Cell Introduction 1.1 Flashcards
What is the cell theory?
- Cells are the smallest unit of life
- All living things/organisms are made up of cells
- All cells come from pre-existing cells
What are exceptions to the cell theory?
- Skeletal muscle = made up of muscle fibres, these fibres are much larger than most cells, and contain hundreds of nuclei
- Giant algae = can grow to large lengths, but only contain one nucleus, so they are not multicellular
- Asesptate fungi = consist of thread-like structures called hyphae. Hyphae are not divided into sub-units containing single nucleus, but instead there are long undivided sections of hypha which contain many nuclei
What are the 7 functions of life?
- Metabolism: Living things undertake essential chemical reactions.
- Reproduction: Living things produce offspring, either sexually or asexually.
- Sensitivity: Living things are responsive to internal and external stimuli.
- Homeostasis: Living things maintain a stable internal environment.
- Excretion: Living things exhibit the removal of waste products.
- Nutrition: Living things exchange materials and gases with the environment.
- Growth: Living things can move and change shape or size.
(MR SHENG)
How does the paramecium (heterotroph) fulfil the basic functions of life?
- Metabolism - Food particles are enclosed within small vacuoles that contain enzymes for digestion.
- Reproduction - Paramecia divide asexually (fission)
- Sensitivity/Responsiveness - Paramecia surrounded by small hairs called cilia which allow it to move .
- Homeostasis - Essential gases enter (e.g. O2) and exit (e.g. CO2) the cell via diffusion.
- Excretion - Solid wastes are removed via an anal pore, while liquid wastes pumped out via contractile vacuoles.
- Nutrition - Paramecia engulf food via a specialised membranous feeding groove called a cytostome.
What does the production of chemical energy (metabolism) by cells require?
The exchange of materials with the environment
How is the rate of metabolism of a cell a function of its mass/volume?
larger cells need more energy to sustain essential functions
How is the rate of material exchange of a cell a function of its surface area?
large membrane surface area equates to more material movement
As a cell grows, what decreases?
SA:Volume ratio
Why does the SA:Volume ratio decrease as the cell grows?
Because the volume increases faster than the surface area
How do you find the SA:Volume ratio?
Surface Area divided by Volume
How do cells and tissues that are specialised for gas or material exchange optimise material transfer?
By increasing their surface area
Which two structures are examples of increasing SA:Volume ratio to optimise material transfer?
- Villi (Intestinal tissue of digestive tract) form ruffled surface to increase SA of inner lining.
- Microvilli (alveolar cells/extensions) which increase total membrane surface of alveoli.
How do you calculate magnification?
Magnification = Image size divided by Actual size
What are the features of a light microscope?
- Use lenses to bend light + magnify images by a factor of roughly 100-fold
- Can be used to view living specimens in natural colour
- Chemical dyes + fluorescent labelling may be applied to resolve specific structures
- Less expensive
- Lower resolution + magnification
What are the features of an electron microscope?
- Use electromagnets to focus electrons resulting in significantly greater magnifications + resolutions
- Can be used to view dead specimens in monochrome
- Transmission electron microscopes can generate cross section
- Scanning electron microscopes can differentiate depth + 3D map
- More expensive
- Higher resolution + magnification
