lectures 5/6 cell & osmosis Flashcards
cell membrane, manufacturing & energy; osmosis; intra/extra cellular features and transcription
which domains are prokaryotic?
bacteria and archaea
what defines prokaryotes (3)?
they are small, bacteria contains a single chromosome composed of double stranded DNA (survival genes), have a cell wall
what are some characteristics of prokaryotic genetics (3)?
no nucleus - has a nucleoid region (DNA is “thrown in a corner”)
some bacteria possess plasmids
DNA is transferred between bacterial cells by pili
what are plasmids?
non essential genes that exist/reproduce independently of chromosome
what are some characteristics of eukaryotic cells (4)?
domain eukarya, big, round/squarish, nucleus, some do not have cell walls
why is cell size limited (3)?
can’t be too small (hold DNA and organelles), can’t be too big (boundaries function as selective barriers for oxygen, waste, etc.), there is only so much surface area for traffic - at a certain point will become to small for cells increased volume
phospholipids (4)
- form micelles when dumbed in water
- amphipathic
- can form a bilayer
- phospholipids can move slightly
describe the structure of a phospholipid?
hydrophillic head (choline, phosphate, glycerol) and hydrophobic tail (fatty acids)
who proposed the fluid mosaic model?
Singer & Nicholson
what is the fluid mosaic model (5)?
- membrane is fluid structure
- proteins embedded in membrane/on it
- phospholipids make up membranes
- membrane is built by endoplasmic reticulum (ER)
- proteins in membrane have hydrophobic regions
what are integral proteins?
- amphipathic & must be properly oriented
- pass into non-polar region of phospholipid layer
- placement maintained by polar vs non polar section and cytoskeleton
- proteins can allow specific polar molecules to pass through
where do you find integral proteins?
proteins that go through cell membrane
what are peripheral proteins?
- never cross membrane
- attached to integral proteins or polar surface of membrane
- decrease in temperature will solidify membrane more and proteins won’t function
- surface proteins inside differ from outside
- have directional orientation
where do you find peripheral proteins?
only on one side of the membrane
how do proteins work in the membrane?
they are a channel for different substances to pass through - they will change shape to allow for these substances which pushes on phospholipids
can you speed up/down the chemical going through the gate?
no you can’t - if you want more of a chemical, you need to add proteins to the cell membrane. if you want less of a chemical, you need to remove proteins from the cell membrane
how does the cell membrane stay together?
the phospholipids are bonded by hydrophobic reactions
what do we mean by fluidity in the cell membrane?
want to hold it together but you want it to move
cholesterol
- helps membrane resist changes in fluidity
- keeps phospholipids in place
- prevents close packing of phospholipids
- adding more cholesterol will make membrane more fluid
- need a normal cholesterol level to function
how does cholesterol affect fluidity
- more cholesterol, phospholipids can’t pack close together - unsaturated hydrocarbon tails = fluid
- less cholesterol, phospholipids are more tightly packed together - saturated hydrocarbon tails = viscous
rules for transport
1- cell membranes don’t all look the same
2- can’t affect speed (speed up add protein, slow down remove protein)
3- inside doesn’t match outside
functions of transport proteins in cell membrane
polar molecules move through membrane proteins, very selective, some are like channels across the membrane, others change shape and hydrolyze ATP as energy
functions of enzyme proteins
so rxns can take place, form teams of enzymes for pathways, built into the membrane and are sometimes many enzymes together organized as a team
function of receptor proteins
outer surface of protein is used to bind a chemical messenger, can cause shape changes in protein, shape is very specific, different cells have different receptors
function of cell to cell recognition proteins
ID tags that are specifically recognized by other cells - all glycoproteins that identify type of cell (skin vs liver), species (human vs dog) or individual (me vs you). ex: blood types
sort cells into tissues and organs in embryo
vary among species/individuals
function of cell to cell anchor proteins
hold cells together with each other, can be mechanical or for communications, joined together so nothing is getting through
function of cytoskeleton anchor proteins
bonds to proteins, anchors keep cell shape and controls where proteins are put
list of cell membrane proteins
transport, enzymes, receptor binding sites, cell to cell recognition (ID tags), cell to cell anchors, cytoskeleton anchors
what two substances don’t require transport across membrane?
oxygen, carbon dioxide
what protein does water require to cross membrane?
aquaporin
what are the 2 basic types of transport across membrane?
passive and active
passive transport
free - no cost, two types: simple diffusion = no protein (oxygen, co2) or facilitated diffusion = needs a protein
active transport
costs energy (ATP) and needs a protein, moves AGAINST concentration gradient - goes UPHILL (LOW-HIGH)
essentially: paying for special protein with ATP to do something weird
ex: Na+/K+ pump
simple diffusion
always high to low concentration, driven by kinetic energy of molecules, no need for protein, more concentrated = faster diffusion (ex: oxygen, co2)
facilitated diffusion
through special membrane proteins - can show saturation: max speed = number of proteins available
needs a protein, can be a channel open all the time or that can open/close, substances move in one direction, obeys high-low concentration gradient
diffusion of water is called what?
osmosis
osmosis
doesn’t need energy, water is diffused across a semi-permeable membrane so that concentration INSIDE = OUTSIDE, solute cannot cross but solvent can, concentration of solutions refers to concentration of solute in water (high solute conc, = low water conc.)
WATER ALWAYS MOVES HIGH TO LOW
what is equal concentration called?
isotonic
what happens to cells in hypertonic solution? (concentrated)
cells shrivel up and die
what happens to cells in hypotonic solution?
cells lyse (explode) and die
hypertonic
more concentrated
hypotonic
less concentrated
isotonic
equal concentration
plasmodyzed
cells become shrunken
lysed
cells explode or break open
why can’t plant cells explode?
they have cell walls
explain animal cells in different types of solution
hypotonic solution - lysed
isotonic solution - normal
hypertonic solution - shriveled
explain plant cells in different solutions
hypotonic solution - turgid (normal)
isotonic solution - flaccid
hypertonic solution - plasmolyzed (plant dead - not coming back)
endomembrane system
- seperates functions in cell
- not all membranes involved are the same
what does the endomembrane consist of?
- organelles: nuclear envelope, endoplasmic reticulum, golgi apparatus, lysosomes, vesicles, vacuole, plasma membrane
what folds the proteins?
organelles
if ribosomes and mitochondria aren’t a part of what?
endomembrane system
where does everything start?
starts at nucleus and radiates outwards - no quality control (can’t go back to fix mistakes)
“manufacturing” steps
1- nuclear envelope connected to rough ER which is continuous with smooth ER
2- membranes/proteins produced by ER flow as transport vesicles to golgi
3- golgi pinches off transport vesicles that give rise to lysosomes and other special vesicles
4- lysosomes are available to fuse with vesicles for digestion
5- transport vesicle carries proteins to plasma membrane
6- plasma membrane expands from fusion of vesicles & proteins are secreted from cell
nucleus
- largest organelle
- dark when stained (under microscope)
- holds DNA (chromatin btwn division, chromosomes during division)
- cell division (makes identical daughter cells)
- stores info/blue prints for making & running cell
- required for long term survival of cells
explain how DNA is contained in the nucleus
the DNA is coiled up in the form of chromatin (later on chromosomes) and holds all the blueprints for the cell, where everything is set up
what is the name of the little dots on nucleus?
ribosomes - involved in making proteins
nuclear membrane
- double membrane called nuclear envelope
- has pores for communication, to pass molecules/RNA/proteins/ribosomal subunits
- only present during interphase (cell not dividing)
nuclear lamina
protein filaments that maintain shape
nucleolus
- dark area in nucleus
- size and # varies
- builds ribosomal subunits (recipe for ribosomes)
- uses RNA
- easy to access because we make so many ribosomes
ribosomes
- not a part of endomembrane system
- make proteins
- large and small subunit
- no membrane (they are solid)
- free (cytoplasm) bound (ER)
endoplasmic reticulum
folded membrane - creates cavity separated from cytoplasm
two types: rough (has ribosomes, folds proteins) smooth (no protein, deals with lipids)
rough ER
- makes, puts together & exports proteins, glycoproteins and membrane proteins
- surface facing cytosol is studded with ribosomes
- stores glycoproteins and proteins in RER cavity until exported
- transitional - between RER & SER produces vesicles
- essentially, protein folding
smooth ER
- looks like RER but without ribosomes
- makes/stores/exports lipids
- detoxifies poisons/drugs
- stores carbs and glycogen (liver)
- exact specialization varies with each cell
- enzymes that make lipids are rich in ER (ex: sex hormones, liver cells)
- always more RER than SER
- amount of SER with vary between individuals
golgi complex
- modification, storage, shipping of products
- manufactures polysaccharides in plant walls
- step after ER
- sacs called cisterna for transport
- polarity because it had shipping and receiving sides
- receiving = cis = next to ER
- shipping = trans = next to cell membrane
- molecules carried from one cisterna to the next
- add signals to vesicle products to direct where to go
explain golgi body
essentially, its the “case” of the phone - everything is put together and works, receives proteins from ER and ships them to next step
which organelles are responsible for manufacturing?
nucleus, nuclear membrane, nuclear lamina, nucleolus, ribosomes, RER, SER, golgi complex
vesicles
temporary, for movement within cell
- endocytosis: enter
- exocytosis: exit
vacuole
- membrane sac (larger than vesicle)
- for storage
animal vacuoles
- food vacuole: intake by phagocytosis
- contractile vacuole: pump out water
plant vacuole
central vacuole: stores molecules (toxins, proteins, inorganic ions, pigments), develops osmotic pressure
lysosomes
- responsible for breakdown
- digestive compartments
- sac with hydrolytic enzymes used to digest
- enzymes work best at pH 5 (pumps H+ in to lower pH)
- if lysosome breaks, enzymes are weak since cell pH = 7
- made by ER and golgi body
phagocytosis
lysosome digesting food (addition of H)
lysosomes - protists vs animals
protists - used to eat food
animals- clean up (janitor), immune system, development
autophagy
lysosome engulfs broken organelle (clean up)
macrophages
- animals have special type of lysosome that destroys invaders
- part of immune system
programmed destruction
lysosomes are used for making developmental changes (ex: tadpole to frog, human embryo - hands and feet)
organelles for transport/breakdown/storage
vesicles, vacuoles, lysosomes,
energy use
two types: autotrophs and heterotrophs
autotrophs
make their own energy from inorganic sources
heterotrophs
digest other organisms for energy
animals are chemoheterotrophs - what does that mean?
digest other organisms to get their biomolecules
subtypes of autotrophs
photoautotrophs, chemoautotrophs
photoautotrophs
energy source: light
carbon source: co2
ex: plants
chemoautotrophs
energy source: inorganic chemicals
carbon source: co2
ex: certain prokaryotes
heterotrophs subtypes
photoheterotrophs, chemoheterotrophs
photoheterotrophs
energy source: light
carbon source: organic compounds
ex: certain prokaryotes
chemoheterotrophs
energy source: organic compounds
carbon source: organic compounds
ex: animals, fungi, some plants, many prokaryotes and protists
plant/animal mitochondria
- amount depends on need (ex: muscle has many, fat has few), you always have more than one
- site of cellular respiration (why we have lungs)
- needs o2
- enclosed by two membranes (smooth outer, folded inner)
- mitochondria have their own DNA (circular)
- mitochondria are technically bacteria we absorbed into our system
what is our #1 energy source?
adenosine triphosphate ATP
where do we get ATP?
glucose
how do we use ATP
body uses ATP as an immediate source of energy, must be made before being used - energy gained by adding & removing phosphate
ex: ATP sits in our bodies - breaking a phosphate bond gives a burst of energy. then we stick it back on for more energy and so on. never remove more than one P. we use mitochondria to put it back together
ATP cycle
“spend energy to make energy”
1 - ATP hydrolosis to ADP+P yields energy
2- use energy for work (sports, anything really)
3- digest glucose
4- mitochondria uses that energy and ATP synthesizes from ADP+P
chemical equation for cellular respiration
C6H12O6 +6 O2 –> 6 CO2 + 6 H20
glucose + oxygen –> carbon dioxide + water
30 ADP + 30P = 30 ATP
where are glucose levels regulated?
pancreas and liver
how do we burn energy?
1 - carbs (sugars) –> glycolysis (default path)
2- fats (glycerol, fatty acids) –> glycolysis
will not burn fat unless there are no carbs left
3- proteins (amino acids) –> glycolysis and NH3
can be burned but creates toxic biproduct - only happens when there is so little food intake you burn muscle (severe anorexia, wartime starvation) not sustainable for long.
how to plants get energy?
photosynthesis - amount of mitochondria and chloroplasts will vary, choloplasts (chlorophyll) is what makes plants green
photosynthesis
requires chloroplasts, light, water and co2
it is the process by which plants make sugars
THEY NEED THE MITOCHONDRIA TO USE THOSE SUGARS
photosynthesis equation
6 CO2 + 6H20 –> C6H12O6 + 6O2
how do plants get their green colour?
chloroplast absorbs every spectrum of light except green
extra mitochondria details
made independently - have their own DNA (like bacteria), RNA, ribosomes and proteins
only increase in number by self-division (like bacteria)
mitochondria are maternally inherited
how did mitochondria and chloroplasts evolve?
they evolved independently through endosymbiosis
why do we, humans, not have chloroplasts
animals were invaded once - mitochondria
plants were invaded twice - mitochondria and chloroplasts
both are bacteria absorbed into cells - every cell has it
who has only mitochondria?
animals, fungi - therefore, we have to eat things to survive
who has both mitochondria and chloroplasts?
protists and plants
extracellular matrix (ECM) - outer surface of cell
- support, adhesion (sticking cells together), movement, recognition, regulation
- has glycoproteins on outer surface of cell
- viruses (ex: covid-19) use ECMs to recognize host cells
- found in most tissues (abundant in connective tissues)
- composed of glycoproteins and fibrous carbohydrate molecules
what are examples of glycoproteins and what do they do?
glycoproteins provide support
elastin - elastic, resists change
collagen - plastic surgery
collagen
most abundant protein of ECM
present in the dermis of skin
provides strong, durable support for overlying epidermis
how are cells attached to the ECM?
by special ECM glycoproteins, ex: fibronectin
fibronectin is bound to cell-surface receptor proteins called integrins, which are built into membrane
within cytoplasm, integrins are bound to microfilaments
ECM of animals
- integrins are positioned to transmit signals between ECM and cytoskeleton (they integrate change outside and inside cell)
- through integrins, ECM regulates a cell’s function
- microfilaments are how integrins transmit signal to nucleus
cytoskeleton
network of fibers in cytoplasm used for support and movement; motor proteins
microtubules (movement)
- made of alpha and beta tubulin and covered by plasma membrane
- centriole/centrosome/spindle fibers: used for cell division
- cilia structure and flagella (sperm): core of microtubules, used for locomotion & moving liquid
- used as railroad for vesicles to move along (ATP is involved so it costs something)
ex of microtubules
sperm moving along, mucus moving down
all tubes are filled with mucus, which it moved down by little hairs (cilia)
microfilaments
- made of actin and myosin filaments
- deform & shape change (angle & push microfilaments to ooze around)
ex: muscles (pair of cylindrical structure - slide into each other when contracting), amoeba (sperm cells), plants (cytoplasmic streaming - circulates in cell)
intermediate filaments
- structural support
- tension bearing
- made of keratin, each type slightly different
- fix position of organelles
- reinforce cell shape
- protection (hair, nails, feathers)
- not a baggy: jelly filled sphere where everything is where it needs to be
cell-to-cell attachment
cells are attached together by 2 proteins: cadherins or integrins
cell junctions
tight junctions, desmosomes, gap junction
tight junctions - NO SPACE BETWEEN CELLS
as if cells are sewn tightly together, any transport must be through special molecule, prevents extra cellular fluid from circulating between cells
desmosomes - STRENGTH
button like rivets, attach two plasma membranes with intermediate filaments, very strong - think muscles
gap junction - COMMUNICATION
permits materials to transfer directly from one cell to another (in plants, plasmodesmata)
