Midterm Study Guide

cell theory

1. basic structural and functional unit

2. structure leads to function

3. all organisms are made of one or more cells

4. cells must make more cells for the organism to live

   Shleiden (plants), Schwann (animals), and Virchow (both) contributed

generalized cell

plasma membrane

cytoplasm

nuclear material

ribosomes

life processes

MRS GREN MD
movement, respiration, stimuli response, growth, reproduction, excretion, nutrition, metabolism, digestion

plasma membrane

first line of defense, separates cell from its environment

modeled with a fluid mosaic structure so parts can easily move from place to place

principle components of the cell membrane

phospholipids: hydrophilic head (glycerol and phosphate group) and hydrophobic tail (two fatty acid chains)

cholesterol (in between lipid heads) → stabilize the membrane and provide support

proteins (channel, peripheral, integral, globular, alpha-helix, etc)

carbs (act as ID of the cell on the outside, attached to proteins to make glycoproteins or lipids to make glycolipids) → only present on the outside of the membrane

aquaporin proteins

AQP

allow water to get through the hydrophobic parts of the membrane

act as a channel for small solutes across the membrane

how do cells bind together?

• their plasma membranes fit together like puzzle pieces

• glycoproteins act as glue

• membrane junctions: desmosomes, gap, tight

integral proteins

reach across the entire membrane

act as transporters of ions and larger solutes; mediate communication between the cells and its environment as communication receptors

contain hydrophilic end (interact with polar heads of lipids at either surface as well as chains of carbohydrates) and hydrophobic ends

peripheral proteins

loosely attached, so can be removed or reattached

hydrophilic side chairs that react with water and the polar heads of lipids

often contain chains of sugars: glycoproteins

cytoplasm

made of cytosol, a jelly-like substance

constantly moving through cytoplasmic streaming

mitochondria

site of cellular respiration: therefore cells that need more energy have more mitochondria

ribosomes

made by the nucleolus and responsible for synthesis of proteins

free-floating or bound to rough ER

cells that make many enzymes (like in the pancreas) have more ribosomes

endoplasmic reticulum

fluid filled channels leading from the nucleus to the cytoplasm

rough ER: makes proteins

smooth ER: breaks down fat molecules

golgi apparatus

packages, sorts, and secretes material that the cell needs or doesn’t need

packages are vesicles [types below:]

• lysosomes carry digestive enzymes

• secretory vesicles carry proteins

• vacuoles carry food or water

• peroxisomes carry enzymes and catalase (mostly in plants and formed from pieces of ER)

microtubules

support the cell and give it shape as part of the cytoskeleton

made of globular proteins that form a hollow tube

easily break down and reform and provide a place for vesicles to move

made by centrosomes

form cilia and flagella (movement) as well as centrioles (play a role in mitosis as polar anchors)

microfilaments

fine filaments composed of protein

provide shape to the cell by resisting external tensions

easily break and reform, so hep the cell change shape during mitosis and phagocytosis of WBCs

involved in muscle contraction: actin and myosin

actin

globular proteins that use ATP

provide a track for myosin filaments to move

myosin

responsible for muscle contraction, cells division, and cytoplasmic streaming

intermediate filaments

intermediate size, made of protein strands in a spiral

provide structure and keep organelles in place; scaffolding

example is keratin

cytoskeleton

network of protein fibers responsible for keeping the cell shape, fixing organelles in their place, enabling the cytoplasm to move, and allowing cells in organisms to move

fibroblasts

protein secreting cells that synthesize elements of connective tissue (connect body tissues together)

elongated shape, lots of ER

erythrocytes

RBCs; carry oxygen

concave center is extra surface area for the uptake of O2 in the bloodstream

no nucleus as a mature cell

epithelial cells

cover/line body organs

flattened, cube, or columnar shape

resist tearing when rubbed or pulled

muscle cells

provide movement

skeletal muscle cells connect to bones, smooth muscle cells line hollow organs, cardiac muscle cells are found in the heart

adipocytes

fat cells that store energy and are used for thermal production/storing

WBCs

fight disease by surrounding foreign bodies or being involved in inflammatory responses

phagocytes, macrophages, lymphocytes, neutrophils

neurons

nerve cells that transmit information through paracrine signaling

gametes

reproductive cells; ovum and sperm

tight junctions

impermeable connections that close the space between cells

among cells that form linings to prevent tearing

epithelial tissue in blood vessels, cavities and skin

desmosomes

anchors that prevent mechanical stress

located along outer skin cells

gap junctions

tubular channels that allow for direct signaling

located in cardiac muscle cells or between embryonic cells

nucleus

control center that carries all information for cells function

has a nucleoplasm (cytoplasm) and nuclear envelope (membrane)

DNA is wrapped around a histone protein to form a nucleosome; a chain of these makes chromatin material that is condensed into chromosomes: WHEN NOT GOING THROUGH MITOSIS

Robert Hooke and Anton van Leeuwenhoek

Hooke named cells

Leeuwenhoek observed single-celled organisms through his microscopes

3 types of cells

archae (prokaryotes)

bacteria (prokaryotes)

• prokaryotes have a cell wall, DNA as a nucleoid, and flagella/pilli used for locomotion

eukaryotes

what is the advantage of prokaryotes being small?

ions and other materials can quickly diffuse once they enter

wastes can exit quickly too

why are cells small?

if cells were larger, the surface area to volume ratio would be dangerous (not enough surface area to hold the volume)

eukaryotic cells are larger because they have organelles with specific jobs

why do scientists believe prokaryotes were the first forms of life on earth

earliest fossil evidence of life are microbial mats that date back 3.5 billion years (out of 4.6 million years)

dead cells here resembled prokaryotic cells

what is the possible explanation for the presence of a rigid cell wall in plants?

plants are subjected to osmotic pressure and a cell wall helps them against bursting or shrinking

macromolecules

made from monomers

carbohydrates, lipids, proteins, and nucleic acids

carbohydrates

made from monosaccharides/simple sugars

sugars and ststarches if not burned to release energy, can turn into fats with a much longer term storage

C, H, O

proteins

made from amino acids

help with blood clotting, hormones, immune responses, building and repairing of cells in hair/muscle/bone

C, H, O

lipids

made from fatty acids and glycerol

store the most energy but hard to breakdown because they are more long term and your body breaks down small carbs first

enter the body through our diet (oil, meat, dairy, eggs)

C and H > O, P (sometimes)

nucleic acids

made of nucleotides with phosphate group, 5 carbon sugar, nitrogen base

largest biological molecules in the body

C, H, O, N, P

order of ‘mers’

monomer, dimer, oligomer, polymer

one, two, a few, many

dehydration synthesis

getting rid of water to create a bond between two monomers

in case of amino acids, getting rid of water leaves one amino acid as a cation and the other as an anion: perfect opportunity for covalent bonding

hydrolosis

adding water to break up a bond between two monomers; starts with a hydrolase enzyme

an enzyme breaks the connection, allowing water to come in and add itself

fats use oxygen to break down, not always water

monosaccharides

glucose (blood sugar, cellular fuel), fructose, galactose

plant sugar, fruit sugar, animal sugar

same formula, different structures so isomers

provide short, fast energy

disaccharides

sucrose, maltose, lactose

table sugar, malt sugar, milk sugar

glucose + fructose, glucose + glucose, galactose + glucose

must be broken down to be absorbed

polysaccharides

best for storage, not sweet/short term energy

starch → from plants like corn, rice and potatoes

glycogen → from animals found in muscles and liver

cellulose → strong and complex, gives cell wall strength

chitin → modified used for exoskeletons in insects (very strong)

H:O ratio in carbohydrates

2:1

fatty acids are…

hydrocarbon chains

glysodic bonds

between fatty acids and glycerol

triglycerides

3 fatty acids + glycerol backbone

protect and insulate organs

major source of stored energy: most abundant and concentrated

phospholipids

2 fatty acids (hydrophobic) + glycerol and phosphate group (hydrophilic)

abundant in brain and nervous tissue

steroids

various purposes in plants and animals: act as hormones, where they activate cell proteins through cell communication

4 carbon rings

what are the three most abundant lipids in our bodies?

steroids, phospholipids, and triglycerides

cholesterol

an essential fat vital to homeostasis made by the liver

present in the plasma membrane, assists in structural support

makes:

1. steroids

2. bile salts (releasked by the liver into the digestive tract to aid in fat digestion: difficult to break down)

3. hormones (estrogen, progesterone, testosterone; deficit in these causes sterility)

4. vitamin D (fat soluble and made from exposure to UV; necessary to absorb calcium and grow bones)

high density lipoproteins (HDL) are good; low density lipoproteins (LDL) are bad

• good bc they carry cholesterol through the blood to the liver, where it is removed and doesn’t lead to coronary heart disease

• bad bc the accumulation of cholesterol causes plaque buildup, which clogs our bloodstream and leads to health problems

unsaturated fats

at least one double C=C bond in their fatty acid chains

• monounsaturated: has only one double bond

• polyunsaturated: has many double bonds

leads to a nonlinear structure and therefore is liquid at room temperature

from plants

saturated fats

all single C-C bonds in fatty acid chains

linear strucutre, and therefore is solid at room temperature

from animals

trans fats

unsaturated fats areturned into saturated fats unnaturally

H atoms attach themselves to C=C bonds, reducing them to single bonds

really bad for your health

omega-3 fatty acids

healthy fats found in cold water fish that decrease the risk of heart disease

oxidation

addition of O to break down macromolecules (lipids)

done through a series of complex reactions (the oxidation process) that starts with the oxidase enzymes

peptide bonds

bonds between amino acids

happens one bond at a time

parts of an amino acid

amino group: NH2

carboxyl/acid group: COOH

H above central carbon and R group below (that is specific to different amino acids)

levels of protein structure

primary: chain

secondary: alpha helix (spiral), beta sheet (pleated skirt)

tertiary: globular protein from polypeptide chains between secondary structures

quarternary: tertiary subunits together

nucleotide

phosphate backbone (linked to 5’ carbon)

ntirogen base (C and T are pyrimidines with one ring, A and G are purines with two rings) (linked to 1’ carbon)

5 carbon sugar (no oxygen for DNA and ribose for RNA)

hydrogen bonds between bases

adenosine triphosphate

provides a form of chemical energy to all body cells: makes and breaks molecules, maintains membranes and life processes

modified RNA with adenine base, ribose sugar, and three phosphate groups (each negatively charged)

the bonds between these groups are called high-energy phosphate bonds

the hydrolosis or dephosphorylation of ATP provides energy to the cell

how many chromosomes?

46: 23 from each parent

anti-parallel

nitrogen bases link together “upside down”, so one side is facing upside and the other downside

larger structure of DNA

1’ linked to base

2’ linked to OH

3’ bound to O at the top of the next phosphate group

5’ linked to phosphate group

at the end of the chain on the top, the 5’ is attached to HO and the 3’ is attached to OH

differences between DNA and RNA

DNA is double strand, RNA is single

DNA doesn’t have an oxygen in its 5 carbon sugar, RNA does

DNA has thymine base, RNA has uracil base

DNA cannot leave the nucleus, RNA can

replication

happens during the s stage of interphase

• antiparallel strands are untwisted from each other by topoisomerase (also keeps it untwisted)

• their hydrogen bonds split at the DNA fork by helicase enzyme

• side with the unattached 3’ at the end is the LEADING strand: made in a continuous strand starting at the end and going toward the fork

• side with the unattached 5’ at the end is the LAGGING strand: made in Okazaki fragments starting toward the fork and working outward

• RNA primase sits as a placeholder before DNA bases are ready to hook up

  • DNA added by DNA polymerase III on leading strand

  • DNA added by DNA polymerase I on lagging strand; DNA ligase joins gap between fragments

• DNA polymerase I, II, and III make sure everything is correct after it’s added

• telomerase enzyme lengthens the strand so that when it twists, there aren’t any bumps

each strand of DNA is made from a strand of old and new nucleotides; the process is semiconservative

cladograms

takes shared characteristics of organisms and forms a hypothesis of how they are related

• common ancestor found between main line and branch where a species goes in separate direction

• out group might not have shared characteristics

• new adapted species can lose or add characteristics as time goes on

Ockham’s razor/the theory of parsimony: the simplest explanation for how things developed over time is likely the most right

you can create cladograms by sequencing DNA in organisms, not just based on physical traits

atomic number versus mass number

atomic number: number of protons (and electrons) (H is 1)

mass number: protons + neutrons (mass number - atomic number = neutrons for isotopes)

ionic vs covalent bonding

covalent: share electrons (relatively same electronegativity)

ionic: one takes electrons (higher electronegativity) from another (lower electronegativity)

anions versus cations

anions have more electrons than their original state

cations have fewer electrons than their original state

carbon dating

through cosmic rays from the sun, N in the atmosphere gains a neutron and loses a proton, making it 14C (isotope of carbon)

plants take this in, and then we take in plants

the amount of carbon in our body is maintained through homeostasis (because we breathe out C too) so that we contain relatively the same amount as the atmosphere

when we die, 14C decomposes back into N slowly, so the amount of 14C in a sample shows how old something is

components of air

C: trace

H: trace

O: 21%

N: 78%

components of our bodies

C: 18%

H: 10%

O: 65%

N: 37%

properties of water

high heat capacity (takes a lot of energy to get water from solid to liquid and liquid to gas)

• high heat of vaporization; strong hydrogen bonds must be broken

  • as water molecules evaporate, the surrounding environment cools: water is taking in energy from the surrounding environment to evaporate

low density in solid form: molecules pushed farther apart in solid form

adhesion: strong temporary attraction between polar molecules and the molecules that make up their container

cohesion: strong attraction between water molecules through hydrogen bonding: creates surface tension, plays a role in high heat of vaporization

capillary action: water “climbs” its container because adhesion is stronger than cohesion

dissociation

the breaking up of molecules to form ions

ions pushed apart by polar attractions with water molecules (at least in the case of water)

buffers

add an acid or a base to the body to regulate hohomeostasis control pH

exothermic reactions versus endothermic reactions

exothermic: frees to form

• energy released for gas → liquid → solid

endothermic: takes to break

• energy required for solid → liquid → gas

homeostasis

the body’s ability to always maintain internal conditions

uses feedback for this

positive: change that continues in the same direction (mostly considered a bad thing)

negative: a change made that is reversed

diffusion

the movement of stuff across a concentration gradient from high concentration to low

can be passive or active

isotonic

equal: reached equilibrium

no concentration gradient

both sides diffusing at the same rate to maintain equilibrium

hypertonic

high amount of solute and low concentration of water

water will want to move out into the solution, leading to a loss of water in cells

hypotonic

low amount of solute and high concentration of water

water will want to move out of the solution, leading to an increase of water in the cells

pinocytosis

the movement of liquids

easier than phagocytosis

usually from high → low

phagocytosis

the movement of larger molecules

like a macromolecule, more solid things

example is phagocyte taking in foreign invaders

bulk transport

many molecules moving at one time

achieved with the help of carrier molecules

exocytosis vs endocytosis

exiting the cell vs entering the cell

• receptor mediated endocytosis is when a very specific substance is the only one accepted (hormones in target cells)

• exocytosis with neurons is the secretion of neurotransmitters from a signaling cell

blood brain border

highly selective semipermeable border of endothelial cells

they regulate the transfer of solutes and chemicals between the circulatory system and central nervous system

prevents bad things in the blood stream from going into your brain (pathogens, large hydrophilic molecules)

BUT allows some small molecules with passive diffusion and selective active transport

• these things include hydrophobic molecules and small nonpolar molecules like O2, CO2, and hormones

hydrophobic is good and hydrophilic is bad because you don’t want stuff to mix with the hydrophilic cerebrospinal fluid, but resist it

faciliatated transport

a type of passive transport: normal process of diffusion from high concentration to low with the help of proteins

channel proteins and carrier proteins in the membrane help, and using one over the other just depends on the molecule being transported (one is an open channel, the other does one thing at a time)

active transport

requires ATP to move molecules against their concentration gradient from low to high

ATP opens up a carrier protein against its will

• primary active transport: moves ions across a membrane, creating a difference in electrical charge and dependent on ATP

• secondary active transport: moves material based on the electrochemical gradient established by primary active transport and does not directly require ATP

  • depends on the energy of primary to occur

electrochemical gradient

combination of concentration gradient (amount of particles)

and electrical gradient (difference in charges)

affect active transport of ions and molecules because they make the use of ATP necessary: why it needs to be active transport

sodium potassium pump

interior of cells:

• more negative than extracellular fluid

• has more potassium ions than sodium ions

  • concentration and electrical gradients drives sodium into cell: Na+ leads into cell based on passive transport, so it needs to be sent out again with active transport to maintain the gradient

  • potassium is driven based only on electrical gradient

1. an enzyme oriented toward the interior of the cell has a high affinity for NA+ and binds to three

2. the carrier uses ATP to change shape and orient toward the exterior of the cell, Na+ leave

3. the shape change increases the affinity for K+, and 2 attach

4. the phosphate group used from hydrolyzation of ATP before detaches, and enzyme changes shape again to face the interior

5. K+ ions are released to the interior and the cycle repeats

• this process maintains that the cell remains more negative (because more positive ions (3) are being released than coming in (2))

• it also sets up secondary active transport to take place, where Na+ enters the cell and drags things along with it

osmosis

the diffusion of water across cell membranes

water will leave the cell if present in a hypertonic solution (the solution has less water than the cell, and the water wants to reach equilibrium)

water will enter the cell if present in a hypotonic solution (the solution has more water than the cell,and the water wants to reach equilibrium)

• can’t use seawater to irrigate our crops, because the water in plants will leave

• can’t drink salt water to quench thirst, because the water in our cells will leave

• saltwater fish lose salt to their surroundings, so should drink more water to compensate; freshwater fish will gain water, so should pee more to compensate