(AP Biology) Chapter 4: A Tour of the Cell & Chapter 5: Membrane Trasnport and Cell Signaling

what type of image does a scanning electron microscopy (SEM) get?

shows 3D images

what type of image does a transmission electron microscopy (TEM) get?

shows a thin section

Where is DNA located in prokaryotes?

concentrated in a region called the nucleoid, it is not membrane bound

Where is DNA located in eukaryotic cells?

the nucleus which is a double membraned organelle

define: cell wall

rigid structure outside of the plasma membrane, made out of different things based on the organism

define: plasma membrane

membrane enclosing the cytoplasm a selective barrier allowing passage of nutrients and waste

define: bacterial chromosome

circular, located in nucleoid

define: nucleoid

region where prokaryotic cell’s DNA is located

define: cytoplasm

region between the nucleus and plasma membrane

* contains cytosol

define: flagella

locomotion organelles

Why are cells so small? and What is the relationship of surface area to volume?

the plasma membrane allows nutrients and waste exchange

* surface area determines the amount of a particular substance that can cross per second

define: microvilli

long thin projections from the surface of intestinal cells

* intestinal cells must exchange a lot of materials w their surrounds, and microvilli increase surface area without appreciable increase in volume

define: nuclear envelope

a double membrane enclosing the nucleus

* perforated by pores and continuous with the ER

define: nuclear lamina

net like array of protein filaments that maintains the shape of the nucleus by mechanically supporting the nuclear envelope (lining it)

define: nuclear matrix

protein filaments running through the nucleus

DNA + histones=

chromatin

When do the thin chromatin fibers condense to become distinct chromosomes?

only visually seen during mitosis

When are the nucleoli visible?

exist when the nucleus is NOT undergoing mitosis

* rRNA is made there

What are the function of ribosomes?

carry out protein synthesis

define: free ribosomes

suspended in the cytosol; makes proteins that function within the cytosol

define: bound ribosomes

attatched to the outside of the ER or nuclear envelope; proteins that are destined for insertion into membranes

List all the structures of the endomembrane system

* nuclear envelope
* endoplasmic reticulum
* golgi apparatus
* lysosomes
* vesicles
* vacuoles
* plasma membrane

Which structure makes up more than half of the total membrane system in eukaryotic cells?

endoplasmic reticulum

3 major functions of the smooth ER

1. synthesizes lipids
2. metabolize carbohydrates/storage of calcium ions
3. detoxification of drug and poisons

Why does alcohol abuse increase tolerance to other drugs such as barbiturates?

alcohol induces the proliferation of smooth ER and its associated detox enzymes, increasing the rate of detox, so greater doses are required to achieve a particular effect

Rough ER is studded with _____.

ribosomes

define: glycoproteins

proteins that have carbohydrates attached to them in the ER

2 major functions of rough ER

1. packaging of secretory proteins into transport vesicles
2. membrane factory

Explain how rough ER is a membrane factory?

it adds membrane proteins and phospholipids to its own membrane, which expands and forms transport vesicles which travel to other parts of the endomembrane system

define: lysosomes

membranous sac of hydrolytic enzymes that many eukaryotic cells use to digest (hydrolyze) macromolecules

* pH is acidic

define and describe: phagocytosis

As the food molecule is engulfed it is surrounded by a membrane. Lysosomes fuse with the membrane and release their contents, which digest the food.

define and describe: autophagy

recycle cellular components

* a damaged organelle or small amount of cytosol is surrounded by a double membrane, the lysosome fuses and breaks down the contents. It is then left to be recycled

What is Tay-Sachs disease and what is the role of the lysosome?

a lipid digesting enzyme is missing or inactive and the brain becomes impaired by an accumulation of lipids in the cell

define: food vacuoles

food is engulged and surrounded by a double membrane

define: contractile vacuoles

pump excess water out of the cell to maintain a suitable concentration of ions and molecules inside of the cell

functions of the central vacuoles in plants

develops by the coalescence of smaller vacuoles

1. carry our enzymatic hydrolysis

2. hold reserves of important organic compounds

3. store compounds that are poisonous or unpalatable

4. pigments

define: endosymbiont

a cell living within another cell

define: endosymbiont theory (and what evidence supports this)

cells engulfed other cells and they merged into a single organism over the course of evolution

• mitochondria and chloroplasts have a double membrane

• they have their own ribosomes and their own DNA

• reproduce on their own in the cell via binary fission

function of the mitochondria

site of cellular respiration

function of the chloroplasts

site of photosynthesis

Why is the inner membrane of the mitochondria highly folded?

more folds increase the surface area over which reactions occur

What role do all the individual thylakoid membranes serve?

to offer more surface area

What do peroxisomes do?

they contain enzymes that remove -H atoms from certain molecules to bind with O2 and make H2O2 used in detoxing processes

define: cytoskeleton

a network of fibers expending throughout the cytoplasm

• offers shape and structure

2 roles of the cytoskeleton

1. gives mechanical support to the cell and maintains shape

2. involved in cell motility

3 main types of fibers that make up the cytoskeleton

1. microtubules (25nm)

2. intermediate filaments (8-12nm)

3. microfilaments (7nm)

what are microtubules made out of

tubulin, each is a dimer made of two subunits

4 functions of microtubules

1. maintenance of cell shape

2. cell motility

3. chromosomes movement in cell division

   1. organelle movements

define: centrosome

centrioles MAY help organize microtubule assembly in animal cells

• it is a region

cilia vs flagella

both act as locomotor appendages

• cilia usually occur in large numbers on the surface of the cell and when they move, they have alternating power and recovery strokes (like oars on a boat)

• flagella usually occurs as one or a few per cell. They are longer and move with an undulating motion (like the tail of a fish)

How do dyneins cause movement of cilia?

dyneins have 2 feet that walk along the microtubule of the adjacent doublet

• one foot maintains contact, while the other releases and reattaches one step farther along the microtubule

• ATP is used for energy

microfilaments are solid, and they are built from a double chain of ____.

actin

What are the motor proteins that move the microfilaments?

myosin

functions of intermediate filaments

reinforce the shape of the cell, fix position of certain organelles

• nucleus sits within a cage of intermediate filaments

• makes up nuclear lamina

3 functions of the cell wall

1. protection

2. shape maintenance

3. prevention of excessive uptake in water

What is the composition of the cell wall?

in plants, microfibrils of cellulose are secreted into the extracellular space (outside the cell)

What is the relatively thin and flexible wall secreted first by a plant cell?

primary cell wall

What is the middle lamella?

located between the primary walls of adjacent cells

• thin layer consisting of pectin (sticky polysaccharides)

• glues adjacent cells together

explain the deposition of a secondary cell wall

deposition between the plasma membrane and the primary wall, often in several laminated layers

animal cells do not have cell walls, but they do have an ECM (extracellular matrix)…

area between; outside of cells, contains mostly glycoproteins

ECM: collagen

strong fibers; 40% at total protein in humans

ECM: proteoglycan

small proteins with big carb chains

ECM: fibronectin

attaches to the ECM

ECM: integrin

proteins that span the cell membrane (connect cytoskeleton to ECM and pass signals

What are the intercellular junctions between plant cells?

plasmodesmata allow water, small solutes, some proteins, and RNA molecules to pass freely from cell to cell

3 types of intercellular junctions seen in animal cells

1. tight junctions- proteins that tightly bind cell membranes together to prevent leakage across cells (all types of tissue that hold fluids in)

2. desmosomes- bind cells together strongly

3. gap junctions- cytoplasmic channels between adjacent cells; like plasmodesmata in plants

phospholipids are amphipathic, define

they have a hydrophilic region (head) and hydrophobic region (tails)

define: fluid mosaic model

protein molecules bobbing in a fluid layer of phospholipids

• proteins exist both on the surface of the phospholipid bilayer and spanning the membrane

describe: membrane fluidity

the lipids and proteins shift around laterally (side to side) lipids can move more rapidly than proteins

describe how each of the following can affect membrane fluidity: decreasing temperature

phospholipids are gonna move slower and eventually settle into a closely packed arrangement

describe how each of the following can affect membrane fluidity: phospholipids with unsaturated hydrocarbon chains

kinks in the tails, cannot pack as closely together so membrane remains more fluid

describe how each of the following can affect membrane fluidity: cholesterol

at high temps- cholesterol makes membranes less fluid by restraining phospholipid movement

at lower temps- hinders the close packing of phospholipids

define: integral proteins

penetrate the hydrophobic interior of the lipid bilayer, majority are transmembrane

define: peripheral proteins

are loosely bound to the surface of the membrane NOT embedded

describe the functions of this membrane protein: transport

proteins that span the membrane

• can form a hydrophilic channel

  • change shape to shuttle a substance trhough

describe the functions of this membrane protein: enzymatic activity

proteins are built into the membrane

• active site can be exposed to substances outside of the cell

• can be organized and act as a team

describe the functions of this membrane protein: attachment to the cytoskeleton and ECM

microfilaments or other elements of the cytoskeleton may be bound to membrane proteins

• proteins can coordinate extracellular and intercellular changes

describe the functions of this membrane protein: cell-cell recognition

glycoproteins serving as ID tags can be recognized by membrane proteins of other cells

describe the functions of this membrane protein: intercellular joining

membrane proteins of adjacent cells can hook together in various kinds of junctions

describe the functions of this membrane protein: signal transduction

a signaling molecules fits into a receptor protein, relaying a message to the inside of the cell

examples of cell-cell recognition

1. the differentiation of cells into tissues in an animal embryo

2. basis of rejection of foreign cells by the immune system

define: glycolipids

short branched chains of 15 or fewer sugar units covalently bonded to lipids

define: glycoproteins

chains of sugar bonded to a protein

define: channel proteins

have a hydrophilic channel that certain molecules or atomic ions can pass through

define: carrier proteins

hold the molecule they are transporting and change shape to shuttle them across the membrane

Are transport proteins specific?

very, a carrier protein in the plasma membrane of a red blood cell is so specific that it will only transport glucose and not its structural isomer, fructose

define: aquaporins

channel proteins that transport water molecules across the plasma membrane at rates of 3 billion water molecules per second

simple diffusion

small hydrophobic molecules can diffuse because the middle is hydrophobic

define: diffusion

movement of particles to spread out into available space

define: concentration gradient

a region along which the density of a substance increases or decreases

define: passive transport

diffusion of a substance across a biological membrane with the gradient

define: osmosis

diffusion of free water across a selectively permeable membrane

define: isotonic

cell has some concentration of solutes as its surrounding environment

define: hypertonic

contains more solutes

define: hypotonic

contains fewer solutes

define: turgid

very firm bc it contains as much water as it can hold (in a hypotonic solution)

define: flaccid

limp bc it does not contain as much water as it can hold (in an isotonic solution)

define: plasmolysis

cell shrivels and the plasma membrane pulls away from the cell walls

define: facilitated diffusion

passive transport with the help of transport proteins

• occurs with the gradient

• uses either channel proteins (like aquaporins) or carrier proteins (like glucose transporters)

define: active transport

uses carrier proteins to transport substances against their gradient

• requires ATP, the terminal phosphate is added to the protein which causes a shape change