Bio study guide: Transport (proteins, blood, lymph, metabolic waste/filtrate, xylem, phloem)

What is the function of the double membrane of a nucleus?

It helps with selective permeability and helps ribosomes exit the nucleus (A double membrane is needed for large pores, which proteins need.)

When and why does a ribosome dock on the rough endoplasmic reticulum?

Ribosomes get attached after they code for amino acid chains and attach because the AA chains need to be folded into proteins.

Describe the steps of a ribosome docking on and releasing from the endoplasmic reticulum.

1. The signal sequence attracts a Signal Recognition Particle (SRP), which stops translation.

2. SRP binds to protein complex receptor on outer membrane of ER.

3. Translation starts again & polypeptide chain grows through protein complex into the ER.

4. When stop codon is reached, signal sequence cleaved, SRP removed, ribosome disassembles, & polypeptide chain folds into a protein in the ER.

Describe the role of clathrin in vesicle formation.

The role of Clathrin is to help the plasma membrane invaginate and pinch off the membrane in order to make vesicles.

What are the two models of vesicle transport in the golgi apparatus?

Model A: Vesicles full of partially processed proteins bud off of one cisterna and merge with the next, dumping their contents.

Model B: Vesicles come together to form a new cisterna on the cis face of the golgi apparatus. The cisternae move from the cis side to the trans side.

What do I mean when I say that hemoglobin is a conjugated protein?

Conjugated means that a quaternary structure has non-amino-acid components in its proteins. That means that hemoglobin has non-amino-acid components in its quaternary structure, which are haem groups (which bind to O₂).

What is the purpose of a heme group?

Each group carries one oxygen molecule.

Why is hemoglobin typically either fully saturated or fully unsaturated with oxygen?

Heme groups are more receptive to O₂ after one O₂ molecule binds to a heme group. So the opposite would be true when one heme group unbinds from an O₂ molecule.

What are two things that affect hemoglobin’s affinity for oxygen?

pH level and temperature.

Describe how the Bohr shift affects an oxygen dissociation curve.

A Bohr shift determines the affinity of hemoglobin for CO₂. Ie, a right shift in the oxygen dissociation curve would mean that a) Increased amount of H⁺ b) increased temp & c) reduced affinity. The opposite is true for a left shift.

How does a long loop of Henle aid in a kangaroo rat’s ability to survive the desert?

More H₂O is reabsorbed.

What is lymph and where does it come from?

Lymph is excess fluid that drains into the lymphatic system. It comes from body cells.

Where does lymph go after it’s collected?

It flows back into the heart through the vein that is connected to the capillary wall, which then dumps the lymph into the heart.

 What is the reason for double circulation in mammals? (w/r to blood circulation)

So that the alveoli in the lungs don’t burst and so that the blood can be distributed to the rest of the body.

What is it about cardiac muscle that allows electrical impulses to move quickly between them?

Their branched cells and connections between plasma membranes.

List 5 important distinctions between xylem and phloem

Xylem: Carries mostly water and some minerals, no cell walls, only one direction, dead cells, transport is passive, and closer to center of stalk.

Phloem: Carries mainly nutrients, cells walls, any direction, cells are alive, transport is active, and further away from stalk center.

Describe the transpiration cohesion-tension theory of water transport in plants. Include definitions of transpiration, cohesion and adhesion, and describe how they work together.

H₂O ascent in plants is because the transpirational pull from continuous H₂O columns in the xylem conduit running from roots to leaves. Water evaporates from stomata, creating negative pressure, which forces water up from the roots of a plant. Adhesion negates gravity’s effects while cohesion ensures that the water stays together as it gets pulled up the roots.

How is active transport involved in water uptake at the roots of a plant?

Positive ions are pumped out of the root and positive ions from the soil are pumped in. Because water follows solutes, the water following solutes causes increased pressure in the roots, which aids in water movement into the shoots.

Describe the need for companion cells in phloem.

Companion cells support sieve tubes by carrying out metabolism and regulation.

Talk only about water potential in describing how water moves from soil to root to leaf to air. Use the terms “less negative” and “more negative”.

Soil is less negative than roots, but the air surrounding the plant is more negative than the roots and soil. Thus, water is pulled upwards through the xylem and out of the leaves. The leaves, with stomata that allow for transpiration, creates negative pressure that keeps water flowing towards the leaves and into the air.

Describe sources and sinks in plants with respect to phloem.

Sources: Tissues that photosynthesize, or where compounds are released from a store. AKA, where sugars are produced or stored and released.

Sinks: Tissues that need to be supplied with substrates for cell respiration or anabolic reactions. AKA, tissues that need sugars or compounds.

Describe the movement of phloem from source to sink. Include xylem, pressure, active transport and osmosis

Sugars produced are actively pumped into sieve tubes, H₂O enters phloem from xylem in vascular bundles(via osmosis), high pressure in phloem, phloem exits sieve tubes toward sink due to high pressure. Thus, a low pressure area for phloem to move into is made.