1. In the heart, an action potential originates in the (E) sinoatrial node.
The cardiac action potential is a term referring to the change in the membrane potential of heart cells causing the heart to contract. Cardiac action potentials are created by a group of specialized cells capable of generating automatic action potentials and are located in the right atrium of the heart. These cells are called sinoatrial node and sometimes are referred to as the natural pacemaker of the heart. This characterization originates from the fact that sinoatrial node continuously provides action potential and sets the rhythm of the heart function.
2. The sequence of travel by an action potential through the heart is (A) sinoatrial node, atrioventricular node, atrioventricular bundle, bundle branches, Purkinje fibers.
As explained above, the cardiac action potential originates from the sinoatrial node. This action potential then travels through the atrioventricular node, which belongs to the electrical conduction system of the heart and is located between the atria and the ventricles. It is responsible for the electrical connection between the right atrium and the right ventricle. The action potential then travels to the atrioventricular bundle (or bundle of His), another part of the electrical conduction system of the heart. The atrioventricular bundle transmits the electrical impulses from the atrioventricular node to the bundle branches. The bundle branches then send the signal to the Purkinje fibers which send the electrical impulses to the ventricles, causing them to contract.
3. The correct answer is A.
The generation of an action potential in the sinoatrial node causes the contraction of the atria. When the action potential passes from the sinoatrial node to the atrioventricular node, it slows down. This causes the transport of the electrical impulse from the atria to the ventricles to slow down. This delay enables the blood (from the contraction of the atria) to fill the ventricles before their contraction.
4. This statement is true.
The interventricular septum is a structure which divides the two ventricles of the heart and it is composed of two branches, the left bundle and the right bundle branch. When the action potential reaches the interventricular septum, it then travels to the apex of the heart from where it travels upwards along the walls of the ventricles and the ventricular contraction begins.
5. This statement is true.
The bundle branches gradually become Purkinje fibers located in the interior of the ventricular walls. Purkinje fibers are specialized cells and are responsible for conducting cardiac action potentials from the bundle branches to the ventricular walls. This signal transduction causes the muscle of the ventricular walls to contract.
Answer:
Proteins and lipids exist as separate but loosely attached molecules that can move around
Explanation:
Cell membranes are mainly composed of lipids, proteins, and also carbohydrates. Phospholipids are the most abundant type of lipid and the main constituent of the cell membranes. Membrane proteins are divided into two types according to their interactions with the cell membrane: 1-integral (intrinsic) and peripheral (extrinsic) proteins. These peripheral proteins are loosely attached by ionic bonds or calcium bridges with the phosphate heads of the phospholipids; whereas integral membrane proteins contain side chains that interact with fatty acyl groups of the phospholipids. Cell membrane fluidity indicates how easily lipids (e.g., phospholipids and cholesterol) and proteins (e.g., intrinsic proteins) diffuse laterally in the cell membrane. This fluidity is affected by the amount of cholesterol, temperature, and the ratio of unsaturated to saturated fatty acids. Saturated fatty acids have no double bonds in the hydrocarbon chain, whereas unsaturated fatty acids have at least one double bond (these double bonds increase fluidity). Moreover, higher temperatures increase membrane fluidity, whereas cholesterol molecules function to regulate membrane fluidity: at high temperatures cholesterol molecules stabilize the membrane, whereas at low temperatures intercalate between phospholipids, thereby preventing them from clustering together.
Answer:
Verdadero
Explanation:
Sabemos que los caracteres dependen de los genes. Y los genes pueden presentarse en forma de alelos dominantes, o alelos recesivos. La expresión de los alelos recesivos son enmascarados o escondidos por el alelo dominante. Es decir, que si ambos alelos se encuentran juntos en un heterocigota, solo el alelo dominante se expresará.
Entonces el alelo dominante expresa la característica que resulta dominante, mientras que el alelo recesivo expresa la característica recesiva.
Genotipo:
- Homocigota dominante ----> Expresa caracter dominante (Solo el alelo dominante esta presente)
- Heterocigota -------------------> Expresa el caracter dominante (Ambos alelos estan presentes, pero el dominante es quien se expresa)
- Homocigota recesivo --------> Expresa el caracter recesivo (solo alelos recesivos estan presentes)
Por ejemplo, si tenemos dos fenotipos rojo y amarillo, y sabemos que el color esta codificado por un gen dialelico llamado M. También supongamos que no sabemos qué alelo expresa qué color. Teniendo solo estos datos, no podemos decir si el rojo es el color dominante o si el amarillo lo es.
Sin embargo, si tenemos los siguientes genotipos acompañando esta información:
- MM--> Amarillo
- Mm--> Amarillo
- mm --> Rojo
Recién ahora podemos deducir que el caracter dominante es el amarillo.
Answer:
d. all of the above
Explanation:
all the above answers are correct about Science
Similarities
Both plant and animal cells have eukaryotic origins
Both have common organelles like the nucleus, mitochondria and ribosomes
Both are surrounded by a cell membrane
differences
plant cells have a regular defined shape while animal cells have an irregular shape
plant cells have a cell wall while animal cells lack a cell wall
plant cells have a chloroplast for photosynthesis while animal cells do not have a chloroplast
