Cells Flashcards
Outline the cell theory.
- living organisms are composed of cells
- cells are the smallest unit of life
- cells come from pre-existing cells
State that unicellular organisms carry out all the functions of life.
Unicellular organisms carry out all the functions of life (metabolism, response, homeostasis, growth, reproduction and nutrition)
Compare relative sizes of molecules, cell membrane thickness, viruses, bacteria, organelles and cells.
Molecule: 1nm Thickness of membrane: 10nm Viruses: 100nm Bacteria: µm Organelles: up to 10µm Most cells: up to 100µm
Calculate linear magnification.
Image = Object x Magnification (I=OxM)
Explain the importance of the surface area to volume ratio as a factor limiting cell size.
- rate of heat/waste production & resource consumption is a function of VOLUME
- rate of exchange of material is a function of SURFACE AREA
- V increases faster then SA
o less cytoplasm have access to SA for exchange of gases, supply of nutrients & loss of waste products - smaller cell = faster cell
o exchange between cytoplasm and environment is easier - max size reached: either stop growing or divides
Explain that cells in multicellular organisms differentiate to carry out specialized functions by expressing some of their genes but not others.
- cells differentiate to carry out specialized functions by expressing some genes or not
- tissue = group of similar cells specialised to perform a particular function
- organ = collection of different tissues to perform a specialised function
- genes can be
o specific region of a chromosome
o specific length of DNA double helix
State that multicellular organisms show emergent properties.
- emergent properties
- properties in total greater than sum of individual parts
- tissues and organs
State that prokaryotic cells divide by binary fission.
Prokaryotic cells divide by binary fission.
State the functions of cell wall, plasma membrane, cytoplasm, flagella, ribosomes and nucleoid.
Cell Wall: mechanical support, limits/controls cell growth, communication (plasmodesmata) Plasma Membrane: Transport of molecules, stabilising cell Cytoplasm: metabolic reactions Flagella: movement Ribosomes: protein synthesis Nucleoid: keeps naked DNA together Mitochondria: aerobic respiration Chloroplasts: capture light energy Cilia: liquid flow
Outline two roles of extracellular components.
- plant’s cell wall maintains cell shape, prevents escessive water uptake, holds plant up against gravity
- animal cells secrete glycoproteins that from extracellular matrix. -> support, adhesion + movement
Explain how the hydrophobic and hydrophilic properties of phospholipids help to maintain the structure of cell membranes.
- Attractions btw. hydrophobic tails on inside and hydrophilic heads and the surrounding water on the outside make a stable, strong barrier.
List the functions of membrane proteins.
- hormone binding sites
- immobilized enzymes
- cell adhesion
- cell-to-cell communication
- channels for passive transport
- pumps for active transport
Define Diffusion and Osmosis.
- Diffusion: passive movement of particles from region of high concentration to region of low concentration.
- Osmosis: passive movement of water molecules across partially permeable membrane from high to low
Explain passive transport across membranes by simple diffusion and facilitated diffusion.
Simple Diffusion
- passive
- high -> low
- non selective – no special proteins required
- ok for small molecule that can get through bilayer
- vital for O2, CO2, H2O
- speed depends on temp., gradient, non-polar solubility of molecules
Facilitated Diffusion
- active (ATP required)
- requires channel protein
- channels are selective
- vital for ions
- speed depends on number of channels, temp., gradient, non-polar solubility of molecules
Explain the role of protein pumps and ATP in active transport across membranes.
- ATP required
- may go UP a concentration gradient
- requires pump protein
- pumps are selective
- vital for ions and medium-sized molecules
- speed depends on number of pumps and ATP supply
