2025 Biology 1st Semester Test

simple diffusion

movement of a solute from an area of high concentration to an area of low concentration, uses no energy

active transport

the movement of materials across a cell membrane against the concentration gradient (low to high concentration), requires energy

hypotonic

the concentration of solutes is greater inside the cell than outside of it, water enters the cell, the cell swells and pops

isotonic

solute concentration is the same inside and outside the cell, normal healthy cell

hypertonic

the concentration of solutes is greater outside the cell than inside it, water leaves the cell, the cell shrinks and dies

DNA

stores genetic information, found in the nucleus of eukaryotic cells

positive feedback system

reinforces a change until a process is carried out, ex. childbirth, blood clotting, fruit ripening

feedback system components

receptor: picks up the change, control center: comes up with a response to the change, effector: carries out the control center's response

phospholipid bilayer

2 molecules wide, arranged tail to tail with the polar, hydrophillic heads outward and the non-polar hydrophobic tails inward

spontaneous generation theory

the theory that living organisms are born from nonliving things, ex. tadpoles are born from mud

Who discovered cells?

Robert Hooke

prokaryotes vs eukaryotes

eukaryotes have a nucleus and membrane bound organelles, prokaryotes don't have either

lysosome

vesicle filled with enzymes needed to break down food and recycle waste/old organelles

ribosome

made of strips of rRNA put together into a small and large subunit, it puts together protein

DNA base pairs

A-T, G-C

RNA base pairs

A-U, G-C

What do most enzyme names end in?

-ase

denaturation

loss of normal shape of a protein due to heat or other factors, results in a loss of function or non functioning protein

reactant

substance that is changed in a chemical reaction

product

substance that is made from the chemical reaction (reactants are taken apart or put together to make products)

lipid structure

hydrophilic head and 2 or 3 hydrophobic tails

What element is found in all organic molecules?

Carbon

adhesion

an attraction between molecules of different substances

cohesion

an attraction between molecules of the same substance

specific heat

the amount of energy required to raise the temperature of 1 gram of a substance by 1 degree Celsius (what allows water to remain a stable temperature)

solute

the substance that is dissolved

solvent

a substance capable of dissolving other substances

surface tension

molecules on the surface of a liquid bond more strongly to the molecules below and next to them which creates a force at the surface of the liquid (allows you to float)

evaporative cooling

evaporation takes heat with it which allows for the temperature of an organism or area to go down (why we sweat)

mitochondria

rod shaped, it is the site of ATP (energy) production, found in eukaryotes only

capillary action

cohesion and adhesion work together to move water up small tubes against gravity, plants use this to move water from their roots to their leaves

chloroplast

contains stacks of thylakoids, only found in eukaryotic plant cells, it is the site of photosynthesis

endosymbiotic theory

certain kinds of prokaryotes began living inside of larger cells and evolved into the mitochondria and chloroplasts of modern-day eukaryotes

specialized cells

cells that have physical or chemical differences that allow them to perform one job very well

cell bulk transport

vesicles are created to move molecules into or out of the cell that are too big to cross through the cell membrane

concentration gradient

difference in the concentration of a substance from one location to another, molecules will move from high concentration to low in order to reach equilibrium

nucleus

mostly hollow with pores on it's surface, provides protection for DNA, only found in eukaryotes

centriole

structure in an animal cell that helps to organize cell division

glucose

the form of sugar that circulates in the blood and provides the major source of energy for body tissues

cytoplasm

a jellylike fluid inside the cell in which the organelles are suspended

DNA structure

double stranded nucleic acid with a deoxyribose sugar backbone and a base pair ladder down the center

lipid functions

long term energy storage, hormones, cell membrane structure

homeostasis

process by which organisms maintain a relatively stable internal environment

photosynthesis reactants and products

reactants: sunlight, carbon dioxide, water, products: glucose, and oxygen

How does being small benefit a cell?

smaller cells have more surface area across which to pass oxygen, nutrients and waste materials

protein structure

long chains of amino acids folded into a 3D shape

cell wall

A rigid structure made of cellulose that surrounds the cell membrane and provides support to the cell

3 things that plant cells have that animal cells don't

large central vacuole, cell wall, chloroplast

central vacuole

a large vacuole used for water storage in plant cells

nucleotide

monomer of nucleic acids made up of a sugar, a phosphate group, and a base

carbohydrate structure

carbon, hydrogen, and oxygen in a 1:2:1 ratio, put together in sugar chains called polysaccharides, arranged in branched or linear structures

What happens to water molecules when they freeze?

they spread out and become less dense (why lakes don't freeze solid in the winter)

protein synthesis steps

1. transcription, 2.translation

Chargaff's Rule

in DNA, the percent composition of adenine is the same as thymine, and the percent composition of cytosine is the same as guanine