Cells and their Functions Flashcards
List three types of microscopes used to study cells
The compound light microscope is the microscope most commonly used in laboratories. This instrument, which can magnify an object up to 1,000 times, usually has two lenses and uses visible light for illumination, although some may use other light sources (such as ultraviolet light).
The transmission electron microscope (TEM) uses an electron beam in place of visible light and can magnify an image up to 1 million times.
The scanning electron microscope (SEM) does not magnify as much as does the TEM (100,000 times) and shows only surface features; however, it provides a three-dimensional view of an object.
Describe the functions of the plasma membrane and its components.
Regulates what can enter and leave the cell. Also participates in many cellular activities, such as growth, reproduction, and communication between cells
Made of:
- Phospholipid bilayer
- Cholesterol`- adds strenghth & flexibility
- Carbohydrates - help cells recognize each other
- Proteins - channels, transporters, receptors, enzymes, markers)
Describe methods by which substances enter and leave cells that do not require chemical energy
1) Diffusion is the net movement of particles from a region of relatively higher concentration to one of lower concentration. Hydrophilic substances can only diffuse across the plasma membrane through a suitable ion channel or transporter
2) Osmosis - the diffusion of water through a semipermeable membrane
3) Filtration is the passage of water and dissolved materials through a membrane down a pressure gradient from an area of higher pressure to an area of lower pressure (e.g. espresso machine)
Explain what will happen if cells are placed in solutions with concentrations the same as or different from those of the cytoplasm.
hypotonic = cells swell (and possibly burst - hemolysis) hypertonic = cells shrink (crenation)
Describe methods by which substances enter and leave cells that require chemical energy (ATP)
Active transport - The movement of solutes against their concentration gradients using membrane transporters (e.g. the nervous system and muscular system depend on the active transport of sodium, potassium, and calcium ions)
Vesicular transport - Small sacs, or vesicles, move large quantities of material into or out of the cell
Describe the composition, location, and function of the DNA in a cell.
DNA is found in chromosomes, in the nucleus of the cell, where it is is grouped as genes. It is made up of nucleotides (each nucleotide has a phosphate unit and a sugar unit attached to a nitrogen base). Paired nitrogen bases (A-T, G-C) form the steps of the ladder in the double helix structure.
Compare the functions of three types of RNA in cells.
mRNA - Messenger RNA is a single-stranded RNA molecule that is complementary to one of the DNA strands of a gene. The mRNA copy leaves the cell nucleus and moves to the cytoplasm where proteins are made.
Transfer RNA (tRNA) molecules bring amino acids to the ribosomes to build each protein.
Ribosomes are composed of an RNA type called ribosomal RNA (rRNA) and also protein.
Explain briefly how cells make proteins
In the first step of protein synthesis, the DNA code is transcribed into messenger RNA (mRNA) by nucleotide base pairing. The mRNA leaves the nucleus and enters the cytoplasm, where an organelle called a ribosome moves along the mRNA, reads its base sequence, and uses the genetic code to translate each nucleotide triplet into its corresponding amino acid. Transfer RNA (tRNA) molecules bring amino acids to the ribosomes to build each protein. The rough ER (endoplasmic reticulum) then folds the protein.
Interphase
DNA replicates itself between one mitosis and the next. DNA uncoils itself and enzymes assemble the copy. The copies are held together at the centromere. Cells spend most of their time in interphase. Mature cells may spend all their time in interphase.
microvilli
Folded projections of plasma membrane found in certain cells that specialize in absorption e.g. in intestine, where they promote absorption of digested foods into the circulation. They are also found on kidney cells, where they reabsorb materials that have been filtered out of the blood.
What is osmotic pressure?
What does it mean in practice?
How is it related to a solution’s concentration?
The pressure needed to counteract osmosis.
In practice, it describes a solution’s tendency to draw in water.
The higher a solution’s concentration, the greater is its osmotic pressure.
What is endocytosis? List three examples.
Describes the movement of materials into the cell using vesicles.
Phagocytosis - large particles are engulfed by the plasma membrane englulfs large particles (The root phag/o means “to eat.”)
Pinocytosis - plasma membrane engulfs droplets of fluid (e.g. protein molecules in suspension) The word pinocytosis means “cell drinking.”
Receptor-mediated endocytosis - involves the intake of substances using specific binding sites, or receptors, in the plasma membrane. The bound material, or ligand, is then drawn into the cell by endocytosis. Some examples of ligands are lipoproteins (complexes of cholesterol, other lipids, and proteins) and certain vitamins.
What is exocytosis? List one example.
The cell moves materials OUT in vesicles. One example of exocytosis is the export of neurotransmitters from neurons.
How many genes do we have?
No more than 25,000 genes
Contrast the location, composition, and structure of DNA and RNA
DNA is almost entirely in the nucleus, contains deoxyribose, and is double stranded. RNA is almost entirely in the cytoplasm, contains ribose, and is a single strand. In terms of nitrogen bases, it has uracil (U) instead of thymine (T).
Locate mitochondria
