Cells Flashcards
5 marks
Compare and contrast the DNA in eukaryotic cells with the DNA in prokaryotic cells.
Comparisons
1. Nucleotide structure is identical
2. Nucleotides joined by phosphodiester bond
3. DNA in mitochondria and chloroplasts same structure to DNA in prokaryotes
Compare
4. Eukaryotic DNA is longer
5. Eukaryotic DNA contain introns, prokaryotic DNA does not
6. Eukaryotic DNA is linear, prokaryotic DNA is circular
7. Eukaryotic DNA is associated with histones proteins, prokaryotic DNA is not
Define pathogen
Microorganism that causes disease/ an immune response
5 marks
Describe difference between active and passive immunity
- Active involves memory cells, passive does not;
- Active involves production of antibody by plasma cells / memory cells;
- Passive involves antibody introduced into body from outside
- Active long term, because antibody produced in response to antigen
- Passive short term, because antibody (given) is broken down;
- Active (can) take time to develop, passive fast acting.
5 marks
When a vaccine is given to a person, it leads to the production of antibodies against a disease-causing organism. Describe how
- Vaccine contains antigen from pathogen
- Macrophage presents antigen on its surface
- T cell with complementary receptor protein binds to antigen;
- T cell stimulates B cell
- (With) complementary antibody on its surface
- B cell secretes large amounts of antibody
- B cell divides to form clone all secreting / producing same antibody.
3 marks
Desribe 3 functions of the golgi apparatus
- Modifies and packages proteins
- Modifies and packages lipids
- Makes lysosomes
How does passive immunity work
Passive involves antibody introduced into body from external source
Adding the antibody would cause agglutination and increase efficiency of phagocytosis
The human papilloma virus contains a double-stranded DNA genome.
Which components are found in a human papilloma virus? Choose one
* Capsid and attachment protein
* Capsid, attachment protein and reverse transcriptase
* Capsule and attachment protein
* Cell-surface membrane and attachment protein
Capsid and attachment protein
5 marks
Outline the similarities in, and the differences between, the structures of chloroplasts and mitochondria.
Similarities
1. Double membrane;
2. Both contain (circular) DNA;
3. Both contain ribosomes;
Differences
4. Thylakoids/lamellae/grana v cristae;
5. Stroma v matrix;
7. Starch grains v no starch grains;
2 marks
Suggest how Streptococcus bacteria with a thicker capsule are more likely to survive and so cause lung disease.
Phagocytes less likely to bind to murein in cell wall
This decreases pahgocytosis as theres more binary fission
3 marks
Explain why phospholipids can form a bilayer but triglycerides cannot.
- Phospholipid both hyrdophillic and hydrophobic
- Triglycerides only hydrophillic
- Hydrophillic phosphate head attracted to water
State one role of a helper T cell.
Stimulating cytotoxic T cells
Stimulating B cells
Stimulating phagocytes;
2 marks
Explain why viruses are described as acellular and non-living.
- Accelular= not made up of cells
- Non living= no metabolic reactions/ need a host cell to replicate
Give one reason why antibiotics are not effective against viruses.
doesnt have a cell wall
The movement of substances across cell membranes is affected by membrane structure. Describe how.
- Phospholids only allows non-polar, lipid-soulube molecules diffuse across phospholipid bilayer
- Phospholipid bilayer prevent diffusion of water- solube, polar molecules across membrane
- Carrier proteins allow active transport
- Carrier proteins and channel proteins allow facilitated diffusion
- Cholestrol affects rigidty/ fluidity
5 marks
Name and describe five ways substances can move across the cell-surface membrane into a cell.
- Simple diffusion of small/non-polar molecules down a concentration gradient
- Facilitated diffusion down a concentration gradient via protein carrier and 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
