Cell Biology: Membrane Structure

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Questions and Answers

What direction does water move during osmosis?

From hypertonic to isotonic

From hypotonic to hypertonic (correct)

From isotonic to hypertonic

From hypertonic to hypotonic

What happens to a cell placed in a hypotonic solution?

The cell swells and may burst (correct)

The cell remains unchanged in volume

The cell shrinks

The cell becomes shriveled

Which process allows large molecules to move out of a cell?

Endocytosis

Facilitated diffusion

Passive transport

Exocytosis (correct)

What characterizes an isotonic solution?

Equal solute concentration as the cell Signup and view all the answers

What is a key characteristic of active transport?

Requires energy to move substances against their concentration gradient Signup and view all the answers

In which part of the cell does glycolysis occur?

Cytoplasm Signup and view all the answers

During which stage of cellular respiration is the electron transport chain located?

Mitochondria Signup and view all the answers

What type of endocytosis involves the uptake of large particles?

Phagocytosis Signup and view all the answers

What is the primary function of NADH and FADH2 in cellular respiration?

They carry high energy electrons to the electron transport chain. Signup and view all the answers

Where in the cell does the electron transport chain take place?

In the inner mitochondrial membrane Signup and view all the answers

What are the two main parts of photosynthesis?

Light reactions and Calvin cycle Signup and view all the answers

What is the end product of the electron transport chain?

Water Signup and view all the answers

Where is chlorophyll primarily located in plant cells?

In thylakoid membranes Signup and view all the answers

Which protein complex is essential for ATP production during cellular respiration?

ATP synthase Signup and view all the answers

What type of reactions occur in the electron transport chain?

Redox reactions Signup and view all the answers

What is the function of pigment molecules in photosynthesis?

To absorb and reflect certain wavelengths of light Signup and view all the answers

Which of the following substances can be used to generate ATP through cellular respiration?

Carbohydrates, fats, and proteins Signup and view all the answers

What occurs when a pigment molecule absorbs a photon of light energy?

The energy is transferred to an electron, exciting it Signup and view all the answers

What role does the enzyme play in the process of photosynthesis related to chlorophyll a?

It splits water to replace lost electrons in chlorophyll a. Signup and view all the answers

Which photosystem absorbs light best at a wavelength of 700 nm?

Photosystem I Signup and view all the answers

What is the regulatory mechanism that controls metabolic pathways like glycolysis?

Feedback inhibition Signup and view all the answers

What happens to the chlorophyll a molecule that loses its high energy electron to the primary electron acceptor?

It is oxidized and needs to be replaced Signup and view all the answers

What is the primary role of the electron transport chain connecting photosystem II to photosystem I?

It generates a hydrogen ion gradient for ATP synthesis. Signup and view all the answers

What distinguishes autotrophs from heterotrophs?

Autotrophs make organic molecules from carbon dioxide and water. Signup and view all the answers

What is the role of a spectrophotometer in photosynthesis studies?

To measure the amount of light absorbed or transmitted Signup and view all the answers

What occurs to the electron from photosystem II after it passes through the electron transport chain?

It replaces an activated electron in photosystem I. Signup and view all the answers

In the overall photosynthesis equation, where do the carbon atoms from carbon dioxide end up?

As glucose in the products Signup and view all the answers

What is the product of the light reactions of photosynthesis?

ATP and NADPH Signup and view all the answers

In what situation might the high energy electron from photosystem I be passed back to the electron transport chain instead of down to NADP+ reductase?

When there is insufficient ATP being produced. Signup and view all the answers

Which of the following is NOT a phase of the Calvin cycle?

Oxidation Signup and view all the answers

What molecule directly carries high energy electrons to the Calvin cycle?

NADPH Signup and view all the answers

Which component is part of the electron transport chain connecting photosystem II to photosystem I?

Plastoquinone Signup and view all the answers

What is the direct product of the Calvin cycle?

Glyceraldehyde 3 phosphate Signup and view all the answers

What happens to the terminal phosphate group when ATP loses it?

It is transferred to another molecule Signup and view all the answers

Which statement correctly describes oxidation in biochemical reactions?

A molecule loses an electron Signup and view all the answers

What is the difference between catabolic and anabolic reactions?

Catabolic reactions involve the breakdown of molecules while anabolic reactions build molecules Signup and view all the answers

What defines free energy in a system?

Energy available to perform work at uniform temperature Signup and view all the answers

What characterizes exergonic reactions?

They release energy as products have less free energy than reactants Signup and view all the answers

What is energy coupling in metabolic processes?

Linking energy release from exergonic reactions to the energy requirements of endergonic reactions Signup and view all the answers

What is the central role of ATP in cellular energy needs?

It provides short-term energy for cellular processes Signup and view all the answers

Which lipid is crucial for the structure of cell membranes due to its amphipathic nature?

Phospholipid Signup and view all the answers

What is the main reason for membrane fluidity?

Hydrophobic interactions between molecules Signup and view all the answers

What distinguishes integral proteins from peripheral proteins in cell membranes?

Integral proteins are embedded within the membrane. Signup and view all the answers

What role do carbohydrates play in cell membranes?

Cell-cell recognition Signup and view all the answers

How do hydrophilic substances typically cross cell membranes?

Using protein channels and carriers Signup and view all the answers

What is selective permeability in the context of cell membranes?

Hydrophobic molecules can pass, but polar molecules cannot. Signup and view all the answers

Which statement correctly describes the effect of cholesterol on membrane fluidity at body temperature?

Cholesterol decreases fluidity. Signup and view all the answers

What characterizes active transport compared to passive transport?

Active transport moves molecules from low concentration to high concentration. Signup and view all the answers

Study Notes

Membrane Structure

Three key molecules for cell membrane structure are lipids, proteins, and carbohydrates.
Phospholipids are a crucial type of lipid found in membranes.
Phospholipids are amphipathic, meaning they have both hydrophilic (water-loving) and hydrophobic (water-fearing) regions.
The current membrane model is the fluid-mosaic model. Membranes are fluid due to component movement and held together by hydrophobic interactions.
Factors affecting membrane fluidity include phospholipid double bonds and cholesterol content.
Membranes contain two main protein types: integral and peripheral proteins. Integral proteins are embedded within the membrane and often span it. Peripheral proteins are attached to the membrane's interior or exterior but are not embedded.
Membrane carbohydrates are important for cell-cell recognition.
Oligosaccharides, typically short chains, are attached to membrane lipids (glycolipids) and proteins (glycoproteins).

Membrane Transport

Selective permeability of membranes means hydrophobic molecules can pass through, but ions and polar molecules cannot without assistance.
Hydrophilic substances cross membranes using protein channels or carriers.
Active transport moves substances against concentration gradients using ATP. Passive transport moves substances from high to low concentration without energy.
Passive transport is driven by thermal motion.
Hypertonic solutions have higher solute concentrations, hypotonic solutions have lower solute concentrations, and isotonic solutions have equal solute concentrations.
Osmosis is the movement of water across a selectively permeable membrane, from a hypotonic to hypertonic solution.
Cells in fresh water may have contractile vacuoles, while plant cells have cell walls to maintain stable volume, reacting differently to isotonic, hypertonic, and hypotonic solutions.
Facilitated diffusion uses transport proteins to move substances passively, while active transport uses energy to move substances against concentration gradients.
Large molecules like polysaccharides and proteins cross membranes via vesicles (exocytosis and endocytosis).

Cellular Respiration

Cellular respiration occurs in three stages: glycolysis (cytoplasm), Krebs cycle (mitochondria), and electron transport chain (mitochondria).
Glycolysis starts with glucose and produces pyruvate, ATP, and NADH.
The Krebs cycle uses acetyl CoA and produces NADH, FADH₂, and ATP.
The electron transport chain uses high-energy electrons from glycolysis and the Krebs cycle to generate ATP via chemiosmosis.
The final electron acceptor in the electron transport chain is oxygen. Water is a by-product of this process.

Photosynthesis

Photosynthesis is the process by which autotrophs convert carbon dioxide and water into glucose and oxygen using light energy.
Chlorophyll, located in thylakoid membranes within chloroplasts, captures light energy.
Photosynthesis has two main stages: light-dependent reactions (thylakoid membranes) and the Calvin cycle (stroma).
Light reactions convert light energy into chemical energy in the form of ATP and NADPH.
The Calvin cycle uses ATP and NADPH to convert carbon dioxide into glucose.
Photosynthesis involves the use of pigments that absorb specific wavelengths of light while reflecting others.

Energy Harvesting (ATP), Enzymes, Metabolism

ATP (adenosine triphosphate) is the central molecule for cellular energy needs.
ATP is important because its phosphate groups store energy. Losing the terminal phosphate releases energy.
Enzymes are proteins that act as catalysts, reducing the activation energy needed for chemical reactions.
Activation energy is the initial energy required to break chemical bonds in reactants.
Enzymes have active sites that bind substrates and lower activation energy, altering their shape to speed up the reaction.
Factors affecting enzyme activity include temperature, pH, and ionic concentrations.
Anabolic reactions build complex molecules, consuming energy. Catabolic reactions break complex molecules, releasing energy.

Additional Cellular Concepts / Metabolism

Co-factors are non-protein helpers (ions like zinc, copper, iron). Co-enzymes are organic molecules (vitamins or vitamin-derived).
Enzyme inhibitors can be reversible or irreversible and bind to the active site, affecting substrate binding or shape-altering.
Feedback inhibition is a common metabolic control mechanism where the product of a pathway inhibits the enzyme controlling an earlier reaction.
Enzyme cooperativity is when one substrate molecule facilitates the binding of additional substrate molecules to the enzyme.

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Description

Explore the intricate details of cell membrane structure in this quiz. Learn about the key molecules, including lipids, proteins, and carbohydrates, and how they contribute to the fluid-mosaic model. Test your knowledge on membrane fluidity and transport mechanisms.