Cells

Question 1

Explain the fluid mosaic model

Answer 1

• Cell membrane is fluid in that phospholipids and proteins are not stationary but can move rapidly across surface of membrane
• Cell membrane is a mosaic in that many different protein molecules are randomly scattered and embedded throughout phospholipid bilayer

Question 2

What can pass through the phospholipid bilayer

Answer 2

• Small hydrophobic molecules

Question 2

Describe structures and functions of cell membrane

Answer 2

• Partially permeable
• Protects cell from surrounding environment
• Controls movement of substances in/out of cell

Question 3

What does cytoplasm contain

Answer 3

• Cytosol
• Cytoskeleton
• Organelles

Question 3

What is cytosol

Answer 3

• Aqueous solution of essential ions, soluble proteins and soluble organic compounds like sugars and amino acids

Question 3

What is cytoskeleton

Answer 3

• Network of protein fibres that give support, motility and regulation to cell

Question 4

Describe structures and functions of nucleus

Answer 4

• Largest organelle in cell
• Spherical
• Consists of nuclear envelope which separates nucleus from cytoplasm
• Contains nucleolus which synthesises ribosomes
• Found in all cells except red blood cells
• Contains hereditary material
• Controls all cell activities

Question 4

Define cytoplasmic streaming

Answer 4

Cytoplasmic streaming is the movement of cytoplasm within a cell, which aids in the transport of materials and organelles around the cell

Question 5

Describe structures and functions of rough endoplasmic reticulum

Answer 5

• System of flattened membrane-bound sacs
• Protein synthesis
• Polypeptide chains synthesised by ribosomes are folded in RER

Question 6

Describe structures and functions of smooth endoplasmic reticulum

Answer 6

• Consists of fine tubules
• Lipid synthesis
• Detoxification of drugs and poisons
• Storage and release of calcium ions

Question 7

Describe structures and functions of Golgi apparatus

Answer 7

• Consists of stacks of flattened membrane-bound sacs
• Chemically modifies products received from ER, packages them, then sends them to destinations in/out of cell via vesicles

Question 8

Describe structures and functions of lysosomes

Answer 8

• Small, spherical vesicles
• Contains hydrolytic enzymes (lipases, proteases, nucleases)
• Digest materials in cell by phagocytosis
• Digest worn-out organelles by autophagy

Question 9

Describe structures and functions of animal vacuoles

Answer 9

• Fluid-filled sac bound by single membrane
• Formed by pinching-off part of cell membrane or by enlargement of vesicle from Golgi apparatus
• Relatively smaller and exist temporarily

Question 10

Describe structures and functions of plant vacuoles

Answer 10

• Large central vacuole is permanent and occupies 80% of cell volume
• Enclosed by single, partially permeable membrane called tonoplast
• Filled with cell sap, a solution of dissolved substances
• Storage of nutrients like proteins and inorganic ions
• Disposal sites for metabolic by-products that would endanger the cell if accumulated in cytosol
• Contains pigments that give colour

Question 11

Describe structures and functions of mitochondria

Answer 11

• Rod shaped or cylindrical
• Bounded by double membrane
• Involved in aerobic respiration
• ATP is the energy molecule in organisms
• Abundant in metabolically active cells

Question 12

Describe structures and functions of chloroplasts

Answer 12

• Bounded by double membrane
• Contains chlorophyll, thylakoids, stroma
• Site of photosynthesis

Question 13

Describe structures and functions of ribosomes

Answer 13

• Small and round
• Occur as free ribosomes suspended in cytosol or bound ribosomes bound to RER
• Site of polypeptide synthesis
• Free ribosomes make proteins that function within cytosol
• Bound ribosomes make proteins destined for insertion into membranes, packaging within lysosomes, or for export out of cell

Question 14

Describe structures and functions of centrioles

Answer 14

• Small, hollow cylinders
• Occurs in pairs
• Only found in animal cells
• Involved in cell division

Question 15

What are the non-membranous organelles

Answer 15

• Ribosomes
• Centrioles

Question 16

Which organelles can only be seen under an electron microscope

Answer 16

• RER
• SER
• Golgi apparatus
• Lysosomes
• Mitochondria
• Ribosomes
• Centrioles

Question 16

Describe protein synthesis and secretion

Answer 16

• Polypeptide chains are synthesised at the ribosomes
• Synthesised polypeptide chains are then folded at the RER
• Transport vesicles containing substances made by the ER are pinched off
• Transport vesicles then fuse and release their substances into the Golgi apparatus
• Substances are chemically modified and packaged in Golgi apparatus
• Secretory vesicles that contain these substances are pinched off the Golgi apparatus
• ATP provides energy for secretory vesicles to move towards and fuse with the cell membrane, releasing substances outside the cell by exocytosis

Question 17

Describe the adaptations and functions of a red blood cell

Answer 17

• No nucleus
• Biconcave shape
• Presence of haemoglobin
• No nucleus allows for more haemoglobin to be packed in cell
• Biconcave shape increases SA:V ratio to increase rate of gaseous diffusion
• Haemoglobin allows cell to carry oxygen

Question 17

Describe the adaptations and functions of a root hair cell

Answer 17

• Long and narrow extension
• Increases SA:V ratio, which increases rate of diffusion and osmosis

Question 17

Describe the formation of lysosomes

Answer 17

• Enzyme contents are synthesised at the RER
• Transport vesicles transport the synthesised enzymes to Golgi apparatus for further processing
• Vesicle containing the processed enzymes buds off from Golgi apparatus, forming a lysosome

Question 18

What is cell specialisation

Answer 18

It is when different cells have different adaptations to perform different specific functions

Question 19

Describe the adaptations and functions of a muscle cell

Answer 19

- Elongated cylinder - Contains many nuclei and mitochondria - Mitochondria provides energy needed for cell contraction

Question 19

State the complexity table from least complex

Answer 19

- Macromolecule - Organelle - Cell - Tissue - Organ - Organ system

Question 20

Which organelles are bounded by double membrane

Answer 20

- Mitochondria - Chloroplasts