Cells Flashcards

Question

Describe active transport

Answer 1

Movement of molecules or ions through a partially permeable membrane By carrier proteins against a concentration gradient Requires energy from the hydrolysis of ATP produced during respiration

Answer 2

Ions e.g. Na+ pass through the protein pore (space in the middle)‎‏‏‎

Answer 3

Polar molecule e.g. glucose diffuses into carrier protein molecule Polar molecule binds to carrier protein - which has a specific tertiary structure complementary to the polar molecule and causes it to change shape Polar molecule diffuses out of carrier protein

Answer 4

Allows the transport of polar molecules e.g. glucose and amino acids across membranes down a concentration gradient through a membrane Involves the use of carrier and channel proteins

Answer 5

Surface area (↑surface area =↑rate of diffusion) Concentration gradient (↑concentration gradient =↑rate of diffusion) Diffusion distance (↑Diffusion distance = ↓rate of diffusion)

Answer 6

Carrier proteins = allow transport of polar molecules by facilitated diffusion and active transport Channel proteins = determines which molecules can be transported across the membrane by facilitated diffusion Embedded proteins = important in 'cell signalling' and act as specific receptors for hormones Glycoproteins = act as receptors and involved in cell-cell recognition as they can act as antigens

Answer 7

Provides strength to the membrane and restricts the movement of phospholipids So that the membrane is less fluid and less ions are lost from the cell‎‏‏‎ ‎‏‏‎ ‎‏‏‎ ‎‏‏‎

Answer 8

Hydrophilic heads of the phospholipid bilayer are oriented outwards towards the watery extra-cellular fluid Hydrophobic tails of phospholipid bilayer are oriented towards each other Phospholipid bilayer enables lipid soluble molecules (e.g. CO2 & O2) to pass quickly through the cell membrane

Answer 9

Fluid structure = phospholipid molecules are constantly moving about Mosaic = uneven distribution of protein molecules throughout the membrane

Answer 10

Proteins / glycoproteins that appear ‘foreign’ to the individual organism exposed to them

Answer 11

Some micro-organisms have a high mutation rate and therefore lead to antigen variation Even though a person may become 'immune' to one strand, this will not provide immunity to new forms as they wont be recognised by memory B cells and antibodies

Answer 12

Phagocyte engulfs (eats) the pathogen Forms a vesicle that fuses with lysosomes Hydrolytic enzymes in lysosome digests the pathogen

Answer 13

Antigen is presented to helper T cell by antigen-presenting cell (phagocyte) Helper T cells with complementary protein receptor will bind to antigen This stimulates the Helper T cells to divide by mitosis to produce clones

Answer 14

Activate cytotoxic T cells - these attach to the specific antigen on a pathogen and secret chemicals to destroy it Develop into more helper T cells which stimulate B lymphocytes to divide into plasma cells and secrete antibodies Develop into memory T cells - these remain in blood after infection for a quicker secondary response

Answer 15

Antigen binding sites on the antibodies have a specific tertiary structure that is complementary to the structure of the antigen to which they attach to This forms an antibody-antigen complex that is stimulates agglutination

Answer 16

Antibody uses its two antigen-binding sites to attach to same antigen present on two different cells This joins the cells together to form a clump (agglutinated mass) of cells Clump is then more easily destroyed by e.g. phagocytosis

Answer 17

Antibody attaches to antigen on the surface of a bacteria and identifies it for destruction by the phagocyte Receptors on the phagocyte recognise and bind to antibody Enables phagocyte to perform phagocytosis

Answer 18

Plasma cells produce antibodies and secret them into blood Antibodies will bind specifically to the antigens to form antibody-antigen complex This stimulates the processes that destroy the antigen/pathogen to occur

Answer 19

Some B cells are simulated to divide into memory B cells If the same antigen is encountered by memory B cells again, they will divide and develop into plasma cells These plasma cells will secrete antibodies quicker and at a higher concentration than primary response which therefore, provides immunity

Answer 20

Vaccine contains antigens from a dead/weakened pathogen T helper cell with a complementary receptor protein binds to the antigen T helper cell stimulates the B cell to release antibodies and develop into plasma and memory B cells These memory cells provide long-term immunity

Answer 21

The higher the percentage of people in a population that are vaccinated against a particular antigen/pathogen, the smaller the chance of infection This is because the probability of encountering an unprotected individual with that particular pathogen will be lower Note: This will most likely come up as an evaluation type question but AQA have stated that you must know what the term herd immunity means

Answer 22

Attachment proteins are used to attach to receptors on helper T cell RNA is injected into the host cell Reverse transcriptase converts RNA to DNA Viral proteins are produced Virus particles assembled and are released from the cell to infect others

Answer 23

Antibiotics affect cellular structures either inhibiting their division or destroying them Viruses do not contain cellular structures

Answer 24

You can attach a therapeutic drug to a monoclonal antibody For instance, cancer cells display a different antigen to healthy cells so can be targeted by attaching a toxic drug to a monoclonal antibody

Answer 25

To detect presence of specific antigens (i.e. pathogens) in body fluids to diagnose if a person is infected with a particular disease To detect presence of specific antibodies produced by a person against an antigen