large concepts - biology Flashcards
structure to function of STARCH
- starch= consists of 2 polysaccharides, amylose and amylopectin
amylose is a long unbranched chain of alpha glucose. it is coiled, making it compact, so more glucose can be stored in a small space.
amylopectin is a long branched chain of alpha glucose. the many branches allow for enzymes to easily break the glycosidic bonds, meaning glucose can be easily released.
starch is also insoluble, so has no osmotic effect.
structure to function of GLYCOGEN
- glycogen= highly branched , so enzymes can easily hydrolyse glycogen into glucose, meaning glucose can be easily released.
highly branched means its also compact, so is hence a good storage molecule.
structure to function of CELLULOSE
- cellulose= long, straight unbranched chains of beta glucose.
cellulose chains are linked by hydrogen bonds to form microfibrils.
because of the many hydrogen bonds and microfibrils, cellulose has a high tensile strength which provides support to cell walls and prevents them bursting under high water pressure
structure to function of TRIGLYCERIDES
- triglycerides= Triglycerides are mainly used as energy storage molecules. This is because the long hydrocarbon tails of the fatty acids in triglycerides contain large amounts of chemical energy, which can be released when the fatty acids are broken down. they are insoluble, meaning that they don’t affect the water potential inside the cell.
structure to function of PHOSPHOLIPIDS
- phospholipids= phosphate group is hydrophilic (water-loving), whereas the two fatty acids are hydrophobic (like in triglycerides).
This makes phospholipids suitable for making up the bilayer of cell membranes, with the fatty acids facing inwards and the phosphate groups facing outwards.
This is also useful as it means the centre of the phospholipid bilayer is hydrophobic, meaning water-soluble substances cannot easily pass through.
This allows the cell membrane to act as a barrier, controlling what substances enter and leave the cell
binary fission process (prokaryotic cells replication)
- the circular DNA and plasmids replicate. the main DNA loop is only replicated once but plasmids, many times.
- the cell gets bigger and the DNA loops move to opposite poles of the cell
- the cytoplasm begins to divide (and new cell walls begin to form)
- the cytoplasm divides and 2 daughter cells are formed. each daughter cell has one copy of the circular DNA, but contains a variable number of copies of the plasmids.
hiv replication stages
- the attachment protein attaches to a receptor molecule on the cell membrane of a T-helper cell
- the capsid (from HIV) is released into the T-helper cell, where it uncoats and releases its genetic material (RNA) into the cells cytoplasm
- inside the cell, reverse transcriptase is used to make a complementary strand of DNA from the viral template
- from this, double stranded DNA is made and inserted into the human DNA
- host cell enzymes are used to make viral proteins from the viral DNA found within the human DNA
- the viral proteins are assembled into new viruses which bud from the cell and go infect other cells.
phagocytosis stages-
- phagocytes detect pathogens when receptors on its surface bind to antigens on the pathogen
- phagocyte engulfs the pathogen
- pathogen is contained within a phagosome
- lysosome containing lysozymes fuses with the phagosome to form a phagolysome
- lysozymes digest the pathogen and destroy it
- phagocyte presents antigen on cell surface (APC), then the digested pathogen will be removed from the phagocyte by exocytosis
transcription stages
- DNA helicase breaks the hydrogen bonds between bases, unzipping DNA helix exposing bases
- free RNA nucleotides bond to the exposed complementary DNA bases, zipping up complementary nucleotides
- RNA polymerase forms phosphodiester bonds between the nucleotides and hydrogen bonds between complementary bases
- once mRNA strand is complete, it detaches from the template and leaves nucleus through nuclear pores
translation stages
- mRNA binds to ribosome at the ‘AUG’ start codon
- complementary tRNA binds to start codon on mRNA
- another complimentary tRNA anticodon binds to the next codon on the mRNA
- a peptide bond is formed between the 2 amino acids
- once a peptide bond is formed, the first amino acid exits the ribosome and the ribosome moves onto the next codon and the process repeats
- this process ends when a stop codon is reached and the primary structure of the protein is completed
what happens during interphase?
interphase= the cell prepares for mitosis by growing larger, replicating Its organelles and synthesising new DNA. Once DNA nas replicated, each chromosome consists of 2 sister chromatids, connected by a structure called the centromere Mitochondria produce more ATP for cell division
what happens during prophase?
prophase= the chromosomes condense, and the nuclear envelope disintegrates. centrioles move to opposite poles and form spindle fibres
what happens during prophase?
prophase= the chromosomes condense, and the nuclear envelope disintegrates. centrioles move to opposite poles and form spindle fibres
what happens during metaphase?
metaphase= the chromosomes line up along the middle of the cell. They attach to the spindle fibres by their centromeres
what happens during anaphase?
anaphase = the centromere splits and the chromatids are pulled to opposite poles of the cell
