Cell Theory and Prokaryotic Cells

Alex Snellgrove
Flashcards by Alex Snellgrove, updated more than 1 year ago
Alex Snellgrove
Created by Alex Snellgrove over 6 years ago


IB Biology (Cells) Flashcards on Cell Theory and Prokaryotic Cells, created by Alex Snellgrove on 11/12/2014.

Resource summary

Question Answer
Outline the cell theory 1. All living things are composed of cells (or cell products) 2. The cell is the smallest unit of life 3. Cells only arise from pre-existing cells
Unicellular organisms carry out all the functions of life Movement Reproduction Sensitivity Growth Respiration Excretion Nutrition
Movement Living things show movement, either externally or internally
Reproduction Living things produce offspring, either sexually or asexually
Sensitivity Living things can respond to and interact with the environment
Growth Living things can grow or change size / shape
Respiration Living things use substances from the environment to make energy
Excretion Living things exhibit the removal of wastes
Nutrition Living things exchange materials and gases with the environment
Importance of the surface area to volume ratio as a factor limiting cell size The rate of metabolism of a cell and the rate of material exchange in and out of a cell is a function of its surface area As the cell grows, volume increases faster than surface area (leading to a decreased SA:Vol ratio)
Multicellular organisms show emergent properties Emergent properties arise from the interaction of component parts, that whole is greater than the sum of its parts Multicellular organisms are capable of completing functions that individual cells could not undertake - this is due to the interaction between cells producing new functions Cells to tissues, to organs, to organ systems to organism
Cells in multicellular organisms differentiate to carry out specialised functions by expressing some of their genes and not others All cells of an individual organisms share an identical genome, each cell contains the entire set of genetic instructions for that organism The activation of different instructions (genes) within a cell by chemical signals will cause it to differentiate from other similar cells Differentiation is the process during development where newly formed cells become specialised and distinct from one another as they develop Active genes are packaged in an expanded and accessible form (euchromatin), while inactive genes are mainly packaged in a condensed form (heterochromatin)
Stem cells retain the capacity to divide and have the ability to differentiate along different pathways Stem cells are unspecialised cells that have two key qualities of self renewal and potency.
Self renewal of stem cells Ability to continuously divide and replicate
Potency of stem cells Ability to differentiate into specialised cell types
Therapeutic process in the use of stem cells Stem cells can be used to replace damaged or diseased cells with healthy and functioning ones This process requires the use of biochemical solutions to trigger differentiation into a desired cell type, the surgical implantation of cells into the patient's own tissue, and careful monitoring of the new cells to ensure they do not become cancerous
Therapeutic use of stem cells Nerve cells, to repair damage caused by spinal injuries to enable paralysed victims to regain movement Blood cells, used for bone marrow transplants in cancer patients who are immuno-compromised as a result of chemotherapy
Cell Wall Cell outer layer made of peptidoglycan that maintains shape and protects the cell from damage or bursting if internal pressure is high
Cell Membrane Semi-permeable barrier that controls the entry and exit of substances
Cytoplasm Fluid component which contains the enzymes needed for all metabolic reactions
Nucleoid Region of the cytoplasm which contains DNA
Prokaryotic Ribosome Complexes of RNA and protein that are responsible for polypeptide synthesis (70S)
Flagella Long thread-like structure which enables cell mobility
Pili Hair-like extensions found on bacteria
Attachment Pili Allow bacteria to adhere to one another or to available surfaces
Sex Pili Allow the exchange of genetic material (plasmids) through a process called bacterial conjugation
How do prokaryotic cells divide? Binary Fission
Binary Fission Binary fission is a form of asexual reproduction and cell division used by prokaryotic cells. The process of binary fission includes circular DNA that is copied in response to a replication signal, the two DNA loops attach to the membrane, which elongates and pinches off, forming two separate cells
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