Cells Flashcards
Describe the function of chloroplasts in plants and algae
Absorbs light energy for photosynthesis
To produce organic substances eg. carbohydrates / lipids
Describe the structure of the cell vacuole in plants
Tonoplast membrane
Cell sap
Describe the function of the cell wall in plants, algae and fungi
Provides mechanical strength to cell
So prevents cell changing shape or bursting under pressure due to osmosis
Describe the function of the cell vacuole in plants
Maintains turgor pressure in cell (stopping plant wilting)
.
Contains cell sap → stores sugars, amino acids, pigments and any waste chemicals
Describe the function of Golgi apparatus and Golgi vesicles
Golgi apparatus
• Modifies protein, eg. adds carbohydrates to produce glycoproteins
• Modifies lipids, eg. adds carbohydrates to make glycolipids
• Packages proteins / lipids into Golgi vesicles
• Produces lysosomes
Golgi vesicles
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Transports proteins / lipids to their required destination Eg. moves to and fuses with cell-surface membrane
Describe the function of mitochondria
Site of aerobic respiration
To produce ATP for energy release
Eg. for protein synthesis
Describe how eukaryotic cells are organised in complex multicellular organisms
Tissue
Group of specialised cells with a similar structure working together to perform a specific function, often with the same origin
Organ
Aggregations of tissues performing specific functions
Organ system
Group of organs working together to perform specific functions
Why do some eukaryotic cells not undergo the cell cycle?
• Within multicellular organisms, not all cells retain the ability to divide (eg. neurons)
• Only cells that do retain this ability go through a cell cycle
Explain the importance of mitosis in the life of an organism
Growth of multicellular organisms by increasing cell number
• Replacing cells to repair damaged tissues
• Asexual reproduction
Describe how tumours and cancers form
• Mutations in DNA / genes controlling mitosis can lead to uncontrolled cell division
• Tumour formed if this results in mass of abnormal cells
• Malignant tumour = cancerous, can spread (metastasis)
Benign tumour = non-cancerous
Explain the role of cholesterol (sometimes present) in cell membranes
Restricts movement of other molecules making up membrane
So decreases fluidity (and permeability) / increases rigidity
Suggest how cell membranes are adapted for other functions
• Phospholipid bilayer is fluid → membrane can bend for vesicle formation / phagocytosis
Glycoproteins / glycolipids act as receptors / antigens → involved in cell signalling / recognition
Explain the limitations imposed by the nature of the phospholipid bilayer
Restricts movement of water soluble (polar) & larger substances eg. Na* / glucose
• Due to hydrophobic fatty acid tails in interior of bilayer
Describe how movement across membranes occurs by facilitated diffusion
Water-soluble / polar / charged (or slightly larger) substances eg. glucose, amino acids Move down a concentration gradient
Through specific channel / carrier proteins
Passive - doesn’t require energy from ATP / respiration
Describe how movement across membranes occurs by osmosis
• Water diffuses / moves
• From an area of high to low water potential (w) / down a water potential gradient
Through a partially permeable membrane
Passive - doesn’t require energy from ATP / respiration (only kinetic energy of substances)
Describe how movement across membranes occurs by active transport
Substances move from area of lower to higher concentration / against a concentration gradient
• Requiring hydrolysis of ATP and specific carrier proteins
Describe the role of carrier proteins and the importance of the hydrolysis of
ATP in active transport
Complementary substance binds to specific carrier protein
2. ATP binds, hydrolysed into ADP + Pi, releasing energy
3. Carrier protein changes shape, releasing substance on side of higher concentration
4. Pi released → protein returns to original shape
Describe how movement across membranes occurs by co-transport
Two different substances bind to and move simultaneously via a co-transporter protein (type of carrier protein)
• Movement of one substance against its concentration gradient is often coupled with the movement of another down its concentration gradient
