unit 2- cells

CELL STRUCTURE AND FUNCTION

Ribosomes:

• Compostion- rRNA and protein non-membrane, subcellular structures(large/small)

• Role- synthesize proteins according to mRNA sequences

• Found- in cells in all forms of life and reflect the common ancestry in all known life

Endomembrane System: group of MBOs and subcellular components that work tg to modify, package, and transport polysaccharides, lipids, and proteins intercellularly

• endoplasmic reticulum(ER)

• golgi complex

• lysosomes

• vacuoles

• transport vescicles

• nuclear envelope

• plasma membrane

Endoplasmic Reticulum:

• Role- provides mechanical support to maintain shape & intracellular transport

• Rough ER: compartmentalization; protein synthesis

• Smooth ER: detoxification of cells; lipid synthesis

Golgi Complex: membrane-bound structure w/ series of flattened membrane sacs

• Role- correctly folding and chemically modifying newly synthesized cellular products; packaging proteins for trafficking

Mitochondria:

• Role- provides compartments for diff metabolic rxns involved in aerobic cellular respiration

• inner membrane(cristae) is highly folded to help ATP to be synthesized more efficiently

Lysosomes: membrane-enclosed sacs w/ hydrolytic enzymes

• Role- intracellular digestion; apoptosis

Vacuoles: membrane-bound sacs

• Role

        central vacuole- maintains turgor pressure w/ nutrient and water storage(plant cells)

        contractile vacuole- maintains osmoregulation in some single celled orgs

        food vacuole- formed from phagocytosis and fuses w/ lysisome

• smaller in size in animal cells compared to plant cells

Chloroplast:

• specialized organelles that are found in plants and photosynthetic algae

• contain a double membrane

• Role- location for photosynthesis

CELL COMPARTMENTALIZATION

MBOS:

• compartmentalize cells intracellular metabolic process and specific enzymatic rxns

• rough & smooth ER

• golgi complex

• lysosomes

• mitochondria

• chloroplast

• vacuoles

Internal Membranes:

• facilitate cellular processes by minimizing competing interactions & increases surface area where rxns occur

• Mitochondria- Cristae - Oxidative Phosphorylation

• Chloroplast- Thylakoid- Light Reactions

CELL SIZE

Surface Area to Volume Ratio affect:

• obtain nutrients

• eliminate waste products

• acquire/dissipate heat

• exchange chemicals/energy w/ environment

• smaller cells typically have a higher surface area-to-volume rater and more efficient exchange of materials w/ the environment

• relationship b/w metabolic rate per unit body mass and the size of multicellular organisms; typically, the smaller the org; the higher the metabolic rate per unit body mass

PLASMA MEMBRANE

Composition:

• phospholipids

• membrane proteins

• glycolipids/glycoproteins

• steroids(i.e. Cholesterol)

Phospholipid:

• Phosphate(head)- POLAR(oriented intracellular/extracellular)

• Fatty Acid(tail)- NONPOLAR(oriented toward interior of membrane)

Cell Wall:

• bacteria, Archaea, Fungi, and Plants — barrier for substances and prevent osmotic lysis

MEMBRANE TRANSPORT

Simple Diffusion:

• passive transport, NO NRG

• down concentration gradient

• small, nonpolar

• no transport protein needed

• ex: CO2, O2, N2, steroids

• small amount of small polar, uncharged mols ( h2o or nh3) leak thru membrane

Facilitated Diffusion:

• passive transport, NO NRG

• down concentration gradient

• small molecules

• requires transport protein(channel vs carrier protein)

• ex: h2o, Na⁺, K⁺, Ca⁺

• membrane becomes polarized due to movement of ions

• aquaporins transport large quantities of water across membranes

Active Transport:

• requires input of NRG

• against concentration gradient

• requires transport protein(carrier protein)

• ex: Na⁺,K⁺,Ca⁺,H⁺

• Na⁺/K⁺ pump and ATPase —> maintains membrane potential

Exocytosis:

• internal vesciles release materials from cells by fusing w/ the plasma membrane and secreting large molecules from the cell

• pathway- rough ER(synthesize), golgi complex(package/modification), transport vescile, plama membrane

Endocytosis:

• takes in large molecules and particulate matter by folding the plasma membrane in on itself and forming new(small) vesciles that engulf material fro mthe external environment

• pinocytosis- cellular drinking

• phagocytosis- cellular eating

• receptor-mediated- endocytosis

TONICITY AND OSMOREGULATION

Hypotonic solution:

• LOW solute concentration

• HIGH free water concentration

• LOSES water to hypertonic solution

Isotonic Solution:

• EQUAL solute concentration(as other solution)

• EQUAL free water concentration(as other solution)

• EQUAL water movement into and out of solution

Hypertonic solution:

• HIGH solute concentration

• LOW free water concentration

• GAINS water from hypotonic solution

Water Potentional:

• High- less solute(hypotonic)

• Low- more solute(hypertonic)

• water moves by osmos from HIGH to LOW water potential