HESI A2 Biology Exam Terms & Definitions for 2024

Classification System

Kingdom, Phylum, Class, Order, Family, Genus, Species

(King Phillip Came Over For Great Spaghetti)

What are the steps to the scientific method?

observation, hypothesis, experiment, conclusion

Hypothesis

a supposition or proposed explanation made on the basis of limited evidence as a starting point for further investigation.

Chemical Makeup of Water

2 hydrogens covalently bonded to an oxygen

Properties of Water

Because of high polarity between bonds, water can form H bonds:

-has a high specific heat

-strong adhesion and cohesive properties

-when frozen, forms a lattice crystal allowing ice to float on water

-acts as a universal solvent

Adhesion

the ability of water to bond to or attract other molecules or substances

ex: water you sprayed on a wall sticks to the wall

Cohesion

the sticking together of particles of the same substance.

ex: water beading up on a freshly waxed car

Carbohydrates

made up of polymers of sugar

-functions: storage, structure, and energy

Fatty Acids

chains of carbon atoms bonded to hydrogen atoms

Unsaturated Fatty Acids

have one or more double bonds, liquid at room temp

Saturated Fatty Acids

no double bonds, solid at room temp

Phospholipids

2 fatty acids bonded to a phosphate group

-phosphate head has a charge and is polar/soluable in h20 (hydrophilic head)

-fatty acid tails are nonpolar/not soluable in h20 (hydrophobic tail)

Steroids

Made of four rings of carbon. Components of the cell membrane and act as precursors to hormones/drugs

Protein

polymers of amino acids

-contribute greatly to cell function

-largest biological molecule

-enzymes facilitate chemical reactions in the body

Nucleic Acids

DNA and RNA

DNA

deoxyribonucleic acid, a self-replicating material present in nearly all living organisms as the main constituent of chromosomes. It is the carrier of genetic information.

RNA

single-stranded nucleic acid that contains the sugar ribose

Metabolism

the sum of all chemical reactions within an organism

Prokaryotic Cell

cell that does not have a nucleus or other membrane-bound organelles.

Eukaryotic Cell

cell that has a nucleus and other membrane-bound organelles

Nucleus

A part of the cell containing DNA and RNA and responsible for growth and reproduction

Ribosomes

Read RNA and make proteins. Found in the ER and in the cytoplasm

Endoplasmic Reticulum (ER)

made of 2 parts: rough and smooth ER

-rough ER has ribosomes and produces proteins/membranes

-smooth ER lacks ribosomes and functions in detoxification and metabolism of multiple molecules

Golgi Apparatus

packages, processes, and ships proteins from the ER throughout the cell

Lysosomes

Uses chemicals to break down food and worn out cell parts (4.5 ph)

Vacuoles

Stores food, water, wastes, and other materials

What 2 organelles produce energy in cells?

mitochondria and chloroplasts in plants

Mitchondria

Power House of the cell where ATP is produced.

Chloroplasts

where energy is produced in plant cells via photosynthesis

Describe the structure of the Plasma membrane

Made up of phospholipids. Heads are hydrophilic (polar), Tails are hydrophobic (non polar).

-have cholesterol, proteins, and glycoproteins embedded in and on the surface

What is the function of the plasma membrane?

Selectively permeable barrier

-protection

-communication

-passage of substances in/out of the cell

What are the 2 pathways for cellular energy production?

aerobic (cellular respiration) and anerobic (fermentation)

Formula for Cellular Respiration

C6H12O6 + 6 O2 -> 6CO2 + 6H20 + ENERGY (ATP)

Glucose+oxygen = carbon dioxide, water and energy

ATP

(adenosine triphosphate) main energy source that cells use for most of their work

NADH

electron carrier that stores energy used to make ATP

What are the 3 steps in cellular respiration?

glycolysis, citric acid cycle, electron transport chain

Gylcolysis

glucose to pyruvate, takes place in the cytosol

(2 atp, 2 nadh, 2 pyruvate)

Citric Acid Cycle

A chemical cycle involving eight steps that completes the metabolic breakdown of glucose molecules to carbon dioxide; occurs within the matrix of the mitochondrion; the second major stage in cellular respiration.

(for each glucose 2 atp, 6co2, and 6 NADH are made)

Electron Transport Chain

series of electron carrier proteins that shuttle high-energy electrons during ATP-generating reactions

28-32 atp molecules produced here

How much ATP is made in cellular respiration?

32-36 atp molecules

Photosynthesis Formula

6CO2 + 6H2O + sunlight ---> C6 H12 O6 + 6O2

(carbon dioxide+ water+ sunlight = glucose and oxygen)

Describe the process of Photosynthesis

1. light reactions- light is absorbed and that energy is used to split a water molecule and transfer electrons. NADH is produced with some ATP

2. Calvin Cycle- atp and NADH used to produce sugar

What are 2 types of asexual reproduction?

binary fission and mitosis

Binary Fission

type of asexual reproduction in which an organism replicates its DNA and divides in half, producing two identical daughter cells

Cytokinesis

division of the cytoplasm

What are the phases of Mitosis?

prophase, prometaphase, metaphase, anaphase, telophase

What happens in each stage of Mitosis?

Prophase- sister chromosomes are visibly separate and has 2 noticeable sister chromatids

Prometaphase- envelope starts to disappear and chromosomes attach to spindle fibers at the axis of cell

Metaphase-all chromosomes line up in the middle of cell

Anaphase- chromosomes start to separate

Telophase- chromosomes gather on either side of cell

Meiosis

a type of cell division that results in four daughter cells each with half the number of chromosomes of the parent cell, as in the production of gametes and plant spores.

Describe the steps in Meiosis

the DNA replicates, the chromosomes line up in the centre and divide twice, four non-identical gametes are formed with half the number of chromosomes

interphase (dna replication), meosis 1 and meosis 2

What happens during prophase 1?

crossing over

Alleles

alternative versions of a gene

Homozygous

An organism that has two identical alleles for a trait

Heterozygous

An organism that has two different alleles for a trait

genotype

genetic makeup of an organism

phenotype

An organism's physical appearance, or visible traits.

Who discovered the structure of DNA and when?

Watson and Crick in 1953

Describe the structure of DNA

double helix that contains the bases adenine, thymine, guanine, and cytosine

Transcription

(genetics) the organic process whereby the DNA sequence in a gene is copied into mRNA

Translation

Process by which mRNA is decoded and a protein is produced

Describe the steps of Translation

mRNA carries the info for making proteins and tRNA and rRNA build amino acid chains from the info.

codon

three-nucleotide sequence on messenger RNA that codes for a single amino acid

hypotonic solution

A solution in which the concentration of solutes is less than that of the cell that resides in the solution (causes cell to swell and burst)

hypertonic solution

A solution in which the concentration of solutes is greater than that of the cell that resides in the solution (causes cell to shrink)

isotonic solution

a solution whose solute concentration is equal to the solute concentration inside a cell

active transport

Energy-requiring process that moves material across a cell membrane against a concentration difference

examples of active transport

sodium potassium pump, endocytosis, exocytosis

passive transport

Requires NO energy, Movement of molecules from high to low concentration, Moves with the concentration gradient

Osmosis

Diffusion of water through a selectively permeable membrane