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Biological membrane

• Phospholipid bilayer that contains protein

• allows the uptake of certain substances

• Has various transporter proteins consuming metabolic energy for selective transport

• regulates the fluxes of ions and metabolites

• described as a fluid-mosaic model

components of a fluid-mosaic model

1. phospholipid bilayer

2. integral proteins

3. peripheral proteins

4. anchored proteins

Integral Proteins

embedded in the bilayer and span the entire width of the bilayer to serves as ion channels

Peripheral Proteins

bound to the surface of the membrane surface by noncovalent bonds, and can be dissociated from the membrane with a high salt solution.

peripheral proteins are involved in interactions between the plasma membrane and components of the cytoskeleton such as ,…..

Microtubules and actin microfilaments

Anchored Proteins

bound to the membrane surface via lipid molecules (covalently)

Plastids are derived from

Proplastids

Proplastids

an organelle found in the meristematic region of the plant that is colorless and small ,and is still underdeveloped. ( when developed they turn to specialized plastids)

Chloroplasts

Plastids with chlorophyll and are involved in photosynthesis

Chromoplasts

involved in producing and storing pigments ( carotene, xanthophylls. etc) and are found in fruits, flowers and roots

Leucoplast

lacks pigments and involved mainly for storing food

types of leucoplast

1. Amyloplast (stores starch)

2. Elaioplast (stores fat)

3. proteinoplast (stores protein)

Mitrochondria

plastids that have their own DNA and ribosomes

Semiautonomous organelles

Organelles that contain their own DNA and protein-synthesizing machinery, however they depend on the nucleus for the majority of their protein

Example of semiautonomous organelles

mitochondria and chloroplasts

DNA of semiautonomous organelles

circular chromosomes that are localized in a specific region (nucleoids)

Cell division in plants are limited to ——— post embryonic growth and development

the meristems

meristems are divided into

1. Shoot Apical Meristem (SAM)

2. Root Apical Meristem (RAM)

3. Lateral Meristem

Shoot Apical Meristem (SAM)

Growth lengthwise upward

Root Apical Meristem (RAM)

Growth lengthwise downwards

Lateral Meristem

Growth in diameter

Cytoskeleton

a three-dimensional network of filamentous protein

Cytoskeletons function

1. Spatial organization for the organelles

2. Scaffolding for the movement of organelles

3. Fundamental role in meiosis, cytokinesis, wall deposition

4. Maintenance of cell shape, and cell differentiation

types of cytoskeletal elements

1. Microtubules

2. Microfilaments

3. Intermediate filaments

Microtubules

a hollow cylinder that are composed of polymer of the protein tubulin

Protofilaments

a single microtubule consists of hundreds of thousands of tubulin monomers arranged in 13 columns

Microfilaments

solid, and composed of a special form of the protein found in muscle (G-actin). consisting of two chains of polymerized actin subunits that intertwine in a helical fashion

Intermediate filaments

a diverse group of tough, helically wound fibrous elements that function in the structural support of membranes ,and are composed of linear polypeptide monomers of various types.

Plasmodesmata

tubular extensions of the plasma membrane that traverse the cell wall and connect the cytoplasm of the adjacent cells

the cytoplasm form a continuum referred to as the symplast because ?

most plant cells are interconnected by the plasmodesmata

Symplastic transport

Intercellular transport of solutes through plasmodesmata

Plasmodesmata Function

regulating macromolecular traffic from cell-to-cell

the complex internal structure of plasmodesmata

contains a narrow tubule of ER called desmotubule

Desmotubule

is a continuous with the ER of the adjacent cells

Plant Cell

Microtubules

Microfilaments

Desmotubule

Plasmodesmata

Activation energy of uncatalyzed reaction

Activation energy of catalyzed reaction

gibbs free energy

Secondary Structure

Primary Structure

Tertiary Structure

Quaternary Structure

Active-site cleft

Substrate entering active site of enzyme

Induced Fit theory

Enzyme/Substrate complex

Enzyme/Products complex

Products leaving active site of enzyme

Temperature Graph

pH Graph

Normal Reaction

Competitive Inhibitor

NonCompetitive Inhibitor

Normal enzyme

Competitive inhibitor

Non competitive inhibitor

Allosteric Inhibition

Allosteric Activation

Enzyme

biological catalysts that greatly increase the rates of biochemical reaction most of which are protein.

Enzymes are usually named after

their substrates by adding the suffix “-ase”

Catalyst

a substance that speeds up a chemical reaction without being a reactant

reaction activation energy

the amount of energy that must be put in for the reaction to begin

Amino Acid

20 different side chains with a large variety of groups that have different chemical and physical properties, including hydrophilic, or hydrophobic groups, charged or neutral polar groups, and acidic or basic groups

Proteins

are composed of long chains of amino acids linked by amide bonds, known as peptide bonds

Protein structure

1. primary structure

2. secondary structure

3. tertiary structure

4. quaternary structure

primary structure

refers to the sequence of amino acid residues

secondary structure

refers to regular, local structural units, usually held together by hydrogen bonds

tertiary structure

the final three-dimensional structure of the polypeptide - results from the packing together of the secondary structure units and the exclusion of solvent

quaternary structure

the association of two or more separate three-dimensional polypeptides

The factors that can affect or control enzyme activity

1. Temperature

2. pH

3. Regulatory molecules

4. Cofactors

5. Compartmentalization

6. Feedback inhibition

How temperature effects enzymes

a higher temperature generally makes for higher rates of reaction to a certain degree. once it hits 40C the protein begins to denature

How does pH affect the enzyme

The active site amino acid residues often have acidic or basic, meaning changes in pH can affect these residues and make it hard for the substrate to bind

Regulatory molecule

where other molecules either increase (activator) or decrease (inhibitor) the enzymes activity

Types of reversible inhibitor

1. Competitive

2. Non Competitive

Competitive

binds to an enzyme to block binding of the substrate and will decrease reaction rate when theres not much substrate but can be out competed by lots of substrates.The enzyme can still reach its maximum reaction rate given enough substrate.

Non Competitive

doesnt block the substrate from binding to the active site. enzyme-catalyzed reaction will never reach its normal maximum rate even with lots of substrate.

Allosteric regulation

the regulatory molecule binds to an enzyme someplace other than the active site

Allosteric site

the place where the regulator binds

Cofactor

inorganic ions that are attached temporarily to the enzyme

Coenzymes

Organic molecule example vitamins

Compartmentalization

that enzyme needed for specific processes can be kept in the places where they act, ensuring they can find their substrates readily, don’t damage the cell, and have the right microenvironment to work well

Feedback inhibition

the end product of a metabolic pathway acts on the key enzyme regulation entry to that pathway, keeping more of the end product from being produced

the water content and rate of water movement in soils depend

on a large extent on soil type and soil structure

sand (1mm)

low surface area per gram of soil and have large spaces or channels between particles

Clay (2um)

greater surface area and smaller cannels between particles

When a soil is heavily water by rain or by irriagtion in Sandy soil

the spaces between particles are so large that water tend to drain from them and remain only on the particle surface and at interstices between particles

When a soil is heavily water by rain or by irriagtion in Clay soil

Channels are small enough that water does not freely drain from them and its held more tightly

Field capacity

is the water content of a soil after it has been saturated with water and excess water has been allowed to drain away

clay soil retain

40%

Sandy soil retain

3%

pressure gradient

water moves through soils predominantly by bulk flow driven by

how does a pressure gradient form

as plant absorb water from the soil, they deplete the soil of water near the surface of the roots. this depletion reduces the negative pressure in the water near the root surface and establishes a pressure gradient

the rate of water flow in soil depends on two factors

1. the size of the pressure gradient through the soil

2. The hydraulic conductivity of the soil

soil hydraulic conductivity

measure of the ease with which water moves through the soil, and it varies with the type of soil and water content.

Sandy soil hydrulic conductivity

large hydrulic conductivity

Clay soil hydrulic conductivity

smaller hydrulic conductivity