Biology ATAR Unit 2 Review - Cells

Describe the differences between prokaryotes and eukaryotes. (4)

Prokaryotic cells are unicellular.

Instead of storing their DNA in the nucleus, they have small rings of DNA within the cytoplasm called plasmids.

They do not have a true nucleus, but rather bacterial chromosomes called nucleotides.

They do not have membrane bound organelles.

Eukaryotic cells are multicellular, consisting of a true nucleus, which contains linear chromosomes.

They have membrane organelles and are more larger and complex.

State the cell theory. (3)

The idea that cells are fundamental units of life is part of the cell theory. The basic principles of the theory (as developed by early biologists) are:

1. All living things are composed of cells 

2. New cells are formed only by division of pre-existing cells

3. The cell contains inherited information (genes) that used as instructions for growth, functioning and development

4. The cell is the functioning unit of life; all chemical reactions of life take place within cells 

Define a heterotroph. (1)

A heterotroph is an organism that cannot produce their own food, thus obtain nutrition by consuming other organisms.

Describe the different types of autotrophs. (3)

An autotroph itself is an organism that can produce its own food by surrounding resources, such as a plant. A photoautotroph is an organism that uses light energy to produce their food via photosynthesis. A chemoautotroph uses chemical reactions to produce their own food via chemosynthesis.

Explain Endosymbiosis. (3)

Endosymbiosis is when eukaryotic cells were formed when a eukaryotic cell was ingested by another primitive prokaryotic cell.

1. A predatory prokaryote engulfs aerobic bacteria, and after a long period of time, the aerobic bacteria became mitochondria.

2. It then splits into the different types of cells, including the primitive eukaryotic animal cell.

3. Another type of cell was when some cells engulf photosynthetic cyanobacteria, which would become chloroplasts in photosynthetic plant cells.

Identify the differences between animal and plant cells. (3)

Plant cells have chloroplasts, a cell wall and a central, permanent vacuole.

An animal cell only has small, temporary vacuoles.

What is the purpose of the cell membrane? (4)

Barrier: boundary between intracellular and extracellular environment
Linkage: pin cells together, a 3D structure
Transport: controls the exit and entry of substances
Communication: recognition of self and changes to cellular activity

What is the fluid mosaic model? (2)

The phospholipid bilayer has the ability to flow and the embedded proteins can move around in the layer.

What are the purposes of the embedded proteins in the fluid mosaic model? (7)

Phosphate head - hydrophilic = water attraction
Fatty acid tail - hydrophobic = water repulsion
Transporter Proteins - carrier and channel proteins, allows specific molecules to cross
Receptor Proteins - binds specific substance to alter cellular activity
Recognition Proteins - contains antigens to identify itself and aid in communication
Adhesive Proteins - allows cells to stick together and maintain 3D shape
Cholesterol - flexibility of membrane

Passive transport - describe simple and facilitated diffusion.

(get old biology workbook to answer)

What are the stages of vesicular transport? (6)

Endocytosis
1. The membrane surrounds the molecule from the ECF
2. Using energy in the form of ATP, it forms a vesicle around the molecule
3. The vesicle can then be transported to its target inside the cell

Exocytosis
1. A vesicle is formed around the molecule, using energy in the form of ATP
2. The vesicle migrates to the cell membrane and fuses
3. The vesicle empties its contents from the ICF to ECF

What are the factors that affect transport across the cell membrane? (6)

Chemical Properties
Physical Properties
Temperature
Transport Proteins
Concentration Gradient
Surface Area to Volume Ratio

How do physical and chemical properties affect transport across the cell membrane? (6)

Physical: a larger particle is slower to move across because it requires a transporter protein or vesicle. A smaller particle is faster because it may be able to directly cross the bilayer.
Chemical
Charged vs uncharged: a charged particle is slower because it needs a transporter protein.
Solubility: lipids are faster because they can pass through directly. Water is slower because it cannot pass directly.