cells topic 2 EQ Flashcards
Name and describe five ways substances can move across the
cell-surtace membrane into a cell (5)
•(Simple) diffusion of small/non-polar molecules down a concentration gradient
•Facilitated diffusion down a concentration gradient via protein carrier/channel
•Osmosis of water down a water potential gradient
•Active transport against a concentration gradient via protein carrier using ATP
•Co-transport of 2 different substances using a carrier protein
The movement of Na* out of the cell allows the absorption of glucose into the cell lining the ileum.
Explain how. (2)
•generates a concentrationgradient
for Na* (from ileum into cell)
•Na* moving (in) by facilitated diffusion, brings glucose with it
Describe and explain two features you would expect to find in a cell specialised for absorption. (2)
•Folded membrane/microvilli so large surface area
•Large number of mitochondria so make (more) ATP (by respiration)
•Large number of carrier proteins for active transport
The movement of substances across cell membranes is affected by membrane structure. Describe how. (5)
•Phospholipid bilayer allows movement of non-polar substances
•Phospholipid bilayer prevents movement of polar substances
•Carrier proteins allow active transport
•Channel/carrier proteins allow facilitated diffusion/co-transport
•Number of channels/carriers determines how much movement
Give two similarities in the movement of substances by diffusion and by osmosis. (2)
-Movement down a concentration gradient
-Passive processes
Eukaryotic cells produce and release proteins.
Outline the role of organelles in the production, transport and release of proteins from eukaryotic cells.(5)
-Dna in nucleus is a code for protein
-ribosomes produce proteins
-mitochondria produce atp for protein synthesis
-golgi apparatus packages
-vesicles transport
The detail shown in the diagram above would not be seen using an optical microscope. Explain why (2)
-Light has longer wavelength
-Lower resolution
Contrast how an optical microscope and a transmission electron microscope work and contrast the limitations of their use when studying cells. (6)
-TEM use electrons and optical use light
-TEM allows a greater resolution
-So with TEM smaller organelles can be observed
-TEM view only dead and optical can view live specimens
-Only optical can show colour
Explain why the solution the biologist used was ice-cold, buffered and the same water potential as the liver tissue (3)
Ice-cold - Slows enzyme activity to prevent digestion of organelles / mitochondria
-Buffered - Maintains pH so that enzymes / proteins are not denatured
-Same water potential - Prevents osmosis so no lysis
Describe the appearance and behaviour of chromosomes during mitosis. (5)
Prophase
-chromosomes condense and become visible
Metaphase
-chromosomes line up at equator of cell
-chromosomes attached by spindle fibres
Anaphase
-centromere devides
-chromosomes pulled to opposite poles
Telophase
-chromosomes become longer and thinner
Contrast the processes of facilitated diffusion and active transport.(3)
-Facilitated diffusion involves channel or carrier proteins whereas active transport only involves carrier proteins
-Facilitated diffusion does not use ATP / is passive whereas active transport uses ATP
-Facilitated diffusion takes place down a concentration gradient whereas active transport can occur against a concentration gradient.
Describe how HIV is replicated. (4)
-Attachment proteins attach to receptors on helper T cell
-Nucleic acid/RNA enters cell
-Reverse transcriptase converts RNA to DNA
-Viral protein/capsid/enzymes produced
-Virus (particles) assembled and released
Describe how a phagocyte destroys pathogen in blood (3)
-engulfs
-phagosome fuses with lysosome
-enzyme digest pathogen
Describe the role of antibodies in producing a positive result in an ELISA test. (4)
-First antibody binds to complementary in shape antigen
-Second antibody with enzyme attached is added
-Second antibody attaches to antigen
-Substrate solution added and colour changes
