Intro to Cells Flashcards
Cell Theory
All living things are composed of one or more cells
The cell is the basic unit of life
New cells arise from pre-existing cells.
Structures & organisms: caveats to cell theory
Aseptate fungal hyphae: Fungi sometimes consist of hyphae, which are long thread-like structures with multiple nuclei and no clear division between the cells via a cell wall. Do not conform to cell theory as contradict statement that every living thing is made of at least once cell, a small simple structure with a membrane which separates its contents from outside world, and the cells are the smallest unit of life, since aseptate fungal hyphae have no membrane dividing the cells, and they are also long, so not small.
Striated muscle: This type of muscle is composed of fibres which are much larger than most cells and which contain multiple nuclei, and contradict statement that cells are the smallest unit of life as well as being simple structures. This is because they are much larger than many cells, and have a complex structure of multiple nuclei.
Red blood cells: Erythrocytes do not have a nucleus when they mature. This means they do not conform to the cell theory since having no nucleus prevents them from passing on DNA or genes, hence they are not able to reproduce, going against the statement that they can perform all functions of life, including reproduction.
Large algae: These living organisms can grow to 100mm in length but only have one nucleus, despite a complex structure of rhizoids (root-like structures), a long stalk and small branches at the top. They are a caveat to the cell theory since they are very large and have a complex structure, contradicting the statements that cells are small and have a simple structure.
Functions of life
Metabolism: sum of chemical reactions that occur within living organisms to sustain life.
Reproduction: production of offspring (asexual or sexual).
Homeostasis: maintenance of constant internal environment
Nutrition: obtaining food to have organic & inorganic material for metabolism (e.g photosynthesis or consuming outside source)
Excretion: removal of toxic waste products of metabolism.
Response: ability of organism to detect & react to changes in its surroundings.
Growth: increase in mass/volume of organism due to cell division/enlargement.
Organisms with one cell
carry out all functions of life in that cell
Functions of life in paramecium
Life as Paramecium sp. – A heterotrophic, unicellular, freshwater eukaryote.
Cilia move differently in response to the environment. E.g. to move the organism towards food. Response
Cilia waft nutrients into the cell’s oral groove and a food vacuole forms. This is then released into cell and digested. Nutrition
Contractile vacuoles fill with water, expand, then suddenly constrict and expel water out of cell. This is a form of osmoregulation. Homeostasis
The cell gets large as food vacuoles are digested. Growth
This occurs in cytoplasm which contains mitochondria for respiration. Metabolism
This usually occurs asexually by mitosis. Reproduction
Waste products of metabolism are expelled through the plasma membrane. Excretion
Why surface area to volume ratio is important in limitation of cell size
Cell size increasing = volume increasing faster than surface area. Cell size increases = surface area to volume ratio decreases. Cell too large = cannot take in raw materials (not able to cross membrane) nor export waste materials fast enough to function in accommodation of cellular volume (+ may overheat). (why cells so small).
Multicellular organisms composed of… and have…
specialised cells…properties that emerge from the interaction of their cellular components.
Differentiation involves
expression of some genes and not others in cell’s genome
How do specialised tissues develop in mulitcellular organisms
In multicellular organisms, tissues are a group of cells that specialise in the same thing to be able to perform the same function (most of time). Development of specialised tissues in multicellular organisms can happen thanks to differentiation: process during development whereby newly formed cells become more specialized and distinct from one another as they mature. In a multicellular organism, there are many different cell types, but all have same set of genes (identical genome). Activation of different instructions (genes) within given cell (different sequences of genes are expressed in different cell types) by chemical signals causes it do differentiate.
Functions of life in chlorella
Life as Chlorella sp. – An autotrophic, unicellular, freshwater eukaryote.
Cilia move differently in response to the environment. E.g. to move organism towards light. Response
The generation of its own food source by photosynthesis in a chloroplast. Nutrition
Contractile vacuoles fill with water, expand, then suddenly constrict and expel water out of cell. This is a form of osmoregulation. Homeostasis
The cell gets large as food vacuoles are digested. Growth
This occurs in cytoplasm which contains mitochondria for respiration. Metabolism
This usually occurs asexually by mitosis. Reproduction
excretion?
