Term
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Definition
1. Living organisms are composed of cells.
2. Cells are the smallest unit of life.
3. Cells come from pre-existing cells.
4. Cells are the unit of structure and function. |
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Term
| Exceptions to the Cell Theory |
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Definition
It is important to note that all "rules" have exceptions. Skeletal muscles and some fungal hyphae are not divided into cells but have a multinucleate cytoplasm.
Some biologists consider:
- unicellular organisms to be acellular - even though they carry out all the functions of life. View Paramecium eating yeast cells.
- Viruses to be acellular structures consisting of DNA or RNA surrounded by a protein coat - even though they carry out most functions of life once they invade host cells
In multicellular organisms, all the cells contain all the genes, but they do not use all of them. The cells of a multicellular organism differentiate to carry out specialized functions by only expressing some of their genes.
It is also important to note:
- that it is the accumulation of evidence that allows a hypothesis to become a theory
- whether a theory should be abandoned when there is evidence that it does not offer a full explanation
- what evidence is needed for a theory to be rejected or adapted
- that theories are not static statements - as evidence is accumulated theories need to be reviewed/altered/abandoned |
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Term
Evidence for the theory: Microscopy, Biochemistry and Genetics
Advantages of Light Microscopes |
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Definition
| - Advantages of using a light microscope include: colour images instead of monochrome images (one colour), easily prepared sample material, the possibility of observing living material and movement, and a larger field of view |
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Term
| Advantages of Electron Microscopes |
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Definition
| - Since the resolution is higher in an electron microscope than a light microscope, one can see more separate particles and have a clearer picture of those particles. Also, an electron microscope has a higher magnification than a light microscope, so one would be able to see smaller objects |
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Term
| State that unicellular organisms carry out all the functions of life. |
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Definition
| - Unicellular organisms carry out metabolism, respond and move in their environments, perform homeostasis, grow, reproduce and gain nutrition |
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Term
| State that unicellular organisms carry out all the functions of life. |
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Definition
| - Unicellular organisms carry out metabolism, respond and move in their environments, perform homeostasis, grow, reproduce and gain nutrition |
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Term
| Compare the relative sizes of molecules, cell membrane thickness, viruses, bacteria, organelles and cells, using appropriate SI units. |
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Definition
- 1000nm (nanometer) = 1um (micrometer), 1000um = 1mm
- Molecules are 1nm while the thickness of a membrane is 10nm. Viruses are 100nm, bacteria are 1um, organelles can be up to 10um, and most cells can be up to 100um. The cell is much larger than all these when taken into consideration the three-dimensional shape. |
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Term
| Compare the relative sizes of molecules, cell membrane thickness, viruses, bacteria, organelles and cells, using appropriate SI units. |
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Definition
- 1000nm (nanometer) = 1um (micrometer), 1000um = 1mm
- Molecules are 1nm while the thickness of a membrane is 10nm. Viruses are 100nm, bacteria are 1um, organelles can be up to 10um, and most cells can be up to 100um. The cell is much larger than all these when taken into consideration the three-dimensional shape. |
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Term
| Calculate linear magnification of drawings. |
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Definition
- magnification = size of image/actual size of specimen
- drawings of microscopic structures must include at least one of:
- scale bars |-----| = 1um
- magnification: x 250 |
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Term
| Explain the importance of the surface area to volume ratio as a factor limiting cell size. |
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Definition
- When a cell grows, the volume increases at a faster rate than the surface area.
- Thus, as the cell grows, the surface to volume ratio decreases.
- A cell needs surface area in order to carry out metabolic functions (chemical reactions need a surface), and as a cell grows, it needs to carry out more and more reactions
- Therefore, since a cell must maintain a certain surface area to volume ratio, its size is limited |
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Term
| State that multicellular organisms show emergent properties. |
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Definition
- Emergent properties arise from the interaction of component parts: the whole is greater than the sum of its parts
- Life itself can be viewed as an emergent property |
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Term
| Explain that cells in multicellular organisms differentiate to carry out specialised functions by expressing some of their genes but not others. |
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Definition
Unicellular Organisms
- must solve all of life's challenges within the confines of a single cell
Multicellular Organisms
- can differentiate into a variety of interdependent cell types
- each specialised to carry out a subset of functions
- thereby achieving a greater efficiency
- through division of labor among a multicellular cooperative
- Cellular Differentiation: is the development of cells in specific ways - Hormones, cell to cell signals, and chemicals determine how a cell develops
- Cells in multicellular organisms differentiate to become specialised
- Each cell is specialised for one particular function, eg. nerve cells transmit messages
- Groups of differentiated cells form a tissue
- Cells contain nucleus' (chromosomes -> DNA -> genes)
- All cells have all genes and could develop in any way but not all are turned on - some are switched on, eg. cells in your toes have information on how to make pigment for your eye colour, but this gene is turned off in your toes
NOTE:
- A tissue is an integrated group of cells that have a common structure and function. An organ is a centre of body function specialised for that one function that is composed of several different types of tissue. An organ system is a group of organs that specialise in a certain function together. |
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Term
| State that stem cells retain the capacity to... |
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Definition
| Divide and have the ability to differentiate along different pathways. |
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Term
| Outline one therapeutic use of stem cell. |
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Definition
- bone marrow transplants use hematopoietic stem cells (HS cells)
- HS cells are found in bone marrow and divide continually, producing a variety of red and white blood cells
- just 100 HS cells can completely replace the blood system of mice when all cells in the marrow have been destroyed by radiation
- HS cells are used in the treatment of numerous blood disorders:
1. acute leukemia
2. SCID (severe combined immune deficiency)
3. multiple myeloma
4. lymphoma
In lymphoma:
1. Cells are removed from the bone marrow of the patient.
2. High doses of chemotherapy drugs are taken by the patient to kill dividing cells in the body.
3. Both cancerous and normal are killed.
4. HS cells from the bone marrow are then transplanted back into the patient.
5. These HS cells can then fully restore healthy production of blood cells in the bone marrow.
- ethical issues: use of embryonic stem cells involves the death of early-stage embryos
- ethical issues: therapeutic cloning could reduce suffering for patients with a wide variety of conditions |
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Term
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Definition
| An organelle is a discrete structure within a cell that has a specific function, it also needs to be covered by its own membrane. |
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Term
| Prokaryotic cells - Cell Wall |
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Definition
-always present
-composed of peptidoglycan
-provides physical protection
-maintains cell shape
-prevents bursting in hypotonic environment |
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Term
| Prokaryotic Cells - Plasma Membrane |
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Definition
- thin layer mainly composed of phospholipids pushed up against the inside of the cell wall
- provides selectively permeable barrier between homeostatically controlled interior and fluctuating exterior environments
- controls entry and exit of substances
- can also pump substances in or out by active transport
- can produce ATP by cell respiration |
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Term
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Definition
- protein filaments protruding from the cell wall
- can be pulled in or pushed out by a ratchet mechanism
- used for cell to cell adhesion
- used when bacteria stick together to form aggregations of cells
- used when two cells are exchanging DNA during conjugation |
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Term
| Prokaryotic Cells - Flagella |
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Definition
- structures protruding from the cell wall with a corkscrew shape
- base is embedded in the cell wall
- using energy, they can be rotated, to propel the cell from one area to another
- unlike eukaryotic flagella, they are solid and inflexible, working like a propeller |
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Term
| Prokaryotic Cells - Cytoplasm |
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Definition
- fluid filling the space inside the plasma membrane
- water with many dissolved substances
- contains many enzymes
- contains ribosomes
- does not contain any membrane-bound organelles
- carries out the chemical reactions of metabolism |
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Term
| Prokaryotic Cells - Ribosomes |
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Definition
- small granular structures (70S)
- smaller than eukaryotic ribosomes which are 80S
- sites of protein synthesis |
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Term
| Prokaryotic Cells - Nucleoid |
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Definition
- region of cytoplasm containing the genetic material (usually one molecule of DNA)
- DNA is circular and naked (not associated with protein)
- total amount of DNA is much smaller than in eukaryotes
- the nucleoid is stained less densely than the rest of the cytoplasm because there are fewer ribosomes in it and less protein |
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Term
| State that prokaryotic cells divide by... |
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Definition
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Term
| Eukaryotic Cells - Free Ribosomes |
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Definition
- sites of protein synthesis for use within the cytoplasm
- ribosomes are constructed in the nuclear region called the nucleolus |
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Term
| Eukaryotic Cells - Rough Endoplasmic Reticulum |
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Definition
- flattened membrane sacs (cisternae)
- ribosomes attached to outside of cisternae
- proteins synthesized by ribosomes enter cisternae
- proteins collected within cisternae are packaged in vesicles
- vesicles transport proteins to Golgi apparatus |
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Term
| Eukaryotic Cells - Lysosomes |
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Definition
- spherical vesicles formed by Golgi apparatus
- contain hydrolytic/digestive enzymes
- enzymes for breaking down ingested food, damaged organelles or entire cells |
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Term
| Eukaryotic Cells - Golgi Apparatus |
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Definition
- consists of flattened membrane sacs called cisternae
- unlike ER, cisternae are curved, shorter, and lack ribosomes
- proteins received from arriving vesicles are processed
- carbohydrates added to proteins to form glycoproteins
- vesicles of glycoproteins exit Golgi for exocytosis or intracellular use |
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Term
| Eukaryotic Cells - Mitochondria |
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Definition
- double membrane bound
- inner membrane invaginated to form cristae
- site of aerobic respiration, producing ATP |
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Term
| Eukaryotic Cells - Nucleus |
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Definition
- double membrane bound, containing pores for transport of proteins and ribosomes
- contains chromosomes, made of DNA + protein
- uncoiled chromosomes = chromatin
- site of DNA replication and transcription into RNA |
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Term
| Compare prokaryotic and eukaryotic cells. |
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Definition
Prokaryotic:
- naked DNA
- DNA in cytoplasm (no nuclear membrane)
- no membrane-bound organelles (no mitochondria, ER< golgi)
- ribosome size = 70S
- only bacteria
- size: 1-10um
- evolved at least 3.5 billion years ago
Eukaryotic
- DNA associated with proteins
- true nucleus (enclosed by nuclear membrane)
- many membrane-bound organelles (mitochondria, ER, golgi) to compartmentalize functions
- ribosome size = 80S
- all cells other than bacteria
- size: 2-1000um
- evolved 1.5-2 billion years ago |
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Term
| State three differences between plant and animal cells. |
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Definition
Plant Cells
1. Cellulose cell walls
2. Chloroplasts
3. Large central vacuole
Animal Cells
1. No cell walls
2. No chloroplasts
3. Lacking or small vacuoles |
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Term
| Outline two roles of extracellular components. |
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Definition
Plant cell wall
- composition: cellulose microfibrils
- functions:
1. provides physical protection
2. prevents excessive water uptake precluding bursting in hypotonic environment
3. produces turgor pressure which holds whole plant up against the force of gravity
Animal extracellular matrix
- animal cells secrete glycoproteins that form the extracellular matrix
- functions: support, adhesion, movement |
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Term
| Explain how the hydrophobic and hydrophilic properties of phospholipids help to maintain the structure of cell membranes. |
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Definition
- Hydrophobic fatty acid tails repel water and form the middle layer of the membrane
- Hydrophilic phosphate heads attract water and form the outer layers of the membrane
- The head of the phospholipid is polar and hydrophilic (water-loving), and these heads make up the outside of the phospholipid bilayer
- The tail of the phospholipid that is located inside the membrane is nonpolar and hydrophobic (water-fearing)
- Because one end of the phospholipid is hydrophobic and the other is hydrophilic, phospholipids naturally form bilayers in which the heads are facing outward (toward the water), and the tails are facing inward (away from the water)
- Therefore, the characteristics of phospholipids enable the phospholipids to form a stable structure |
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Term
| List the functions of membrane proteins, including: |
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Definition
- Hormone binding sites
- Immobilized enzymes
- Cell adhesion
- Cell-to-cell communication
- Channels for passive transport
- Pumps for active transport |
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Term
Define:
1. Diffusion
2. Osmosis |
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Definition
1. Diffusion: the passive movement of particles from a region of higher concentration to a region of lower concentration.
2. Osmosis: the passive movement of water molecules, across a partially permeable membrane, from a region of lower solute concentration to a region of higher solute concentration. |
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Term
| Explain passive transport across membranes in terms of simple diffusion and facilitated diffusion. |
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Definition
Concentration gradient: Molecules can diffuse across membranes form areas of higher to lower concentration by:
- Simple diffusion: travelling directly through the membrane if they are small and uncharged, thus avoiding repulsion by the hydrophobic, non-polar tails of phospholipids in the middle of the membrane
- Facilitated diffusion: travelling through special transport proteins, if they match the shape and charge requirements to fit through the channels provided by the transport proteins |
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Term
| Explain the role of protein pumps and ATP in active transport across membranes. |
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Definition
Against the concentration gradient: Moves substances from an area where it is in lower concentration to an area where it is in higher concentration.
Protein pumps:
- Integral protein pumps embedded within membranes
- Specific to molecule transported
Requires energy:
- Usually provided by ATP
- Often by phosphorylating the protein pump as ATP is hydrolyzed |
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Term
| Explain how vesicles are used to transport materials within a cell between the rough endoplasmic reticulum, Golgi apparatus, and plasma membrane. |
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Definition
- Protein synthesis: rER produces proteins which travel through the lumen of the ER
- Transport in vesicles: Membranes produced by the rER flows in the form of transport vesicles to the Golgi, carrying proteins within the vesicles
- Modification: Golgi apparatus modifies proteins produced in rER
- Transport to membrane: Golgi pinches off vesicles that contain modified proteins and travel to plasma membrane
- Exocytosis: Vesicles then fuse with plasma membrane, releasing their contents outside the cells |
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Term
| Describe how the fluidity of the membrane allows it to change shape, break and reform during endocytosis and exocytosis. |
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Definition
- Lipids move laterally in a membrane, but flip-flopping across the membrane is rare
- Unsaturated hydrocarbon tail of phospholipids have kinks that keep the molecules from packing together, enhancing membrane fluidity
- Cholesterol reduces membrane fluidity by reducing phospholipid movement at moderate temperatures but it also hinders solidification at low temperatures |
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Term
| Outline the stages in the cell cycle, including interphase (G1, S, G2), mitosis and cytokinesis. |
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Definition
Interphase
- G1: growth, protein synthesis, increase in the number of mitochondria and/or chloroplasts
- S: DNA replication
- G2: growth, protein synthesis, preparation for mitosis/cytokinesis
Mitosis = nuclear division
- prophase
-metaphase
- anaphase
- telophase
Cytokinesis = cellular division |
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Term
| State that tumors (cancers) are the result of... |
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Definition
| uncontrolled cell division and that these can occur in any organ or tissue. |
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Term
| State that interphase is an active period in the life of a cell when... |
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Definition
| many metabolic reactions occur, including protein synthesis, DNA replication and an increase in the number of mitochondria and/or chloroplasts. |
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Term
| Describe the events that occur in the four phases of mitosis. |
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Definition
Prophase:
- Chromosomes condense by supercoiling, becoming visible
- Centrioles move to opposite poles
- Nucleolus disappears
- Nuclear membrane disappears
- Microtubular spindle apparatus forms at each pole
Metaphase:
- Spindle microtubules attach to chromosome centromeres
- Chromosomes move to the equator
Anaphase
- Centromeres split as spindle microtubules pull chromatids to opposite poles (after centromeres split, sister chromatids are known as sister chromosomes)
- Sister chromosomes move to opposite poles as microtubules shorten
Telophase
- Sister chromosomes have arrived at poles
- Spindle disappears
- Centrioles replicate
- Nuclear membrane becomes visible
- Nucleolus becomes visible
- Chromosomes decondense, becoming chromatin |
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Term
| Explain how mitosis produces two genetically identical nuclei. |
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Definition
- DNA replication during S phase of interphase produces two identical copies of DNA
- Identical sets of DNA are attached to each other as sister chromatids of each of the cell's chromosomes
- Mitosis segregates the two chromatids of each chromosome to opposite poles, forming two identical nuclei, each with one complete copy of the original DNA
- Cytokinesis separates the two daughter nuclei into two identical daughter cells |
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Term
| State that growth, embryonic development, tissue repair and asexual reproduction involve... |
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Definition
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