Topic 1.1 Introduction to Cells Flashcards
State the 4 Hypotheses of Cell Theory
- All cells exist from pre-existing cells
- Cells are capable of independent existence, and are the smallest unit of life
- All living things are composed of cells
- All actions of the cell are controlled by the chemical reactions occurring in the cell.
Exceptions to cell theory
- Skeletal/Striated Muscle fibres
- Aseptate Fungal Hyphae
- Giant algae
Skeletal/Striated Muscle Fiber
- Each Fiber is very long (30mm compared to 0.03mm)
2. Has hundreds of nuclei (multinucleated)
Aseptate Fungal Hyphae
- Hyphae are thread-like structure that have cell membranes and cell walls
- Each hyphae is a multinucleate coenocyte (multinucleated and enclosed in a single membrane)
- Hyphae is not partitioned by septa, challenges the idea that all organisms are made of discrete cells
How does Giant Algae contradict cell theory
- Each Cell is 7-10cm
2. Contradicts the concept of SA:V ratio for cell size
Purpose of Surface area to Volume Ratio
- Limit the cell size (larger cell has higher SA:V)
- If the ratio is too small, exchange will be very slow –> Overheating, low metabolic rate, accumulation of waste products
Define Metabolism
Conversion of organic molecules/chemical reactions in an organism
Define Response
Reaction to stimuli
Define Homeostasis
Maintaining constant interior environment
Define Growth
Increase in size/mass/number of cells within an organism
Define Reproduction
Production of similar cells/offspring
Define Nutrition
Process by which organism take in and make use of food/nutrients
Define excretion
Elimination of metabolic wastes
What are the structure of Paramecium and their functions?
- Nutrition: Feeds on smaller organisms by ingesting through oral groove and digesting them in vesicles (endocytosis)
- Excretion: Expels waste products of metabolism through the anal pore
- Homeostasis: Expels excess water using contractile vacuole
- Response: Reverse its direction of movement using contractile vacuoles when it touches a solid object
- Reproduction: Reproduces asexually using mitosis or sexually using meiosis and gametes
- Movement: Through the cilia and contractile vacuole
- Metabolism: Produces enzymes which catalyse many different chemical reactions in the cytoplasm
What is the structure of Amoeba?
Pseudopodium are fake arms used for phagocytosis to engulf and ingest food.