Biology IB SL

The Cell Theory

- cells are the basic unit of life
- all organisms are composed of one or more cells
- all cells come from pre-existing cells
- cells have an energy release system that powers its metabolism
- all cells are surrounded by a plasma membrane
- contains enzymes which allows metabolic processes to occur

cell wall (prokaryotes + eukaryotes)

prokaryotes: made of peptidoglycan
eukaryotes: cellulose or chitin

cell wall function

protection, structural support

cytoplasm

where metabolism occurs

ribosomes (prokaryotes + eukaryotes)

prokaryotes: 70S
eukaryotes: 80S

ribosomes function

protein synthesis

nucleoid region

- prokaryotes only
- contains naked DNA
- contains circular chromosomes

flagellum

- prokaryotes only
- used for locomotion
- only in some bacteria

pillus

- prokaryotes only
- allows adhesion to other prokaryotes or surfaces and exchange of genetic material
- only in some bacteria

plasma membrane

- eukaryotes only
- composed of phospholipids
- controls what enters and exists cell

nucleus

- eukaryotes only
- contains chromosomes with histone proteins
- has a double membrane that allows mRNA to enter

chromosomes

prokaryotes: only 1, circular, naked
eukaryotes: composed of DNA wrapped around histone proteins

mitochondria/mitochondrion

- eukaryotes only
- produces ATP through respiration

lysosome

- eukaryotes only
- specialised vesicles containing enzymes
- digestion of large molecules

rough endoplasmic reticulum (rough ER)

- eukaryotes only
- has ribosomes attached
- site of protein synthesis
- transports proteins to Golgi apparatus

smooth endoplasmic reticulum (smooth ER)

- eukaryotes only
- without ribosomes attached
- lipid synthesis and detoxification

Golgi apparatus

- eukaryotes only
- modifies and packages proteins to be exported from cell

cytoskeleton

- eukaryotes only
- composed of protein microtubules
- involved in maintaining cell shape, moving organelles and nuclear division

prokaryotes vs eukaryotes

prokaryotes:
- no nucleus, only nucleoid region
- singular, circular chromosomes
- naked DNA
- cell wall made of peptidoglycan
- 70S ribosomes
- no membrane bound organelles

eukaryotes:
- contains nucleus
- many chromosomes composed of DNA wrapped around histone proteins
- contains membrane-bound organelles
- cell walls made of cellulose or chitin
- contains membrane-bound organelles

both:
- cytoplasm
- plasma membrane
- cell wall

no membrane organelles

- ribosomes
- proteasome
- centriole
- nucleolus
- microtubules

single membrane organelles

- rough ER
- smooth ER
- vesicle
- lysosome
- vacuole
- Golgi apparatus

double membrane organelles

- nucleus
- mitochondrion
- chloroplast
- chromoplast
- amyloplast

amyloplast

- eukaryotes only
- plastids found in plants
- involved in production and storage of starch molecules

choromoplast

- eukaryotes only
- plastids found in plants
- developed from chloroplasts
- acts as colour pigment in fruit

advantages of organelle separation

- large surface area of membrane for exchange processes to occur
- organelles and contents can be moved around easily
- conditions within cells are maintained
- enzymes can be concentrated within organelles
- greater efficiency of processes

stem cell

undifferentiated cells which have an unlimited capacity to divide and can divide into specialised cells

totipotent stem cell

stem cells that can divide and produce all the differentiated cells in an organism

pluripotent stem cell

a stem cell that can differentiate into any cell type found in an embryo, but not extra-embryonic cells

multipotent stem cell

a stem cell that can differentiate into a range of closely related cells

blastocyst

a ball of cells that forms in the early stages of pregnancy

morphogen

a group of gene-regulating chemicals, that determines the specialized cell that develops through different concentrations

stem cell niches

specific locations in the body where adult stem cells reside e.g. bone marrow, hair follicles

diffusion

passive transport of molecules/particles from a region of high concentration to a region of low concentration through a semipermeable membrane

active transport

movement of particles from region of low concentration to region of high concentration using energy from respiration via protein pumps

physical properties of water

- buoyancy
- viscosity
- thermal conductivity
- specific heat capacity

isotonic solution

a solution that has the same water potential as another solution/inside the cell

hypertonic solution

a solution that has lower water potential as another solution/inside the cell

hypotonic solution

a solution that has higher water potential as another solution/inside the cell

osmoregulation

maintenance of constant osmotic pressure in the fluids of an organism by the control of water and salt concentrations

condensation reaction

the process that allows monomers to form polymers by releasing a water molecule

hydrolysis reaction

the process that breaks bonds in polymers that revert it to monomers, where a water molecule is added

buoyancy

upward force exerted by a fluid onto an object immersed in fluid

viscosity

the measure of a fluid's resistance to flow

thermal conductivity

a measure of a material's ability to conduct heat

specific heat capacity

the energy required to raise the temperature of 1g of a substance by 1 K (or 1°C)

solvent

substance that dissolves a solute to form a solution, water can dissolve a substance if the forces of attraction between the ion and water molecule is greater than the oppositely charged ions

solute

dissolves by interacting with solvent particles through intermolecular forces (e.g hydrogen bonding)

hydrogen bond

formed between water molecules due to weak electrostatic attraction between slightly positively charged hydrogen and slightly negatively charged oxygen of another water molecule

homogeneous mixture

mixture with uniform composition and evenly distributed throughout, formed when a solute is

hydration shell

the sphere of water molecules around each dissolved positively charged ion with the negatively charged oxygen of the water molecule being attracted to the ion

osmosis

passive movement of water molecules from hypotonic to hypertonic across a semi permeable membrane that only water but not solutes can move across

plasmolysis

plant cell placed in hypertonic solution with higher solution concentration, the net movement of water molecules flow out of the cell causing it to shrink

crenation

animal cell placed in hypertonic solution with a higher solute concentration, the net movement of water molecules flow out of the cell causing it to shrink

cytolysis

since animal cells have no cell walls, in a hypotonic solution the plasma membrane bursts as the net movement of water flows into the cell increasing internal pressure

contractile vacuole

when unicellular organisms without cell walls are placed in hypotonic solutions, this helps remove excess water from the cell and prevents cell lysis and helps maintain osmotic pressure

Turgor pressure

when internal pressure of a cell increases this is exerted by the cytoplasm against rigid cell wall to prevent bursting and preserve turgid shape of cell

Macromolecules

large molecules made of small monomers by condensation reactions

monosaccharide

biological molecules that serve as a source of energy and can't be broken down by hydrolysis

glycosidic bond

bond between adjacent monosaccharides (carbohydrate molecules)

Carbohydrates

family of molecules with same 3 atoms that conform to the formula Cn H2n On

Ribose

Pentose sugars with 5 carbons + used to form DNA and RNA

Glucose

common monosaccharide with 2 isomers, is soluble due to polarity, can be oxidised, and can release energy

Starch

polysaccharide of long chained insoluble glucose molecules that are forms of glucose storage in plants, broken down by hydrolysis when a plant needs glucose

Amylose

long liner chains of alpha glucose monomers linked by 1,4 glycosidic bonds

Amylopectin

long branching chains of alpha glucose, branching structure allows for complex structure and compact coiling for efficient glucose storage

Glycogen

highly compact, coiled, and branched insoluble polymers of glucose that act as storage for animals, linked by 1,4 glycosidic bonds + structure allows for efficient storage of glucose, stored mainly in liver and muscle to maintain blood glucose levels and provide energy for contraction

Cellulose

unbranched linear polysaccharide chains from beta glucose molecules, stored in the cell wall of plants, alternates in orientation with every second beta glucose molecule being flipped

Microfibrils

unbranched chains of cellulose molecules grouped into bundles and held together by hydrogen bonding between each chain, giving the cell walls has high tensile strength to maintain structure of cell, and strong lattice shape from hydrogen bonds

Glycoproteins

integral proteins on phospholipid bilayer with one or more chain of carbohydrate attached

cell to cell recognition

glycoproteins act as markers on cell surfaces to identify and interact with other cells

receptors

glycoproteins can receive signals from other cells on the environment

cell to cell adhesion

glycoproteins can interact with other glycoproteins on neighboring cells to form tissues

Ligands

ion molecules that bind to glycoprotein receptor to initiate signalling pathways

cell to cell communication

neurotransmitters can bind to glycoproteins for _______

ABO blood group system

system based on the presence of specific glycoproteins (A or B) on red blood cells since the immune system doesn't produce antibodies against antigens present in their own red blood cell, so with incompatible antigens immune system reacts by clumping red blood cells, type O = universal donor

Benedict's solution

used to test for reducing/simple sugars, the solution is warmed in a test tube with the sample and changes color from blue to green/yellow/orange/brick red depending on the concentration

fatty acid

long hydrocarbon chains with little to no oxygen and has a carboxylic acid group at one end

Lipids

organic compounds with fatty acid chains that are non polar with low water solubility, making them hydrophobic, repelling water and making the, insoluble in aqueous solutions but dissolvable in non polar solvents

Triglyceride

1 glycerol forms an ester bond with 3 fatty acids formed by condensation reactions with a water molecule being released each time a fatty acid joins with glycerol

ester bond

a bond between glycerol and fatty acid chains that releases water

phospholipid

formed through condensation reactions with 2 fatty acid chains, 1 glycerol phosphate molecule, ester bond forms between glycerol and fatty acid chains releasing water

Saturated fatty acid

no double bonds between carbons in fatty acid chains = straight and linear which allow fatty acids to pack tightly together, therefore they are solid at room temperature (e.g animal products), relatively higher melting points

Unsaturated fatty acids

one or more double bond between carbon atoms which bend the fatty acid chain, preventing molecules from tightly packing together, therefore liquid at room temperature (e.g oil), relatively lower melting points

Cis and Trans Unsaturated Fatty Acids

cis = hydrogen atom around double bond is located on the same side, giving the chain a less linear structure, trans = hydrogen atoms around double bond on opposite sides, giving it a more linear structure making it more rigid

endotherms

animals that rely on metabolic reactions to generate heat and maintain internal body temperatures, they require a constant supply of energy of food and store fat in adipocytes as liquid droplets, can be broken to ATP

fats as insulators

animals store fats and oils, (triglycerides) in adipose tissue under skin, since fats have a lower thermal conductivity they act as insulators which help endotherms maintain constant body temperatures

steroids

group of naturally occuring hormones with characteristic shape of 4 carbon rings and a hydrocarbon chain, are hydrophilic and can diffuse directly through the phospholipid bilayer

Testosterone and oestradiol

steroids vital for the development of the reproductive system, hydrophobic nature of steroids allow them to pass through the phospholipid bilayer and dissolve with fatty acid tails, giving cells a faster response to the presence of steroids, allowing signals to occur efficiently

amino acids

monomers that make up proteins, exists in 20 unique forms, all have the same structure but unique r group side chain

peptide bond

when amino acids through condensation reactions a _______ forms between the carboxyl group of one amino acid and the amino group of another, water molecules are released as a by product

polypeptides

have any number of amino acids that occur in any order so no. polypeptides = infinite, when genetic codes of DNA are transcribed to mRNA, the mRNA is translated by ribosomes to polypeptide chains

essential and non essential amino acids

11 non essential amino acids that humans can synthesize naturally, 9 essential amino acids that must be consumed in diets (typically meat and animal products that have all 9, most plant sources don't have all so range of plant protein sources eaten to ensure all essential amino acids consumed)

Nucleic acids

chains of repeating monomers called nucleotides joined together through polymerisation, makes up genetic material for life found in chromosomes and contains information for growth and development of cells

Nucleotides

2 types of nucleic acids in living organisms; DNA and RNA which are long chains of nucleotides with a phosphate group, pentose sugars, and a nitrogenous base

phosphodiester bond

the covalent bond between a phosphate head of one nucleotide attaching to the bottom left of a pentose sugar, releasing 1 water molecule in each strand of DNA and RNA

Nitrogenous bases of RNA

adenine, uracil, guanine, cytosine, has the pentose sugar ribose

Nitrogenous bases of DNA

adenine, thymine, cytosine, guanine, has pentose sugar deoxyribose

Double helix

2 antiparallel strands of nucleotides linked by hydrogen bonds between complementary bases

Complementary base paring of Adenine

Thymine, 2 hydrogen bonds

Complementary base pairing of Cytosine

Guanine, 3 hydrogen bonds