Essay on Biology notes

Submitted By Emiliaz5
Words: 1984
Pages: 8

Topic 1: Cell Biology
1.1 Introduction to cells

Outline the cell theory and the evidence supporting it.
1. All living organisms are composed of one or more cell.
Robert Hooke (1665) discovered cork cells through a microscope.
(few years later) Antonie Van Leeuwenhoek saw first living cells ‘animalcules’.
Matthais Schleiden (1838)stated that plants are made of ‘independent separate beings’.

2. Cells are the smallest units of life.
No living entity composed of at least one cell has been found.
Cells are the simplest collection of matter that can be alive.

3. All cells come from pre-existing cells.
Louis Pasteur (1880s).
Boiled 2 containers of chicken broth.
The exposed container was found to have bacterial growth.
Life has the ability to re-establish itself only after being exposed to pre-existing cells.

Exceptions to the cell theory
Striated muscles
Multinucleated more than one nucleus per cell.
300mm thus very long one.
Bigger than animal cells.
Don’t continue to replicate

Aspetate fungal hyphae
Multinucelured very large.
Continous cytoplasm.

Giant Algae
One cell
One nuclei
Gigantic in size 5-100mm

Viruses
Can only produce inside a host cell.

Unicellular organisms carry out all functions of life.
MR HRENG
Metabolism
All the chemical reactions that occur in an organism.
Response
Action or movement to stimuli.
Homeostasis
Regulation and maintenance of a stable internal environment (pH, water)
Reproduction
Production of offspring.
Involves hereditary: transmission of traits from one generation to the next molecules that can be passed to offspring.
Excretion
Removal of waste
Such as toxic or harmful chemical compounds.
Nutrition
Energy necessary to maintain life.
Takes in and makes use of food substances
Autotroph: gain energy from the sun or oxidation of inorganic substances to form organic molecules from inorganic ones.
Heterotroph: Gain organic food molecules from the consumption of other organisms or substances derived.
Growth
Increase in size or biomass.

Investigation of functions of life in paramecium and Scenedemus.
Paramecium
Homeostasis: contractile vacuole fill up with water and expel through the plasma membrane to manage the water content.
Reproduction: asexual- mitosis.
Metabolism: most metabolic pathways happen in the cytoplasm
Growth: after consuming and assimilating biomass from food the paramecium will get larger until it divides.
Response: the wave action of the cilia moves the paramecium in response to changes in the environment, e.g. towards food.
Excretion: the plasma membrane controls the entry and exit of substances including expulsion of metabolic waste.
Nutrition: Heterotroph: food vacuoles contain organisms the paramecium has consumed.

Scenedesmus
Reproduction: asexual or sexual
Growth: asexual- small daughter colony cells and individual (adult size)
Response: light stimulus
Nutrition : photosynthesis- autotroph
Excretion: plasma membrane – oxygen diffused
Homeostasis: contractile vacuoles fill with water and expel through PM

Cell surface to volume is an important limitation to cell size.
Cell membrane is needed for transport of heat, nutrients & waste products in and out of the cell.
As cell size increases the surface area is no longer sufficient to allow these exchanges to occur at a rate that supports life.
A larger surface area ratio simply means that the cell can act more efficiently- For every unit of volume that requires nutrients or produces waste there is more membrane to serve it.
Larger organisms are composed more cells rather than larger ones.
Metabolism is function of volume of cell
Material exchange is function of surface area of cell]
Surface area serves volume

Calculate magnification of drawings and size of cell structures in light and electron micrographs and in drawings.
Ensure that all measurements are the same.

Explain how multicellularity results in the emergence of new properties.

Multicellular organisms have the capacity to complete functions that individual…