Bio Unit 2 test

What are Phospholipids made of [5]

Polar head [1] composed of a glycerol and phosphate molecule

Two non-polar tails [1] composed of fatty acids (hydrocarbon chains) [1]

are amphipathic [1] (hydrophobic and phillic)

Lipid bilayer structure [3]

annotate image [5]
B2.1.1—Lipid bilayers as the basis of cell membranes

Hydrophobic tails point inwards

• Hydrophobic interactions between tails hold bilayer together [1]

• Naturally forms a continuous sheet in water [1]

• Hydrophilic heads attracted to water in cytoplasm or extracellular fluid [1]

Photo annotation [5]

Lipid bilayer as barriers [4]
1 example for each permeability level [4]

B2.1.2—Lipid bilayers as barriers

Hydrophobic hydrocarbon chains have low permeability to:

• Large molecules [1]

• Hydrophilic particles [1]

  • Ions [0.5]

  • Polar molecules [0.5]

⇒ Membrane functions as an effective barrier between aqueous (extra-intracellular fluid) solutions[1]

Students should understand that the hydrophobic hydrocarbon chains that form the core of a membrane have low permeability to

large molecules and hydrophilic particles, including ions and polar molecules, so membranes function as effective barriers between

aqueous solutions.

What is simple diffusion in the case of lipid bilayers [3]

B2.1.3—Simple diffusion across membranes

Passive transport. Movement of small uncharged molecules [1]

moves from High concentration to low until equalibrium [1]
They ‘squeeze between’ the polar phospholipid heads then move through the membrane to the other side [1]

Use movement of oxygen and carbon dioxide molecules between phospholipids as an example of simple diffusion across membranes.

What is faciliitated diffusion in the case of lipid bilayers [1]

Role of channel proteins [2]

B2.1.6—Channel proteins for facilitated diffusion

Passive transport using a membrane protein [0.5]

• Movement of large polar molecules (ex sodium ions) from high to low concentration [0.5]

---

open → allows specific ions to diffuse through (ex sodium channel)

close → stops diffusion

[1]

⇒ allow for selective permeability of membranes [1] (control how many go in and out)

Students should understand how the structure of channel proteins makes membranes selectively permeable by allowing specific

ions to diffuse through when channels are open but not when they are closed

EXTRA > Good to know
what is a carrier protein?

Carrier proteins bind to solutes then change conformation to transport them to the other side [1]

What are Integral and Peripheral proteins [3]

B2.1.4—Integral and peripheral proteins in membranes

Integral proteins are embedded into one or both lipid layers [1] → Are amphipathic and can thus extend into the bilayer [1]

Peripheral proteins are attached to only one surface (inner or outer) of the bilayer [1]

Emphasize that membrane proteins have diverse structures, locations and functions. Integral proteins are embedded in one or both

of the lipid layers of a membrane. Peripheral proteins are attached to one or other surface of the bilayer

Functions of membrane proteins [2]

What is osmosis? [2]

what are aquaphorins and it’s role? [3]

B2.1.5—Movement of water molecules across membranes by osmosis and the role of aquaporins

Include an explanation in terms of random movement of particles, impermeability of membranes to solutes and differences in solute concentration [3 main points to hit]

Movement of water molecules across a semipermeable membrane from low solute concentration to high [2] (water concentration)

---

An integral protein that rapidly transports water molecules [1]

Bc Water is polar and cannot pass through the bilayer Aquaporin is lined hydrophilic side chains [1]

allows water to move in and out of cell via osmosis [1]

(Water can move bidirectionally depending on the concentration gradient)

---

Membrane impermeable to solutes

Water moves until both sides have equal solute concentration

Random movement of water molecules but no net movement of wate [3]

What are pump proteins? [2]

Compare and contrast between Facilitated diffusion and active transport and simple diffusion [2]

B2.1.7—Pump proteins for active transport

Pump proteins use energy [1] (from ATP) to move specific particles against their concentration gradient [1]

---

Facilitated diffusion and active tran

sport allow membrane selective permeability [1]

Simple diffusion is not selective (depends only on particle size and hydrophilic/hydrophobic properties) [1]

---

Students should appreciate that pumps use energy from adenosine triphosphate (ATP) to transfer specific particles across

membranes and therefore that they can move particles against a concentration gradient

Draw & label the Fluid Mosaic Model [9]

B2.1.10—Fluid mosaic model of membrane structure

Students should be able to draw a two-dimensional representation of the model and include peripheral and integral proteins,

glycoproteins, phospholipids and cholesterol. They should also be able to indicate hydrophobic and hydrophilic regions

what are attatched to Glycoproteins and Glycolipids and what are their roles [3]

Glycoproteins: short carbohydrate chain (oligosaccharide) attached to proteins [1]

Glycolipids: carbohydrate group attached to lipids [1]
Responsible for cell adhesion and cell recognition [1]

Where do H bonds form during solvation and which sides are more positive and negative [3]

Describe process of solvation [2]

2.3.1—Solvation with water as the solvent

Hydrogen bonds form between polar solute and polar water molecules [1]

● Slightly positively charged H atom of water attracted to negative ions [1]

● Slightly negatively charged O atom of water attracted to positive ion [1]

---

Water molecule surround charged ions using “hydration shells” [1]

Solute particles separated and surrounded by water [1] → solvation

---

Include hydrogen bond formation between solute and water molecules, and attractions between both positively and negatively charged ions and

polar water molecules.

What is Tonicity [2]

What are hypotonic, hypertonic and isotonic solutions [6]

D2.3.2—Water movement from less concentrated to more concentrated solutions

D2.3.3—Water movement by osmosis into or out of cells

the ability of an extracellular solution to make water move in or out of cell [2]

---

HYPERTONIC: High solute concentration outside cell than inside cell → water moves out [1]

• (cell will shrink/shrivel) [1]

HYPOTONIC: Low solute concentration outside cell than inside cell → water moves in [1]

• (cell will swell) [1]

ISOTONIC: Equal solute concentration outside cell than inside cell → water moves in and out in equilibrum [1]

• (cell will remain the same) [1]

---

Students should express the direction of movement in terms of solute concentration, not water concentration. Students should use the terms “hypertonic”, “hypotonic” and “isotonic” to compare concentration of solutions

---

Students should be able to predict the direction of net movement of water if the environment of a cell is hypotonic or hypertonic. They should

understand that in an isotonic environment there is dynamic equilibrium rather than no movement of water.

How can animal cells be affected by different tonicity environments and why? [6]

What to organisims in hypotonic enviroments do to live? [2]

D2.3.5—Effects of water movement on cells that lack a cell wal

Hypotonic: Can burst (Lysis)

Hypertonic: can shrink and crenate

Isotonic: No change

[3]

---

Animal cells lack a cell wall [1]

• Isotonic tissue fluid in multicellular organisms [1] needs to be maintained to prevent harm to cells and maintain proper function [1]

---

have contractile vacuoles to constantly expel water to prevent bursting

(contain store expel water when the vacuole contracts) [2]

---

Include swelling and bursting in a hypotonic medium, and shrinkage and crenation in a hypertonic medium. Also include the need for removal of

water by contractile vacuoles in freshwater unicellular organisms and the need to maintain isotonic tissue fluid in multicellular organisms to prevent

harmful changes

What happens to plant cells in hypertonic and hypotonic environments? [5]

D2.3.6—Effects of water movement on cells with a cell wall

Hypertonic: Causes increase in internal pressure called turgor pressure against the rigid cell walls [2]

• Cell walls prevent bursting and allow plant cells to maintain a “turgid” shape

Hypotonic

Plasmolysis: cell membranes shrink away from cell walls [2]

Lose turgor pressure and cell shrinks [1]

---

Include the development of turgor pressure in a hypotonic medium and plasmolysis in a hypertonic medium

Medical applications of isotonic solutions [7]

D2.3.7—Medical applications of isotonic solution

Organ transplantation

• Organ needs to be bathed in a fluid that is isotonic to the cytoplasm of organ’s cells [1]

• Prevent loss or gain of water → reduce risk of damage for a successful transplant [1]

Intravenous (IV) fluids

• Replace lost fluids, administer drugs, blood transfusion [3]

• More rapid and direct absorption into circulatory system if fluid is isotonic to blood/tissue fluid [2]

---

Include intravenous fluids given as part of medical treatment and bathing of organs ready for transplantation as examples

Why do cells need energy? [7]

C1.2.2—Life processes within cells that ATP supplies with energy

Metabolism [1]: synthesis of macromolecules (nucleic acids, proteins,) [1]

Active transport [1]: moving substances in and out of cells [1]

Whole cell movement [1]: muscle contraction [1]

Cell component movement [1]: chromosomes during cell division [1]

Energy is needed to sustain fundamental functions, maintain homeostasis, and sustain life processes.[1]

---

Include active transport across membranes, synthesis of macromolecules (anabolism), movement of the whole cell or cell components such as

chromosomes

How do cells get energy? [3]

from carbon compounds [1]

• carbohydrates and lipids mainly

  • glucose and fatty acids [2]

What form of energy do cells use and it’s properties? [4]

draw simple diagram of ATP [3]

C1.2.1—ATP as the molecule that distributes energy within cells

Chemical energy [1] in the form of the nucleotide adenosine triphosphate (ATP) [1]

adenine + ribose + 3 phosphates [1]

Properties: unstable, readily releases energy [1]

---

Include the full name of ATP (adenosine triphosphate) and that it is a nucleotide. Students should appreciate the properties of ATP that make it suitable for use as the energy currency within cell

How is ATP formed and the definition of cellular respiration? [6]

C1.2.3—Energy transfers during interconversions between ATP and ADP

C1.2.4—Cell respiration as a system for producing ATP within the cell using energy released from carbon compound

Cellular Respiration is a system in cells for producing ATP,[1] controlled by enzymes [1]

hydrolysis of ATP releases energy for cell activities [1] and releases ADP [1] ATP → ADP + Pi (Pi = phosphate when not bonded to an organic compound.) Energy is released for these processes when ATP is broken down

Glucose & fatty acids are broken down to release energy, energy from food (glucose, fatty acids/carbon compounds) [1] used in the phosphorylation (adding a phosphate group) of ADP to ATP [1]

---

Students should know that energy is released by hydrolysis of ATP (adenosine triphosphate) to ADP (adenosine diphosphate) and phosphate,

but energy is required to synthesize ATP from ADP and phosphate. Students are not required to know the quantity of energy in kilojoules, but

students should appreciate that it is sufficient for many tasks in the cell

---

Students should appreciate that glucose and fatty acids are the principal substrates for cell respiration but that a wide range of

carbon/organic compounds can be used. Students should be able to distinguish between the processes of cell respiration and ga s exchange

How do cells turn organic compounds into energy [7]

C1.2.5—Differences between anaerobic and aerobic cell respiration in humans

Aerobic respiration [1]

• glucose + oxygen → carbon dioxide + water [1]

• ADP + P → ATP (high yield) [1]

• mitochondria [1]

Anaerobic respiration [1]

• glucose → lactate [1]

• ADP + P → ATP (low yield) [ ]

• cytoplasm [1]

---

Include which respiratory substrates can be used, whether oxygen is required, relative yields of ATP, types of waste product and where the

reactions occur in a cell. Students should be able to write simple word equations for both types of respiration, with glucose as the substrate.

Students should appreciate that mitochondria are required for aerobic, but not anaerobic, respiration

Compare and contrast aerobic and anaerobic respiration. [12]

Rate Calculation [1]

List and outline all processes in life [8]

Metabolism: chemical reactions which occur in a cell [1]

Response to stimuli: reacting to changes in the external environment [1]

Homeostasis: the maintenance of constant internal conditions [1]

Movement: some control over their place and position [1]

Growth: cells can increase in size and/oran increase in the number of cells that make up an organism (in multicellular organisms) [1]

Reproduction: the production of offspring. Can be sexual or asexual [1]

Excretion: the removal of metabolic waste products [1]

Nutrition: the intake or production of nutrients [1]

List and outline cell theory [3]

A2.2.1—Cells as the basic structural unit of all living organisms

cell theory states that:

1. All living things are made of individual units called cells [1]

2. Cells are the basic units of life [1]

3. All cells arise from other pre-existing cells (division) [1]

---

Students should be aware that deductive reason can be used to generate predictions from theories. Based on

cell theory, a newly discovered organism can be predicted to consist of one or more cells

What is magnification and it’s formula [23]

How much larger the object appears compared to its real size [1]

eyepiece lens power x objective lens power = magnification [2]

What is resolution and three example values [4]

Measure of the clarity of the image [1]

● Human eye: 100 μm [1]

● Light microscope: 200 nm [1]

● Electron microscope: 0.01nm [1]

(increasing)

Light microscopes vs electron and benefits on electron

Electron microscopes has higher resolution and magnification

four developments in Microscopy and theri advantages

Freeze fracture microscopy

• Samples are frozen and then broken apart [1] using special tools.

• The pieces are observed using an electron microscope to see the internal structure [1]

Cryogenic electron microscopy

• Samples are frozen to cryogenic temperatures (-180°C or colder) [1]. This makes the molecules more stable [1].

• Improves resolution and reduces damage from the electron beam. [1]

• Often used in imaging of molecules [1]

Fluorescent stains

• Used in light microscopy [1]

• Added dye will attach to specific structures [1]

• Labelled areas appear at bright spots [1]

• e.g. shows molecules too too small to be seen

(neurotransmitters or proteins).

Immunofluorescence

• Used in light microscopy

• Allows very specific visualization

• e.g. fluorescent tags may be attached to antibodies which attach to specific molecules (proteins, carb’s, etc)