☛ The Heart Is Basically Two Muscular Pumps
The right side pumps deoxygenated blood to the lungs, and the left side pumps oxygenated blood to the body.
1) The left ventricle has thicker, more muscular walls that the right ventricle, because it needs to contract powerfully to pump blood all the way round the body. The right side only needs to get blood to the lungs.
2) Ventricular walls are thicker than the walls of the atria: the ventricles have to push blood out of the heart, but the atria only have to push blood a short distance to the ventricles.
3) The atrioventricular valves (AV valves) link the atria to the ventricles and prevent the backflow of blood from the contracting ventricles into the atria.
4) The semi-lunar (SL) valves link the ventricles to the pulmonary artery and aorta, and stop blood flowing back into the heart after the ventricles contract.
5) The cords attach the AV valves to the ventricles, stopping them from being forced up into the atria when the ventricles contract.
Valves only open one way: whether they’re open or closed depends on the relative pressure of the heart chambers. If there’s higher pressure behind a valve, it’s forced open, but if pressure is higher in front of the valve it’s forced shut.
All living organisms require a source of nitrogen from which to manufacture PROTEINS, NUCLEIC ACIDS and other nitrogen-containing compounds. Few can use nitrogen gas (N₂) directly, as nitrogen in this form is fairly unreactive.
Plants take up the majority of the nitrogen they require in the form of nitrate ions [NO₃-] (very soluble, can leach through soil easily) from the soil; this is where nitrogen enters the living part of the ecosystem, as animals obtain nitrogen-containing compounds by eating and digesting plants. When animals and plants decompose, microorganisms replenish the nitrate levels in the soil by hydrolysing plant and animal proteins.
Four main stages of the nitrogen cycle: ammonification, nitrification, nitrogen fixation, denitrification.
Aerobic Respiration within a Eukaryotic cell, approx. net gain of 38 ATP (adenosine triphosphate) molecules. 02 is the oxidising agent (electron acceptor).
C₆H₁₂O₆ (s) + 6O₂ (g) → 6CO₂ (g) + 6H₂O (l) + heat (ΔG= -2880kJ per mole of gluecose)
The energy flowing through all organisms has one distinct source: the Sun. This solar energy enters the ecosystem through plants, which contain chloroplast organelles, transforming light energy into chemical energy. The molecules formed through photosynthesis are also used by the plant during respiration to produce ATP. Non-photosynthetic organisms which feed on the molecules produced by plants then use these molecules to create ATP, and so the original solar energy is passed on.
ADP (adenosine diphosphate) + INORGANIC PHOSPHATE+ 30.6 kJ energy per mole of ATP ⇔ ATP (adenosine triphosphate) + H2O
(catalysed by ATP Synthase)
The SITE of PHOTOSYNTHESIS
Photosynthesis takes place within cell organelles called chloroplasts; these vary in shape/size, but are typically disc-shaped, and surrounded by a double membrane (phospholipid bilayer).
Within the chloroplast membranes are two important features:
Eukaryotes: A Breakdown of Organelles
Organelles are unique to eukaryotes and act like organs in the cell, each performing their own specific functions to keep the whole cell running. Since they’re all in their own little sealed-off membrane-bound areas, they can provide the ideal environment for whatever function they perform—for example, they can adjust the pH or temperature—and thus this allows for much more complexity in the cell.
Most organelles fit into a single functional unit called the Endomembrane system, because they evolved in the same way. The only organelles that don’t fit into this category are the mitochondria and chloroplast—for reasons that will become clear in the next article.
So let’s take a look at the functions of the organelles in the Endomembrane system:
- Nuclear envelope: This compartment contains the cell’s genetic material—the DNA. Its main function is to protect and package the DNA, but it also synthesises RNA, another kind of genetic material.
- Endoplasmic reticulum: Interconnected with the outer membrane of the nuclear envelope, the ER consists of flattened tubes and sacs called cisternae. The endoplasmic reticulum is subdivided into two: the rough ER, where protein synthesis and packaging takes place, and the smooth ER, where lipid and carbohydrate synthesis takes place. Basically, the endoplasmic reticulum uses the information in DNA to create the building blocks of the cell.
- Golgi body: This is composed of a group of flat, membranous sacs that deal with the goods produced in the endoplasmic reticulum. Proteins are transported by vesicles from the cis face (the part facing the nucleus) and a trans face (the part facing away from the nucleus), being packaged, modified and matured along the way. When they emerge the proteins are sent out into the wider environment.
- Lysosome: This is the recycling plant of the cell, containing digestive enzymes that sort, degrade and recycle waste products. It’s actually a perfect example of how organelles can create niche environments: the lysosome maintains an acidic pH of 5, which is ideal for the breakdown of products.
- Vesicle: Membrane-bound sacs used to store and transport material.
- Vacuole: A large, fluid-filled “bubble” in plant cells, where food and waste products are
- Cell membrane: Made mostly of lipids, this encloses the cell and separates it from the outside world. It’s selectively permeable, meaning that only some substances are allowed passage in and out.
And now the functions of those loners not in the Endomembrane system:
- Mitrochondria: This is where cellular respiration takes place—where the cell’s energy (ATP) is extracted from glucose (a sugar). It’s present in all plant and animal cells.
- Chloroplast: Present in plants, the chloroplast takes in light energy and converts it into chemical energy through the process of photosynthesis, ready for use in the mitochondria.
I know I’ve just dumped a whole host of terms onto you, and if they’re totally unfamiliar then they might be difficult to juggle. But trust me, we’ll come back to almost all of these in more detail later, so you’ll have time to digest and memorise.
Further resources: An interactive look at animal, plant, and bacterial cells
Precisely. So like, YEAH.
Can’t go to work today, I have a case of the snorgles