Answer:
Carbohydrates, particularly glycoproteins act as ligands for cell surface receptors.
Explanation:
Glycoproteins
- Glyproteins are conjugate molecules comprising of carbohydrates conjugated with proteins.
- Glycoproteins play a vital role in cell-cell recognition, pathogen recognition and and cell adhesion.
- Glycoproteins on the surface of pathogens act as prominent antigens for the immune system.
Glycoproteins in Fertilization:
Several glycoproteins are attached to the surface of the zona pellucida, the envelope of the oocyte. In humans, these have been termed as ZP1-4.
Glycoprotein-sperm interaction is one of the most crucial steps in fertilization. This receptor-ligand interaction ensures the entry of the sperm into the zona pellucida, the extracellular coat, covered in glycoproteins that surrounds the oocyte or egg.
Carbohydrate binding proteins present on the surface of the sperm recognize the glycoproteins on the zona pellucida (ZP). This enables them to adhere to the surface of the ZP and also to gain access to the oocyte.
False - they send messages out to the brain
The bases are at the interior of the double helix and are neatly stacked.
The phosphate groups groups are at the exterior of the DNA molecule
The sugar groups are at the interior of the DNA molecule
Most genes contain the information needed to make functional molecules called proteins. (A few genes produce other molecules that help the cell assemble proteins.) The journey from gene to protein is complex and tightly controlled within each cell. It consists of two major steps: transcription and translation. Together, transcription and translation are known as gene expression.
During the process of transcription, the information stored in a gene's DNA is transferred to a similar molecule called RNA (ribonucleic acid) in the cell nucleus. Both RNA and DNA are made up of a chain of nucleotide bases, but they have slightly different chemical properties. The type of RNA that contains the information for making a protein is called messenger RNA (mRNA) because it carries the information, or message, from the DNA out of the nucleus into the cytoplasm.
Translation, the second step in getting from a gene to a protein, takes place in the cytoplasm. The mRNA interacts with a specialized complex called a ribosome, which "reads" the sequence of mRNA bases. Each sequence of three bases, called a codon, usually codes for one particular amino acid. (Amino acids are the building blocks of proteins.) A type of RNA called transfer RNA (tRNA) assembles the protein, one amino acid at a time. Protein assembly continues until the ribosome encounters a “stop” codon (a sequence of three bases that does not code for an amino acid).
The flow of information from DNA to RNA to proteins is one of the fundamental principles of molecular biology. It is so important that it is sometimes called the “central dogma.”
The position of Met seems incorrect.The amino acid sequences of all proteins begin with Met because it is the amino acid that is attached to the anticodon for the AUG start codon.<span>It looks like the student might have worked in a backward direction for transcription. </span>
