science exam

Mutation

An error in DNA caused by a substitution, an insertion, or a deletion of a base

Catalyst

A chemical substance that increases the rate of chemical reaction without being used up

Mixture

Made up different substances physically combined

Molecule

Made up of two or more atoms chemically joined together. smallest unit of a covalent compound that can take part in a chemical reaction

Element (pure substance)

a substance that contains only one type of particle

matter

a physical substance that has mass and takes up space

Polyatomic ion

two or more ions bonded together and acting as a single charge unit

Compound

A substance made up of two or more types of atoms bonded together in fixed ratios

Friction

A force that opposes motion between surfaces in contact.

Acceleration

The rate at which velocity changes.

Stem cell

A cell type that is unspecialized and can develop into other types of cells

Isotope

Atoms of the same element with different mass number(neutrons)

Speed

Distance travelled per unit time.

Velocity

Speed in a given direction.

Covalent bond

formed due to sharing of valence shell electrons between two or more non metals.

Ionic bond

formed by transfer of valence sheel electrons between a non-metal anion and metal cation. due to electrostatic force of attraction between the ions, ionic bond is formed.

Metallic bond

formed due to strong electrostatic force of attraction between the metal cations and delocalised electrons.

Genotype

refers to the genetic code for a gene or an organism’s entire genome.

Phenotype

how a genotype is physically expressed.

Factors that affect rate of a reaction

Concentration, Temperature, Pressure, Surface area, Catalysts/enzymes, Agitation (stirring) 

Explain why the rate of reaction increases with the increase in surface area ? 

Rate of reaction increases with the increase in surface area because increasing the surface area causes the frequency of successful collisions to increase. Higher the surface area higher the rate of a reaction. 

Explain why the rate of reaction increases with the increase in temperature? 

With the increase in temperature, rate of a reaction increases due to : 

• the particles have more (Kinetic energy) energy and will collide with greater force 

• the frequency of collisions will increase, increasing the rate of a reaction 

Explain what a catalyst is and give an example of a catalyst.

A catalyst is a substance that increases the rate of a chemical reaction without being used up.   

Catalysts enables/helps the reaction to occur at a lower temperature.  

Example: Catalytic convertors(containing Platinum) in the car converts toxic carbon monoxide into carbon dioxide 

Explain how enzymes are a type of a catalyst .

Enzymes are biological catalysts. They are proteins that help speed up chemical reactions in the body e.g. digestive enzymes 

What is activation energy?

Activation energy is the energy required to start a reaction.

Karyotype

An image that shows the number and appearance of chromosomes in the nucleus

What chromosomes is for down syndrome

trisomy 21

write one similarity between meiosis and mitosis

Mitosis and meiosis are both process of cell division

mitosis

mitosis is a simple process of cell division, two new cells are formed, its used for growth and repair, daughter cells are identical to parent cells

meiosis

meiosis is a complex process of cell division, 4 new cells are formed, its used for reproduction and daughter cells are all genetically different to sisters cells and parent cells.

gene

A segment of DNA; the basic functional unit of heredity

DNA

stands for deoxyribonucleic acid. found in nucleus of the cell and is carrier of genetic information.

IVF

In vitro vertlisisation is when the sperm and ovum cells are fused in a petri dish in a lab, outside of the human body. after the embryo is developed, its implanted into the wall of the uterus. after this natual pregency and IVF go ahead the same way.

things that make meiosis cells diff

crossing over and independant assortmant