Cell Physiology: Plasma Membrane and Organelles
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Questions and Answers

What is the structure of the plasma membrane?

Consists of two layers of phospholipids with embedded proteins and sugars, along with cholesterol.

What is the function of the membranes in cell survival?

They control the passage of substances into and out of the cell, regulating the intracellular environment.

What are the components of the plasma membrane?

Phospholipids, proteins, sugars, and cholesterol.

How are phospholipid molecules arranged in the plasma membrane?

<p>The hydrophilic heads are aligned on the outer surfaces, and the hydrophobic tails form a central water-repelling layer.</p> Signup and view all the answers

What do membrane proteins that extend through the plasma membrane provide?

<p>Channels that allow the passage of electrolytes and non-lipid soluble substances.</p> Signup and view all the answers

What is the role of cholesterol in the plasma membrane?

<p>It is present in the membrane structure.</p> Signup and view all the answers

What is the function of membrane proteins with branched carbohydrate molecules attached to the outside of the cell?

<p>They give the cell its immunological identity - 'self' markers.</p> Signup and view all the answers

What is the role of the plasma membrane in regulating the cell's internal environment?

<p>It controls the entry or exit of many substances, thereby regulating the composition of its internal environment.</p> Signup and view all the answers

How do lipid-soluble materials cross the membrane?

<p>By dissolving in the lipid part of the membrane.</p> Signup and view all the answers

What is the process used by some substances that are unable to diffuse through the semipermeable membrane unaided?

<p>Facilitated diffusion.</p> Signup and view all the answers

What is osmosis?

<p>Passive movement of water down its concentration gradient towards equilibrium across a semipermeable membrane.</p> Signup and view all the answers

What drives the transport of substances across the membrane in active transport?

<p>Chemical energy in the form of adenosine triphosphate (ATP).</p> Signup and view all the answers

What is the principal intracellular cation?

<p>Potassium (K+).</p> Signup and view all the answers

What is the principal extracellular cation?

<p>Sodium (Na+).</p> Signup and view all the answers

What is the process of engulfing particles too large to cross cell membranes?

<p>Phagocytosis.</p> Signup and view all the answers

What is the function of lysosomes in phagocytosis?

<p>Adhering to the vacuole membrane and releasing enzymes to digest the contents.</p> Signup and view all the answers

What is the reverse process of phagocytosis where waste material is extruded through the plasma membrane?

<p>Exocytosis.</p> Signup and view all the answers

What are organelles?

<p>Individual and highly specialised structures enclosed by their own membrane within the cytosol.</p> Signup and view all the answers

What is the largest organelle in the cell?

<p>The nucleus</p> Signup and view all the answers

What is the genetic material present in the nucleus?

<p>Deoxyribonucleic acid (DNA)</p> Signup and view all the answers

What is the fine network of threads called in a non-dividing cell?

<p>Chromatin</p> Signup and view all the answers

What is the roughly spherical structure involved in the synthesis and assembly of the components of ribosomes in the nucleus?

<p>Nucleolus</p> Signup and view all the answers

What is the function of mitochondria in the cell?

<p>Aerobic respiration and production of ATP</p> Signup and view all the answers

What are ribosomes composed of?

<p>RNA and protein</p> Signup and view all the answers

Where are ribosomes found when they make proteins for use within the cell?

<p>In the cytoplasm (free units or in small clusters)</p> Signup and view all the answers

What is the function of smooth endoplasmic reticulum?

<p>Synthesis of lipids and steroid hormones, and detoxification of some drugs</p> Signup and view all the answers

What is the site of synthesis of proteins in the cell?

<p>Rough endoplasmic reticulum</p> Signup and view all the answers

What is the function of the Golgi apparatus?

<p>Packaging proteins into membrane-bound vesicles</p> Signup and view all the answers

What do lysosomes contain?

<p>Enzymes involved in breaking down fragments of organelles and large molecules</p> Signup and view all the answers

What is the function of lysosomes in white blood cells?

<p>Digesting foreign material such as microbes</p> Signup and view all the answers

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