topic 1.1- introduction to cells Flashcards
Define cell theory
all living organisms are composed of cells (the basic structural, functional and organisational units).
State and explain 4 features common to all cells
- cell membrane- to separate the cell from it’s surroundings
- genetic material that can be passed on (excluding erythrocytes)
- enzymes- to catalyse reactions within the cell
- energy release system (eg respiration)
State 3 atypical examples of cell theory
- striated muscle
- giant algae
- aseptate fungal hyphae
explain how a striated muscle fibre (SMF) does not conform to standard cell theory
muscle cells fuse, forming SMFs that are very long
=> fibres have multiple nuclei despite being surrounded by a single, continuous plasma membrane.
(challenges idea that cells always function as autonomous units)
explain how aseptate fungal hyphae do not conform to standard cell theory
fungi may have hyphae (filamentous structures), which are separated into cells by septa (internal walls)
=> some fungi not partitioned by septa and hence have a continuous cytoplasm along the length of the hyphae
(challenges idea that living structures are composed of discrete cells)
explain how giant algae do not conform to standard cell theory
certain species of unicellular algae may grow to very large sizes
(challenges idea that larger organisms are always made up of many microscopic cells) up to 100 mm in length
give an example of a giant unicellular algae
acetabularia, which may exceed 7cm in length
explain why the ultrastructure of a unicellular organism may be more complex than an individual cell in a multicellular organism
- unicellular must be able to carry out all the functions of life in a single cell.
- multicellular can carry out different functions in different parts of body.
give a eukaryotic and prokaryotic example of a unicellular organism
eukaryotic- amoeba
prokaryotic- s. cervisiae (baker’s yeast)
state the 7 functions of life
metabolism
response
nutrition
excretion
reproduction
growth
homeostasis
homeostasis
the maintenance of a constant, stable environment to keep conditions inside the organism within tolerable limits
growth
irreversible increase in size
reproduction
production of offspring, either sexually or asexually
nutrition
obtaining food to provide energy and materials needed for growth
response
ability to react to changes in the environment
metabolism
chemical reactions inside the cell
excretion
removal of waste products of metabolic reactions
why is size often limited in unicellular organisms?
- surface area affects the rate at which materials enter and leave the cell
- volume affects the rate at which materials are used and produced by the cell
- the surface area to volume ratio affects the rate of metabolism in a cell
- the bigger the cell, the smaller the SA ratio is
- cells having a low SA ratio cannot exchange materials fast enough
what will happen if the SA:VOL ratio of a cell is too small? (3)
- substances will not enter the cell quickly enough
- waste products will accumulate (produced more rapidly than excreted)
- cells may overheat as metabolism produces heat faster than is lost over cell’s surface
what is an emergent property?
a property which a collection or complex system has, but which the individual members do not have, as it arises from the interactions of those individual components
what does an emergent property arise from?
the interaction of cellular components in an organism.
give 3 examples of emergent properties
cells form tissues, tissues form organs, organs form organ systems
what type of organism is paramecium and where does it live
- unicellular eukaryote
- freshwater environments
how does paramecium provide energy for itself?
it is a heterotroph (eats smaller unicellular organisms in order to obtain energy/matter).
