Untitled Flashcards Set

B2.1: Membranes and membrane transport

B2.1.1 + B2.2.2: Lipid bilayers as the basis of cell membranes + Lipid bilayers as barriers

- Seymour + Nicolson (1972) proposed that proteins are inserted into phospholipid bilayer

and DONT form layer on phospholipid bilayer surfaces --> formed mosaic floating in

fluid bilayer of phospholipid

- They created the fluid mosaic model

- Phospholipid structure --> phospholipid = backbone of membrane + each composed of a

3-carbon compound called glycerol --> 2 of the glycerol carbons have fatty acids

combined to them and third carbon is attached to a tightly polar organic alcohol that

bonds to phosphate group

- Fatty acid = not water soluble because non-polar (hydrophobic) + Phosphate head =

hydrophilic and polar / making the phospholipid amphipathic (hydrophobic and

hydrophilic properties)

- Because fatty acid tails don’t attract each other strongly, the membrane is FLEXIBLE

and FLUID, allowing for endocytosis

- Once bilayer is formed, big molecules can’t pass through easy because molecules are

tightly packed

- Smaller hydrophilic molecules = hard time passing too because of the hydrophobic region

in the middle

- * structure of the phospholipid bilayer allows cell to control what passes through

membrane

B2.1.3: Simple diffusion across membranes

- Diffusion: particles move from region of higher concentration to region of lower

concentration (crosses a membrane)

- Ex--> cellular respiration: oxygen used by cells --> oxygen diffuses into cell because

there’s lower oxygen inside cell compared to outside of the cell, BUT CO2 diffuses in

opposite direction because CO2 is produced by mitochondrial respiration inside cell and

is present in higher concentrations inside cell compared to outside

B2.1.4: Integral and peripheral proteins in membrane

- Proteins: create extreme diversity in the membrane function

- Integral protein: amphipathic character with both hydrophilic and hydrophobic regions;

hydrophilic region = exposed to H2O molecules on either side of membrane +

hydrophilic region = middle of phospholipid backbone

- Peripheral protein: remain bound to surface of the membrane (inner + outer sides); often

anchored to integral protein

- Hormone binding protein: specific chapes exposed to exterior that fit shape of specific

hormones

- Enzymatic protein: either in or exterior of membrane surface --> sequence of metabolic

reactions

- Cell adhesion protein allows temporary or permanent connections between cells

- Cell-cell communication protein: provide identification label so organisms can

distinguish between self and non-self material

B2.1.5 + B2.1.6: Movement of water molecules across membranes by osmosis and the role of

aquaporins + channel proteins for facilitated diffusion

- Passive transport: no cellular energy; substance moves from high to low concentration;

along concentration gradient; energy comes from kinetic energy of the molecules and

stops when equilibrium is reached (ex: simple diffusion, facilitated diffusion, glucose

through protein channels, osmosis)

- Active transport: against concentration gradient; equilibrium is not reached; low to high

(ex: sodium-potassium pump)

- Osmosis: passive transport; only involves passive movement of H2O across a partially

permeable membrane (only allows certain substances to pass; depends on solute

concentrations

- Hypertonic: solution that has higher concentration of solutes than a hypotonic solution

- H2O moves from a hypotonic solution to a hypertonic one across a selectively permeable

membrane

---> Picture of osmosis in a plant cell

- Aquaporin: used to speed movement of H2O in and out of cell

- Carrier protein: can change shape to carry a specific substance from one side of the

membrane to the other; can carry substance along or against concentration gradient; carry

both H2O soluble and insoluble molecules

- Channel proteins: have pores that allow molecules of appropriate size and charge to pass;

gates that open and close in response to chemical or mechanical signals; channel proteins

don't change shape like carriers do

B2.1.7: Pump proteins for active transport

- Sodium-potassium pump uses ATP to move ions directly against a concentration

gradient. This is especially important in nerve cells also called neurons.

---> Picture of active and passive transport comparison

B2.1.8: Selectivity in membrane permeability

- SIZE and CHARGE is what depends how easily substances can pass

- Small + non-polar = easy (ex: O2, CO2, N2); Polar + large = hard (glucose, sucrose,

chloride, potassium, sodium)

- *Diffusion of small molecules are NOT selective, BUT large molecules are (through

integral protein)

B2.1.9: Structure and function of glycoproteins and glycolipids

- Glycoprotein: cell membrane proteins that have chains of carbohydrates attached to them

- Glycolipid: cell membrane phospholipids that have carbohydrate chains attached to them

- *Both important to cell identification and adhesion

- Blood (A, B, O) results from carbohydrate chains/ chains allow body to work out which

cells belong to itself and which cells are from outside of the body/ important in

transplants/ if carbohydrate chains aren’t compatible, then rejection will occur --> death

- Glycocalyx: thin sugar made up of carbohydrate chains attached to proteins; cover cell

- Function --> cell-cell adhesion, cell-cell recognition; reception of various signaling

chemicals

- Present on bacterial cells where it has both adhesion and protective function; in plant

cells, it helps anchor the plant cell membrane to the cell wall

B2.1.10: Fluid mosaic model of membrane structure

- Need peripheral, integral, glycoprotein, phospholipid, cholesterol, and indicate

hydrophilic and hydrophobic

---> picture of fluid mosaic model

- Cholesterol: in hydrophobic region; determine membrane fluidity which changes with

temperature (interact with fatty acid tails)

B2.1.11: Relationships between fatty acid composition of lipid bilayers and their fluidity

- *Because of weakness of H+ bonds, individual phospholipid and unanchored proteins

associated with them are relatively free to move about --> allows fluidity of membrane

- Fatty acid with double bonds and fewer attached H+ atoms = unsaturated --> cause

molecules to become less straight and they don’t pack together as tight

- Lower melting points --> survive cooler temperatures

- Saturated bonds: fatty acid is straighter, allowing tighter arrangements; makes them

stronger and more able to remain effective at higher temperatures

- Fatty acid desaturases: in bacterial membranes; speed up reactions that result in double

bonds within fatty acid tails

B2.1.12: Cholesterol and membrane fluidity in animal cells

- Cholesterol is an adjuster of cell membrane fluidity; stabilizes membranes at higher

temperatures and maintain flexibility at lower temperatures

- More cholesterol in membranes than ER because membrane is subjected to more

extremes in temperature

- *Plants don’t need cholesterol because they possess cell walls that keep stabilization in

their membranes

---> Picture of cell membrane at lower vs. At higher temperature and cholesterol

B2.1.13: Membrane fluidity and the fusion and formation of vesicles

- Endocytosis (active transport): allows macromolecules to enter cell

- Exocytosis (A.T): allows to leave

- Depends on fluidity of membrane

- Endocytosis--> membrane pinches itself off to enclose big molecules (changes shape of

them) --> results in formation of vesicle that enters cytoplasm --> ends of membrane

reattach

- Ex--> phagocytosis: intake of large particulate matter/ Pinocytosis: intake of extracellular

fluids

- Exocytosis--> protein exocytosis begins in ribosomes of rER and progresses through

these steps...

- 1. protein produced by ribosomes of rER enter lumen (the inner space) of rER

- 2. the vesicle carrying the protein fuses with the cis side of the golgi

- 3. as the protein moves through the golgi, it is modified and exits on the trans face inside

another vesicle

- 4. the vesicle with the modified protein inside moves towards and fuses with the plasma

membrane, resulting in the secretion of the contents from the cell

B2.1.14: Gated ion channels in neurons

- Gated ion channels: allow ions to pass quickly through cell membranes; have openings

that can be opened or closed because of chemical and electrical stimuli

- Nicotinic acetylcholine receptors = neurotransmitter-gated or chemically gated ion

channel

- When acetylcholine attaches to nicotinic acetylcholine receptor, the channel through the

membrane is opened and positive ions such as K+, Na+, Ca2+ can pass through; this

causes the membrane potential to change so that an impulse can be generated; nerve

impulses can be carried along many neurons; when the neurotransmitter is released at the

junction between nerve and muscle, the opening of this receptor and movement of

possible ions cause muscle movement

- Voltage gated ion channels: opened by changes in membrane polarity

- Ex--> Na+ and K+ channels; electrical stimulus opens and closes gates on these proteins;

Na+ opens first and sodium ions move inside neuron (depolarizes membrane); Na+

closes quickly and K+ opens slowly

---> Picture of neuron

B2.1.15: Sodium-potassium pumps as an example of exchange transporters

- In pump, the higher concentration of positive sodium ions outside cell than positive

potassium ions inside cell creates a difference in electrical charge across membrane -->

membrane potential

---> Picture of sodium-potassium pump

- Steps of the pump

- 1. the pump protein with attached ATP molecule binds to 3 Na+ ions. ATP = chemical

that gives energy

- 2. binding of Na ions causes pump to split ATP, providing usable energy and leaves

phosphate attached to carrier. The addition of a phosphate is called phosphorylation. ATP

has 3 attached phosphates when it carries out phosphorylation of pump, it loses a

phosphate and becomes ADP

- 3. phosphorylation causes protein to change shape, expelling Na ions into extracellular

fluid

- 4. 2 extracellular K+ ions bind to different regions of proteins, causing the release of a

phosphate group

- 5. loss of phosphate group restores the protein’s original shape, causing the release of the

K+ ions into the intracellular space, ready to repeat.

B2.1.16: Sodium-dependent glucose cotransporters as an example of indirect active transport

- Indirect active transport uses energy produced by movement of one molecule down a

concentration gradient to transport another molecule against the concentration gradient

- Ex--> glucose into cells of lining of intestines

- Steps of indirect active transport

- 1. there are more sodium ions outside than inside intestinal cell

- 2. sodium ions and glucose molecules bind to specific transport protein on the

extracellular surface

- 3. Na ions pass through carrier to the inside of cell down the concentration gradient, with

the carrier capturing the energy released by this movemment

- 4. the captured energy is used to transport the glucose molecules through the same

protein into the cell

- Protein carrier is known as the sodium-dependent glucose transporter

B2.1.17: Adhesion of cells to form tissues

- Cell adhesion molecule (CAM): is involved in cell connections --> several different types

of CAM, and each is used for different cell to cell junction

- Desmosomes: form sturdy but flexible sheets of cells in organs such as the heart,

stomach, and bladder. Tissues in these organs get stretched, but desmosomes hold the

cells together.

- Plasmodesmata: tubes connecting the cytoplasm of adjacent cells. These tubes allow the

exchange of material, especially water and small solutes, between connected cells.

B2.2: Organelles and compartmentalization

B2.2.1: Organelles as discrete subunits of cells that are adapted to perform specific functions

- Organelle: discrete structure within a cell that is adapted to form specific functions

- Cell compartmentalization: isolation of reactions

- Cell wall = NOT organelle = encloses and protects plant cells

- Cytoplasm = NOT organelle = most of metabolic rx occur here

- Cytoskeleton = NOT = maintain cells shape, anchors organisms, cell movement

- Nucleus = YES = genetic control

- Vesicles = YES = storage and transport

- Membrane = YES = regulate movement in and out of cell

- Ribosomes = YES = protein synthesis

- Cilia/ flagella = YES = movement

- Golgi = YES = stores ER products, forms lysosomes, and trans. Vesicles

- Mitochondria = YES = cellular energy production

- Chloroplast = YES = light to chemical energy

- Lysosome = YES = digest debris

B2.2.2: Advantage of the separation of the nucleus and cytoplasm into various compartments

- Transcription: DNA strand serves as a template or copy strand for formation of mRNA

- Translation: ribosomes use code carried by mRNA to produce polypeptide protein

- Transcription and translation occur in nucleus, eukaryotes, and cytoplasm

- Separation of these two processes allows for post-transcriptional modification of mRNA

to occur in nucleus before translation happens in cytoplasm

- In prokaryotes, there’s no isolation of these two processes, and mRNA can immediately

come into contact with ribosomes and initiate translation

- *Compartmentalization of cells allows for this greater efficiency

B2.2.3: Advantages of compartmentalization in the cytoplasm of cells

- All eukaryotic cells possess compartments involved with --> 1. energy production 2.

metabolism 3. biosynthesis 4. degradation

- Compartmentalization: allowed a division of labor within cell with specific tasks carried

out by a single organelle; keeping reactions separate in different parts of the cell means

that the metabolites and enzymes for each particular process can be concentrated in a

particular area --> pathways can run smoothly, enzymes can be kept in areas where

they’ll be most effective

- Lysosomes in compartmentalization --> breaks down wastes; requires some potentially

destructive enzymes that could cause damage to cell without isolation by membrane

- Phagocytic vacuole --> protects cellular contents from damage when phagocytosis

occurs; when formed, the phagocytic vacuole will move around in the cell until it

contacts a lysosome; vacuole then fuses with acidic lysosome, allowing inactivation and

digestion of threat

B2.2.4: Adaptations of the mitochondrion for production by aerobic respiration

- Outer membrane --> separates contents of mito. From rest of the cell

- Matrix --> internal cytoplasm-like substance that contains enzymes for first stages of

respiration

- Cristae --> tubular regions surrounded by membranes that increase surface area for rx

that take place towards the end of respiration

- Inner membrane --> a mem. That contains carriers and enzymes for final stages of

respiration

- Inter membrane space --> reservoir for H+ ions allowing a high concentration for protons

- Ribosome --> make proteins

- MtDNA --> circular compact allows for fast replication and transcription

---> Picture of mitochondria

B2.2.5: Adaptations of the chloroplast for photosynthesis

- Double membrane --> control movement of substances in and out of chloroplast;

maintains stable internal environment

- Thylakoid membrane --> has chlorophyll and electron transport proteins; site of light-

dependent rx; capture light energy

- Photosystems --> organized protein-pigment complexes in thylakoid membrane;

efficiently absorb light

- Compact thylakoid lumen --> small space enclosed by the thylakoid membrane; allows

fast accumulation of H+ ions to create proton gradient for ATP synthesis

- Stroma --> site of light dependent rx (calvin cycle)

- Ribosomes (70s) --> translate chloroplast-encoded proteins to call for photosynthesis

- Chloroplast DNA (cpCNA) --> enables chloroplast to produce some of their own proteins

---> Picture of chloroplast

- What do mitochondria and chloroplast have in common:

- Extra outer membrane, own DNA, near in size to typical prokaryotic cell

B2.2.6: Functional benefits of the double membrane of the nucleus

- Nuclear envelope: provides area where DNA can carry out its functions without being

affected by processes occurring in other parts of the cell

- Nuclear membrane has many pores which allow ions and small molecules to diffuse

between nuclear material

- Nucleoplasm and cytoplasm --> control passage of mRNA, proteins, and RNA protein

complexes

- These RPC’s become ribosomes and are produced in nucleolus

- Chromatin: inactive form of DNA; what the inner membrane of the nuclear envelope

interacts with; maintain shape

- Nuclear envelope in mitosis and meiosis--> nuclear membrane breaks down to allow

movement of DNA structures; nuclear envelope breaks, becoming vesicles freely

circulating in cytoplasm; once DNA is correctly positioned at conclusion of mitosis and

meiosis, these vesicles attach to surface of chromosomes and undergo a series of changes

to reform nuclear envelope

B2.2.7: Structure and function of free ribosomes and of the rough ER

- Ribosomes in prokaryotic cells are smaller than eukaryotic ones

- Composed of proteins and ribosomal RNA

- Amino acids bond to attachment sites

- Produce proteins; attached to ER or in cytoplasm

- RER: ER with ribosomes attached

- Free ribosomes: produce proteins that are used within cells such as in supporting

cytoskeleton; proteins used in nucleus, by mitochondria, etc.

- Membrane ribosomes: produce proteins that are transported through the ER and exported

from the cell

- Secretory proteins (hormones and enzymes) are made by membrane ribosomes and are

sent to the golgi apparatus where they’re packaged

B2.2.8: Structure and functions of the golgi apparatus

- Structure of Golgi --> flattened sacs; stacks of flattened sacs = cisternae; position of golgi

gives evidence for its cellular function; one side of flattened sacs located near ER and

other towards plasma membrane

- Flow of proteins --> protein or lipid filled transport vesicles received on cis side from

sER or eER (trans side); protein moves through cisternae --> modified so they can carry

out specific functions; once modified, its then taken to trans side; often the modification

of the substance includes the attachment of signal chemical that directs the destination

B2.2.9: Structure and function of vesicles in cells

- Vesicles: small membrane-bound sacs in which various substances are transported or

stored in the cell

- Ex--> peroxisomes, lysosomes, transport vesicles, secretory vesicles, etc.

- Clathrins: proteins in the cell membrane that anchor certain proteins to specific sites,

especially on the exterior plasma membrane in receptor-mediated endocytosis

- Allows receptors to bind to specific molecules --> when an appropriate collection of

molecules occurs in the lined pit, the pit deepens and will eventually sear off, forming a

vesicle

- This process is highly specific and the sealing off and formation of a vesicle occurs

rapidly

- The advantage of receptor-mediated endocytosis is that it is selective and efficient,

especially compared to ordinary endocytosis

B2.3: Cell specialization

B2.3.1: Production of unspecialized cells following fertilization and their development into

specialized cells by differentiation

- Zygote: unspecialized cell produced from fertilization

- Cell signaling process by which information is transferred from cell surface to nucleus;

essential for controlling gene expression and differentiation

- Morphogens: signal molecules that control cell differentiation; occurring gradients in

different regions of embryo

- Embryo impacted --> concentration of the morphogen controls the regional development

of first cells into head and tail structures; results in different genes being expressed in

different parts of embryo – different parts of embryo develop different features

B2.3.2: Properties of stem cells

- Stem cell: population of cell within organisms that continue their ability to divide and

differentiate into various cell types/ continue ability to divide indefinitely and can

differentiate along different pathways

- Function --> can self-renew and recreate functional tissue

- Meristematic tissue: where stem cells are; found near root and stem tips; composed of

fast reproducing cells

B3.3.3: Location and function of stem cell niches

- Stem cell niche: stem cells are present in high numbers as a result of regular proliferation,

but also show differentiation

- Stem cell niches in humans are bone marrow and hair follicles

- Multipotent stem cell ex--> bone marrow= stem cells that produce blood found alongside

self-renewing stem cells; as blood cells are produced, the differentiated cells are

transported away through a large array of supporting blood vessels/ hair follicles = in

skin; large numbers of epithelial stem cells found in bottom of hair follicle; involved with

hair growth, skin, and hair follicle regeneration, and sebaceous glands

B3.2.4: Differences between totipotent, pluripotent, and multipotent stem cells

- Totipotent (zygote): capable of continued division and possesses ability to produce any

tissue in organism; few cells are totipotent; only exists in the early stages of embryonic

development; they may form a complete organism

- Pluripotent (embryonic cell): arise from totipotent and only exist in early stages of

embryonic stage because needed to form all different cell types; can mature into almost

all different cell types that exist in an organism; can’t produce complete organism

- Multipotent (hair follicles and bone marrow): only forms a limited number of cell types;

bone marrow tissue that produces different types of blood cell = multipotent; occur later

in the development of embryo

B3.2.5: Cell size as an aspect of specialization

- Sperm cell--> 3 um in diameter, 50 um in length

- Egg --> 120 um

- RBC --> 7.5 um

- WBC --> 12-15 um

- Skeletal muscle --> 10-50 um width; 40 um length

- RBC’s adaptations --> contain hemoglobin that combines with and release O2/ have

biconcave disc shape allowing for more surface area for O2 absorption; lack

mitochondria and nucleus; flexible and size limited because need to move through narrow

blood capillaries

- WBC’s adaptations --> fight against infections; retain nucleus; has vesicles with enzymes

that can kill microorganisms

- Neurons --> motor neurons = carry impulses from brain or spinal cord and allow muscles

to respond; has long fibers (axons) and carry impulses; axons of motor neurons can

extend up to 1 meter in human body

- Striated muscle fiber --> specialized cells in skeletal muscle; cylindrical, 12 um long

---> picture of striated muscle fiber/ skeletal muscle fiber

- Cell size dictated by --> basic processes of cell phycology and cell division apparatus

B2.3.6: Surface area-to-volume ratios and constraints on cell size

- Size limited by SA:V --> as width of cell increases, the SA of the cell also increases but

at a slower rate; this means that a large cell, compared to a small cell has less SA to bring

in materials that are needed and to rid of waste

- Activities occur in surface and volume of cell --> heat waste production; rate of resource

consumption; at surface, membrane controls what materials move in and out of cell

- SA= 6a^2 /V= a^3

B2.3.7: Adaptations to increase surface area-to-volume ratios of cells

- Modifications to increase SA:V of cells --> changes in cell shape; cellular projections;

location relative to sources of nutrients; means of transporting away wastes; how the cells

fit together at specific location

- Erythrocytes: has adaptations; their size coupled with their flexibility allows them to

squeeze through small capillaries to deliver O2 to all cells of body

- Proximal convoluted tubule --> closely packed together; tiny projections/ microvilli's

pointing outwards into the lumen of tubule in which fluid flows, increasing surface area

of the cell; large numbers of mitochondria are found in cells

B2.3.8: Adaptations of type I and type II pneumocytes in alveoli

- Alveolar epithelium: example of a tissue where more than one cell type is present

because different adaptations are required for overall function of tissue

- Alveolus: functional unit of lungs; increases SA of lung to maximize gas exchange

- Type I pneumocytes: cover 95% of alveolar surface; allow gas exchange between alveoli

and capillaries; thin and flat in shape to increase SA and minimize diffusion distance;

shared basement membrane with lining of lung capillaries; tightly joint together so fluids

cannot enter alveoli from capillaries

- Type II pneumocytes: 5% of surface; bound between type I pneumocytes; produce

pulmonary surfactant (reduces surface tension and prevents alveoli from collapsing and

sticking to each other); cube shape; microvilli oriented towards alveolar sac; increasing

SA and allowing more surfactant secretion; can transform into type I pneumocytes;

cytoplasm contains many organelles involved with surfactant production

B2.3.9: Adaptations of cardiac muscle cells, smooth muscle cells and striated muscle cells

- Cardiac muscle: branched fibers; usually 1 nucleus per cell; Striated; Only in heart;

Involuntary (automatic nervous system); Who split their body; Intercalated discs

(Specialized connections between cells that include gap junctions for fast electrical

signaling); Rhythmic and self-initiated contractions.

- Striated skeletal muscles: long; cylindrical; multinucleated; striated; attached to bones via

tendons; voluntary (stomatic nervous system); body movement, posture, heat production;

contracts quickly; organized in sarcomeres; many mitochondria for ATP production

- Smooth muscles: spindle-shaped discs; single nucleus; non-striated; found in walls of

internal organs; involuntary; more substances through body; slower and sustained

conditions; fatigue resistance

- Compare and contrast striated skeletal muscle and cardiac muscle?

- Cardiac muscles = shorter than striated. Because of their branching cells, the connection

between them, cardiac muscle fibers coordinate contractile process involving the whole

heart in order to pump blood successfully. Skeletal muscles don’t follow a usual pattern

of cell division; they don’t expand by producing more cells; when damaged, they do not

go through the usual process of apoptosis

B2.3.10: Adaptations of sperm and egg cells

- Gamete (egg + sperm) function --> carry 1⁄2 genetic information from each parent and

diffuse during fertilization to form zygote

- Egg: size = large (100 um) / non-motile (doesn’t move on its own)

- Different parts of egg and their functions

- 1. Haploid nucleus: contain 1⁄2 genetic material to combine with sperm

- 2. Binding proteins: help recognize and bind a sperm cell of same species

- 3. zone pelludica: protective glycoprotein layer around egg; only allows one sperm to

enter and triggers the acrosome rx in sperm

- 4. cortical glands: release enzymes after fertilization to harden zona pellicudia,

preventing other sperm from entering

- 5. yolk: provide nutrients for embryo

- 6. mitochondria: supply ATP for eggs’ cellular process

- Sperm: small size (5um head, 50um with tail)/ very motile

- Different parts of sperm and their functions

- 1. head: contains haploid nucleus (holds genetic info)

- 2. acrosome: cap-like structure at tip of head containing enzymes to help sperm penetrate

egg

- 3. plasma membrane receptors: proteins on sperm’s outer membrane; bind to specific

molecules

- 4. binding proteins in acrosome: proteins withing acrosome that bind to zona pellidudia

- 5. halploid nucleus: carries single set of chromosomes

- 6. midpiece: has helical mitochondria; provide energy for tail

- 7. microtubules: structural support and movement in tail

- 8. tail: propells sperm forward

B3.1: Gas exchange

B3.1.1: Gas exchange as a vital function in all organisms

- Gas exchange: O2 is taken into an organism and Co2 is released

- Diffusion in gas exchange --> allow gases to move passively from high to low

concentration without energy

- Large organisms struggle --> their volume increases faster than their surface area as they

grow; simple diffusion is not enough to supply O2 to cells; they develop gills, lungs,

leaves, etc. To overcome this

B3.1.2: Properties of gas exchange surfaces

- 1. permeability: allows gases like O2 and CO2 to pass freely through membrane for

diffusion

- 2. thin tissue layer: refuces diffusion distance --> gas exchange faster

- 3. moisture: dissolve gases, enabling them to diffuse easier

- 4. large SA: provides more space for gases to diffuse; increases rate of gas exchange

B3.1.3: Maintenance of concentration gradients at exchange surfaces in animals

- Why concentration gradient must be maintained at exchange surfaces? --> because O2

and CO2 are exchanged by diffusion; has to be maintained at surface for oxygen to

diffuse into blood and CO2 out of blood

- 2 events that occur to keep gradient in place? --> water has to be continuously passed

over gills/ air must be ventilated in lungs; AND must be a continuous flow of blood to

dense the network of blood vessels in both vody tissues and tissues of gills or lungs

- Example --> Lungs and air --> mechanism = breathing constantly refreshes air in alveoli,

bringing in O2 and removing CO2, maintaining a gradient between alveolar air and blood

- Example --> gills --> mechanism = water flows constantly over gill surfaces, often

opposite direction to blood flow; ensures that H2O always has more O2 than the blood it

is next to, preserving a steep diffusion gradient

B3.2: Transport

B3.2.1: Adaptations of capillaries for exchange of materials between blood and its internal or

external environment

- Capillaries receive blood from the smallest of arteries called: arterioles

- Arteriole branches into capillary beds

- Capillary bed: network of capillaries that all receive blood from the same arteriole

- Capillary beds dump the blood into venules

- Venule: smallest of veins

- When blood enters capillary bed, a lot of its pressure and velocity is lost

- Blood cells line up in a single file because the lumen (inside diameter) of each capillary is

only large enough to accommodate 1 cell at a time.

- Each capillary is a small tube composed of a single celled thickness of inner tissue and a

single cell thickness of outer tissue --> both very permeable

- Total Surface area and extensive branching of capillary beds = high.

- Highly vascular tissue: metabolically active tissues in the body that are enriches with

capillary beds

- Fenestrated capillaries: a type of blood capillary characterized by pores or "fenestrae" in

their endothelial cells, allowing for the rapid exchange of molecules and fluids (ex: small

capillaries of kidneys and areas of intestine

- Capillaries are adapted to their function by...

- 1. having a small inside diameter

- 2. being thin walled

- 3. being permeable

- 4. having large SA

- 5. having fenestrations

- How are structures of capillaries adapted to their function?

- 1. Lumen Diameter

- Structure: Extremely narrow lumen, just wide enough for red blood cells to pass through

in single file/ Function: Ensures maximum surface area of red blood cells is in contact

with the capillary wall for efficient gas exchange (especially oxygen and carbon dioxide).

- 2. Extensive Branching

- Structure: Capillaries form dense networks (capillary beds) that spread throughout

tissues/ Function: Increases the surface area for exchange and reduces the diffusion

distance between capillaries and cells.

- 3. Thin Walls

- Structure: Walls are made of a single layer of endothelial cells (only one cell thick)/

Function: Minimizes diffusion distance, allowing for rapid exchange of gases, nutrients,

and waste products.

- 4. Fenestrations (Pores)

- Structure: Some capillaries, especially in organs like the kidneys and intestines, have

small pores in the endothelial walls/ Function: These fenestrations increase permeability,

allowing small molecules (like glucose, ions, and water) to pass more freely.

B3.2.2: Structure of arteries and veins

- Artery: vessel receives blood from the heart and takes it to capillary bed

- Vein: receives blood from capillary bed and takes it to heart

- Arteries are lined with a thick layer of smooth muscle and elastic fibers because they

receive blood directly from the heart and blood is under relatively high pressure.

- The lumen of arteries is relatively small compared to veins.

- Veins receive low pressure blood from capillary beds and so they are relatively thin

walled with a large lumen that carry the slow-moving blood

- Compare the diameter, relative wall thickness, lumen size, number of wall layers,

abundance of muscle and elastic fibers and presence of valves in arteries and veins?

- Arteries --> Diameter: Narrower/ Wall thickness: Thick walls to handle high pressure/

Lumen size: Small lumen/ Wall layers: 3 layers (tunica intima, media, externa)/ Muscle

& elastic fibers: Abundant (especially in tunica media)/ Valves: None (except near the

heart)

- Veins --> Diameter: Wider/ Wall thickness: Thin walls due to low pressure/ Lumen size:

Large lumen/ Wall layers: 3 layers (thinner and less muscular than arteries)/ Muscle &

elastic fibers: Fewer than in arteries/ Valves: Present (especially in limbs to prevent

backflow)

---> micrograph of vein and artery (p. 289)

B3.2.3: Adaptations of arteries for the transport of blood away from the heart

- Each artery has a thick layer of smooth muscle controlled by the automatic nervous

system (ANS)

- The smooth muscle changes the lumen diameter of arteries to help regulate blood

pressure

- The wall of each artery contains the proteins elastin and collagen

- The muscular and elastic tissues permit arteries to withstand the high pressure of each

blood surge and keep blood continuously moving.

- When blood is pumped into an artery, the elastin and collagen fibers are stretched and

allow the blood vessel to accommodate the increased pressure --> Once the blood surge

has passed, the elastic fibers recoil and provide further pressure which propel the blood

forward within the artery, allowing for the blood in arteries to maintain a high pressure

between pump cycles of the heart

B3.2.4: Measurements of pulse rates

- Pulse rate: measurement of the number of times your heart beats in a minute. Each time

the heart contracts and sends blood directly into arteries, the pulse of pressure can be felt

in an artery

- Unit measurement of pulse = beats per minute (bpm)

B3.2.5: Adaptations of veins for the return of blood to the heart

- Blood loses a great deal of pressure and velocity in capillary beds.

- To account for this, veins have thin walls and a larger internal diameter.

- Thin walls allow for veins to be easily compressed by surrounding structures like muscles

and helps squeeze blood towards heart

- Skeletal muscle contractions ---> mechanism = surrounding skeletal muscles contract

during body movement/ effect on veins = compress veins, pushing blood through them

and ensure that blood moves in the correct direction

- Valves prevent blood backflow, and the walls’ flexibility allows it to be compressed by

muscle action

B3.2.6: Causes and consequences of occlusion of the coronary arteries

- Coronary arteries: the arteries that supply blood to cardiac muscle

- Plaque: buildup of cholesterol and other substances in lumen of arteries, causing an...

- Occlusion: the blockage or closing of an opening, blood vessel, or hollow organ

- May result in a heart attack because the heart is deprived of its oxygen

- Coronary heart disease: Narrowing of coronary arteries due to plaque buildup, reducing

oxygen to heart.

- Atherosclerosis --> Hardening/narrowing of arteries from fatty deposits (plaque).

- Atherosclerosis risk factors --> Smoking, high cholesterol, hypertension, diabetes, obesity, sedentary lifestyle.