phospholipids that have the ability to move in the same plane. this lets the cell perform things like endocytosis and exocytosis without the membrane breaking.
- fluidity is closely controlled to make sure it doesn’t solidify or become too fluid
- cholesterol helps maintain flexibility
- membrane maintains internal environment from the outside
- any changes in membrane structure affects exchange of substances, or homeostasis
65
What does the fluid mosaic model showcase?
| Who came up with it, and what is it
Proposed by Singer and Nicolson in 1972. Shows a biological membrane consisting of phospholipid bilayers with proteins embedded in the bilayer, so the membrane looks like a mosaic.
66
Define a triglyceride
Type of lipid made of one glycerol and three fatty acid molecules
67
Whats the difference between a phospholipid and a triglyceride?
Triglycerides are lipids made of one glycerol and three fatty acid molecules. In a phospholipid, one fatty acid is replaced with a phosphate group
68
Outline the properties of a phospholipid
Consist of a polar, hydrophilic head which faces the water in the bilayer. The head is composed of a glycerol and a phosphate molecule. They are amphipathic, meaning they have both hydrophilic (water-loving) and lipophilic (fat-loving) regions. This makes them arrange into a bilayer in water to keep their heads wet and tails dry.
69
Draw a diagram of a phospholipid
https://file.notion.so/f/f/e52fcf8a-d6ea-4a2d-a3c3-d8bce0c54560/ee541312-f063-4c10-88ee-e39c00b06121/Untitled.png?id=ccc20960-6de3-4d63-b1cd-d434ecc47688&table=block&spaceId=e52fcf8a-d6ea-4a2d-a3c3-d8bce0c54560&expirationTimestamp=1713398400000&signature=GN9nzbux69zR-IV79LKbOOy6sERh8vZo34822n0CjBY&downloadName=Untitled.png
70
What are the properties of phospholipid bilayers?
- bilayer has two layers
- held together by weak hydrophobic interactions between tails
- Hydrophilic/hydrophobic layers restrict passage of many substances
- Individual phospholipids can move within the bilayer, allowing for membrane fluidity
- phospholipid bilayer has two layers of phospholipids arranged according to properties
- phosphate heads are hydrophilic (water-loving) because of their charge
- fatty acids (non-polar) are hydrophobic (afraid of water)
71
What are the two types of membrane proteins?
Integral proteins: Amphipathic (have both hydrophobic and hydrophilic properties), embedded in plasma membrane, pass completely through and across the membrane
Peripheral proteins: Polar (hydrophilic), temporarily attached to outside of plasma membrane
72
What are some types of integral proteins?
| Include diagrams
- channels - have a pore/channel that lets passive transport (no ATP or energy required) of substances in and out
- carriers - bind to substances on one side of membrane, and change shape to transport them. Active transport (use energy to change shape). Termed protein pumps Can go against concentration gradient.
- recognition - help the cell differentiate between self and non-self cells to help trigger an immune response
- receptors - usually span the whole membrane to relay information from the inside or outside of the cell
- enzymes - proteins that enhance rate of reactions that happen at the membrane level
https://file.notion.so/f/f/e52fcf8a-d6ea-4a2d-a3c3-d8bce0c54560/a29e5e63-ff49-4e27-9312-72aceabfcd02/Untitled.png?id=cc5c1d57-f1f3-4426-b1e3-e882c98b7de5&table=block&spaceId=e52fcf8a-d6ea-4a2d-a3c3-d8bce0c54560&expirationTimestamp=1713398400000&signature=_9dXWQAqABiPPfZS6seWtbefLfu5vGGwDgS-C8DR7YA&downloadName=Untitled.png
73
What are the non-protein parts of the cell membrane?
- glycolipids - phospholipid and carbohydrate attached together. important in maintaining structure of cell membrane and in differentiation between self and non-self cells.
- glycoproteins - proteins with an oligosaccharide (oligo = few, saccharide = sugar) chain attached. important for cell recognition. help maintain structure of membrane. aid in differentiating between self and non-self cells. important for cell recognition by the immune system and as hormone receptors.
- cholesterol - steroid only in animal cell membranes. vital in helping maintain structure of cell membrane. Makes phospholipids pack more tightly and regulates fluidity and flexibility.
74
Draw the fluid mosaic model
https://file.notion.so/f/f/e52fcf8a-d6ea-4a2d-a3c3-d8bce0c54560/9c770500-d192-41ea-9b70-cb54bc76f046/Untitled.png?id=7978a06c-d013-480a-8433-00899242aa88&table=block&spaceId=e52fcf8a-d6ea-4a2d-a3c3-d8bce0c54560&expirationTimestamp=1713398400000&signature=18_c2X_kYEAByrFr6jbMCHoQ0NofiBGXybWBFmqtmTY&downloadName=Untitled.png
Ensure:
- individual molecules are shown by the symbol of a circle with two parallel lines
- range of membrane proteins is shown, including peripheral and integral
- labels are included:
- phospholipid bilayer
- phospholipid molecule
- glycoprotein
- glycolipid
- integral and peripheral proteins
- cholesterol
75
What is the role of cholesterol?
Some important hormones (i.e. sex hormones) are synthesized from cholesterol. Helps control membrane fluidity and permeability by disrupting the regular packing of hydrocarbon tails of phospholipid molecules, preventing solidification of membrane. Disrupts regular packing of hydrocarbon tails of phospholipid molecules, preventing solidification of membrane.
76
Define Permeability
The ability to let liquids and gases pass through
77
Define cholesterol and it's structure
| Draw a diagram
Steroid made of non-polar part comprising four ring structures, a hydrocarbon(hydrogen and carbon compound) tail, and a polar hydroxyl group (hydrophilic). This lets it insert itself into cell membranes by interacting with amphipathic phospholipids. https://file.notion.so/f/f/e52fcf8a-d6ea-4a2d-a3c3-d8bce0c54560/ade2d0c8-f18e-4575-86ee-2598dac35da0/Untitled.png?id=3465bcaf-3cb9-45aa-a62b-cbe39357b3c4&table=block&spaceId=e52fcf8a-d6ea-4a2d-a3c3-d8bce0c54560&expirationTimestamp=1713571200000&signature=vzJPDK_ykeg2rIC5accktTXz6B8qrH9jPw9X0THfrRI&downloadName=Untitled.png
78
What is the Davson-Danielli model?
## Footnote
previous work, davson-danielli model, when it was first proposed, shortcomings
Was first proposed in 1935, but released a revised version in 1954. Earlier work in 1925 by Gorter and Grendel suggested the ratio of lipid surface area to cell membrane surface area was 2:1, concluding that cells were covered in a layer of fatty molecules which is two molecules thick. The Davson-Danielli model suggests that cell membrane comprises a lipid bilayer where two layers of polar lipid molecules are arranges with hydrophilic heads outwards, and the lipid bilayer is sandwiched between two protein layers. It follows evidence from electron microscopy, which shows membrane having three layers.
Shortcomings:
- assumed all membranes had identical structure, neglecting the fact that different membranes can carry out different functions
- proteins are amphipathic, but are largely hydrophobic, which makes it improbable they’re be found in contact with the environment on either side of the membrane
79
How was the Davson-Danielli model discredited?
- In 1972, Singer and Nicolson proposed the fluid mosaic model, suggesting proteins were individually embedded in the phospholipid bilayer, allowing hydrophilic portions of proteins and phospholipids to be maximally exposed to water, meaning a stable membrane structure and hydrophobic portions of proteins and phospholipids were in the non bilayer
- evidence from freeze fracture techniques confirmed proteins were embedded in the membrane
- biologists delaminated (separated) membranes along the middle of the bilayer, revealing an irregular rough surface inside the phospholipid bilayer
- was deduced that proteins penetrate into the interior of the membrane
80
What is the role of membranes?
- cells need to import and export for survival
- movement across membranes occurs through passive or active transport
- passive doesn’t require energy and includes processes like simple diffusion, facilitated diffusion, and osmosis
- active transport is energy-demanding and can occur via a pump protein or might involve bulk transport through endocytosis and exocytosis
81
Define diffusion
Diffusion is a movement of particles from region of high concentration to region of low concentration. It is the result of random motion of particles. It does not require energy. A concentration gradient is required. Diffusion results in an equilibrium.
82
What factors affect movement during diffusion?
- temperature - higher temperature results in faster diffusion
- surface area of membrane - increase in surface area allows more molecules to diffuse
- size of particles - smaller molecules diffuse faster than larger ones
- concentration gradient of diffusing particles - bigger gradient results in faster diffusion
83
What are the two types of diffusion?
Simple diffusion, facilitated diffusion
84
Define simple diffusion
Simple diffusion occurs in a gas or liquid. It occurs in living and non-living systems. if particle is too big, it cannot pass through phospholipid bilayer of membrane. In simple diffusion, charged particles/ions are repelled by hydrophobic tails in membrane. when simple diffusion fails, facilitated diffusion can take place.
85
Define facilitated diffusion
Similar to simple diffusion. requires channel proteins or carrier proteins, specific to molecules being transported. size and shape of protein carriers and channels determines what kind of substance can cross the membrane. Important application is in movement of K+(potassium) ions in neurons during generation of action potential. It helps move K+ ions out of axons to cause repolarisation. K+ channels involved only allow movement of K+. Voltage gated, meaning they open and close with changes in electric potential to control movement of ions.
Types: Channel-mediated (molecule flows through channel in protein) and carrier-mediated (molecule binds to transport protein, making it change shape and allowing the molecule to enter the cell).
86
Define osmosis
A form of diffusion involving only water molecules. Involves the movement of water from lower solute(higher water) concentration to higher solute concentration.
87
Define hypertonic, isotonic, and hypotonic
- hypertonic - solution is ‘salty’
- isotonic - solution is in an equilibrium with the cell
- hypotonic - solution is less ‘salty’ than the cell
88
Define osmolarity
Osmolarity is the tendency to induce osmosis. The greater the concentration of a solute, the greater the osmolarity. Think of osmolarity as ‘saltiness’. Liquids will move to solutions with higher osmolarity. Solutes do not move during osmosis, but they help decide the direction that the water molecules move
89
Define osmotic pressure
Osmosis is the tendency to induce osmosis. The greater the concentration of a solute, the greater the osmolarity. Think of osmolarity as ‘saltiness’. Liquids will move to solutions with higher osmolarity.
90
Define osmotic pressure
hydrostatic pressure that builds up in confined fluid due to osmosis. Change in water volume in confined space changes osmotic pressure. important to life, especially single-celled organisms. if too much water enters cell, cell might burst or lyse. if too much water leaves cell, cell becomes flaccid and may die.
91
How are tissues and organs kept in tact during medical procedure, considering osmosis.
- kept in saline storage
- essential osmolarity(measure of solute concentration) is the same as cytoplasm of the cells in the tissue to prevent osmosis which would damage the cells
- use terms hypertonic, isotonic, and hypotonic to describe difference in solute concentration
- usually comparing solution outside the cell and cytoplasm inside the cell
- solution with higher concentration of solutes is hypertonic and lower is called hypotonic.
- water always moves by osmosis from the hypotonic solution to the hypertonic solution
92
Define active transport
- movement of particles across membranes, requiring energy in form of ATP
- energy is used to move substances against concentration gradient, from low concentration to higher concentration
93
Define hydrolysis and it's role in active transport
Integral protein pumps use energy from hydrolysis(hydro - use water, lysis - split) of ATP to move ions or large molecules across cell membrane. Molecules are moved against concentration gradient. The hydrolysis of ATP releases on phosphate and lots of energy
94
How does active transport happen in sodium-potassium pumps?
| define the pumps then talk about the active transport
- Active transport can be seen in Sodium-potassium (NA+/K+) pumps (so-dum, get out)
- these pumps are very important in nervous system for maintaining resting potential in neurons
- concentration of sodium ions needs to be higher outside a neuron than inside, while potassium is more concentrated inside
- active transport by sodium-potassium pumps:
- pump is open to the inside of the axon, three sodium ions enter the pump and attach to the binding sited
- ATP donates a phosphate group to the pump. ATP → ADP + P
- causes the protein to change shape, expelling sodium(NA+) to the outside
- two potassium ions from outside enter and attach to their binding sites
- binding of potassium leads to release of phosphate, causing pumps to change shape again so it is open to the inside of the axon
- potassium is released inside
- sodium can enter and bind again
- ions are pumped AGAINST concentration gradient
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Define endocytosis. Include an example
- cellular process where cells take in molecules or substances by ingulfing them in the cell membrane
- use ATP and are dependent on flexibility of plasma membrane.
- can be divided into phagocytosis or pinocytosis
- pinocytosis is taking in liquid substances (cell drinking)
- phagocytosis is absorbing solids (cell eating)
- example is when white blood cell or phagocyte engulfs a pathogenic microbe
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Define exocytosis. Include an example.
- opposite of endocytosis
- ejection of waste products or useful substances (i.e. hormones) from the inside
- use ATP and are dependent on flexibility of plasma membrane.
- excretion and secretion
- excretion comes after phagocytosis, as any undigested remains of the microbe that are useless are excreted
- secretion is where proteins synthesized by ribosomes on the R.E.R. are passed to the golgi apparatus via vesicles, where they’re processed and packaged (to give enzymes or hormones the right conformations) before being released in vesicles that in turn fuse with the plasma membrane for secretion outside the cell
97
What is the role of vesicles in exocytosis and endocytosis? How does this work.
- allow movement of materials
- many organelles are membrane-bound meaning they can make their own vesicles
- making vesicles is a common way for cell to move molecules around
- enzymes might be made by bound ribosomes in the rER. rER will package enzymes in a vesicle formed from membranes. Vesicle carrying enzymes will move to golgi apparatus, and fuse with golgi apparatus membrane. enzymes will be modified and packed in a vesicle using golgi apparatus membrane. Vesicle will move toward plasm membrane and undergo exocytosis.
98
How was it proved that cells must come from pre-existing cells?
- cell theory assumes living organisms are made up of cells which come from pre-existing cells
- Louis Pasteur (1822-1895) (famous French microbiologist) gave evidence to support the hypothesis. he disproved theory of spontaneous generation, which stated life could appear from combination of dust, air, and other factors
- he hypothesized that cells must come from cells
- https://file.notion.so/f/f/e52fcf8a-d6ea-4a2d-a3c3-d8bce0c54560/ebc34552-67ee-4f6a-9534-3480cf5f3610/Untitled.png?id=07b8c68f-fd50-4b95-9f74-42b832a134dc&table=block&spaceId=e52fcf8a-d6ea-4a2d-a3c3-d8bce0c54560&expirationTimestamp=1713657600000&signature=OAGMNxnwvYA0kvBditD0yT21WAj0-71oz807_wJilhA&downloadName=Untitled.png
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What was the Miller-Urey experiment?
- a possible explanation is that life was transported to earth from elsewhere. but there’s no evidence supporting this
- first cell may have come from non-living material
- miller and urey recreated conditions of early earth by including a low oxygen atmosphere with high radiation levels, high temperatures, and electrical storms. after a week, some amino acids and complex oily hydrocarbons were found in the reaction mixture, proving non-living synthesis of simple organic molecules was possible.
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What are the conditions for the emergence of life?
1. Simple organic molecules, such as amino acids, fatty acids, and carbohydrates must be formed
2. Larger organic molecules like phospholipids, RNA and DNA, must be assembled from simpler molecules
3. Organisms reproduce, so replication of nucleic acids must be possible
4. Biochemical reactions require set conditions (i.e. pH), so self-contained structures like membranes are necessary.
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What is the endosymbiotic theory?
- probable that first cells were prokaryotic, but evolution of eukaryotic cells is better understood
- proof that first were prokaryotic lies in double membrane structure of organelles in eukaryotes, and comparison of dna between eukaryotes and prokaryotes
- endosymbiotic theory explains origin of eukaryotic cells
- supports idea that mitochondria and chloroplasts were prokaryotes originally that were then taken in by larger prokaryotes by endocytosis. but instead of being digested, they stayed in the host cells.
- cells which could carry out aerobic respiration and provide energy to the host cell (host cells were probably anaerobes who didn’t need oxygen) evolved into mitochondria
- prokaryotic cells could convert light energy to chemical energy (probably cyanobacteria) became chloroplasts and passed sugar produced during photosynthesis to the host cell
- evidence supporting endosymbiotic theory (about both mitochondria and chloroplasts):
- have double membranes, as expected when a cell is taken in by endocytosis
- have circuler naked DNA like in prokaryotes
- DNA is formed as a single chromosome
- have 70S ribosomes like in prokaryotes
- divide by binary fission like prokaryotic cells
- are susceptible (likely to be influenced) to some antibiotics
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What are some reasons cells divide?
growth, tissue repair, reproduction, maintain efficiency of transfer/surface area to volume ratio
103
Why must cell division be controlled?
Uncontrolled growth can lead to tumors
104
What are the stages of the cell cycle?
1. Interphase
1. G0 phase
2. G1 phase
3. S phase - DNA replication
4. G2 phase
2. Mitosis
3. Cytokinesis
105
What happens in interphase? Define and outiline.
- most active and longest phase of cell cycle
- encompasses three important phases: G1(Gap 1), S(Synthesis), and G2(Gap 2)
- G1 - Cytoplasm
- cell grows and functions normally
- rapid protein synthesis lets the cell grow in size
- proteins required for DNA synthesis are made
- mitochondria and chloroplasts (in plant cells) are replicated, and continue to be replicated in the S phase
- S - Nucleus
- amount of DNA doubles and DNA replication takes place
- genetic material is duplicated but no chromosomes are formed
- G2 - Cytoplasm
- protein synthesis occurs to make proteins for cell division, like microtubule proteins that make up a mitotic spindle
- cell prepares for cell division
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What happens during mitosis?
- nucleus divides into two identical daughter nuclei
- involves separation of sister chromatids into individual chromosomes which are distributed among daughter nuclei
107
What happens during cytokinesis?
The cytoplasm is divided
108
What are cyclins and what is their function? Draw a diagram too.
- family of protein controlling progression of cells through cell cycle
- cells can’t progress unless the specific cyclin reaches a certain concentration
- cyclins bind to enzymes called cyclin-dependent kinases (CDKs) and activate them
- activated CDKs attach phosphate groups (phosphorylation) to other proteins
- attachment of phosphate triggers other proteins to become active and carry out tasks
- https://file.notion.so/f/f/e52fcf8a-d6ea-4a2d-a3c3-d8bce0c54560/2201d7ba-a3a2-494c-8fa6-4c0f149cd4e3/Untitled.png?id=d449026b-e339-4255-9f86-5b0b7253e32b&table=block&spaceId=e52fcf8a-d6ea-4a2d-a3c3-d8bce0c54560&expirationTimestamp=1713657600000&signature=_PTolUHSWSJ3lxfDrS97eti2ePFHu1gWlStm1BrBwMY&downloadName=Untitled.png
- G1 - D levels gradually increase
- S - Cyclin E is vital to DNA replication, and promotes centromere duplication
- G2 - Cyclin A helps induce DNA replication
- Mitosis - Cyclin B is essential for the formation of mitotic spindles and alignment of chromatids
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What is the role of chromosomes in eukaryotic cells and the cell cycle?
- chromosomes are formed from the replication of DNA in the S phase
- Eukaryotic chromosomes consist of DNA that’s tightly wound around proteins known as histones. Histones are alkaline(basic) proteins that form nucleosomes.
- Many nucleosomes are coiled together in a pattern to form a chromosome
- during interphase, chromosomes are unpacked so protein synthesis and replication can take place. DNA is only visible during mitosis.
- - DNA is initially packaged by histones to form chromatin, which then gets even more condensed to form chromosomes.
- Chromatin is a lower order of DNA organisation, and chromosomes are a higher order of DNA organisation
- use correct terminology when describing chromosomes, sister chromatids, or chromatin
- in Interphase, DNA is in chromatin
- after prophase when DNA supercoiling takes place, DNA is visible as a pair of sister chromatids connected by a centromere
- after sister chromatids are separated in anaphase, they are called chromosomes
110
What are the phases of mitosis and what happens during each?
- prophase
- dna supercoils and chromatin condenses as a result
- nucleolus disappears
- nuclear membrane disintegrates
- spindle fibres (made of microtubules) start to form and are formed by the end of prophase
- centrioles (not in plant cells) move to opposite sides
- metaphase
- spindle fibres bind to the centromere and cause the sister chromatids to move toward the equatorial plate
- sister chromatids are aligned at the equatorial plate at the end of metaphase
- anaphase (shortest one)
- sister chromatids are separated and become chromosomes, as they’re pulled to opposite poles by the spindle fibres
- telophase
- chromosomes reach the poles
- nuclear membrane starts forming at each pole
- nucleolus appears in each new nucleus
- spindle fibres disintegrate
- cell elongates to prepare for cytokinesis
- sometimes, the invagination of the membrane is visible, marking beginning of cytokinesis
111
What is the miotic index?
miotic index is the ratio of the number of cells undergoing mitosis to the total number of cells. The formula: # of cells in mitosis / total number of cells.
112
How is cytokinesis different in plant cells and animal cells?
- a cell wall is present in plant cells
- animal cells
- ring of protein/microfilaments located beneath the plasma membrane at the equator pulls the membrane inwards
- inward pull on plasma membrane makes the characteristic cleavage furrow
- when the cleavage furrow reaches the centre of the cell, it’s pinched apart
- plant cells
- golgi apparatus forms vesicles that consist of material to build a new cell wall
- vesicles merge and form the cell plate
- cell plate grows and divides into two daughter cells
113
What is tumorigenesis? Include types and all relavant details.
- formation of a tumor(s) which is defined as mass of cells dividing uncontrollably
- two types: benign and malignant
- cancer is caused by a malignant tumour
- benign tumor is localized, does not spread, and normally responds well to treatment
- malignant tumour is cancerous and often resistant to treatment, may spread, and sometimes may recur after it’s been removed
- tumour can form when events of cell cycle are disrupted due to a mutation in one of the cyclins, CDKs, or a protein associated with the cell cycle. example:
- p54 is a protein involved in regulation of cell cycle
- mutation in p53 gene can lead to a tumour forming
- over 50% of all tumours have a mutation in the p53 gene
- mutation in a cell making it lose ability to enter G1 phase, and instead continuing to divide rapidly can cause a tumour. mutation is passed onto daughter cells and then a clump of cells forms. when this growth continues, a tumour is formed.
114
What is mutation?
- change in an organisms genetic code
- change in base sequence can result in tumour formation
- some parts of a gene do not code for anything, so mutation in these areas will not affect the organism
- not all gene mutations lead to uncontrolled cell division
115
What are mutagens?
- agents that cause gene mutation
- anything that causes a mutation has the potential to cause cancer
- can be:
- chemicals that cause mutations. these chemicals are referred to as carcinogens, i.e. asbestos or dioxin
- high-energy radiation such as x-rays
- short-wave ultraviolet light
- some viruses like hepatitis B
116
What is an oncogene?
- gene that’s undergone a mutation that contributes to the development of a tumour
- when they’re in their normal non-mutated state, they’re termed proto-oncogenes. these proto-oncogenes assist in regulation of cell division.
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How do secondary tumours form from primary tumours?
- after abnormal cell division starts, a malignant primary tumour begins forming. if left untreated, it may follow a particular development pathway to form secondary tumours. we can say that a tumour has metastasized.
- steps:
- cancerous cells detach from the primary
- some cancerous cells gain ability to penetrate walls of lymph or blood vessels and circulate around the body
- circulating cancerous cells invade tissues at different locations and develop by uncontrolled division into secondary tumours
118
Define metastasis
movement of cells from primary tumour to other parts where they develop into secondary tumours
