Biology IB SL Flashcards

Flashcards covering key vocabulary and concepts from biology lectures, designed for exam preparation.

Covalent Bonds

A bond between atoms where pairs of electrons are shared.

Polar Molecule

A molecule with an unequal distribution of electrical charge, having one end slightly positive and the other slightly negative.

Ionic Bonds

Bonds formed by the attraction between positive and negative charges.

Hydrogen Bonds

Weak intermolecular force- attraction between 2 water molecules.

Cohesion

The sticking together of water molecules due to hydrogen bonds.

Adhesion

Property of water, sticking to a solid surface.

Solution

A mixture of solvent and solutes.

Hydrophilic

Substances that dissolve in water; polar molecules.

Hydrophobic

Non-polar substances that do not dissolve in water, such as fats and lipids.

Metabolism

All the biochemical reactions that occur within an organism.

Buoyancy

The upward force that a fluid exerts on an object immersed in it.

Viscosity

The stickiness of a fluid that determines how easily it can flow.

Thermal Conductivity

Absorption and transfer of heat

Specific Heat

The amount of heat required to raise the temperature of a substance; water has a high heat capacity.

DNA

Deoxyribonucleic acid; used by living organisms to store hereditary information.

RNA

Ribonucleic acid; a polynucleotide chain.

Nucleic Acids

Polynucleotide chain of one or two types: DNA or RNA

Polynucleotide Chain

Long unbranched chain of nucleotides (DNA or RNA)

Genetic Code

Order of bases in DNA that determines the sequence of amino acids in a protein

Pentose Sugar

5 carbon monosaccharide sugar

Phosphate Group

Acidic and negatively charged

Purine

Nitrogenous base; Adenine (A) and Guanine(G)

Pyrimidine

Nitrogenous base; Cytosine (C) and Thymine (T)

Cell Membrane

Outer boundary of cells that encloses all its contents

Cytoplasm

Jelly like substance where all the organelles are suspended

Prokaryotes

Does not have a nucleus- just a strand/ loop of DNA floating around in the nucleoid.

Peptidoglycan

Cell wall is made of this

Eukaryotes

Plants, animals, fungi, etc all are

Plastids

A family of organelles with 2 outer membranes and internal membrane sacs

Vacuole

Flexible fluid filled compartment surrounded by a single membrane

Centrioles

Cylindrical objects that organise the assembly of structures composed of microtubules

Undulipodia

Cilia and flagella used to generate movement of the cell

Homeostasis

The maintenance of a constant internal environment

Essential amino acids

Cannot be synthesized in sufficient amounts so must be obtained from diet

Non-essential amino acid

Can be synthesized as are found in the body

Denaturation

Change to the conformation of a protein is called denaturation, which is permanent

Phospholipid Bilayer

Bilayer of phospholipids and other amphipathic molecules that form a continuous sheet- controls passage of substances and is maximum 10 nm

Phospholipids

Polar head consisting of glycerol and phosphate molecules and 2 nonpolar tails made of fatty acid chains

Amphipathic

Hydrophilic heads + hydrophobic tails

Integral Proteins

Hydrophobic on at least one part of their surface and therefore are embedded in the hydrocarbon chains- extend across the membrane

Peripheral Proteins

Hydrophilic on the surface and so not fully embedded in the the bilayer

Glycolipids

One of the phospholipids attached to a single monosaccharide carbohydrate chain- usually facing out of the cell

Glycoprotein

Protein embedded in the membrane attached to a single carbohydrate chain

Simple Diffusion

Net movement of substances from a region of high concentration to low concentration (down the concentration gradient) to reach equilibrium.

Facilitated Diffusion

Net movement of large polar molecules and ions down the concentration gradient till the point of equilibrium, without ATP

Channel Proteins

Integral Lipoproteins that contain a hydrophilic pore for ions to cross through

Carrier Proteins

Integral glycoproteins that bind to a solute and undergo conformational change to translocate solutes across the membrane

Osmosis

Net movement of water molecules down the concentration gradient to the point of equilibrium

Tonicity

Is the way cell membranes react to different osmotic conditions

Organelles

Discrete structures in cells that are adapted to perform one or more vital functions

Compartmentalization

Mechanism of creating compartments inside the cell

Expression of Gene

Use of gene in a cell (switches on)

Cell Differentiation

Expression of certain genes in different cell types

Stem Cell Niche

Precise location of these stem cells, provides an environment for them to remain inactive and proliferate for a long time

Totipotent Cells

Found in early stages of embryonic development and can differentiate into any cell type

Pluripotent Cells

Embryonic stem cells; totipotent→ pluripotent; can differentiate into a variety of cell types but not all

Multipotent Cells

Can differentiate into a limited number of cells with a specific tissue and is found in adults

Enzymes

Mainly proteins that function as biological catalysts

Catalysts

Substances that increase the rate of chemical reactions but are not changed by the reactions themselves.

Metabolism

Complex network of independent and interacting chemical reactions that occur in living organisms

Anabolic Reactions

Anabolic reactions build up smaller molecules into larger ones and require energy to do so

Catabolic Reactions

Catabolic reactions break down larger molecules into smaller ones and release energy

Active Site

Specific region of enzymes where substrates bind

Induced Fit

Molecular motion: Allows substrates to move closer to the active site by the chemical properties of the enzyme

Immobilized Enzymes

Enzymes attached to an insoluble material, enabling recovery, reuse and increased enzyme stability

DNA Replication

Production of new strands of DNA with base sequences identical to existing ones

Helicase

Ring shaped protein that separates the two strands of DNA by cleaving the hydrogen bonds

DNA Polymerase

Assembles new strands of DNA using the two original strands as a template

Transcription

Synthesis of RNA, using DNA as a template

Translation

The process of polypeptide synthesis using mRNA

mRNA

Messenger RNA that has a site to which the ribosome can bind

tRNA

Transfer RNA that translates the mRNA base sequence into the amino acids

Codons

Three bases coding for amino acids. Required triplets as only 2 bases aren't enough.

Gene Mutation

Change to the base sequence of the gene

Substitution mutation

One base in the coding sequence of a gene is replaced by another.

Insertion mutation

One extra nucleotide is added resulting in an extra base in the sequence of the gene

Deletion mutation

One nucleotide is removed resulting in one less base sequence of the gene

Non-sense mutation

Change of a codon into a stop codon

Missense mutation

Alteration of one amino acid in the sequence of amino acids. If it is positioned at an uncritical point, it does not have an effect, otherwise it can be lethal.

Parent cells

Cells that divide to form daughter cells by mitosis or meiosis

Daughter cells

Cells produced when a cell divides by mitosis and meiosis

Mitosis

Nuclear division resulting in 2 genetically identical daughter cells

Meiosis

Nuclear division consisting of two parts in order to result in 4 haploid daughter cells

Sister Chromatids

2 Chromatids that make up the double structure of the chromosome

Euchromatin

Active genes are loosely packed to make them easily accessible

Heterochromatin

Inactive genes tightly packed for better economy of space

Nondisjunction

Failure of homologous chromosomes or sister chromatids to separate properly during cell division

Alleles

Different versions of the same gene

Genotypes

The combination of alleles

Phenotype

The physical appearance/ characteristics expressed by the organism by the alleles

Dominant allele

Allele that is usually expressed and masks the expression of the other allele

Recessive allele

Allele which does not have an effect on the phenotype if the dominant allele is present

Phenotypic Plasticity

Organisms can respond to their environment by varying their patterns of gene expression.

Single nucleotide Polymorphisms

SNPs: Position in a gene where different bases can be present

Karyogram

Arrangement of chromosomes in order of size

Sex Chromosomes

X and Y chromosomes

Sex Linkage

A special case of linkage occurring when the affected gene is located on the sex chromosome (Usually X)