Cell Structure - Basic Biology - Lecture Slides, Slides for Biology. Baddi University of Emerging Sciences and Technologies


Description: Its the important key points of Basic Biology are: Cell Structure, Fundamental Units of Life, Plasma Membrane, Cytoplasm, Region of DNA, Eukaryotic Cells, Lipid Bilayer, Cell’s Outermost Membrane, Foundation of Cell Membranes, Semifluid Substance
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Cell Structure

Chapter 3


3.2 What, Exactly, Is a Cell?

Cells are the fundamental units of all life

• All cells start life with a plasma membrane, cytoplasm, and a region of DNA which, in eukaryotic cells only, is enclosed by a nucleus


Cell Structure

• A plasma membrane surrounds the cell and

controls which substances move in and out

Plasma membrane – A cell’s outermost membrane

Lipid bilayer

– Structural foundation of cell membranes; mainly phospholipids arranged tail-to-tail in a bilayer



• An important part of homeostasis is maintaining the composition of cytoplasm, which differs from fluid outside the cell

Cytoplasm – Semifluid substance enclosed by a cell’s plasma




• Cell metabolism occurs in cytoplasm and internal compartments, including organelles

Organelle – Structure that carries out a specialized metabolic

function inside a cell


Prokaryotes and Eukaryotes

• Cells are classed as eukaryotes or prokaryotes based on how DNA is housed in the cell


– Organelle with two membranes that holds a eukaryotic cell’s DNA


– Region of cytoplasm where DNA is concentrated in a prokaryotic cell


The Cell Theory

• Cell theory is the fundamental theory of biology

Cell theory

– All organisms consist of one or more cells – The cell is the smallest unit of life – Each new cell arises from another cell – A cell passes hereditary information to its offspring


3.3 Measuring Cells

• Most cells are visible only with the help of microscopes

• Different types of microscopes use light or electrons to reveal different details of cells


Bacteria on the Tip of a Pin

• Bacteria are the smallest and simplest cells


“Animalcules and Beasties”

• No one knew cells existed until microscopes were invented

• 1600s: van Leeuwenhoek’s microscope


Hooke, Schleiden, and Schwann • 1600s: Robert Hooke improved the

microscope and coined the term “cell”

• 1839: Matthias Schleiden and Theodore Schwann realized cells were alive and proposed the cell theory


3.4 The Structure of Cell Membranes

• The plasma membrane is basically a lipid bilayer balloon filled with fluid

• The nonpolar tails of both layers are sandwiched between the polar heads


The Fluid Mosaic Model

• A cell membrane is a mosaic of proteins and

lipids (mainly phospholipids) that functions as a selectively permeable barrier that separates an internal environment from an external one

Fluid mosaic model – A cell membrane can be considered a two-

dimensional fluid of mixed composition


Membrane Proteins

• Proteins associated with a membrane carry out

most membrane functions – Transport proteins passively or actively assist specific

ions or molecules across a membrane Enzymes speed chemical processes – Adhesion proteins help cells stick together – Recognition proteins tag cells as “self” – Receptor proteins bind to a particular substance

outside the cell


3.5 Introducing Prokaryotic Cells

• Domains Bacteria and Archaea make up the prokaryotes

• Prokaryotes are single-celled organisms with no nucleus, but many have a cell wall and one or more flagella or pili


3.6 A Peek Inside a Eukaryotic Cell

• All eukaryotic cells start life with a nucleus, ribosomes, organelles of the endomembrane system (including endoplasmic reticulum, vesicles, Golgi bodies), mitochondria, and other organelles


The Nucleus

• Pores, receptors, and transport proteins in the

nuclear envelope control the movement of molecules into and out of the nucleus

Nuclear envelope – A double membrane that constitutes the outer

boundary of the nucleus


The Endomembrane System

• The endomembrane system includes rough and

smooth endoplasmic reticulum, vesicles, and Golgi bodies

Endomembrane system – Series of interacting organelles between the nucleus

and plasma membrane – Makes and modifies lipids and proteins – Recycles molecules and particles such as worn-out cell

parts, and inactivates toxins


The Endomembrane System

Endoplasmic reticulum (ER) – A continuous system of sacs and tubes that is an

extension of the nuclear envelope – Rough ER is studded with ribosomes (for protein

production) – Smooth ER has no ribosomes


The Endomembrane System

Vesicle – Small, membrane-enclosed, saclike organelle – Stores, transports, or degrades its contents


– Enzyme-filled vesicle that breaks down amino acids, fatty acids, and toxic substances


– Vesicle with enzymes for intracellular digestion


The Endomembrane System

Golgi body

– Organelle that modifies polypeptides and lipids – Sorts and packages the finished products into

transport vesicles

Vacuole – A fluid-filled organelle that isolates or disposes of

wastes, debris, or toxic materials Docsity.com

Mitochondria and Chloroplasts

• Mitochondria and chloroplasts have their own

DNA – they resemble bacteria and may have evolved by endosymbiosis

Mitochondrion – Double-membraned organelle that produces ATP


– Organelle of photosynthesis


The Cytoskeleton

Cytoskeleton – Dynamic network of protein filaments that

support, organize, and move eukaryotic cells and their internal structures

• The cytoskeleton interacts with accessory proteins, such as motor proteins


Cilia and False Feet

Cilia – Short, hairlike structures that project from the

plasma membrane of some eukaryotic cells – Coordinated beating stirs fluid, propels motile cells – Moved by organized arrays of microtubules – Example: clears particles from airways



• Eukaryotic flagella are whiplike structures that

propel cells such as sperm through fluid – Different internal structure and motion than

prokaryotic flagella


False Feet

Pseudopod (false foot) – Extendable lobe of membrane-enclosed

cytoplasm for movement or to engulf prey – Moved by motor proteins attached to

microfilaments that drag the plasma membrane – Example: amoebas


3.7 Cell Surface Specializations

Cell junctions

– Connect a cell structurally and functionally to another cell or to extracellular matrix (ECM)

Extracellular matrix (ECM)

– Complex mixture of substances secreted by cells – Supports cells and tissues – Functions in cell signaling


Types of Animal Cell Junctions

Tight junction – An array of fibrous proteins that joins epithelial cells

and prevents fluids from leaking between them

Adhering junction – Anchors cells to each other or to extracellular matrix

Gap junction

– Forms a channel across plasma membranes of adjoining animal cells


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