Cell Structure and Function
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Questions and Answers

What is the main function of the plasma membrane?

  • To provide a rigid structure to the cell
  • To produce energy for the cell
  • To store genetic information
  • To regulate what enters and exits the cell (correct)

What type of macromolecule primarily makes up the plasma membrane?

  • Carbohydrates
  • Lipids (correct)
  • Nucleic Acids
  • Proteins

Which of the following describes the tails of phospholipids?

  • Hydrophilic
  • Ionic
  • Polar
  • Hydrophobic (correct)

What is the function of integral proteins in the cell membrane?

<p>Transport of materials (D)</p> Signup and view all the answers

What is a solution?

<p>A liquid mixture of two or more substances (C)</p> Signup and view all the answers

Which of the following describes a selectively permeable membrane?

<p>Allows only some substances to pass through (D)</p> Signup and view all the answers

In a hypertonic solution, the concentration of solutes is ______ outside the cell than inside the cell.

<p>Higher (C)</p> Signup and view all the answers

Which type of transport does not require energy?

<p>Passive transport (D)</p> Signup and view all the answers

What is the movement of molecules from an area of high concentration to an area of low concentration called?

<p>Diffusion (A)</p> Signup and view all the answers

Which process involves the expulsion of materials from a cell?

<p>Exocytosis (D)</p> Signup and view all the answers

Flashcards

Prokaryotic Cells

Cells that lack a defined nucleus, genetic material dispersed in the cytoplasm.

Eukaryotic Cells

Cells that have a defined nucleus.

Plasma Membrane

Thin flexible barrier around all cells; allows nutrients in and wastes out.

Homeostasis

Regulation of an organism's internal conditions to maintain life.

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Selective Permeability

Allows some substances to pass while keeping others out.

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Lipids

A macromolecule that composes most of the molecules in the plasma membrane.

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Phospholipid Head

Polar phosphate group that is attracted to water

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Phospholipid Tails

Nonpolar fatty acid tails that are repelled by water

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Integral Membrane Proteins

Integral proteins extend from outside to inside of membrane and are used for transport.

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Exocytosis

Expulsion or secretion of materials from a cell.

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Study Notes

Cell Membrane Structure & Function

  • Addresses how substances move into and out of cells

Types of Cells

  • There are two types of cells: Prokaryotic and Eukaryotic

Prokaryotic

  • These cells lack a defined nucleus
  • Dispersed genetic material in the cytoplasm characterizes them

Eukaryotic

  • These cells have a defined nucleus

Plant Cell

  • Have a cellulose cell wall with chloroplasts and vacuoles

Animal Cell

  • These cells have a rigid cell wall, may have flagella

Protist

  • Can have a cell wall, but they lack differentiated tissues

Fungal

  • Have a chitin cell wall and are heterotrophs

The Cell (Plasma) Membrane

  • It is a thin, flexible barrier around all cells
  • Allows nutrients to enter and wastes to exit
  • Maintains homeostasis within the cell

Homeostasis

  • Regulation of conditions to maintain life in balance

Selective Permeability

  • Allows some substances to pass through while preventing others

Structure of the Plasma Membrane

General Info

  • Most of the molecules in the plasma membrane are lipids
  • Lipids are made of glycerol and fatty acids
  • If a phosphate group replaces a fatty acid, a phospholipid is formed
  • The plasma membrane features a phospholipid bilayer due to water existing both inside and outside of a cell

The Phospholipid Bilayer

  • Has a head and two tails
  • The phosphate group makes the head polar, attracting it to water
  • The fatty acid tails are hydrophobic, repelled by water

Other Components of the Plasma Membrane

Proteins
  • Two main types exist in the cell membrane, Integral and Peripheral
Integral proteins
  • Extend from the outside to the inside of the membrane
  • Used for transport, forming channels and pumps to move materials
Peripheral proteins
  • Found on the inside or outside of the cell membrane
  • Used as receptors or anchors for the cytoskeleton
  • Receive chemical signals like hormones from outside the cell
Carbohydrates
  • Important for cellular recognition
  • Help the cell to be recognized as a certain type
Cholesterol molecules
  • Prevent fatty acid tails from sticking together

  • The plasma membrane is often referred to as the cell membrane

Cell Transport Definitions

  • A solution is a liquid mixture of two or more substances
  • A solute is the substance being dissolved in a solution
  • A solvent is the substance doing the dissolving
  • Concentration is the measurement of the amount of solute
  • A permeable membrane allows every substance through
  • An impermeable membrane allows nothing through
  • A selectively permeable membrane allows some substances through, but not others

Types of Solutions

  • Hypertonic solution has a higher concentration of solutes outside the cell than inside, resulting in "above" strength
  • Hypotonic solution has a higher concentration of solutes inside the cell compared to outside, leading to "below" strength
  • Isotonic solution has the same concentration of solutes inside and outside the cell, resulting in the same strength

How Cells are Effected by Different Solutions

  • Water accounts for over 70% of the human body
  • Unregulated water levels can lead to cell damage, swelling, blood cell bursting or brain damage
  • Cells regulate and maintain their water content through specific processes

Types of Transport

Passive Transport

  • Passive transport doesn't require energy to move substances across cell membranes
  • Substances move from an area of high concentration to an area of low concentration, following the concentration gradient

Active Transport

  • Requires energy (ATP) to move molecules across the cell membrane
  • Molecules move from a region of lower concentration to a region of higher concentration, against the concentration gradient

Active Transport Movement

  • Molecules or ions move across a cell membrane from a region of low concentration to a region of higher concentration, requiring cellular energy

Passive Transport Types

Hypertonic/Hypotonic Solutions

  • Passive transport include Hypertonic & Hypotonic solutions

Facilitated Diffusion

  • Diffusion of a solute from high to low concentration through an integral protein (channel or carrier)

Diffusion

  • Solute particles move from an area of high concentration to one of low concentration
  • Examples include: baking in an oven, nail varnish, food dye and the smell of a fart

Dynamic Equilibrium

  • Amount coming in equals the amount coming out, resulting in no net movement

Osmosis

  • Movement of water from hypotonic solution to a hypertonic solution

  • Solutes cannot pass through the membrane due to their size, however water can

  • Small amounts of water pass straight through the membrane, large amounts through aquaporins to areas with higher solute concentration

  • Glucose/ions are too large to go between phospholipids needing integral/transport proteins

  • Very small, unchanged/nonpolar molecules like O2 and CO2 can pass

  • H2O can pass in small amounts, but large amounts need proteins known as aquaporins

Movement of Large Materials through Vesicle Formation

Exocytosis

  • The expulsion or secretion of materials from a cell

Endocytosis

  • A cell surrounds and takes in material from its environment

How Cells Obtain Materials from Environment

  • Cells get materials they need through the cell membrane (passive/active transport)

  • Once inside, the cell transports those materials to all the different regions

  • Each organelle has a specific structure and function for the cell to maintain homeostasis

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Description

Exploration of cell structure and function, covering both prokaryotic and eukaryotic cells. Includes plant, animal, protist, and fungal cells. Addresses cell membrane structure, function, homeostasis and selective permeability.

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