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PREVIOUS IB CELL EXAM QUESTIONS

Cells

2.1.1
Cell Theory:
-Cells are the smallest unit of life
-All cells come from pre-existing cells
-All organism are composed of one or more cells

2.1.2
-Robert Hooke utilized the microscope and looked at thin slices cork seeing that it was composed of smalls components late looked like prison cells. There ore the name "cells" is used.
-Leeuwenhook observed single cellular organisms
-Schleiden found that plants where constructed of cells and Schwann found that all animals were made of cells as well.
-Pasteur debunked "spontaneous generation" therefore proving that all cells came from pre-existing cells

2.1.3
Singled cellular organism carry out all the functions of life.

2.1.4


List the functions of membrane proteins including hormone binding sites, enzymes, electron carriers, channels for passive transport and pumps for active transport.
(Acronym to help remember) PEECH:
  • Pumps for active transport.
  • Enzymes
  • Electron carriers
  • Channels for passive transport
  • Hormone binding sites.
- Hormone binding sites: Exposed on the outside of the membrane which allows it to bind to one specific hormone. A signal is transmitted to inside of cell.
- Enzymes: Located in membranes and catalyze reactions inside or outside of cell depending on its position (inner/outer active site).
- Electron carriers: Arranged in chains in the membrane which allows electrons to pass from one carrier to another.
- Channels for passive transport: Passages through the centre of membrane proteins that allows a specific substance to pass through
- Pumps for active transport: Release energy from ATP and use it to move specific substances across the membrane.

Define diffusion and osmosis.


  • Diffusion: is the passive movement of particles from a region of higher concentration to a region of lower concentration, as a result of the random motion of particles.
  • Osmosis: the passive movement of water molecules, across a partially permeable membrane, from a region of lower solute concentration to a region of higher solute concentration.
Explain passive transport across membranes in terms of diffusion.

  • A molecule or ion that crosses the membrane by moving down a concentration or electrochemical gradient and without expenditure of metabolic energy is said to be transported passively/diffused. All molecules and ions are in constant motion and it is the energy of motion - kinetic energy - that drives passive transport. Transport of uncharged species across a membrane is dictated by differences in concentration of that species across the membrane - that is, by the concentration gradient. For ions and charged molecules, the electrical potential across the membrane also becomes critically important. Together, gradients in concentration and electric potential across the cell membrane constitute the electrochemical gradient that governs passive transport mechanisms.

Explain the role of protein pumps and ATP in active transport across membranes.
Active transport is the movement of substances across membranes using energy from ATP. Active transport can move substances against a concentration gradient. Protein pumps in the membrane are used for active transport. Each pump only transports particular substances so cells can control what is absorbed and what is expelled.
Explain how vesicles are used to transport materials within a cell between the rough endoplasmic reticulum, Golgi apparatus, and plasma membranes.
Proteins are synthesized by ribosomes and then enter the rough endoplasmic reticulum. Vesicles bud off from the rough ER and carry the proteins to the Golgi apparatus. The Golgi apparatus modifies the proteins. Vesicles bud off from the Golgi apparatus and carry the modified proteins to the plasma membrane.
Describe how the fluidity of the membrane allows it to change shape, break and reform during endocytosis and exocytosis
In endocytosis part of the plasma membrane is pulled inwards. A droplet of fluid becomes enclosed when a vesicle is pinched off. Vesicles can then move through the cytoplasm carrying its contents. In exocytosis vesicles fuse with the plasma membrane. The contents of the vesicles are then expelled. The membrane flattens out again.

9. Multicellular organisms show emergent properties.
10. Explain that cells in multicellular organisms differentiate to carry out specialized functions by expressing some of their genes but not others.
This is called cellular differentiation which is the differentiation of cells in specific ways. Things such as hormones and chemicals determine how cells develop. Each and every cell in a multicellular organism's body specializes for one particular function.All cells contain a nucleus, chromosomes, and DNA which is split up into genes. Every single cell contains genes which can develop in any way but not all of the genes are turned on while others are. An example of this would be that the cells in our skin contain genes to make the pigment of our eye color but the genes are just turned off, they are there but just not currently being used.
11. and 12. Annotated diagram of the Ultrastructure of Escherichia Coli (E.coli) as a prokaryote.


prokaryotic_cell.jpg.
13. Electron Micrograph of E.Coli

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14. Diagram of the ultrastructure of a liver cell as an example of an animal cell.
liver.jpg

15. A prokaryotic cell is a type of cell that lacks a membrane-enclosed nucleus and membrane-enclosed organelles. Organisms with prokaryotic cells (bacteria and Archaea) are called prokaryotes.
A eukaryotic cell is a type of cell with a membrane-enclose nucleus and membrane-enclosed organelles. Organisms with eukaryotic cells (protists, plants, fungi, and animals) are called eukaryotic.
16. Plant cells have a cell wall, chloroplasts, tonoplasts and vacuoles whereas animal cells do not. Animal cells have lysosomes, an extracellular matrix, and flagellum whereas plant cells do not.
17. The cell wall of plant cells help distinguish them from animal cells and also protects the plant cell, maintains its shape, and prevents the excessive uptake of water.
18.
external image Cell_membrane.png



19. The cell membrane consists primarily of a thin layer of phospholipids which arrange so that the hydrophobic "tail" regions are shielded from the surrounding fluid, causing the more hydrophilic "head" regions to associate with the cytosolic and extracellular faces of the resulting bilayer. This forms a continuous, spherical lipid bilayer.
The arrangement of hydrophilic heads and hydrophobic tails of the lipid bilayer prevent polar solutes (e.g. amino acids, nucleic acids, carbohydrates, proteins, and ions) from diffusing across the membrane, but generally allows for the passive diffusion of hydrophobic molecules.