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IB biology topic 2
| Question | Answer |
|---|---|
| Outline Cell Theory (3 points) | All living things are made up of cells. All cells come from pre-existing cells. The cell is the smallest function unit of a living organism. |
| Evidence for cell theory | 1665: Robert Hooke first observed cells and stated that cork cells ‘consisted of a great many little boxes’ 1770: cell shapes were revealed 1800: Jean Baptiste de Lamarck and Matthias Schleiden proposed cell theory 1862:Louis Pasteur disproved sp |
| Unicellular organism carry out functions of life (6 points) | Metabolism, Response, Homeostasis, Growth, Reproduction, Nutrition (My Rat Has Grown Rapidly North) |
| Comparison of relative sizes, using appropriate SI unit (Molecules, Thickness of Membranes, Viruses, Bacteria, Organelles and Cells of Eukaryotes) | Molecules: 1nm Thickness of cell membrane: 10nm Virus: up to 100nm Bacteria: up to 1µm Organelles: up to 10µm Cells of Eukaryotes: up to 100µm |
| Equation for magnification | Magnification = size of image / size of specimen |
| Explain importance of surface area to volume ratio (3 points) | 1) The needs of a cell, in terms of resource consumption, heat production and waste production depend on the volume. 2) Exchange of materials and energy is a function of surface area 3) As cell INCREASES in size, the SA:R DECREASES |
| Multicellular organisms (2 points) | Multicellular organisms show emergent properties Emergent properties arise from interaction of component parts |
| Explain that cells in multicellular organisms differentiate (4 points) | 1) Cells differentiate to carry out specific functions 2) Become specialised in feeding, support or defence 3) Express some genes and not others 4) Loses ability to complete all functions, eg. red blood cells has no nucleus, therefore cannot repr |
| Stem cells | Stem cells retain their capacity to divide and have ability to differentiate along different pathways. |
| Therapeutic use of stem cells (Umbilical cord blood stem cell transplant) | 1) UCB contains multipotent stem cell blood 2) Can treat same problems that require bone marrow as treatment 3) Are better because they less prone to rejection; haven't developed features that can be attacked by immune system 4)No graft vs host d |
| How do prokaryote cells divide? | They divide through binary fission. |
| What are the three similarities between prokaryote and eukaryote cells? | 1) Both contain DNA 2) Both have outside boundaries that involves plasma membrane 3) Both carry out all the functions of life |
| What are the six differences between prokaryote and eukaryote cells? | 1) P: DNA in ring form. E: DNA with proteins as chromosomes 2) P: DNA free in cytoplasm. E: DNA in nucleus 3) P: No mitochondia. E: has m 4) P: 70S ribosomes. E: 80S ribosomes 5) P: no IC. E: IC 6) P: less than 10µm. E: greater than 10µm |
| State the three differences between animal and plant cells. | Plant cells contain: Cell wall Starch granules Chloroplast |
| Outline the role of the two extracellular components (plant cell wall and animal extracellular matrix) | PCW – Composed of cellulose, maintains shape, provides structural support against gravity and prevents excessive intake of water AEM – Secrete glycoproteins that from ecm. Provides structural support, adhesion and movement. |
| Explain properties of phospholipids and their role in maintaining cell structure (4 points) | 1) Have hydrophilic head made from glyceril and phosphate: + 2) Hydrophobic tail made from two fatty acids: - 3) Align themselves into a bilayer: tail facing inside membrane 4) Surface creates a boundary with cell and its surroundings |
| Function of membrane proteins: Hormone binding sites | These have specific shapes exposed to the exterior that fit to the shape of specific hormones. Attachment between protein and hormone cause a change in the shape of the protein and a message is relayed to the interior to the interior of the cell. |
| Function of membrane proteins: Enzymatic action | Cells have enzymes attached to the membrane that catalyse reactions. May be on the interior or exterior of the cell. |
| Function of membrane proteins: Cell adhesion | Proteins that hook together in various ways to provide temporary or permanent connections |
| Function of membrane proteins: Cell to cell communication | Many of the communication proteins include attached carbohydrate molecules. They provide an identification label representing cells of different types. |
| Function of membrane proteins: Channels for passive transport | Does not involve energy. Two types; diffusion and osmosis |
| Function of membrane proteins: Pumps for active transport | Involve energy |
| Define diffusion (4 points) | 1) Is the passive movement of a substance from a region of HC to LC 2) When concentration is equal there is no net movement 3) Occurs when there is a different concentration btwn 2 regions 4) Occurs along concentration gradient |
| Define osmosis | The passive movement of water molecules across a partially permeable membrane from a region of lower solute concentration to higher concentration |
| Define solution, solute and solvent | Solution: A substance in which solute is dissolved in a solvent. Generally solvent is clear. Solute: a substance that dissolves solvent. Solvent: the substance that dissolves solute |
| Define endocytosis | Is the taking of things into the cell. It is where a substance is ingested into a cell. Can be phagocytosis (cell eating) or pinocytosis (cell drinking) |
| Define exocytosis | Is where a substance is removed or secreted from a cell |
| Explain passive transport across membranes by simple diffusion (3 points). Substances that diffuse easily are steroid hormones, oxygen and carbon dioxide | 1) SD is the net movement of molecules or ions from a region of their high concentration to a region of low concentration 2) Always occurs along concentration gradient 3) Membranes are partially permeable therefore allow some substances to pass through |
| Explain passive transport across membranes by facilitated diffusion (4 points). Glucose, nucleic acids, amino acids and proteins are some examples. | 1) Form of PD of molecules down CG 2) Uses a special carrier protein with a central channel 3) Specific molecule binds to protein, protein then changes shape to move the molecule down the membrane where it is released into cell 4)Occur in either direct |
| Explain role of protein pumps and ATP in active transport (4 points) | 1) PP found in membrane and are used in active transport. 2) Each PP only absorbs particular substances 3) This allows it to control what is absorbed and expelled 4) Particle enters PP, ATP expended; allowing pump to change shape and particle then rele |
| Explain how vesicles are used to transport materials (5 points) | 1) Protein is present in rER; moves through rER it changes shape. 2)V formed at end with protein inside 3) Goes to GA 4) V fuses with membrane of GA, allowing protein to be released into lumen 5)Changed - new V forms - moves to PM fuses and then excr |
| Outline the three stages of cell division: INTERPHASE | Interphase: G1:Protein synthesis, mitochondria replication and chloroplast replication S: DNA replication G2: Preparation for cell division |
| Outline the three stages of cell division: MITOSIS | One copy of each chromosome moves into two newly forming nuclei |
| Outline the three stages of cell division: CYTOKINESIS | Division of the cytoplasm to form two daughter cells |
| Tumours and cancers (state point) | Tumours (cancers) are the result of uncontrolled cell division and that these can occur in any organ or tissue. |
| Interphase (state point) | Interphase is an active period in the life of a cell when many metabolic reactions occur, including protein synthesis, DNA replication and an increase in the number of mitochondria and/or chloroplasts. |
| Four phases of mitosis: PROPHASE | Sister chromatids have condensed by super coiling. Spindles begin to form. Nuclear membrane begins to disintegrate. |
| Four phases of mitosis: METAPHASE | The mitotic spindle organises the chromosomes on the equator of the cell. Some spindle microtubules attach at the centromere and some span the cell. |
| Four phases of mitosis: ANAPHASE | The centromeres split and the spindle microtubules that are attached to the chromatids shorten, pulling the sister chromatids apart. The sister chromatids move to the opposite poles. |
| Four phases of mitosis: TELOPHASE | Two new nuclei form. At the poles there are separate groups of the replicated chromosomes. The spindles begin to degenerate. |
| Explain how mitosis produces 2 genetically identical nuclei | In the S phase of interphase the DNA replicates and makes identical copies of each chromosome. Mitosis then occurs, where one copy of each chromosome moves into the two newly forming nuclei. This ensures that there are two genetically identical nuclei. |
| 4 points that involve mitosis | Growth, embryonic development, tissue repair and asexual reproduction involve mitosis. |
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chantelleispony
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