Biology – Quick Reference Sheet

Cells Cellular Growth and Development
Basics of Cells

All living organisms are made up of cells.
Cells vary in structures and function.
A cell’s genetic information, housed in the DNA, determines the specific function of the cell.
Cell Structure

Cell Membrane: flexible outer boundary of a cell made of a double layer of non-polar fatty acids, proteins, and other elements that float freely around; selectively permeable so it regulates what leaves/enters a cell
Cell Wall: rigid, outermost boundary that holds the cell’s shape; only found in plant cells
Central Vacuole: large membrane bound space used for storage; only in plant cells
Chloroplasts: organelles that converts light energy into carbohydrates to use as a food source; only in plant cells
Cilia: short hair-like fibers outside of the cell membrane used to move a cell or move objects along the cell’s membrane
Cytoplasm: the fluid within the cell membrane that houses all other organelles
Endoplasmic Reticulum (ER): system of internal membranes that moves proteins within a cell and produces membrane for other
Flagella: long threadlike fibers used to propel a cell for movement
Golgi Apparatus: “protein warehouse” that modifies and packages newly made proteins
Lysosomes: small organelles that breaks down material using digestive enzymes
Microfilaments: protein fibers used to hold the cell’s shape
Microtubules: hollow tubes made of protein that serve as “tracks” along which information from DNA can pass
Mitochondria: organelle which uses chemical potential energy from the breakdown of food to produce energy (in the form of ATP) that allows the cell to do work
Nucleus: membrane-bound organelle that contains the cell’s DNA
Organelle: unit within a cell that carries out a specific function
Ribosome: organelle that makes proteins using the instructions given by DNA; can be free-floating inside cell or bound to rough endoplasmic reticulum
Rough Endoplasmic Reticulum (RER): part of the endoplasmic reticulum with ribosomes attached to it; responsible for building proteins
Smooth Endoplasmic Reticulum (SER): part of the endoplasmic reticulum with no ribosomes; builds lipids and breaks down toxic substances
Vesicle: small, membrane bound sac used for transport
Prokaryotic vs. Eukaryotic

All cells are separated into two categories: Prokaryotic cells and Eukaryotic cells
Prokaryotes: single-cell organisms that do not have a nucleus or membrane bound organelles; includes most bacteria
Eukaryotes: : both single and multi cell organisms that have a nucleus and membrane bound organelles; includes all plant, animal, protest and fungi cells
Growth of Organisms

All organisms originate from a single cell.
Multi-cell organisms are formed from the division of this single cell, which follows the genetic instructions from DNA.

Mitosis: reproduction in which an exact copy is made of the original cell
Meiosis: reproduction to form sex cells containing only half the original chromosomes

ATP: a molecule that serves as the primary source for cellular energy
Glycolysis: a pathway in which organic compounds are broken down into pyruvic acid and a small amount of ATP
Levels of Organization

Cells of multi cellular organisms are organized into a hierarchy of
structures, in increasing order of their complexity:
Cells→tissues→organs→organ systemsorganisms
Tissue: a group of cells that share a common task
Organ: a group of tissues that share a common task
Organ system: a group of organs that perform a function
Cell Stability and Protection

Cells need to keep a stable environment to function properly.
Physical, chemical, and temperature changes, as well as diseases, can all disrupt a cell.
Animal’s have an immune system to protect themselves from invading pathogens.
T Cells: attack and kill abnormal or infected cells
B Cells: recognize foreign invaders and produce antibodies
Macrophages: traps and engulfs foreign invaders
Antigen: protein that triggers an immune response
Natural Selection

Different traits of organisms give it different strengths and weaknesses over similar organisms.
The organisms with the traits that are most adapted to the environment are more likely to survive in the long run. These specialized traits will therefore be passed down to offspring and increase the percentage of the specialized traits in the population.
Evolution of Cells

Fossil records indicate that all organisms derived from single cell prokaryotes.
Two groups evolved from the early prokaryotes: Eubacteria and Archaebacteria.
Eukaryotic cells appeared about 1 billion years later. Eukaryotic cells were much more complex. All multi-cellular organisms derived from
these Eukaryotic cells.
Charles Darwin

Published the book On the Origin of Species by means of Natural Selection in November of 1859.
Used fossil records to prove that organisms changed over time
Contradicted biologists’ previous beliefs that organisms did not evolve, and that behaviors learned during life could be passed down to offspring.

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