Vocabulary
Levels of organization
Matter in living beings is organized in a series of levels of increasing complexity, ranging from the atomic level to the multicellular level with tissues and organs. Only plants and animals reach the highest one, whereas bacteria stay at the unicellular level.
Bioelements
The most abundant chemical elements in a livig being, which are not much the same ones that you can find in a rock. The top six are C, H, O, N, P, S, and they're called the primary bioelements.
Biomolecules
The most abundant types of molecules in living beings are always the same ones, no matter if it is a bacterium or a human. They may be organic (with a skeleton of carbon atoms: carbohydrates, lipids, proteins, nucleic acids) or inorganic (without it: water, mineral salts).
Cell
The basic unit of Life. If something is not made up of cells, then it is not a living being. Cells can reproduce and interact with their environment (exchanginng matter and energy, and being able to notice its features). All cells have a plasma membrane, some organelles and genetic material.
Genetic material
In all cells the genetic material is DNA associated to proteins and organized in chromosomes. Bacteria have one chromosome, while humans have 46 in each cell. Its function is to store, express and transmit to the offspring the instructions that tell how every cell and living being will be self-constructed and how will they work.
Prokaryotic / Eukaryotic
Cells without a real nucleus (no nuclear membrane) are the first type. Cells with a real nucleus (genetic material enclosed in a nuclear membrane) are the second type. Bacteria and Archaea are prokayotes; Algae, Protozoa, Fungi, Plants and Animals are eukaryotes.
Mitosis
Cells with more than one chromosome, once they've synthesized a full copy of the whole set of chromosomes, have to carefully organize their division in order to produce two daughter-cells with exactly the same genetic information. Mitosis is the complex process whereby most eukaryotic cells tackle such a task.
Tissues
In multicellular beings there may be different types of cells, each type being specialized in an specific function, and having the specific shape that allows them to fulfill that function the best. Each of those types is called a cellular tissue; examples are the vascular tissue (plants) or the blood tissue (animals). One tissue may have several subtypes of cells (e.g. white blood cells and red blood cells).
Organs / Organ Systems
There are some tasks in a multicellular being that must be achieved by cells of different kinds working together (such as pumping blood throughout the human body). In this case, cells of different tissues gather and make up an organ (epithelial, connective, muscle and adipose cells make up the heart). Several organs working together in a common general task make up an organ system (the heart and the blood vessels make up the circulatory system).
Autotrophs / Heterotrophs
Or Producers and Consumers. The former don't feed off other living beings: they transform inorganic substances to produce the organic substances they need; plants and algae are autotrophs. The latter need to feed on other beings and then transform the organic substances they have eaten into their own organic substances (i.e.: your proteins come partly from the proteins in that beef-steak you ate yesterday); animals, fungi and protozoa are heterotrophs.
Common Structures in Eukaryotic Cells
Description
Function
Where
Cell Wall
Outermost layer on a plant cell composed of cellulose and other complex carbohydrates.
Helps to support and protect the cell.
P
Cell Membrane
Outer layer composed of lipids and proteins.
Controls the permeability of the cell to water and dissolved substances.
A, P
Flagella (flagellum)
Long and scarce threadlike structures that extends from the surface of the cell.
Used for movement of the cell or to move fluids over the cell's surface for absorption.
A
Cilia (cilium)
Short and abundant threadlike structures that extends from the surface of the cell.
Used for movement of the cell or to move fluids over the cell's surface for absorption.
A
Cytoplasm
Semifluid mixture that occupies most of the cell's interior. Contains sugars, aminoacids, and proteins. Also, contains a protein fiber network.
Medium in which organelles and other internal structures exist in. Fiber network support the shape of the cell and anchor organelles to fixed positions.
A, P
Mitochondria (mitochondrion)
Elongated organelles enclosed in a double membrane, the inner one being creased
Sites of respiration: converts sugars and fats into energy through oxidation.
A, P
Chloroplasts
Elongated organelles enclosed in a double membrane and with vesicles containing chlorophyll.
Sites of photosynthesis.
P
Ribosomes
Tiny organelles composed of protein and RNA, not enclosed in a membrane. Often attached to endoplasmic reticulum.
Sites of protein synthesis.
A, P
Endoplasmic Reticulum
Extensive system of internal membranes. May be smooth or rough: the latter has ribosomes attached to its membrane.
Site of transport and synthesis of various cell substances.
A, P
Golgi Complex
Flattened stacks of membranes.
Used in the collection, packaging, and distribution of synthesized molecules.
A, P
Secretory Vesicles
Membrane enclosed sacks created at the Golgi complex.
These structures contain cell secretions, like hormones and neurotransmitters. The secretory vesicles are transported to the cell surface where they release those substances outside the cell.
A, P
Lysosomes
Spherical organelles enclosed in a membrane.
Contain digestive enzymes for breaking down old cellular components or ingested food (smaller cells, big macromolecules).
A, P
Vacuoles
Elongated organelles enclosed in a membrane. Few and large in plant cells.
Used to store water and waste products.
A, P
Centrosome
A pair of hollow tubes (the centrioles) surrounded by protein fibers in a star-like arrangement.
Move chromosomes during reproductive division. Plant cells have an equivalent structure to fulfill this function.
A
Peroxisomes
Spherical organelles enclosed in a membrane.
Formed by the endoplasmic reticulum. Converts fats into carbohydrates. Detoxifies potentially harmful oxidants.
A, P
Nucleus
Double membrane structure that encases chromosomes.
Cell structure which directs protein synthesis and cell reproduction.
A, P
Chromatine
Long strands of DNA and protein. During cell division it is packaged into chromosomes.
Stores hereditary (= genetic) information.
A, P
Nucleolus
Aggregations of rRNA and ribosomal proteins.
Area were ribosomes are manufactured.
A, P
Main Human Tissues
Epithelial tissue
Composed of layers of cells that line organ surfaces such as the surface of the skin or the inner lining of the digestive tract. Serves for protection of organs (as in the skin), secretion of substances (when it forms glands - in the skin, in the digestive tract, etc.), and absorption of substances (as in the intestine).
Muscle tissue
Composed of very long cells (up to several cm) called muscle fibres. They have more than one nucleus, are able to expand and contract, and so, are specialized in movements. There are three kinds: cardiac muscle (found in the heart), skeletal muscle (attached to bones) and smooth muscle (not in the heart or attached to bones, as in the stomach).
Nervous tissue
Composed of cells with many projections that are specialized in contacting other cells and transmitting messages via electrical signals.
Connective tissues
Usually specialized in holding together different organs or tissues. It is composed of cells usually very separated by an abundant extracellular matrix. The main types are the bone tissue (in bones), the cartilage tissue (in cartilages), the adipose tissue (as in the fatty layer under the skin - the hypodermis), the fibrous connective tissue (in ligaments and tendons), the loose connective tissue (as in the skin's dermis) and the blood.
Levels of organization
Matter in living beings is organized in a series of levels of increasing complexity, ranging from the atomic level to the multicellular level with tissues and organs. Only plants and animals reach the highest one, whereas bacteria stay at the unicellular level.
Bioelements
The most abundant chemical elements in a livig being, which are not much the same ones that you can find in a rock. The top six are C, H, O, N, P, S, and they're called the primary bioelements.
Biomolecules
The most abundant types of molecules in living beings are always the same ones, no matter if it is a bacterium or a human. They may be organic (with a skeleton of carbon atoms: carbohydrates, lipids, proteins, nucleic acids) or inorganic (without it: water, mineral salts).
Cell
The basic unit of Life. If something is not made up of cells, then it is not a living being. Cells can reproduce and interact with their environment (exchanginng matter and energy, and being able to notice its features). All cells have a plasma membrane, some organelles and genetic material.
Genetic material
In all cells the genetic material is DNA associated to proteins and organized in chromosomes. Bacteria have one chromosome, while humans have 46 in each cell. Its function is to store, express and transmit to the offspring the instructions that tell how every cell and living being will be self-constructed and how will they work.
Prokaryotic / Eukaryotic
Cells without a real nucleus (no nuclear membrane) are the first type. Cells with a real nucleus (genetic material enclosed in a nuclear membrane) are the second type. Bacteria and Archaea are prokayotes; Algae, Protozoa, Fungi, Plants and Animals are eukaryotes.
Mitosis
Cells with more than one chromosome, once they've synthesized a full copy of the whole set of chromosomes, have to carefully organize their division in order to produce two daughter-cells with exactly the same genetic information. Mitosis is the complex process whereby most eukaryotic cells tackle such a task.
Tissues
In multicellular beings there may be different types of cells, each type being specialized in an specific function, and having the specific shape that allows them to fulfill that function the best. Each of those types is called a cellular tissue; examples are the vascular tissue (plants) or the blood tissue (animals). One tissue may have several subtypes of cells (e.g. white blood cells and red blood cells).
Organs / Organ Systems
There are some tasks in a multicellular being that must be achieved by cells of different kinds working together (such as pumping blood throughout the human body). In this case, cells of different tissues gather and make up an organ (epithelial, connective, muscle and adipose cells make up the heart). Several organs working together in a common general task make up an organ system (the heart and the blood vessels make up the circulatory system).
Autotrophs / Heterotrophs
Or Producers and Consumers. The former don't feed off other living beings: they transform inorganic substances to produce the organic substances they need; plants and algae are autotrophs. The latter need to feed on other beings and then transform the organic substances they have eaten into their own organic substances (i.e.: your proteins come partly from the proteins in that beef-steak you ate yesterday); animals, fungi and protozoa are heterotrophs.
Common Structures in Eukaryotic Cells
Description
Function
Where
Cell Wall
Outermost layer on a plant cell composed of cellulose and other complex carbohydrates.
Helps to support and protect the cell.
P
Cell Membrane
Outer layer composed of lipids and proteins.
Controls the permeability of the cell to water and dissolved substances.
A, P
Flagella (flagellum)
Long and scarce threadlike structures that extends from the surface of the cell.
Used for movement of the cell or to move fluids over the cell's surface for absorption.
A
Cilia (cilium)
Short and abundant threadlike structures that extends from the surface of the cell.
Used for movement of the cell or to move fluids over the cell's surface for absorption.
A
Cytoplasm
Semifluid mixture that occupies most of the cell's interior. Contains sugars, aminoacids, and proteins. Also, contains a protein fiber network.
Medium in which organelles and other internal structures exist in. Fiber network support the shape of the cell and anchor organelles to fixed positions.
A, P
Mitochondria (mitochondrion)
Elongated organelles enclosed in a double membrane, the inner one being creased
Sites of respiration: converts sugars and fats into energy through oxidation.
A, P
Chloroplasts
Elongated organelles enclosed in a double membrane and with vesicles containing chlorophyll.
Sites of photosynthesis.
P
Ribosomes
Tiny organelles composed of protein and RNA, not enclosed in a membrane. Often attached to endoplasmic reticulum.
Sites of protein synthesis.
A, P
Endoplasmic Reticulum
Extensive system of internal membranes. May be smooth or rough: the latter has ribosomes attached to its membrane.
Site of transport and synthesis of various cell substances.
A, P
Golgi Complex
Flattened stacks of membranes.
Used in the collection, packaging, and distribution of synthesized molecules.
A, P
Secretory Vesicles
Membrane enclosed sacks created at the Golgi complex.
These structures contain cell secretions, like hormones and neurotransmitters. The secretory vesicles are transported to the cell surface where they release those substances outside the cell.
A, P
Lysosomes
Spherical organelles enclosed in a membrane.
Contain digestive enzymes for breaking down old cellular components or ingested food (smaller cells, big macromolecules).
A, P
Vacuoles
Elongated organelles enclosed in a membrane. Few and large in plant cells.
Used to store water and waste products.
A, P
Centrosome
A pair of hollow tubes (the centrioles) surrounded by protein fibers in a star-like arrangement.
Move chromosomes during reproductive division. Plant cells have an equivalent structure to fulfill this function.
A
Peroxisomes
Spherical organelles enclosed in a membrane.
Formed by the endoplasmic reticulum. Converts fats into carbohydrates. Detoxifies potentially harmful oxidants.
A, P
Nucleus
Double membrane structure that encases chromosomes.
Cell structure which directs protein synthesis and cell reproduction.
A, P
Chromatine
Long strands of DNA and protein. During cell division it is packaged into chromosomes.
Stores hereditary (= genetic) information.
A, P
Nucleolus
Aggregations of rRNA and ribosomal proteins.
Area were ribosomes are manufactured.
A, P
Main Human Tissues
Epithelial tissue
Composed of layers of cells that line organ surfaces such as the surface of the skin or the inner lining of the digestive tract. Serves for protection of organs (as in the skin), secretion of substances (when it forms glands - in the skin, in the digestive tract, etc.), and absorption of substances (as in the intestine).
Muscle tissue
Composed of very long cells (up to several cm) called muscle fibres. They have more than one nucleus, are able to expand and contract, and so, are specialized in movements. There are three kinds: cardiac muscle (found in the heart), skeletal muscle (attached to bones) and smooth muscle (not in the heart or attached to bones, as in the stomach).
Nervous tissue
Composed of cells with many projections that are specialized in contacting other cells and transmitting messages via electrical signals.
Connective tissues
Usually specialized in holding together different organs or tissues. It is composed of cells usually very separated by an abundant extracellular matrix. The main types are the bone tissue (in bones), the cartilage tissue (in cartilages), the adipose tissue (as in the fatty layer under the skin - the hypodermis), the fibrous connective tissue (in ligaments and tendons), the loose connective tissue (as in the skin's dermis) and the blood.
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