Bio 210 Exam 2

w/ Prof Greg Tyson

Efficiency of transport of materials within a cell decreases

with size, limiting the maximum cell size

A researcher growing cells in culture observed that the cells

always divided once they reached a certain size, regardless of her

adjustments to nutrients and temperature in the growth

chamber. What could explain these observations?

a. Increasing cell size is accompanied by increasing cellular

reactions, which produce more heat that threatens cell

survival.

b. Efficiency of transport of materials within a cell decreases

with size, limiting the maximum cell size.

c. The cell’s surface area increases faster than its volume as it

increases in size, leading to an inability of the cell to feed

itself

1. more efficent to perform a specialized function

2. seperate enviroments (acidic levels vary)

Why do organelles exist?

They are synthesized from within membranes

Most proteins are in the cytosol because they are

hydrophilic; how are membrane proteins (which

are hydrophobic) made?

A) They simply diffuse from the cytosol to the appropriate membrane

B) They are synthesized from within membranes

C) They have a hydrophobic shell that encases them to maintain

proper folding

D) There are actually no proteins in the cell membrane

Which types of proteins would leave a cell

entirely?

• Could be cell signaling

• Antibodies

• Enzymes to break down food

Some other organelles have DNA

The book says: “The nucleus contains most of the

genetic information”. Why not all?

A) Some of the DNA is exported out of the nucleus

B) Some other organelles have DNA

C) DNA is often released outside the cells

D) Other???

rough er analogy

production factory

vesicle analogy

delivery truck

lysosome analogy

recycling factory

plasma membrane analogy

final delivery site

golgi analogy

shipping warehouse

smooth er

rough er

mitocondria

golgi apparatus

lysosome

cell membrane

nucleus

Membranes are the borders between different regions of a cell.

• Where membranes exist, differing cell environments can be

maintained.

• The plasma membrane borders the entire cell separating the

internal environment from the external environment

• Like food packaging, it’s shape and structure is based on what’s inside

What is a membrane

lipids

proteins

carbohydrates

Which of the below are cell membranes made of?

A) Lipids

B) Carbohydrates

C) Proteins

D) Nucleic acids

What is a cell surface antigen and what is it made

of?

• Something on the cell surface that can be recognized

• Sometimes immune system will react to

• Proteins, but can also be carbohydrates

Why do materials move?

Molecules are in motion and their motion increases the

entropy of the system (less order)

• Molecular collisions result in molecules being moved along

a gradient (concentration gradient or free energy gradient)

• Through random molecular collisions directional motion can be

accomplished

Biological membranes are semipermeable

What does this mean?

small uncharged molecules can pass through the hydrophobic lipid bilayer

large polar molecules and ions cannot pass through the lipid bilayer

which molecules can freely pass across the membrane?

• Hydrophobic molecules (e.g. lipids)

• NOT charged molecules (ions) or polar molecules

• Transport proteins may assist ions and polar molecules

across the membrane

In which direction can molecules go across the membrane?

high concentration → low concentration

A) Water will move from left to right

Imagine a semipermeable membrane that can

allow osmosis to occur. What will happen?

A) Water will move left to right

B) Water will move right to left

C) Red particles will move left to right

D) Red particles will move right to left

Where does most energy for life on earth come from?

1. water

2. the sun

3. soil

4. air

the sun

The polysaccharide requires a membrane protein

A lipid and a polysaccharide are both moving

from high to low concentration. Which is true?

A) Both require carrier proteins

B) Both involve facilitated diffusion

C) Both are active transport

D) The polysaccharide requires a membrane protein

Receptor-mediated endocytosis can be

hijacked: when does this occur?

Viruses! Have surface proteins that can mediate this to gain cell

entry

• Part of what makes viruses specific

The dna in a prokaryotic cell is not enclosed in a membrane- bound nucleus

What is a difference between a prokaryotic and eukaryotic cell?

• Cellular processes in a prokaryotic cell are compartmentalized, whereas compartmentalization is absent in a eukaryotic cell

• a prokaryotic cell is not enclosed by a cell membrane, and a eukaryotic cell is enclosed.

• The DNA in a prokaryotic cell is not enclosed in a membrane- bound nucleus

• A prokaryotic cell does not use DNA as its genetic material

• A prokaryotic cell does not use ribosomes for protein synthesis, whereas a eukaryotic cell does

Cell A, because it has a larger surface area to volume ratio than cell B

The villi of the small intestines are lined with epithelial cells that absorb nutrients from digested food on one side and transfer these nutrients into the blood on the other side. Which cell shown in the figure would be most efficent as an epithelial cell in the intestinal villi, and why?

• Cell B, because it has a greater volume than the cell A

• Cell A, because its volume is greater than its surface area

• Cell B, because it has a greater surface area than cell A

• Cell A, because it has a larger surface area to volume ratio than cell B

• Cell B, becuase it has a larger overall size than cell A

7, 2, 6, 3

Which numbers represent cytoplasm, pili, ribosome, and cell wall, in that order?

• 2,8,6,4

• 5,2,6,3

• 5,6,1,4

• 7,2,6,3

• 7,6,5,3

trans-golgi

A vesicle carries a protein to the cell membrane, where it is inserted into the phospholipid bilayer. The vesicle budded off from which subcellular structure before making the trip through the cytoplasm to the cell membrane?

• trans-golgi

• cic-golgi

• rough er

• smooth er

• medial- golgi

microtubules, intermediate filaments, and microfilaments

The cytoskeleton consists of

• calcifed microtubules

• cilia, flagella, and microfilaments

• internal cell wall

• microtubules, intermediate filaments, and microfilaments

ribosomes on the rough endoplasmic reticulum; golgi apparatus

Some proteins on the surface of a mammalian cell contain carbohydrates. These proteins are synthesized by ___ and the sugars are added in the ___.

• ribosomes on the rough endoplasmic reticulum; golgi apparatus

• cytoplasmic ribosomes: smooth endoplasmic reticulum

• the golgi apparatus: rough endoplasmic reticulum

• cytoplasmic ribosomes: cell membrane

• mitocondrial ribosomes: smooth endoplasmic reticulum

proteins in the cytosol would break down

If all the lysosomes within a cell suddenly ruptured, what would be the most likely result?

• proteins in the cytosol would break down

• more proteins would be made

• the DNA in mitochondria would break down

• the mitochondria and chloroplasts would divide

• there would be no change in cell function

mitocondria and plastids have DNA that encodes some proteins used by the organelles

Which statement can be used as evidence for the endosymbiosis theory?

• In eukaryotes, the endoplasmic reticulum is continuous with the nuclear envelope

• Compartmentalization of individual functions in separate organelles allows eukaryotes greater ability to carry out a wide diversity of functions

• Vacuoles are membrane-bound organelles that store toxic molecules and waste products

• mitocondria and plastids have DNA that encodes some proteins used by the organelles

• internal membranes are the sites of photosynthesis in photosynthetic prokaryotes

Cell Theory

Theory that all living things are made of cells, cells are the basic unit of life, and all cells come from pre-existing cells

Eukaryote

An organism whose cells contain a nucleus and membrane- bound organelles (plants, animals, fungi, protist)

Prokaryote

An organism whose cells lack a nucleus and membrane-bound organelles (bacteria, archaea)

surface to volume ratio

the amount of cell surface area compared with its volume. SMaller cells have a higher ratio, allowing more efficent exchange of materials

Plasma Membrane

The selectively permeable membrane, primarily made of phospholipids, surrounding a cell that controls what enters and leaves

nucleoid

the region in a prokaryotic cell where its DNA is located

Organelle

A specialized structure within a eukaryotic cell that performs a specific function

nucleus

membrane bound organelle that contains most of a eukaryotic cells DNA

Cytoplasm

Everything inside the plasma membrane except the nucleus, includes the cytosol adn organelles

nuclear pore

an opening in the nuclear envelope that controls movement of proteins into and out of the nucleus

ribosome

A structure that builds proteins using instructions from messenger RNA. They can be free in the cytosol or bound in the rough ER.

smooth endoplasmic reticulum

A membrane network involved in lipid production nd detoxification (lacks ribosomes)

rough endoplasmic reticulum

a membrane network covered with ribosomes that make membrane proteins

golgi apparatus

an organelle that modifies, sorts, and packages proteins and lipids for transport

vesicle

a small membrane bound sac that transports or stores substances inside or outside a cell, including to and from the ER, golgi, lysosomes, adn plasma membrane

Lysosome

an acidic organelle containing digestive enzymes that break down waste, damaged cell parts, and materials taken into the cell. A cells “stomach”

emdomembrane system

A group of membranes and organelles, including the nuclear envelope, ER, golgi, vesicles, lysosomes, and plasma membrane, that make, modify, and transport cell materials

mitochondria

organelles that produce ATP

chloroplasts

a plant organelle where photosynthesis occurs

endosymbiont theory

the theory that mitochondria and chloroplasts evolved from free living bacteria that were engulfed by larger cells and formed a mutually beneficial relationship

vacuole

a membrane bound storage compartment thats typically for nutrient storage or structure

peroxisome

an organelle that breaks down fatty acids and detoxifys harmful substances, producing and breaking down hydrogen peroxide

cytoskeleton

a network of protein fibers that supports cell shape and helps with movement, and cell division

microfilaments

the thinnest cytoskeletel fibers; they help maintain cell shape, enable movement, and assist in cell division

actin

the protein that makes up microfilaments

intermediate filaments

cytoskeletal fibers that provide mechanical strength and help stabalize the cell and its organelles

microtubules

hollow cytoskeletal tubes that help maintain cell shape, move organelles, and seperate chromosomes during cell division

tubulin

the protein that makes up microtubules

extracellular matrix

a netwok of proteins and carbohydrates outside animal cells that provides support, attachments, and communication

cell wall

a rigid layer outside the plasma membrane that supports and protects cells. Made of different components in different cell types, but present in plants, fungi, and bacteria

Both a and c

Which of the following describes how your body uses the foods you eat?

a. The food is broken down through catabolic reactions

b. the food is broken down through anabolic reactions

c. The components of the food are used in anabolic reactions

d. The components of the food are used in catabolic reactions

e. Both a and c

f. both b and d

The exergonic reaction provides free energy that helps drive the endergonic reaction

In biology, exergonic and endergonic reactions are often paired. Which statement is most accurate?

A. The endergonic reaction becomes exergonic on its own

B. The exergonic reaction provides free energy that helps drive the endergonic reaction

C. The two reactions cancel each other out, so neither occurs.

D. Coupling eliminates the need for enzymes

What is the energy currency of cells?

ATP

ATP releases energy to endergonic reactions

Which describes how ATP is used by the cell?

a. ATP stores energy from teh anabolic reactions

b. ATP releases energy to endergonic reactions

c. ATP accepts energy from exergonic reactions

d. ATP is used once, then broken down by the cell

OIL RIG

Oxidized, I Lose (electrons)

Reduced, I Gain (electrons)

Phospholipid

A molecule with a hydrophilic phosphate head and hydrophobic tail: they form the basic structure of a cell membrane

amphipathic

having both hydrophilic and hydrophobic regions (phospholipid)

fluid mosaic model

the description of the membrane as a flexible phospholipid bilayer containing moving proteins, cholesterol, and carbohydrates

Cholesterol

A lipid in animal cell membranes that helps regulate membrane fluidity and stability

integral membrane protein

a protein permanently attached to or embedded in the membrane, often spanning the entire bilayer

Peripheral membrane protein

A protein temporarily attached to the membrane surface or to an integral membrane protein

Glycolipid

A lipid with the carbohydrate attached

glycoprotein

A protein witha carbohydrate attached

Semipermeable

allowing some substances to cross a membrane while preventing others from crossing

passive transport

movement of substances across a membrane without the cell using energy (down a concentration gradient)