Biology IB HL - 1.1 Cell Introduction Part 1
The three main principles of cell theory are that all living organisms are made of cells or their products, the cell is the basic unit of structure and function in living things, and all cells come from pre-existing cells through division.
What are the 3 main principles of cell theory?
All living things are composed of cells (or cell products)
The cell is the smallest unit of life
Cells only arise from pre-existing cells
Key Terms
What are the 3 main principles of cell theory?
All living things are composed of cells (or cell products)
The cell is the smallest unit of life
Cells only arise from pre-existing cel...
What are 3 examples of cells/tissues that do not conform to cell theory?
striated muscle fibres
aseptate fungal hyphae
giant algae
What component of cell theory do striated muscle fibres not conform to ?
Challenges the idea that cells always function as autonomous units
How doe s a striated muscle fibre challenge cell theory?
Muscle cells fuse to form fibres that may be very long (>300mm)
Consequently, they have multiple nuclei despite being surrounded by a sing...
How does aseptate fungal hyphae challenge cell theory?
Fungi may have filamentous structures called hyphae, which are separated into cells by internal walls called septa
Some fungi are not partiti...
What component of cell theory does aseptate fungal hyphae challenge?
Challenges the idea that living structures are composed of discrete cells
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| Term | Definition |
|---|---|
What are the 3 main principles of cell theory? | All living things are composed of cells (or cell products) The cell is the smallest unit of life Cells only arise from pre-existing cells |
What are 3 examples of cells/tissues that do not conform to cell theory? | striated muscle fibres aseptate fungal hyphae giant algae |
What component of cell theory do striated muscle fibres not conform to ? | Challenges the idea that cells always function as autonomous units |
How doe s a striated muscle fibre challenge cell theory? | Muscle cells fuse to form fibres that may be very long (>300mm) Consequently, they have multiple nuclei despite being surrounded by a single, continuous plasma membrane |
How does aseptate fungal hyphae challenge cell theory? | Fungi may have filamentous structures called hyphae, which are separated into cells by internal walls called septa Some fungi are not partitioned by septa and hence have a continuous cytoplasm along the length of the hyphae |
What component of cell theory does aseptate fungal hyphae challenge? | Challenges the idea that living structures are composed of discrete cells |
How does giant algae challenge cell theory? | Certain species of unicellular algae may grow to very large sizes (e.g. Acetabularia may exceed 7 cm in length) |
What component of cell theory does giant algae challenge? | Challenges the idea that larger organisms are always made of many microscopic cells |
What 7 characteristics are all living organisms capable of carrying out? | metabolism reproduction sensitivity homeostasis excretion nutrition growth |
Define metabolism | Living things undertake essential chemical reactions - a total of all the chemical reactions that take place within an organism |
Define reproduction | Living things produce offspring, either sexually or asexually |
Define sensitivity | Living things are responsive to internal and external stimuli |
Define homeostasis | Living things maintain a stable internal environment |
Define excretion | Living things exhibit the removal of waste products |
define nutrition | living things exchange materials and gases with the environment |
define growth | Living things can move and change shape or size |
Give an example of a unicellular heterotroph | paramecium |
Explain how paramecium show sensitivity | Paramecia are surrounded by small hairs called cilia which allow it to move |
Explain how paramecium show nutrition | Paramecia engulf food via a specialised membranous feeding groove called a cytostome |
Explain how paramecium show metabolism | Food particles are enclosed within small vacuoles that contain enzymes for digestion |
Explain how paramecium show excretion | Solid wastes are removed via an anal pore, while liquid wastes are pumped out via contractile vacoules |
Explain how paramecium shows homeostasis | Essential gases enter (e.g. O2) and exit (e.g. CO2) the cell via diffusion |
Explain how paramecium reproduce | Paramecia divide asexually (fission) although horizontal gene transfer can occur via conjugation |
Give an example of a unicellular autotroph | scenedesmus |
Explain how scenedesmus shows nutrition/excretion | Scenedesmus exchange gases and other essential materials via diffusion |
Explain how scenedesmus shows metabolism | Chlorophyll pigments allow organic molecules to be produced via photosynthesis |
Explain how scenedesmus shows reproduction | Daughter cells form as non-motile autospores via the internal asexual division of the parent cell |
Explain how scenedesmus shows responsiveness/sensitivity | Scenedesmus may exist as unicells or form colonies for protection |
What is important in the limitation of cell size? | Surface area to volume ratio is important in the limitation of cell size |
What do cells need to do to survive? | Cells need to produce chemical energy (via metabolism) to survive and this requires the exchange of materials with the environment |
What is the rate of metabolism affected by? | The rate of metabolism of a cell is a function of its mass / volume (larger cells need more energy to sustain essential functions) |
What is the rate of material exchange affected by? | The rate of material exchange is a function of its surface area (large membrane surface equates to more material movement) |
How does the SA:VOL ratio change with increasing cell size? | As a cell grows, volume (units3) increases faster than surface area (units2), leading to a decreased SA:Vol ratio |
What will happen if the metabolic rate exceeds the rate of exchange of vital materials and wastes? | If metabolic rate exceeds the rate of exchange of vital materials and wastes (low SA:Vol ratio), the cell will eventually die |
How doe cells prevent the SA:VOL ratio becoming to low? | Hence growing cells tend to divide and remain small in order to maintain a high SA:Vol ratio suitable for survival |
What type of cells/tissue would be adapted to have a bigger SA:VOL ratio? | Cells and tissues that are specialised for gas or material exchanges will increase their surface area to optimise material transfer |
How is intestinal tissue adapted to increase SA:V ratio? | Intestinal tissue of the digestive tract may form a ruffled structure (villi) to increase the surface area of the inner lining |
How are alveoli adapted to increase SA:V ratio? | Alveoli within the lungs have membranous extensions called microvilli, which function to increase the total membrane surface |
How does light microscopy work? | Light microscopes use visible light and a combination of lenses to magnify images of mounted specimens |
What can be seen/looked at with a light microscope? | Living specimens can be viewed in their natural colour, although stains may be applied to resolve specific structures |
What can be seen in bacteria w/ a light microscope? | cell wall (if stained) flagella (if stained) ~1-10μm |
What can be seen in a protist with a light microscope? | nucleus pseudopodia food vaculoes ~50 - 500μm |
What can be seen in a plant cell with a light microscope? | nucleus chloroplasts cell wall ~10 - 100 μm |
What can be seen in an animal cell with a light microscope? | nucleus mitochondria (only if stained) ~10-50μm |
When do emergent properties arise? | Emergent properties arise when the interaction of individual component produce new functions |
How do multicellular organisms differ from unicellular organisms differ and how? | Multicellullar organisms are capable of completing functions that unicellular organisms could not undertake – this is due to the collective actions of individual cells combining to create new synergistic effects |
What do cells join together to form? | Cells may be grouped together to form tissues |