ALL BIO
L1: Understanding Living Things
Cells and Organisation
Energy use and Metabolism
Response to Environmental Changes
Regulation and Homeostasis
Reproduction
Growth and Development
Biological Evolution
Cells and Organisation
(small molecules, large molecules…)
Cells – smallest most basic unit of life (Organisms may be Unicellular or Multicellular)
Tissues – made up of different cells
Organs – made up of tissues
Organ Systems – organs working together
..To form a complex organism
Energy use and Metabolism
Organisms need energy to carry out activities
They obtain this energy source through food
The Sun is the source of energy for the world
Photosynthesis transforms solar energy into chemical energy for food
; Metabolism = Sum of all the chemical processes/reactions in an organism
The energy currency of life (energy-carrying molecule) =
Adenosine Triphosphate (ATP)
Shows the flow of energy, one trophic level down
Sun = Provides solar energy
Plants (Autotrophs) = Primary Producers, using solar energy from the sun to convert to chemical energy and store it into sugars, starch etc to form ATP using photosynthesis.
Herbivores = Primary Consumers, consumes primary producers
Carnivores = Secondary Consumers, consumes primary consumers (may be more in between)
Apex Predators = Top of the food chain
Metabolism
-> Catabolism + Anabolism
Catabolism is the breaking down of compounds to generate energy (ATP)
Anabolism is the building up of compounds which requires energy (ATP)
Response to Environmental Changes
Living things make changes in response to a stimulus in their environment
; Stimulus = Anything that causes a reaction or change in organism or any part of an organism
The stimulus can be chemicals, lights, sounds, touch, heat etc
To respond to a stimuli, the organism must first be able to detect that stimuli with the particular receptor (Correct receptor to the correct stimuli)
Stimulus - Receptor - Messenger - Effector (Causes the response) - Response
Rare medical condition: Cognitive Insensitivity to pain (CIP) is a condition that inhibits of person of their sensitivity to pain, making them unaware to danger
Regulation and Homeostasis
Regardless of what happens in the external environment, organisms must regulate their cells and body to maintain a stable internal environment through Homeostasis
(e.g of Parameters organisms would try to keep constant)
Temperature
Ionic balance
Acidity
Conc. of nutrients and waste
(The hypothalamus (part of the brain with its primary function is to maintain homeostasis) - One of the most important functions of the hypothalamus is to link the nervous system to the endocrine system via the pituitary gland)
Reproduction
All living things are able to reproduce to sustain life over many generations.
They can do this through
Asexual reproduction (1 parent produces offspring)
(e.g. Bacteria splits into two through binary fission)
Bacteria duplicates its DNA through DNA Replication, Bacteria is ready to split into two (Cytokineses), then splits into two identical daughter cells.
Sexual reproduction (2 parents produces offspring)
(e.g. Union of egg and sperm to produce embryo, Fertilisation which produces an embryo/zygote)
23 Chromosomes in the sperm, 23 Chromosomes in the egg
Humans have 46 Chromosomes (23 Pairs)
22 pairs of autosomal chromosomes and 1 pair of sex chromosomes.
Living things contain genetic material (Deoxyribonucleic Acid, DNA)
DNA contains biological information necessary for cell replication and maintenance
Male = XY
Female = XX
6. Growth and Development
Whether an organism is unicellular or multicellular, it grows and develops
In addition to getting larger, living things may develop and change as they grow
There is programmed growth – determined by the DNA
Some young organisms may look like their parents, although this may differ.
Inherited information carried by the genes control the pattern of growth and development of organisms. (Complete metamorphosis)
Chick (young) similar to chicken (Parent) // Caterpillar (young) not similar to butterfly (parent)
7. Biological Evolution:
Populations of organisms change over the course of many generations via
Genetic variation
Natural Selection
Evolution results in traits that promote survival
Birds like hawks have adaptations that allow them to catch fish from the water
Penguins have adaptations for swimming and surviving in very cold temperatures.
Common ancestor -> Changes over time
Basic foundational structures are present, but used in different ways to adapt to the environment
These traits are passed down to the next generation
Carbohydrates
Found in a variety of foods.
Provide the body with glucose, which is converted to energy.
Support bodily functions and physical activity.
Carbohydrate quality is important.
Healthy sources:
Unprocessed or minimally processed whole grains, vegetables, fruits, and beans.
Fibers – non-digestible (food for good gut bacteria).
Unhealthy sources:
White bread, pastries, sodas, and highly processed or refined foods.
Contain easily digested carbohydrates, which contribute to weight gain, interfere with weight loss, and promote diabetes.
3 different types of carbohydrates:
Monosaccharide: 1 sugar unit.
Disaccharide: 2 sugar units.
Polysaccharide: up to 1000s (oligosaccharide: 3-10 sugar units).
Most carbohydrates are composed of carbon (C), hydrogen (H), and oxygen (O) in a 1:2:1 ratio (CH2O)n.
Role: provide the major source of energy for daily activities or serve as structure materials.
Macromolecules: a very large molecule, such as a polymer which consists of many smaller structural units (monomer) linked together.
Monosaccharides
Saccharide comes from the Greek word 'sugar'.
Monosaccharide is the most basic form of carbohydrates.
Single sugar molecule.
Simple sugars: 3 to 7 carbons.
Most common are 5 or 6 carbons.
Aldehyde and Ketone functional groups are Carbonyl groups
Pentoses
Ribose (C5H10O5) and deoxyribose (C5H10O4)
Found in RNA and DNA.
Hexose
Glucose (C6H12O6).
Energy source of choice.
Cell breaks down glucose to generate ATP = respiration.
Examples of Hexoses (C6H12O6) include Glucose, Fructose, and Galactose
All are isomers with the same chemical formula, but the structures are different.
Different physical and chemical properties.
Between glucose and galactose: hydroxyl group (OH) / hydrogen (H) are rearranged differently.
Between glucose and fructose: carbonyl group (C=O) at different carbon.
Different ways to depict structures:
Ring
Linear
In aqueous solutions, glucose molecules, as well as most other five- and six-carbon sugars, form rings because they are the most stable form of these sugars under physiological conditions.
To form the glucose ring, carbon 1 bonds to the oxygen attached to carbon 5.
Two forms:
Alpha α (OH group downwards at carbon 1)
Beta β (OH group upwards at carbon 1)
Roles:
Energy Source: monosaccharides such as glucose are broken down to form ATP via cellular respiration.
Structural role as the backbone of macromolecules: Monosaccharides form the carbon skeletons which are raw material for the synthesis of other types of organic molecules, such as amino acids, nucleic acids & fatty acids.
Disaccharides
Two monosaccharides join together via a glycosidic bond to form a disaccharide in a dehydration/condensation reaction.
Examples include:
Maltose (Glucose + Glucose) can be found in malt from barley grains
Sucrose (Glucose + Fructose) found in table sugar
Lactose (Galactose + Glucose) found in milk sugar
Roles: Disaccharides need to be broken down to monosaccharides before being used as an energy source.
Polysaccharides
Many monosaccharides are linked together to form long polymers.
Some function as energy storage molecules.
Plants store glucose as starch.
Animals & fungi store glucose as glycogen.
Some function as structural components.
Cellulose in plant cell walls.
Chitin in crab, lobster, insect exoskeletons, etc.
Starch: Amylose and Amylopectin (Found in plants)
Both from plants
Both use a-glucose
Amylose contains alpha 1-4 glycosidic bonds while Amylopectin contains both 1-4 bonds and 1-6 bonds
Glycogen (Found in animals)
Glycogen: stored in the liver and muscles.
Glycogen is structurally quite similar to amylopectin.
Glycogen is more highly branched (8–12 glucose units between branches).
The branches are shorter.
Glycogen are energy reserves – it will be broken down to glucose units - for energy production.
Cellulose
β-glucose makes it so the shape is straight
Comparison between starch and cellulose:
Human enzymes that digest starch do so by hydrolyzing its α linkages are unable to hydrolyze the β linkages of cellulose due to the different shapes of these two molecules.
Chitin
Glucose monomers.
Modified form of cellulose with a nitrogen component (amyl group attached that consists of carbon and nitrogen).
Comparison between cellulose and chitin:
Cellulose: a structural polysaccharide found in the cell walls of plants; its glucose subunits are joined in a way that cannot be broken down readily. Cleavage of the links between the glucose subunits in cellulose requires an enzyme most organisms lack. Some animals, such as cows, are able to digest cellulose by means of bacteria and protists they harbor in their digestive tract, which provides the necessary enzymes.
Chitin: a type of structural polysaccharide found in the external skeletons of many invertebrates, including insects and crustaceans, and in the cell walls of fungi. Chitin is a modified form of cellulose with a nitrogen group added to the glucose units. When cross-linked by proteins, it forms a tough, resistant surface material.
Reducing Sugars
Any sugar that can be oxidised by mild oxidising agents such as Benedict's reagent are called reducing sugars.
Reducing sugars act as reducing agents.
Need a free aldehyde group or a free ketone group.
All monosaccharides are reducing sugars.
Some disaccharides are reducing sugars: maltose, lactose.
Sucrose is a non-reducing sugar. It does not contain any free aldehyde / ketone group for reducing properties.
Fructose / glucose in the sucrose molecule will not be able to open up into the linear form to provide a free ketone/aldehyde for reducing properties.
Proteins
Amino acids are composed of carbon, hydrogen, oxygen, and nitrogen. CHON
These elements are crucial for the structure and function of amino acids.
Some amino acids contain sulfur in their R side chain.
There are 20 amino acids, with 9 being essential, meaning the body cannot synthesize them and they must be acquired from the diet.
Essential amino acids are: HILL MTV TPHistidine
Isoleucine
Leucine
Lysine
Methionine
Threonine
Valine
Tryptophan
Phenylalanine
Monomers of proteins are amino acids.
Amino acids link together through peptide bonds.
Two amino acids bound together form a dipeptide.
Dipeptides can have biological activity, but they are more commonly seen as intermediates in protein digestion.
Many amino acids bound together in a long chain form polypeptides, which are polymers of amino acids.
Polypeptides are the precursors to functional proteins; they must fold correctly to function.
A protein is a biologically functional molecule consisting of one or more polypeptides, each folded and coiled into a specific three-dimensional structure.
The 3D structure is crucial for protein function, dictating how it interacts with other molecules.
Functions of Proteins
Proteins are necessary for many essential functions (8):
Structure: Hair, nails, collagen.
A protein called alpha-keratin forms hair and nails, and is the major component of feathers, wool, claws, scales, horns and hooves
Movement: Muscles.
Actin and myosin are the proteins enable all muscle movement
Oxygen transport: Hemoglobin in blood.
Hemoglobin binds to oxygen in the lungs and transports it to every part throughout the body.
Cell signaling:
Ion channel proteins control brain signalling by allowing small molecules into and out of nerve cells
Enzymes:
Enzymes in saliva, stomach and small intestine are proteins that help digest food
Antibodies – part of the immune system:
Antibodies are proteins that defend against foreign invaders like bacteria and viruses.
Cellular components involved in other processes: DNA replication, cell division, protein synthesis, etc.
Antibodies are proteins that defend against foreign invaders like bacteria and viruses.
Huge clusters of proteins form molecular machines that do a lot of the cells’ work, such as copying genes during cell division and making new proteins.
Amino Acids
Structure of Amino Acids
A central carbon is bonded to:
Hydrogen atom
Amino group (Purple)
Carboxyl group (Green)
Side chain or R group
Functional groups include:
Amino group (-NHH)
Carboxyl group double bond(-COOH)
Number of Amino Acids that make up living things
Living things use 20 amino acids to build thousands of proteins.
These amino acids can be combined in numerous sequences to create diverse protein structures.
These 20 amino acids differ based on their R group, which is variable.
R-Side Group
The R-side group determines the unique characteristics of a particular amino acid, affecting its functional role in a polypeptide.
The properties of the R-side group influence protein folding and interactions.
Types of R side groups:
Nonpolar (GAVLIMFP)
Polar (STCYNQ)
Electrically charged (ions) (DEKRH)
Peptides
Peptides are formed when amino acids are joined together by peptide bonds.
Peptide bonds are covalent bonds that link the carboxyl group of one amino acid to the amino group of the second amino acid
Formation of dipeptide: Dehydration synthesis reaction
Formation of two amino acids from dipeptide: Hydrolysis
Peptide = 2 or more amino acids linked.
A peptide bond is formed by a dehydration reaction between two amino acid monomers.
Water molecules are removed during the formation of a peptide bond (H2O).
The bond occurs between the carboxylic group of the first amino acid and the amino group of the second amino acid.
Polypeptides
Polypeptide = a polymer which is a chain of many amino acids joined by peptide bonds. (Can be from a few amino acids to thousands of amino acids long)
The sequence and properties of amino acids in a polypeptide determine its structure and function.
Each specific polypeptide has a unique linear sequence of amino acids, known as the primary sequence.
The primary sequence is genetically determined and critical for the protein's function.
The sequence in which it is organized/bonded is very important for the protein to function properly.
Even a single amino acid change can alter the protein's function.
Protein Structure
There are four levels of protein structure: Primary, Secondary, Tertiary, and Quaternary.
Primary Structure
Primary structure refers to the amino acid sequence.
It is the linear order of amino acids, from the amino terminus (-NHH) to the carboxyl terminus (-COOH).
The primary structure of a protein is a linked series of amino acids with a unique sequence that dictates its properties
The primary structure is not a random linking of amino acids but is determined by inherited genetic information.
The precise sequence in the primary structure determines the secondary structure (How it folds).
Any change in the sequence can alter the structure and function of the protein.
Secondary Structure
Secondary structure involves the folding of the polypeptide chain into alpha helices or beta-pleated sheets.
These structures are stabilized by hydrogen bonds between the amino and carboxyl groups of the peptide backbone.
Alpha helix: repeated coils held together by hydrogen bonds.
Beta-pleated sheets: two or more strands of the polypeptide chain lying side by side (called β strands) are connected by hydrogen bonds between parts of the two parallel polypeptide backbones.
Tertiary Structure
The tertiary structure is the folding of secondary proteins.
It gives the overall 3D shape complex.
Bonds involved between side chains include:
Disulfide bridge
Hydrogen bonds
Hydrophobic interactions
Ionic bonds
Shape is important for the function of the protein, e.g., enzyme specificity.
The active site of an enzyme is shaped to bind a specific substrate.
Quaternary Structure
The Quaternary Structure: Some proteins are made up of multiple polypeptide chains. When several polypeptide chains (subunits) come together, they can form a structure known as a quaternary protein.
These subunits can be identical or different.
May bind with other components, such as heme.
Heme is a non-protein component required for the function of some proteins.
E.g., hemoglobin consists of four polypeptide chains.
(Orange circles = Heme)
Protein Shape (Denaturation)
A polypeptide chain of a given amino acid sequence can spontaneously arrange itself into a three-dimensional shape, determined and maintained by the interactions responsible for secondary and tertiary structure.
Protein structure can be affected by pH, temperature, and salt concentration.
Changes in these conditions can disrupt the bonds and interactions that stabilize the protein structure.
This can cause a loss of structure, leading to a loss in function.
This is known as ‘denaturation’: Protein unravels, losing its 3D shape
Lipids
Introduction to Lipids
Lipids are a diverse group of nonpolar macromolecules composed of carbon, hydrogen, and oxygen. CHO
Some also contain nitrogen, sulfur, or phosphorus.
They are important for cellular processes and as part of cell structure.
Three biologically important types are fats, steroids, and phospholipids.
Lipids are hydrophobic and do not dissolve in water but dissolve in organic solvents like chloroform and benzene.
Example of lipids that play an important role in cellular function include:
Fats (Triglycerides)
Steroids (4 fused carbon rings)
Phospholipids (Phosphate head instead of third fatty acid)
Fats (Triglycerides)
Triglycerides are constructed from three fatty acids and one glycerol molecule.
Types: Saturated, Unsaturated, Trans
Formed via an ester linkage, a bond formed by a dehydration reaction between a hydroxyl group and a carboxyl group. Forming a total of 3 water molecules (3H20)
Fatty acids are long hydrocarbon chains with a carboxylic group; the three fatty acids in a triglyceride can be different or identical.
Saturated and Unsaturated Fats
Saturated fatty acids have carbons bound to as many hydrogens as possible with no double bonds, allowing them to pack tightly and be solid at room temperature. Examples include meat (beef, lamb, pork) and butter. High consumption can lead to cardiovascular disease.
Unsaturated fatty acids have one or more carbon-to-carbon double bonds; more double bonds mean a higher degree of unsaturation. The double bonds create kinks in the structure, preventing adjacent fat molecules from packing together. They tend to be liquid at room temperature and are referred to as oils, such as vegetable oils (corn oil, sunflower oil) and fish fats.
Monounsaturated fats have one double bond.
Polyunsaturated fats have more than one double bond.
a) Saturated fatty acids b) Unsaturated fatty acids
Cis and Trans Fats
Natural unsaturated fatty acids are in the cis configuration
Cis: Two hydrogen atoms on the same side of the double bond (Has a kink)
Trans: Two hydrogen atoms are on the opposite side of the double bonds (Very small amounts occur naturally as trans, occur industrially through hydrogenation) (Has no kink)
Hydrogenation converts healthy unsaturated fats to fully saturated fats.
Most trans fat is formed through hydrogenation that adds hydrogen atoms to unsaturated fats
High intakes of saturated and trans fats may raise blood cholesterol and increase the risk of heart disease and stroke.
Importance of Fats
Essential fatty acids (EFA), omega-3 and omega-6, are required for important body functions and must be obtained through diet.
Fats serve as a long-term energy source, with the average-sized person storing about 16 kg of fat compared to 0.5 kg of carbohydrates as glycogen.
Carbohydrates: Short-term rapidly available energy
Fats: Long-term energy source
Fats provide insulation, such as a layer of fat beneath the skin.
They are precursors for cell membranes and contribute to eye and brain health and development.
Insulation: A layer of fat beneath skin
Sources of Essential Fatty Acids
Fish, shellfish, flaxseed, soya oil, canola oil, leafy vegetable oil, chia seeds, pumpkin seeds, sunflower seeds, and walnuts.
Steroids
Steroids are characterized by a carbon skeleton consisting of four fused rings, and are insoluble in water.
Cholesterol is the most important steroid, a component of animal cell membranes that provides rigidity and is largely absent from plant cells.
Vegetable oils are considered cholesterol-free.
Cholesterol is a precursor for synthesizing steroid hormones like testosterone, progesterone, and estrogen.
The body (liver) can make cholesterol (85%), with the remainder (15%) coming from the diet.
Phospholipids
Phospholipids are constituents of cell membranes and form the bulk of the plasma membrane.
Water-soluble, hydrophilic, polar phosphate head.
Water-insoluble, hydrophobic, nonpolar fatty acid tail.
Instead of a third fatty acid chain, the 1st block is the Phosphate head.
Nucleic Acids
Introduction to Nucleic Acids
Nucleic acids include Deoxyribonucleic Acid (DNA) and Ribonucleic Acid (RNA).
Nucleic acids composed of carbon (C), hydrogen (H), oxygen (O), nitrogen (N) and phosphorous (P). CHONP
DNA stores genetic information.
RNA is involved with protein synthesis.
Nucleic acids are macromolecules that exist as polymers called polynucleotides.
DNA: Double-helix, RNA: Single-Helix
Nucleotides
Monomers of nucleic acids are nucleotides which consist of phosphate + sugar (pentose, 5 carbon) + base.
DNA contains deoxyribose sugar (H atom at carbon 2).
RNA contains ribose sugar (OH at carbon 2).
5 nitrogenous bases:
Purines (single ring structure): PuGA
Guanine (G)
Adenine (A)
Pyrimidines (double ring structure): PyCUT
Cytosine (C)
Uracil (U)
Thymine (T)
DNA: Adenine, Thymine, Guanine, and Cytosine.
RNA: Adenine, Uracil, Guanine, and Cytosine.
Polynucleotides
Forming a polynucleotide involves a dehydration reaction, releasing 1 molecule of water.
Adjacent nucleotides are joined by phosphodiester linkage, which consists of a phosphate group that links the sugars of two nucleotides.
The phosphate group attached to the 5’ carbon of one nucleotide forms an ester bond with the hydroxyl on the 3’ carbon of the next nucleotide.
This bonding results in repeating patterns of sugar-phosphate units called the sugar-phosphate backbone. (Nitrogenous bases are not part of backbone)
Deoxyribonucleic Acid (DNA)
Double helix structure.
Deoxyribose sugar.
Complementary base pairing: Purine (PuGA) pairs with Pyrimidine (PyCUT)
(Adenine = Thymine; Guanine = Cytosine).
Via hydrogen bonding.
Antiparallel / reverse direction.
Double helix structure is important for DNA role because:
It is very long and stores lots of information.
The sugar-phosphate backbone makes the molecule more stable.
The double helix makes it stable as the base pairs are on the inside and so are less likely to get damaged.
the bases are held together by weak hydrogen bonds allowing the molecule to ‘unzip’ (separate) easily when it replicates
complementary base pairing allows the molecule to replicate itself accurately.
The sequence of bases allows it to carry coded information for making proteins.
Involved in Storing Genetic Information
Ribonucleic Acid (RNA)
Single chain structure.
Ribose sugar.
Bases: Adenine, Guanine, Cytosine, and Uracil.
Three types:
ribosomal RNA (rRNA)
messenger RNA (mRNA)
transfer RNA (tRNA).
Involved in Protein Synthesis
Central Dogma of Biology
(Dogma: Set of rules)
DNA → RNA → Protein via transcription and translation.
Genomic DNA is a blueprint set of instructions.
Messenger RNAs (mRNAs) are the specific, short-lived, gene transcripts.
Proteins perform structural and catalytic functions.
Classification of Living Things
Introduction
Taxonomy is the science of naming, describing, and classifying organisms and includes all plants, animals, and microorganisms of the world.
3 Domains and 6 Kingdoms.
Prokaryotes and Eukaryotes
There are 1.3-1.8 million of known species of organisms.
In 1969, Whitaker proposed five kingdoms: Plantae, Animalia, Fungi, Protista, and Monera (bacteria).
Hierarchy of Taxonomic Groups
Domain → Kingdom → Phylum → Class → Order → Family → Genus → Species
Eukarya is a domain.
Plantae is a kingdom.
ExamplePlantae → Angiospermae → Dicotyledonae → Rosales → Rosaceae → Rosa → Rosa gallica
Domain Dumb
Kingdom King
Phylum Philip
Class Came
Order Over
Family For
Genus Ginger
Species Soup
Binomial Nomenclature
The modern system of naming of organisms is known as binomial nomenclature, and uses two words for name (genus & species).
Latin or Greek.
Italicized in print.
Capitalize genus, but NOT species.
When writing in pen and paper, genus and species would be underlined
Example: Ursus arctos (Brown bear).
3 Domains
Archaea, Bacteria, and Eukarya.
Domain Archaea; Kingdom Archaebacteria
Archaebacteria are prokaryotes that have diverged from bacteria.
They are more closely related to eukaryotes than to bacteria.
Biochemically and genetically, they are as different from bacteria.
Found in extreme and severe environments such as volcanoes, hot springs, salty lakes, and acidic environments.
e.g. Thermus aquaticus
Domain Bacteria; Kingdom Eubacteria
Contains a single kingdom, Eubacteria.
Bacteria are prokaryotes
Prokaryote word originates from Old Greek
Pro: Before or incomplete
Karyon: Nut or kernel, referring to the cell nucleus.
Lack of membrane-bound nucleus and organelles.
Bacteria are found in practically every environment on Earth.
Domain Eukarya (All Eukaryotes)
Includes Kingdoms Plantae, Animalia, Fungi, and Protista.
Kingdom Plantae
Plants contain a pigment - chlorophyll that allows plants to make their own food.
Plants are complex multicellular autotrophs.
Autotrophs: capable of synthesizing its own food from simple inorganic substances; photosynthesis
Plants also release oxygen gas to the atmosphere.
Kingdom Animalia
Animals are complex multicellular heterotrophs.
Heterotrophs: dependent on complex organic substances for nutrition because it cannot synthesize its own food.
Animals are able to move rapidly in complex ways.
Movement enables animals to avoid predators and to look for food.
Kingdom Fungi
Unicellular (yeast) and multicellular (bread mould, mushrooms etc).
Unique feature: hyphae & mycelium (furry appearance).
Fungi cannot photosynthesise.
Non motile (cannot move).
Enzymes are secreted out of the cell to digest the food outside the cell, and then these nutrients (eg sugars), are absorbed through their cell walls.
Many fungi live on dead organisms.
Example: Penicillium sp.
Dots: Spores Strands: Hyphae
Kingdom Protista
Protista is the most diverse group of the six kingdoms.
They are eukaryotes that are not fungi, plants, or animals.
Protists live in almost any environment that contains liquid water.
Many are unicellular.
Most are microscopic, but some are large.
Algae are plant-like protists.
Protozoans are animal-like protists.
Slime and water molds are fungal-like protists.
L9) Categorization of Cells
Content
Cell Theory
What are cells?
Categorization of Cells
Type of organisms
Cell number
Cell size
Cell shape
Cell Theory (CT)
All living things are composed of one or more cells.
Cells are organisms' basic units of structure and function.
Cells come only from existing cells.
Discoveries
Matthias Schleiden
In 1838, the German Botanist discovered that all plants were composed of cells. (CT 1&2)
Theodor Schwann
In 1838, the German zoologist discovered that all animals were composed of cells. (CT 1&2)
Rudolph Virchow
In 1855, the German physician was doing experiments with diseases when he found that all cells come from other existing cells.
Virchow believed that outside stimuli affected cells and diseased cells came from already diseased cells. (CT 3)
Other Discoveries
Cells were discovered much earlier.
The first person to see a cell was Robert Hooke.
He used a very primitive microscope.
He saw cork cells under the microscope and then called them "cells”.
The first person to see living cells was Anthony Van Leeuwenhoek.
Saw Sperm, bacteria
Structures in Common
Structures which have the following three things in common
DNA (except RBC)
Cell membrane / Plasma membrane
Cytoplasm
Characteristics of Living Things - Cells and Organisation (Definition)
All living things have an internal order.
The simplest/basic unit of life is the cell
All important processes to sustain life happens in a cell
A cell is a membrane-covered structure that contains all of the materials necessary for life.
Categorization of Cells
Type of Organism
Cell Number
Cell Size
Cell Shape
Type of Organism
Prokaryote
Eukaryote (Kingdoms Protista, Fungi, Animalia, Plantae)
Cell Number
Unicellular (Bacteria, Protozoa, Yeast)
Bacteria Protozoa Yeast
Multicellular (Plants, animals, fungi (mold))
Cell Size
Smallest known cells: Mycoplasma
0.0001 mm in diameter.
10,000 mycoplasmas in a row are only as wide as the diameter of a human hair
Largest known cells: nerve cells that run down a giraffe's neck
these cells can exceed 3 m in length
In humans
Smallest cells: Red blood cells (0.00076 mm)
unique because no DNA in circulatory RBCs
Largest cells: liver cells (10 times bigger than RBCs)
*About 10,000 average-sized human cells can fit on the head of a pin.
Cell Shape
Prokaryotes
Cocci (sphere shape)
Bacilli (rod shape)
Eukaryote
Plant Cell: boxes/cubes
Animal Cell: different shapes
Skin cells: flat and tightly packed
Nerve cells: elongated, tentacle-like extensions and dendrite
Red blood cells: biconcave, flattened disc
Shape of a cell is typically tailored to the FUNCTION of the cell.
Skin cells (surface) -> flat -> tightly packed -> protect the underlying tissues from invasion by microorganism.
The cells on the surface are constantly falling off (shedding): this is called desquamation
Nerve cells -> elongated and extended -> enable it to connect to several other nerve cells in order to send and receive messages rapidly and efficiently.
Red blood cells -> biconcave (both sides of the cell's surface curve inward like the interior of a sphere), flattened disc
Main function: transport O2 from lungs to cells in body; CO2 from cells to lungs
Biconcave & flattened disc shape:
gives flexibility to RBC’s. Allow RBCs to manoeuver/squeeze through tiny blood vessels
increases surface area for gaseous exchange
Other features of RBC that help with its function: small size to squeeze through blood vessels; No nucleus – to increase flexibility and increase space for haemoglobin
Components of the Cell (1) Prokaryote
Topics
Structure of a prokaryotic cell
Components of a prokaryotic cell
cell wall: gram positive/ negative
cell membrane
cytoplasm
chromosomal DNA
ribosome
flagella
capsule
pili
plasmid
Revision
The simplest basic unit of life is the cell
Cell
Prokaryote (From Archaea, Bacteria)
Eukaryote (Kingdoms Protista, Fungi, Animalia, Plantae)
Components of a Prokaryotic Cell (Focusing on bacteria)
Prokaryotes lack membrane bound organelles, the only organelle is the ribosome (found-free moving)
Cell Wall
Cell/Cytoplasmic Membrane
Cytoplasm
Chromosomal DNA
*Ribosome
Flagella (tail)
Capsule
Pili (Hair)
Plasmid
Cell Wall
Unique structure which surrounds the cell membrane (protective) and maintains the cell's characteristic shape.
Key component is Peptidoglycan.
Contains tiny pores that:
Allow water and dissolved substances (e.g. oxygen) to flow into the cell and
Allow wastes to flow out
Not a regulatory structure, will let molecules small enough to flow through.
NAM (N-acetylmuramic) has an amino acid tetrapeptide chain.
NAG (N-acetylglucosamine)
The peptide interbridge links the backbones together
In bacteria, it is classified as gram positive cell wall and gram negative cell wall.
Gram positive cell wall contains Teichoic acid to increase rigidity/strength of cell wall.
During the gram staining procedure, the cells will stain purple
Peptidoglycan layer is quite thick
Gram negative cell wall does not contain teichoic acid
Peptidoglycan layer is quite thin
Has an additional layer called the outer membrane
Contains lipopolysaccharides
Periplasmic space is where the peptidoglycan is
NAM (N-acetylmuramic) has an amino acid tetrapeptide chain.
NAG (N-acetylglucosamine)
The peptide interbridge links the backbones together
During the gram staining procedure, the cells will stain pink
Comparison between Gram positive and Gram negative bacteria cell walls
Cell membrane / Cytoplasmic membrane / Plasma membrane
Thin membrane found on the inner surface of the prokaryotic cell wall.
Separates the cell’s contents from its surrounding fluids.
Composed of two layers of flexible (fluid like) lipid molecules (i.e. phospholipid bilayer), interspersed with proteins.
Selectively permeable
Allows easy diffusion of small molecules (water, oxygen and carbon dioxide).
Regulates passage of larger molecules (amino acids and sugars).
Contains specialized transport proteins which form an intricate system of pumps and channels which regulate what goes in and out of the cell.
Cytoplasm
Enclosed by Plasma membrane / Cell membrane
Semi-fluid (gooey, liquid substance) that fills the cell.
Composed of about 65 % water (Favorable conditions for many biochemical reactions). The rest is made up of proteins, vitamins, ions, nucleic acids, amino acids, sugars, carbohydrates and fatty acids.
Chromosomal DNA
Found within the cytoplasm of all prokaryotes.
Is located in a region of the cell called the nucleoid (not enclosed in the nucleus which is found in eukaryotes).
Prokaryotes have a single circular chromosome.
The chromosome lacks the associated proteins (histones) found in eukaryotes; it consists of only DNA.
Ribosomes
The only organelles in prokaryotic cells and are located in the cytoplasm.
Referred to as the cell’s protein factories (i.e. sites of protein synthesis).
Prokaryotic ribosomes have 2 subunits which assemble together during protein synthesis.
S=Svedberg units; sedimentation rate
Small subunit 30S+ large subunit 50S = 70S ribosome
rRNA = ribosomal ribonucleic acid
Flagella
Main role is locomotion.
Also serves as a sensory unit so that bacteria can “choose” to move forward towards a favorable environment or away from a hostile environment.
Capsule
Thick covering of the cell wall that provides protection from white blood cells, chemicals and dehydration.
Sticky nature allows it to adhere to other cells or surfaces.
Pili (Plural Pilus)
Hair-like projections surrounding the outer layer of the cell.
Enables bacteria to stick-on surfaces or latch-on other cells.
Also involved in a process called conjugation where genetic material is transferred from one bacterium to another.
Plasmid
Small, circular double-stranded DNA.
Referred to as extra-chromosomal DNA – different from chromosomal DNA.
Able to replicate autonomously.
Can be single or multiple copies.
Contain certain genes beneficial to the bacteria e.g antibiotic resistance.
Fertility plasmids – contain genes that code for sex pilus & enzymes required for conjugation.
Summary
Although simple in construction, prokaryotic cells have a great range of biochemical reactions.
The extraordinary biochemical diversity of prokaryotic cells is manifested in the wide- ranging lifestyles of bacteria.
Habitats include polar ice, deserts, volcanic regions and deep regions of the ocean under great pressure.