Cell Biology - 1.1 Introduction to Cells Flashcards
Cell theory:
- living organisms are composed of (one or more) cells
- the cell is the most basic unit of life
- All cells arise only from pre-existing cells by division
- the activity of an organism depends on the total activity of independent cells
- Energy flow (metabolism and biochemistry) occurs within cells
- Cells contain DNA which is found specifically in the chromosome and RNA found in the cell nucleus and cytoplasm
- Cells are basically the same in chemical composition in organisms of similar species
- Organisms consisting of only one cell carry out all functions of life in that cell.
Aristotle’s “spontaneous generation”
theorised that cells came from nothing - the idea was upheld for 2000 years proved wrong by: Louis Pasteur in 1860
Pasteur’s experiment (to go against spontaneous generation)
=> evidence from Pasteur’s experiments that spontaneous generation of cells and organisms does not now occur on Earth
- He set up 2 flasks filled with broths and then sealed them with a snake-like entrance, heated both (ie. sterilising them), waited to see if there was microbial growth -> broke the snake-neck off one (allowing bacteria stuck on dust to get in). The one that was open went milky the one that was still closed stayed the same
Exceptions to cell theory - ATYPICAL CELLS
=> questioning the cell theory using atypical examples (including: striated muscle, giant algae and aseptate fungal hyphae)
Striated muscle (refer to notes for diagram)
- Has more than one nucleus per cell (despite being surrounded by a single, continuous plasma membrane)
- Muscle cells fuse to form fibres that can be very long (300mm)
- Challenges the idea that cells always function as autonomous units
Aseptate Fungal Hyphae (refer to notes for diagrams)
- Fungi may have filamentous structures called hyphae, which are separated into cells by internal walls (composed of chitin) called septa
- Some fungi are not partitioned by septa and hence have a continuous cytoplasm along the length of the hyphae (with no end cell wall or membrane)
- very large with many nuclei and continuous cytoplasm
- challenges the idea that: a cell is a single unit
Giant algae (Acetabularia) (refer to notes for diagrams)
- single-celled organism
- giant in size (5-100 mm)
- has a SINGLE nucleus
- Challenges the idea that larger organisms are always made of many microscopic cells
Consists of 3 anatomical parts:
- bottom rhizoid (single nucleus found here)
- long stalk
- top umbrella of branches that may fuse into a cap
Cells
All living things are either:
Unicellular (composed of 1 cell)
Multicellular (composed of many cells)
- structure is related to its function (may be differentiated by activating or deactivating genes that code to alter cell shape, organelles, metabolism, chemical reactions, etc.
Functions of living organisms (MR H GREN)
Metabolism - the web of all enzymes - catalysed relations in a cell or organism eg. respiration
Response - living things can respond/interact w/ the environment
Homeostasis - the maintenance and regulation of internal cell conditions (eg. H2O)
Growth - living things can grow/change in size/shape
Excretion - the removal of metabolic waste
Reproduction - living things produce offspring, either sexually or asexually
Nutrition - feeding via the synthesis of organic molecules (eg. photosynthesis) or the absorption of organic matter
Is a Virus alive and cellular
No and no, the do not exhibit the characteristics of MR H GREN
Their features:
- non cellular
- very small size (20-300nm)
- Contain no cytoplasm or organelles
- no chromosome, just DNA/RNA strand
- covered in protein coat
- depend of host cell for metabolism/reproduction
Protoctista (protist) cells
- Protists are free-living unicellular organisms.
- most live in water
- some are heterotrophic (eg. paramecium), some autotrophic (with chloroplasts) (eg. Chorella) and some are both (Euglena)
Contain most of the same structure found in animals cells - but also include:
- cilia or flagella: for movement
- Eye spot: light/dark detection
- Contractile vacuoles to regulate water levels inside cells (especially in freshwater habitats),
Paramecium - ((protist cells) heterotrophic)
{Learn MR H GREN features for this organism}
it is a heterotrophic unicellular organism
- widespread in freshwater and marine environments (often in stagnant basins and ponds)
- size = approx. 100um (0.1mm)
M = most metabolic pathways happen in the cytoplasm eg respiration, food particles are enclosed in all vacuoles that contain enzymes for digestion
R = The nucleus can divide asexually (fusion) although horizontal gene transfer can occur via conjugation
H = contractile vacuole fill up with water and expel through the plasma membrane to manage the water content - essential gasses enter (eg O2) and exit (eg CO2) via diffusion
G = after consuming and assimilating biomass from food the paramecium will get larger until it divides
R = the wave action of the cilia moves the paramecium in response to changes in the environment (eg. towards food)
E = the plasma membrane controls the entry and exit of substances including expulsion of metabolic waste - solid wastes removed via anal pore, liquids pumped out via contractile
N = food vacuoles contain organisms the paramecium has to consume, engulf food via specialised membranous feeding vacuoles groove called a cytostome
- as these animals live in french water it has the problem of water pouring in by osmosis - it has two CONTRACTILE VACUOLES to pump out the water
- It eats bacteria = channels through an oval groove with beating cilia and digests in a food vacuole.
cilia
small beating hairs that can beat backwards and forwards allowing for movement (responsiveness)
Euglena - ((protist cells) heterotrophic and autotrophic)
- features both plant and animal cells - makes it hard to classify if it is part of the Plantae and Animalia kingdom
Chlorella - ((protist cells) autotrophic)
{Learn MR H GREN features for this organism}
it is an autotrophic single-cell green algae (spherical in shape)
M = most metabolic pathways happen in the cytoplasm (eg. photosynthesis, respiration)
R = the nucleus can divide to support cell division, by mitosis (these cells are undergoing cytokinesis)
H = contractile vacuole fill up with water and expel through the plasma membrane to manage the water content
G = after consuming and assimilating biomass from food the algae will get larger until it divides
R = the wave action of the cilia moves the algae in response to changes in the environment (eg. towards light)
E = the plasma membrane control the entry and exit of substances including the diffusion out of waste oxygen
N = photosynthesis happens inside the chloroplasts to provide the algae with food
Scenedesmus - ((protist cells) autotrophic)
- Scenedesmus exchange gases and other essential materials via diffusion (nutrition / excretion)
- Chlorophyll pigments allow organic molecules to be produced via photosynthesis (metabolism)
- Daughter cells form as non-motile autospores via the internal asexual division of the parent cell (reproduction)
- Scenedesmus may exist as unicells or form colonies for protection (responsiveness)
Surface Area and Volume:
SA:Vol ratios
- surface area is fetermined by the cell membrane
- Surface area and volume ratio are important in the LIMITATION OF CELL SIZE.
- the rate of metabolism of a cell is a function of its mass/volume (leading to a DECREASED SA:Vol ratio)
- If metabolic rate > rate of exchange of vital materials and wastes = cell will die (Ie. cell must keep dividing for this to not happen = restoring a viable SA:Vol ratio)
- cells and tissues specialised for gad/material exchange (eg. alveoli) will increase their SA to optimise the transfer of materials (eg. biconcave disc shape of red blood cells)
SA and Vol calculations (formulas)
Surface area (LxWx(no. of sides)) Volume (LxWxH) SA:Vol ratio (eg. 24:8 = 3)
Define Tissue
A tissue is a group of cells that specialise in the same way and perform the same function
SA and Vol calculations (formulas)
Surface area (LxWx(no. of sides)) Volume (LxWxH) SA:Vol ratio (eg. 24:8 = 3)
What happens to the ratio of SA to Vol as the cell becomes bigger:
The ratio gets smaller as the diffusion of essential nutrients (eg. O2) become inefficient.
-> small cells are more efficient than large cells as they can undergo diffusion at a faster rate (ie. their SA:Vol ratio is smaller)
Life Functions of MULTICELLULAR ORGANISMS - (information)
- Multicellular organisms have properties that emerge from the interaction of their cellular components
- Emergent properties arise from the interaction of the component parts
- Due to interactions between cells producing new functions, multicellular organisms are capable of completing functions that individual cells found not undertake
Life = an emergent property of billions of chemical reactions that result in metabolism - the interactions of cells, tissues, organs and organ systems create the complexity of the organism
BIOLOGICAL SYSTEMS ARE MORE THAN THE SUM OF THEIR PARTS - for even though we could have 2 cells, each could be responsible for more than 1 thing.
