Biology Unit 1 SAC 1 Summary Notes PDF

Preview

Summary

The entire course/notes from the Unit 1 SAC. All notes...

Description

BIOLOGY SAC REVISION CHAPTER 1.1 – IMPORTANT PRINCIPLES IN BIOLOGY: Biology is the study of living organisms and is divided into many specialised fields covering aspects such as morphology, behaviour, physiology, origin, anatomy and distribution. CHARACTARISTICS OF ORGANISMS: - must meet all criteria  Move  Respond to stimuli  Reproduce  Are made of call  Grow  Are chemically complex  Take in nutrients  Are highly organised  Respire  Evolve over generations  Produce waste For example, the bark on the outside of a tree is dead, while the inside of the tree is living. ORGANISMS CONSIST OF CELLS: Cells are the basic building blocks of all organisms. The cell theory states that 1. All organisms are made up of cells (and the products of cells), 2. All cells come from pre-existing cells and 3. The cell is the smallest living organisational unit. There are many different types of cells, but there are some features common to all cells. These features being that all cells have a plasma membrane, all cells have a liquid cytoplasm, and all cells contain forms of genetic material.

COMMON REQUIREMENTS FOR LIFE: If an organism is going to survive in its environment, there are certain requirements that need to be met. All organisms need a source of energy, a source of nutrients and water, a means for removing waste and favourable environmental conditions.

EVOLUTION – ORGANISMS ARE ADAPTED TO THEIR ENVIRONMENT: Over time, species become structurally, physiologically and behaviourally adapted to the particular environment they live in. Adaptation is the result of natural selection (aka survival of the fittest) and leads to a species becoming well-suited to its lifestyle and environment.

CHAPTER 1.2 – THE MOLECULAR COMPOSITION OF ORGANISMS: The cells that make up living organisms are composed of key chemical elements. There are 92 naturally elements, however only 11 of these are found in organisms in more than trace amounts. Major elements are H, C, N and O (these elements make up 99% of an organism’s mass). Other elements are Na, Mg, P, S, Cl, K and Ca. Trace elements include Zn, Cu and Fe. Compounds produced by chemically combining different elements can be classified into two distinct groups. These groups are organic compounds and inorganic compounds. Organic compounds: are chemical compounds that contain C and H and sometimes O, N, P and/or S (they must contain C and H). They are called ‘organic’ because they were first discovered produced by organisms or found in them. Examples of these include carbohydrates, lipids (fats), proteins, nucleic acids and vitamins. Inorganic compounds: are chemical compounds that lack C (CO2 being the exception). Any compound that isn’t organic is considered inorganic. Examples of these include water, oxygen, minerals, carbon dioxide and nitrogen.

CHEMISTY DEFINITIONS: Atoms: the basic unit of all matter Elements: substances consisting of only one type of atom Molecules: are two (or more) atoms (that can be the same or different) held together by chemical bonds Compounds: consist of two (or more) different elements held together by chemical bonds. For example, sodium chloride (NaCl)

WATER: Life evolved in water and most organisms are composed or approx. 70-90% water. All chemical reactions in organisms occur in a watery environment. Water is cohesive (likes to stick together), which allows water to travel up very tall trees and support the weight of small insects due to the surface tension. Water has a high heat capacity which allows it to absorb a lot of heat with very little increase in temperature. This is excellent for temperature regulation. Water has a high heat of vaporisation which allows a lot of heat to be lost when water changes from liquid to gas. This is excellent for cooling the body (through sweating).

OXYGEN: Oxygen is needed to release energy from the food we eat (the process of cellular respiration). Due to this we need a constant supply of oxygen to keep out cells alive. C6H126O2 – 6CO2+6H2O+Energy. The air we breathe contains approx. 21% oxygen, but there is much less in water (as it doesn’t dissolve well), therefore aquatic organisms need a different ventilation system (gills) which can easily absorb the limited amount of oxygen in the water.

CARBON DIOXIDE: The air we breathe contains approx. 0.033% carbon dioxide, yet carbon is the key atom in all organic molecules. CO2 is taken in by plants and converted into glucose (simple sugar) via photosynthesis. 6CO2+12H2O – C6H12O6+6O2+6H2O. CO2 is returned back into the atmosphere via the decay of dead organisms and the end result of cellular respiration.

NITROGEN: The are we breath contains approx. 78% nitrogen gas (N2). Nitrogen is needed in large amounts because it is a key component of proteins. Unfortunately, plants and animals cannot use nitrogen in its gas form, so it needs to be converted into ions (NH4+, NH3-).  Special bacteria found in the roots of legumes (beans) can transform N2 into the unstable ions. This process is known as nitrogen fixation. Nitrogen is recycled through the environment via the nitrogen cycle.

MINERALS: Humans require more than 20 minerals to maintain health. Minerals are produced by the weathering of rocks. The ions produced enter the food chain by being absorbed into the roots of plants. Biologically important minerals include phosphorous – P, potassium – K, calcium – Ca (healthy bones, breastfeeding women have more), magnesium – Mg, iron – Fe (healthy blood, females more likely to be deficient), sodium – Na, iodine – I (salt, can get goitre if you don’t have enough), sulfur – S. Other minerals are only needed in trace amounts.

CHAPTER 2.1 – CELL THEORY, TYPES AND MICROSCOPY CELL THEORY:

Early biologists believed in the theory of spontaneous generation. Some examples of their beliefs included that maggots just arose from rotten meat, that frogs grew from water and that worms grew from mud. In 1859, Louis Pasteur played a key role in disproving this theory. His work was the foundation for cell theory. Pasteur showed that boiling and cooling milk or win killed the microorganisms in them, which is why the process (pasteurisation) is named after him. Another important consequence of Pasteur’s experiments is that it provided the scientific basis for the germ theory of infection which states that germs (pathogens) are present in the environment and can cause many different diseases. This understanding of germ theory led to the development of antiseptic procedures in medicine.

COMMON CELL FEATURES: There are many different types of cells, but there are some features that are common to all cells. These being, a plasma membrane (separates the internal and external environment), a cytoplasm (contains dissolved substances), genetic material which is often DNA (carries hereditary information and directs the cell’s activities) and ribosomes (synthesis proteins).

CELL TYPES – PROKARYOTIC AND EUKARYOTIC: There are two main types of cells, prokaryotic and eukaryotic.

PROKARYOTES:  

Are unicellular (like bacteria) and have a simple cell structure Are relatively small, with a large SA: V (surface area:volume) that allows for efficient exchange with the environment.

 



   



Lack membrane bound organelles (examples being mitochondria and a nucleus), although they do contain ribosomes Genetic material usually consists of a single, cellular DNA chromosome. This is known as genophore and is located in a region known as the nucleoid. Is attached to cell’s membrane by a region known as the origin. Some contain small rings of DNA (plasmids) in addition to their own DNA. Replicate independently of the bacterial chromosome. They can carry antibiotic resistant genes. They can be transferred to other bacteria. Have a cell wall surrounding their plasma membrane. Some have an additional capsule surround their cell wall adding further protection Many have flagella to assist movement (like sperm tail) Many have pili and cilia (hair-like) that assist with movement (both), the transfer of DNA between organisms (pili only) and attachment to surfaces (both) Can be found in all environments Include bacteria, cyanobacteria (photosynthetic bacteria) and archaea

BACTERIA:  

      

Fossil evidence dated at 3.5 billion years old confirms that bacteria were the first type of living organism on Earth Having a very diverse metabolism (all chemical reactions that occur in the body, not just digestion) which allows them to survive is a great range of habitats and conditions, however they prefer moderate temperature (20 C), moist environments, low [salt] ([] = concentration), plenty of sunlight and a large oxygen source Need little oxygen to survive as they can extract energy in different ways Can be photosynthetic or chemosynthetic (photosynthesis is powered by sunlight while chemosynthesis runs on chemical energy) Are an extremely important part of the ecosystem, acting as decomposers (generally involved in decomposition) Are used to make foods such as cheese, in medicine to create antibiotics, human insulin and other medicines and for pollution control to break down oils and plastics Have a cell wall containing murein (aka peptidoglycan – made of proteins and carbs) Gram-positive bacteria have a thicker (harder to kill) layer of murein to absorb and hold onto more stain eg staph and strep Gram-negative bacteria have a thinner layer of murein and doesn’t hold stain well eg cyanobacteria

ARCHAEA:  





Are not the most ancient group of organisms – evolved from eukaryotes Include extremophiles (love extreme locations) such as high and low temperature, upper atmosphere, very alkaline, very acidic (acidophiles), very salty (halophiles), no oxygen, without light, petroleum deposits Similar to bacteria, but they don’t have a cell well composed of murein (they have a pseudomurein) and are the only prokaryote that produces methane as a part of their metabolism Are different to other organisms due to the nature of lipids found in their membranes. These lipids keep the membrane functional throughout a wide range of conditions

EUKARYOTES:    

Larger and more complex than prokaryotes Have membrane bound organelles (nucleus, mitochondria, chloroplasts) Usually multicellular Include animal, plant, fungi and protist kingdoms

CELL SIZE AND CYTOLOGY:     

Cells may vary in size, but most can only be seen using a microscope Usually measured in micrometres (µm) (1000 micrometres in 1 mm) Cytology is the study of cells and the main took used by cytotechnologists is the microscope There are many different types of microscopes, but two of the main types are light microscopes and electron microscopes The type of microscope that a scientist will use in the laboratory depends on the size of the specimen that they are trying to observe and the detail that they require

LIGHT MICROSCOPE:

   

The most common form of microscope Uses light and a system of lenses to create a magnified image of the specimen (up to x1000) ADVANTAGES: cheap, easy and fast to use, image is in colour (natural or due to stain), able to observe living specimens DISADVANTAGES: the specimen must be thing enough to allow light to pass through, usually low resolution

FLOURESCENCE MICROSCOPY:   

Used to examine cells that are naturally or artificially fluorescent Fluorescence cells contain molecules that absorb light energy (UV) and them emit it as a different colour It the cells does not fluoresce naturally; dyes can be added that attach to the areas we want to investigate (used in DNA analysis)

CONFOCAL MICROSCOPY:  

Allows scientists to obtain ‘optical sections’ of a specimen without actually slicing through it These ‘optical sections’ can then be used to build detailed 3D images of the specimen

ELECTRON MICROSCOPY:   

Specimens are observed using electron beams rather than light. ADVANTAGES: extremely high magnification possible (up to x10,000,000), very highresolution images are produced. DISADVANTAGES: expensive and difficult to use, images are in black and white (can be coloured to highlight important features), cannot be used with live specimens

TRANSMISSION ELECTRON MICROSCOPY (TEM): 

Electron beams are passed through ultrathin sections of a specimen which makes very fine details of cellular structures are visible.

SCANNING ELECTRON MICROSCOPY (SEM): 

Electrons are bounced off a specimen that has been coated in a very thin layer of gold which provides us with high resolution images of the surface of a specimen, but not its internal details

AUTORADIOLOGY:  

Allows scientists to identify active organelles and/or the location of molecules within a specimen The specimen is injected with a radioactive substance, sliced into sections and placed onto a type of photographic film. The radioactive particles then emit energy which produces an image on the photographic film.

CHAPTER 2.2 – CELL ULTRASTRUCTURE: COMPARTMENTALISATION – THE ROLE OF ORGANELLE MEMBRANES:   

All cells (pro and eukaryotic) have a cell membrane surrounding their cytoplasm, but only eukaryotes possess specialised membrane-bound compartments within the cell This is known as cell compartmentalisation The membrane-bound compartments are known as organelles, which are subcellular structures that have their own specialised function within the cell (NOTE: not all organelles have a membrane ie ribosomes)



 

The membrane surrounding the organelles controls movement of substances in and out of the organelle and allows the organelle to have a different composition to its surrounding environment The benefits of this are include improved organelle efficiency (organelle can have its own enzymes and environmental condition that suit the role of the cell) Allows different (even incompatible) chemical reaction to occur at the same time and makes the cell less vulnerable to changes in the external environment

MEMBRANE AND NON-MEMBRANE BOUND CELLS:

FUNCTION OF ULTRASTRUCTURE OF ORGANELLES: 

The functions of organelles can be classified into 3 categories: synthesis and processing of proteins and lipids, energy transformation, storage and maintenance of cell structure

SYNTHESIS AND

PROCESSING OF PROTEINS AND LIPIDS: 



 





Nucleus: most of the DNA in eukaryotes is here, has a double membrane, however, the membrane contain pores which line to the cytoplasm to allow messenger RNA (mRNA) to exit the nucleus and find its way to the ribosomes (NOTE: copying DNA into mRNA is known as transcription). The most visible part of the nucleus is the nucleolus which is composed of DNA, RNA and proteins, ribosomes are made here Ribosomes: Tiny organelles made of 2 subunits that are only visible using an electron microscope that are made of proteins and ribosomal RNA (rRNA), are the site of protein synthesis, translate the code on mRNA into amino acids (the building blocks of proteins) and can be found free in the cytoplasm (produce proteins that will function within the cell's cytoplasm), attached to an endoplasmic reticulum (produce proteins that will be secreted out of the cell, packaged into organelles and/or inserted into cell membranes. Endoplasmic Reticulum: A network of membranous sacs and tubules (cisternae). Rough Endoplasmic Reticulum (RER): Has ribosomes attached, which synthesise proteins, proteins then enter the endoplasmic reticulum to be processed further. (Enzymes attach sugar molecules to the proteins glycoproteins), processed proteins are then transported to the Golgi apparatus for final packaging and export from the cell, RER's are abundant in cells that actively produce and secrete proteins eg pancreatic cells and cells that secrete digestive enzymes. Smooth Endoplasmic Reticulum (SER): Do not have ribosomes attached, synthesise lipid-based molecules such as phospholipids (found in membranes) and steroids (hormones), SER’s are abundant in steroid-secreting cells eg Testes, ovaries, adrenal glands. Golgi Apparatus (AKA - Golgi body / Golgi complex / Golgi): Composed of a stack of smooth, flattened membranous sacs (cisternae). When proteins produced by the RER reach the Golgi, they are packaged into vesicles and transported from one cisternae

to the next, being further modified along the way, the final product is then able to be transported out of the cell. The Golgi has two sides - a cis face and trans face. Cis face: the side facing the endoplasmic reticulum. Trans face: the side facing the cell membrane. Golgi are abundant in secretory cells, such as salivary glands.



    

 

Lysosomes: Specialised vesicles that digest (break down) unwanted matter, which can be thought of like the “recycling units” of the cells, scientists believe that they are only present in animal cells (this is under debate). Are formed when an enzymecontaining vesicle (released from Golgi) fuses with another vesicle containing unwanted matter such as a damaged organelle or foreign material. Small molecules that can be re-used diffuse back into the cytoplasm, but the rest stay within the lysosome or are released out of the cell. Summary: The instructions for proteins are coded for in DNA, which is found in the nucleus. A specific piece of DNA is copied (transcribed) into mRNA. mRNA leaves the nucleus via the pores found in the nuclear membrane and joins a ribosome. The ribosome will “read” the code on the mRNA to create a protein (translation). - Free ribosomes tend to create proteins that stay within the cell. - Ribosomes found on the RER tend to create proteins that are transported out of the cell. The RER creates and processes the protein and then transports it to the Golgi. The Golgi further modifies the protein and then packages it into a vesicle which allows the final product to be transported out of the cell.

ENERGY TRANSFORMATIONS: 

Mitochondria: The site of cellular respiration, have a double membrane, the inner membrane is heavily folded – known as the cristae, within the folded inner membrane is the mitochondrial matrix (fluid interior). Mitochondria have their own ribosomes (which are similar to those seen in bacteria), their own circular DNA – mtDNA (which is what you would find in bacteria), mitochondria reproduce independently of the cell that they are in via binary fission (again, like bacteria), the number of mitochondria in a cell is related to the cell’s energy needs, eg heart muscle cells contain thousands of mitochondria.



Chloroplasts: The site of photosynthesis, have a double membrane. Inside, there is a fluid matrix (liquid

interior) known as the stroma. Many enzymes needed to carry out photosynthesis are located here. Inside, there is a highly complex membrane system where chlorophyll is found which includes thylakoid – a flat, hollow disk, a stack of thylakoids is called a granum (pl. grana) and thylakoid lamellae join the grana together. Like mitochondria, chloroplasts have their own circular DNA – cpDNA, replicate independently of the cell they are in via binary fission and have their own ribosomes that are similar to those found in bacteria.

STORAGE AND CELL STRUCTURE: 

Vacuoles: Membrane-bound, liquid filled spaces that store materials, animal cells tend to have many, small and sometimes temporary vacuoles, plant cells tend to have one, large, permanent vacuole, provides structural support, lysosome functions may occur in some plant vacuoles (NOTE: the membrane of a plant cell vacuole is known as the tonoplast)



Plastids: Involved in the synthesis and/or storage of differen...