Important things Flashcards
What are the steps of heart excitation causing a heartbeat?
Sinoatrial node produces an electrical signal that travels through the atria, causing them to contract.
This signal then travels down the Atrioventricular node to the ventricles along the bundles of His. (Left and right) after a short delay to allow blood filling.
The electrical signal then travels to the base apex of the heart and moves upwards, causing a contraction originating at the apex. It starts at the base to ensure that all blood is emptied from the heart.
What are the steps of translocation?
- Sucrose from photosynthesis is co-transported with hydrogen ions into companion cells
- Sucrose therefore decreases Ψ in phloem, so water enters from xylem. This creates hydrostatic pressure that pushes fluid along the phloem.
- Companion cells actively transport sucrose out of the phloem
- The surrounding cells then have a more negative Ψ than the phloem, so water leaves the phloem and enters the cells.
- Cells either use the sucrose or convert it into starch for storage, and thus the concentration remains low, keeping a Ψ gradient.
What are the steps of oxygen dissasociation?
Carbon dioxide diffuses into erythrocytes and is reacted with water by carbonic anhydrase to form carbonic acid
Carbonic acid dissociates into hydrogen carbonate, which diffuses out of the cells, and hydrogen ions
Negative chloride ions diffuse into the cell to balance the positive hydrogen ions – chloride shift.
The hydrogen ions bind to haemoglobin, producing haemoglobinic acid and causing dissociation of oxygen
What are the four mains points of interest in an electrocardiogram?
- The atrioventricular valve closing
- The semilunar valve opening
- The semilunar valve closing
- The AV valve opening
What are the apoplast and symplast?
Apoplast = Water moves between/around cells. Dissolved substances are transported this way. Symplast = Water enters cells and moves through cytoplasm via plasmodesmata
What are the channels that water travels through called?
Aquaporins
What precautions must you take when setting up a potometer?
Cut shoot underwater Cut shoot at a slant Dry off leaves Make sure there are no bubbles Keep (named) conditions constant - Temp, wind, humidity, light
What is transpiration?
The evaporation of water into the atmosphere via stomata out of a leaf
How do xerophytic plants decrease water loss by transpiration?
- Photosynthesis in stem - Reduces water loss through leaves - Do not say if asked
- A thick waxy cuticle increases diffusion distance
- Large volume for storage
- Hairs can trap moist air, making air around humid
- Roll leaves into cylinders keeps stomata on inside
- Needle leaves reduce SA:Vol ratio
Why is transpiration in plants unavoidable?
Gas exchange means stomata have to open which causes a water potential gradient, and so water moves out into the drier air.
How do fish ventilate?
The buccal (mouth) cavity is increased to draw water in and the operculum (gill flaps) ensure water flows continuously over the gills to maintain the concentration gradient. High-oxygenated water meets high-oxygenated blood at the front of the filament, and low oxygenated water meets deoxygenated blood towards the back of the filament. This maintains the concentration gradient along the length of the lamellae. This is called counter-current exchange.
What are the main parts of insect gas exchange systems?
Spiracle - Small pores forming the entrance to the tracheae. Can be closed.
Tracheae - Main tubes
Tracheoles - Small tube that connect to muscles. The ends are filled with water.
What are the steps of passive ventilation?
Inhalation
• Diaphragm contracts
• Intercostal muscles contract
• Chest expands
• This increases the volume of the thorax and so pressure decreases below atmospheric pressure.
• Due to this change in pressure, air is sucked into the lungs until the pressure is regulated.
Exhalation
• Diaphragm relaxes
• Intercostal muscles relax
• Therefore, the chest returns to normal size
• The thorax volume decreases, increasing pressure to above active pressure.
• Air is pushed out of the lungs into the surroundings, returning the pressure to normal.
How is forced ventilation different to passive ventilation?
Forced
Inhalation
• As well as the intercostal muscles and the diaphragm moving, the accessory muscles in the neck may also move to elevate the sternum and the first 2 ribs.
• This, along with maximum contraction means that the pressure decreases much more and so much more air flows in.
Exhalation
• The abdominal muscles contract and force the diaphragm upward.
• Contraction of the internal intercostal muscles actively pulls the ribs downwards.
• Therefore, a much higher pressure is created due to the smaller lung volume.
Why is DNA an ideal genetic substance?
It is degenerate - 1 amino acid has multiple codons
It is a stable molecule
It can replicate accurately
What is antigenic drift?
What is antigenic shift?
Antigenic drift = When a virus mutates over time, so that the antibody is slightly different and so people are less immune to it.
Antigenic shift = When two or more viruses combine to form a new subtype with a mixture of antigens, often coming from other animals.
What type of pathogen is malaria?
A protoctist, meaning it travels using a vector and mutates often.
What are the cell signalling molecules called?
Cytokines
How thick is the cell surface membrane?
7nm
What are the roles of glycoproteins?
stabilises membrane structure by forming hydrogen bonds with water molecules;
antigens for cell recognition;
binding sites, for, chemicals/ drugs / hormones / neurotransmitters/ antibodies /T cells;
receptors for cell signalling / triggers chemical reactions inside cell;
What are the roles of cell surface membranes?
S1 separate cell from environment;
S2 control, entry/exit (of molecules/ions/suitable substance); A selective/partial R semi-permeable
S3 use of phospholipid layer (in allowing or preventing passage) of suitable example;
S4 reference to facilitated diffusion;
S5 reference to active uptake; R channel protein
S6 reference phagocytosis/pinocytosis/endocytosis/exocytosis;
S7 cell recognition/cell surface antigens;
S8 cell to cell attachment;
What are the roles of cell membranes inside a cell?
W1 compartmentalise/surrounds organelles;
W2 prevents disruption of, reactions/process; A reaction more efficient
W3 e.g. reaction/process, and organelle;
W4 reactions take place on membranes; A named example of membrane
W5 enzymes attached to membranes; A named example
W6 isolates/separates, DNA/nucleus;
W7 (nuclear pore) permits RNA to leave nucleus;
W8 (forms) ER/(Golgi) vesicles/lysosomes/other named organelle; (not the same e.g. as W3 or W6)
W9 attachment of ribosomes;
W10 intracellular transport;
What are the steps of transcription?
- The DNA unzips in the region of the gene to be transcribed. This is done by DNA helicase.
- Free RNA nucleotides are then attracted by base complementarity (to the antisense strand)
- These RNA nucleotides are joined together to form mRNA by RNA polymerase
- This mRNA leaves the nucleus and goes to the ribosomes, and the DNA returns to normal
What are the steps of translation?
- The ribosome binds to mRNA at a specific area.
- The ribosome starts matching tRNA anticodon sequences to the mRNA codon sequence.
- Each time a new tRNA comes into the ribosome, the amino acid that it was carrying gets added to the elongating polypeptide chain.
- The ribosome continues until it hits a stop sequence, then it releases the polypeptide and the mRNA.
- The polypeptide forms into its native shape and starts acting as a functional protein in the cell.
