topic 2 - cells Flashcards

Question

What is facilitated diffusion?

Answer 1

Passive process but differs from simple diffusion as proteins are used to transport molecules The movement of ions and polar molecules, which cannot simply diffuse, can be transported across membranes using protein channels and carrier proteins

Answer 2

Carrier proteins - take substances from one side of the membrane to the other Often done by co-transport e.g. when the ion potassium is transported along the main substance glucose Protein channels - protein pores that open or close to control the passage of selective ions e.g. potassium , sodium

Answer 3

The movement of water particles from an area of higher water potential to an area of lower water potential across a partially permeable membrane

Answer 4

A measure of how easily water can move When many water molecules are present they can move easier and so the higher the water potential Measured in kilopascals (kPa)

Answer 5

The movement of molecules and ions from an area of lower concentration to an area of higher concentration using ATP and carrier proteins. The carrier proteins act as pumps to move substances across the membrane Very selective as only certain molecules can bind to the carrier proteins to be pumped ATP binds to the protein on the inside of the protein and is hydrolysed into ADP and Pi. This causes the protein to then change shape and open towards the inside of the membrane, releasing the contents when the Pi molecule is released, the protein reverts back to its original shape

Answer 6

Free DNA that possesses the genetic info for the replication of bacterial cells Plasmids - small circular DNA strands Cell wall- physical barrier against certain substances Capsule - protects bacterium from other cells Flagellum - to move Mesosome - site of respiration

Answer 7

Extrinsic - on the surface or only partially embedded in membrane. Give mechanical support to cell/ act as cell receptors for molecules such as hormones Intrinsic - completely span the membrane and act as carriers to transport water-soluble materials across the membrane

Answer 8

A parent cell divides to produce 2 genetically identical daughter cells Needed for growth of multicellular organisms and for repairing damaged tissues

Answer 9

Mitosis - cycle starts and ends here G1 - Gap phase 1 - cell grows and new organelles and proteins are made S- Synthesis - cell replicates all DNA, ready to divide by mitosis G2 - Gap phase 2 - cell keeps growing, and proteins needed for cell division are made

Answer 10

1 - Interphase - cell grows and DNA replicates, chromosomes not yet formed (DNA in the form of chromatin) NOT apart of mitosis 2- Prophase - chromatin condenses to form chromosomes. Centrioles move to opposite ends of cell, nuclear envelope breaks down 3- Metaphase - chromosomes align along equator of cell -Spindle fibres connect centrioles to chromosomes by their centromeres 4- Anaphase - centromeres split, allowing chromatids to split 5. Telophase - chromatids reach opposite ends of the poles - nuclear envelopes reform, forming 2 nuclei. 5- Cytokinesis - cytoplasm divides, 2 daughter cells have now formed

Answer 11

Foreign proteins present on the cell surface membrane that stimulate an immune response.

Answer 12

A phagocyte is a type of white blood cell a phagocyte recognises the foreign antigens on a pathogen the cytoplasm of the phagocyte moves around the pathogen, engulfing it the pathogen is now contained in a phagocytic vacuole a lysosome fuses with the phagocytic vacuole and uses its lysozymes to break down the pathogen the phagocyte then presents the pathogen's antigens on its surface, becoming an antigen-presenting cell this activates other immune system cells

Answer 13

T-cells are another type of white blood cell/ they have receptor proteins on their surface that bind to complementary antigens presented to them by phagocytes - this activates the T-cell. Helper T-cells release chemical signals that activate and stimulate phagocytes and cytotoxic T-cells which kill abnormal and foreign cells T-cells also activate B-cells

Answer 14

B-cells are also a type of white blood cell They are covered with antibodies that bind to antigens to form an antigen-antibody complex. This activates the B-cell to divide into plasma cells Plasma cells are clones of B-cells They secrete loads of antibodies specific to the antigen An antibody has 2 binding sites so can bind to 2 pathogens at the same time. this means pathogens can become clumped together (agglutination). Phagocytes then bind to the antibodies and phagocytose as many pathogens at once