mcdb 6 midterm 2

light microscope

• visible light passed through glass lenses

• CANNOT see organelles

robert hooke

observing cork (dead plant cells) saw box like cavities and coined the term “cells”

parameters of microscopy

1. magnification

2. resolution

3. contrast

scanning electron microscope (SEMs)

produces 3D structures of external structures

transmission electron microscope (TEMs)

beam electrons though a specimen, used to study internal structures

cell fraction

breaks up cells (sonication) and separates the components using centrifugations

• cell components separate based on their relative size

prokaryotic cells

bacteria and archea

eukaryotic cells

protists, fungi, animals, and plants

plasma membrane

selective barrier that allows the passage of oxygen, nutrients, and waste to service the volume of a cell

what is the structure of the plasma membrane

a double layer of phospholipids (bilayer)

• polar head, non-polar tails

cytosol

semifluid substance, the fluid contained in the cell cytoplasm

chromatin/chromosomes

carry genes

ribosomes

make proteins

what is cell size limited by

diffusion

• nutrients must be able to reach all parts of the cell

• waste must leave efficiently

what sets the upper limit on the size of a cell?

metabolic requirements

• the ratio of surface area to volume of a cell is critical

• surface area increase by n² so volume increases by n³

surface-to-volume ratio equation

surface area / volume

nuclear envelope

encloses the nucleus separating it from the cytoplasm

• a double membrane, each consists of a lipid bilayer

nuclear lamina (TEM)

• mechanical support

• chromatin organization

• anchors the nuclear pore complexes

pore complexes (TEM)

facilitates selective transport across membrane

chromatin

DNA and protein together

• condenses to form discrete chromosomes

• one long DNA molecule bunched up

where do ribosome carry out protein synthesis

1st — cytosol, for free ribosomes

2nd — outside of the endoplasmic reticulum, for bound ribosomes

what are the components of the endomembrane system

1. nuclear envelope

2. ER, smooth and rough

3. golgi apparatus

4. lysosomes

5. vacuoles

6. plasma membrane

endoplasmic reticulum (ER)

accounts for more than half of the total membrane in many eukaryotic cells

• continuous w/ the nuclear envelope

smooth ER

• lack ribosomes

• synthesis of lipids

  • cholesterol, sex hormones

• metabolism of carbohydrates

• dextoifications

• storage of calcium ions

  • lots in muscle cells

rough ER

• surface studded w/ ribosomes that secrete glycoproteins

• distributes transport vesicles

• membrane factory for the cell

glycoproteins

proteins covalently bonded to carbohydrates

golgi apparatus

consists of flattened membranous sacs called cisternae

golgi apparatus functions

• like amazon, shipping and receiving center

• modifies productions of the ER

• manufactures certain macromolecules

• sorts and packages materials into transport

cis face — golgi apparatus

receiving side

trans face — golgi apparatus

shipping side

lysosome

a single membrane bound organelle — digestive compartments

lysosome functions

involves in cellular process of secretion, plasma membrane repair, and energy metabolism

• fuses w/ the food vacuole and its enzyme digest the molecules

• autophagy — self devouring

autophagy

use enzymes to recycle the cell’s own organelles and macromolecules

phagocytosis

engulf another cell to form a food vacuole

tay-sachs condition

lysosomes are unable to degrade certain membrane glycolipids due to a defect in an enzyme

• inherited

• glycolipids accumulate abnormally in the brain cells

• causes death at 3-4 yrs old

vacuoles

vesicles derived from the ER and golgi

central vacuoles

found in many mature plant cells, holds organic compounds and water

food vacuoles

formed by phagocytosis

contractile vacuoles

found in many freshwater protists, pump excess water out of cells

peroxisome

single membrane bound organelles in most eukyorotic cells that lack their own genetic material

peroxisome function

• specialized metabolic compartments primarily involved in lipid metabolism and the conversion of reactive oxygen species

• produce H2O2 and convert it to H2O

• detoxifying and oxidizing a number of molecules, metabolic byproducts and drugs

• prominate part of the kidney and liver cells

what do cellular functions arise from

celular order

mitochondria

sites of cellular respiration, a metabolic process that uses oxygen to generate ATP

chloroplasts

found in plants and algae, the sites of photosynthesis

endosymbiont theory

an early ancestor or eukeryotic cells engulfed an oxygen using prokaryotic cell, which formed an endosymbiont relationship w/ the host

• host cells and endosymbiont merged into a single organism, a eukaryotic cell w/ a mitochondrion

what are the similarities of mitochondria and chloroplasts

• enveloped by a double membrane

• contain ribosomes and multiple circular DNA molecules

  • grow and reproduces somewhat independent cells

mitochondia

chemical energy conversion

• in nearly all eukaryotic cells

• generates large quantities of energy in the form of ATP

mitochondria structure

• smooth double membrane

• cristae present, large surface area for enzymes that synthesize ATP

• structure → function

what site is mitochondria at

cellular respiration

• moving around

• changing shape

• fusing or dividing in two

• forming a branched tubular network

chloroplast

site of photosynthesis

• contains the green pigment chlorophyll as well as enzymes and other molecules that function in photosynthesis

• has double membranes, inner and outer

cytoskeleton

support and mobility

• helps cell maintain its shape

• provides the rails for motor proteins to walk on

microtubules

the thickest, made of protein tubular, alpha and beta

microtubules functions

• shape and support the cell

• guide movement of organelles

• separate chromosome during cell division

intermediate filaments

are fibers w/ the middle diameter

• only found in the cells of some animals, including vertebrates

• they reinforce cell shape and fix organelles in place

• intermediate filaments are more permanent cytoskeleton elements than the other two classess

centrosome

microtubule organizing center

• has a pair of centrioles, each w/ nine triplets of microtubules arranged in a ring

flagella

limited to one or a few per cell

• controlled by microtubules

cilia

occur in large numbers on cell surfaces

• controlled by microtubules

dynein arms

alternatively contract, move, and release the outer microtubules

microfilaments

thin solid rods, built from protein molecules or globular actin subunits (dynamic polymers)

microfilaments role

• bear tension

• function in cellular motility interact w/ the motor protein myosin

• actin and myosin interact to cause muscle contraction, amoeboid movement of white blood cells, and cytoplasmic streaming in plant cells

microvilli

bundles of microfilaments makes up the core of microvilli of intestinal cells that increase the cell’s surface area

selective permeability

allowing some substances to cross it more easily than other

plasmodesmata

• cell junction

• plant cells

• channels that perforate plant cell walls

  • water and small solutes (sometimes proteins and RNA) can pass from cell to cell

desmosomes, tight, and gap junctions

• animal cells

tight junctions

can be between small epithelial cells

demosome

can be between heart muscle cells

gap junctions

how ions move

extracellular matrix of animal cell

• since they lack cell wells but are covered by an elaborate extracellular matrix (ECM)

• ECM are made up of glycoproteins such as collagen, proteoglycans, and fibronectin

• ECM protein bind to cell surface receptor proteins in the plasma membrane called integrins

phospholipids

most abundant lipids in cellular membranes

• they are amphipathic molecules containing hydrophobic and hydrophilic regions

• the bilayer can exist as a stable boundary between two aqueous compartments

plasma membranes faces

have distinct inside and outside faces

fluidity of membranes

• must be fluid to work properly

  • usually as fluid as olive oil

• temp cools → switch from fluid to solid

• phospholipid movement rapid → proteins move more slowly

do membrane proteins move

they fuse

• they are also amphipathic

• reside in the bilayer w/ their hydrophilic portion protruding

fluid mosaic model

the PM membrane is a mosaic of proteins molecules bobbing in a fluid bilayer of phospholipids

moving through the permeable PM

• small — move through easily

• hydrophobic (nonpolar) — molecules, such as hydrocarbons, can dissolve in the lipid bilayer of the membrane and cross it easily

  • polar molecules (like sugars) — DON’T cross the membrane easily

integral proteins

penetrate the hydrophobic interior of the lipid bilayer

• the majority of these span the membrane and are called transmembrane proteins

peripheral proteins

loosely bound to the surface of the membrane

six major functions of membrane proteins

1. transport

2. enzymatic activity

3. signal transduction

4. cell-cell recognition

5. intercellular joining

6. attachment to the cytoskeleton and ECM

transport proteins

allow passage of hydrophilic substances across the membrane (H2O and amino acids)

• some are called channel proteins

channel proteins

have a hydrophilic channel that certain molecules or ion can use as a tunnel

• allow specific molecules or ions to cross the membrane

aquaporins

• facilitate the passage of water

  • a channel protein

passive diffusion

no energy investment

diffusion

tendency for molecules to spread out evelyn into available space

osmosis

diffusion of free water molecules across a selectively permeable membrane from an area of diluted solution to an area of concentrated solution until the solute concentration is equal on both sides

facilitated dissuasion

transport proteins speed the passive movement of specific molecules across the membrane

carrier proteins

undergo a subtle change in shape that translocated the solute binding site across the membrane

• doesn’t alter the direction of transport

active transport

moves substance across membranes against their concentration gradients

• require energy !!

sodium-potassium and proton pump

one type of transport system, which exchanges Na+ for K+ across the plasma membrane in animal cells

electrogenic pump

a transport protein that generates voltage across a membrane

proton pump

the main electrogenic pump of plants, fungi, and bacteria

cotransport

occurs when a transport protein can couple the downhill diffusion of a solute to the uphill transport of a solute against its gradient

bulk transport

water and small solutes enter or leave the cell through the lipid bilayer or means of transport proteins

exocytosis

transport vesicles migrate to the membrane, fuse w/ it and release their contenets

endocytosis

the cell takes in molecules and particulate matter by forming new vesicles from plasma membrane

tonicity

ability of a surrounding area to cause a cell to gain or lose water

isotonic solution

solute concentration is the same on either side of the membrane

• no net water movement across the plasma membrane

hypertonic solution

solute concentration is greater outside than inside the cell

hypotonic solution

solute concentration is less outside than that inside the cell

osmoregulation

the control of solute concentrations and water balance

• is a necessary adaption for life in such enviroments

contractile vacuole of paramecium function

• protect a cell from absorbing too much water and potentially exploding

• wastes are excreted from the cell along w/ excess water

hypotonic solution in plant cells

cell becomes turgid — very firm