Cells Flashcards
Explain the fluid mosaic model
- 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
What can pass through the phospholipid bilayer
- Small hydrophobic molecules
Describe structures and functions of cell membrane
- Partially permeable
- Protects cell from surrounding environment
- Controls movement of substances in/out of cell
What does cytoplasm contain
- Cytosol
- Cytoskeleton
- Organelles
What is cytosol
- Aqueous solution of essential ions, soluble proteins and soluble organic compounds like sugars and amino acids
What is cytoskeleton
- Network of protein fibres that give support, motility and regulation to cell
Describe structures and functions of nucleus
- 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
Define cytoplasmic streaming
Cytoplasmic streaming is the movement of cytoplasm within a cell, which aids in the transport of materials and organelles around the cell
Describe structures and functions of rough endoplasmic reticulum
- System of flattened membrane-bound sacs
- Protein synthesis
- Polypeptide chains synthesised by ribosomes are folded in RER
Describe structures and functions of smooth endoplasmic reticulum
- Consists of fine tubules
- Lipid synthesis
- Detoxification of drugs and poisons
- Storage and release of calcium ions
Describe structures and functions of Golgi apparatus
- 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
Describe structures and functions of lysosomes
- Small, spherical vesicles
- Contains hydrolytic enzymes (lipases, proteases, nucleases)
- Digest materials in cell by phagocytosis
- Digest worn-out organelles by autophagy
Describe structures and functions of animal vacuoles
- 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
Describe structures and functions of plant vacuoles
- 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
Describe structures and functions of mitochondria
- Rod shaped or cylindrical
- Bounded by double membrane
- Involved in aerobic respiration
- ATP is the energy molecule in organisms
- Abundant in metabolically active cells
Describe structures and functions of chloroplasts
- Bounded by double membrane
- Contains chlorophyll, thylakoids, stroma
- Site of photosynthesis
Describe structures and functions of ribosomes
- 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
Describe structures and functions of centrioles
- Small, hollow cylinders
- Occurs in pairs
- Only found in animal cells
- Involved in cell division
What are the non-membranous organelles
- Ribosomes
- Centrioles
Which organelles can only be seen under an electron microscope
- RER
- SER
- Golgi apparatus
- Lysosomes
- Mitochondria
- Ribosomes
- Centrioles
Describe protein synthesis and secretion
- 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
Describe the adaptations and functions of a red blood cell
- 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
Describe the adaptations and functions of a root hair cell
- Long and narrow extension
- Increases SA:V ratio, which increases rate of diffusion and osmosis
Describe the formation of lysosomes
- 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
What is cell specialisation
It is when different cells have different adaptations to perform different specific functions
Describe the adaptations and functions of a muscle cell
- Elongated cylinder
- Contains many nuclei and mitochondria
- Mitochondria provides energy needed for cell contraction
State the complexity table from least complex
- Macromolecule
- Organelle
- Cell
- Tissue
- Organ
- Organ system
Which organelles are bounded by double membrane
- Mitochondria
- Chloroplasts
