THE CELL

THE CELL

Structure and

Function

THE CELL: Structure and Function

Objectives– Alabama Course of Study– Alabama High School

Graduation Exam– Teacher/Text objectives

Cellular basics The cell membrane

– Structure and function– transport

Organelle structure and function

Animal cells vs. Plant cells Quiz

Objectives

Alabama Course of StudyAlabama Course of Study– 17. Identify the basis of the cell theory17. Identify the basis of the cell theory– 18. Analyze relationships among cell structure, 18. Analyze relationships among cell structure,

function, and organization in prokaryotes and function, and organization in prokaryotes and eukaryotes.eukaryotes.

– 20. Relate cellular functions to specialized 20. Relate cellular functions to specialized structures within cells.structures within cells.

Active and passive transport or materials (osmosis, Active and passive transport or materials (osmosis, diffusion)diffusion)

Waste disposalWaste disposal

Objectives continued…

Alabama High School Graduation ExamAlabama High School Graduation Exam– Standard V: The student will understand concepts of cellsStandard V: The student will understand concepts of cells

Objective 1: Distinguish relationships among cell structures, Objective 1: Distinguish relationships among cell structures, functions, and organization in living organisms.functions, and organization in living organisms.

Eligible content:Eligible content:– Define and identify representations of diffusion and Define and identify representations of diffusion and

osmotic systems.osmotic systems.– Recognize differences between active and passive Recognize differences between active and passive

transport of substances and the energy requirements transport of substances and the energy requirements associated with each.associated with each.

Objectives continued…

AHSGE Eligible content continued:AHSGE Eligible content continued:– Identify and define similarities and differences between Identify and define similarities and differences between

plant and animal cells.plant and animal cells.– Classify organisms and prokaryotic or eukaryotic. Classify organisms and prokaryotic or eukaryotic. – Describe cell locomotion by means of cilia and flagella.Describe cell locomotion by means of cilia and flagella.– Identify cell organelles and define functions of cell Identify cell organelles and define functions of cell

organelles.organelles.– Distinguish and identify examples of cellular organization Distinguish and identify examples of cellular organization

at the cell, tissue, organ, system, and organism level.at the cell, tissue, organ, system, and organism level.

Teacher / Text Objectives

Differentiate between active and passive transport. Describe the structure and functions of the cell

membrane. Relate each organelle to a task essential to the life

of the cell. Explain the structural differences between plant

and animal cells.

Cellular basics review

Cell – basic unit of living organisms Prokaryote – cell without membrane-bound structures.

Example: bacteria Eukaryote – cell with membrane-bound structures. Examples: multicellular organisms such as plants and animals;

and some unicelllular organisms. Cilia – short, numerous, hair-like structures that aid in

locomotion or feeding. Flagella – long, whip-like structure used for locomotion. Organelle – membrane-bound structures within a cell that carry

out a specific function.

The Plasma Membrane - structure

The plasma membrane is a selectively permeable phospholipid bilayer surrounding the cell.

Contents of the plasma membrane:– Phospholipids have a polar (water-loving) head region and a

nonpolar (water fearing) tail. The fluid mosaic model of phospholipids allow fexibility

– Proteins are scattered throughout the membrane and allow for transport of materials, identification, and transfer of information.

– Cholesterol provides stability and prevents the fatty acids of phospholipids from sticking together.

Cell membrane – function

Through transportation, the cell membrane regulates the raw materials (glucose, amino acids, and lipids) that enter the cell and waste products that leave the cell.

This process of maintaining a cell’s internal environment is called homeostasis.

The cell membrane also protects the cell from its external environment.

Organelles

Cytoplasm Cytoskeleton

– Microtubules– Microfilaments

Mitochondria Ribosomes Endoplasmic Reticulum

– Smooth – Rough

Golgi Apparatus Lysosome Nucleus

– Nucleolus– Chromatin

Special plant structures Large Central Vacuole Cell wall Chloroplasts

Cytoplasm and Cytoskeleton

Cytoplasm is a clear gelatinous fluid inside the cell that surrounds the organelles.

The cytoskeleton is a framework of microtubules and microfilaments that help shape and support cells, and to assist organelles in moving from place to place.

Mitochondria

The mitochondria is the site of energy production through respiration.

It consists of two membranes; The inner membrane is folded into structures called cristae.

Nicknamed “the powerhouse”

Endoplasmic Reticulum

The endoplasmic reticulum (ER) resembles a folded membrane that forms a network of interconnected compartments in the cytoplasm

Smooth ER does not contain ribosomes

Rough ER is covered with ribosomes

Function: transportation of materials between the nucleus and the cytoplasm.

Ribosomes

Ribosomes are the site for protein synthesis in the cell.

– Produced in the nucleolus– Found floating free in the

cytoplasm– Also exist on the rough

endoplasmic reticulum

Golgi Apparatus

The Golgi apparatus resembles closely stacked flattened membranous sacs

Function: processing, packaging, and secreting proteins, lipids, etc.

Vesicles are membranous pouches that may bud from the ER or golgi apparatus filled with protein.

Nucleus

The nucleus is the control center of the cell that manages cellular functions.

Nucleolus – structure inside the nucleus that produces ribosomes.

Chromatin – thin strands of DNA

Nuclear pore – holes in the nuclear envelope through which ribosomes leave the nucleus.

Lysosome

Lysosomes are small, spherical organelles surrounded by a single membrane and contain digestive enzymes.

Function: to digest excess or worn out cell parts, food particles, and invading viruses or bacteria

Vacuole

Vacuoles are found only in plant cells.

Stores food, water, enzymes, and waste products.

Vacuoles fill with water through osmosis and can fill up to 90% of the cell. The pressure that results inside the cell as a result of this is called turgor pressure.

Chloroplast

Chloroplasts are the sites for photosynthesis – where light is converted into chemical energy.

Chloroplasts are a type of plastid (organelle that contains pigments)

They contain chlorophyll - a green plant pigment that traps energy from sunlight and gives plants their green color.

Cell wall

The cell wall is found outside the cell membrane.

made of cellulose. They are found in plants,

bacteria and fungi that give cells their shape.

Centrioles

Centrioles are small, rod-shaped structures that appear during mitosis.

Only found in animal cells.

CENTRIOLES

Plant vs. Animal Cells

Only animal cells contain centrioles and lysosomes. Only plant cells contain a cell wall, chloroplasts, and

large central vacuole.

Two Major Types of Transport

– Passive transport – materials enter and exit the cell through diffusion without the use of energy.

Diffusion – mixing of two substances through random motion of molecules.

Osmosis – diffusion of water molecules through the plasma membrane (Types of solutions)

Facilitated Diffusion – transports with the aid of a protein molecules

– Active transport – Cells use energy to bring raw materials into the cell and export waste products.

sodium-potassium pump, proton pump

Examples of Cellular Transport

Water moves into a cell placed in ?? Solution Ans: hypotonic Water moves out of a cell if the cell is placed in

a ?? Solution Ans: hypertonic solution Cells placed in a strong sugar solution, water

will ?? Ans: Pass from the cells to the sugar solution

Review : Cellular Transport

Passive: region of higher concentration to lower concentration

Passive: facilitated diffusion, diffusion, osmosis Active: region of lower concentration to higher

concentration. Active: endocytosis, exocytosis Plants wilt due to a loss of turgor pressure Water enters or leaves due to Osmosis

Review: Cellular Transport

Plasma Membrane: structure most responsible for maintaining cell homeostasis.

Exocytosis: release of wastes or cell products from inside to outside a cell

Osmosis: diffusion of water molecules through a selectively permeable membrane

Plasmolysis: loss of water from a cell resulting in a drop in turgor pressure.

Review: Cellular Transport

Contractile Vacuole: Structure inside protists that collects excess water and squeezes it outside through the membrane.

Dynamic equilibrium: continuous movement of particles but no overall change in concentration

Diffusion: Movement of particles from an area of higher concentration to one of lower concentration.

Active transport: This is a process by which the cell maintains differences on concentration of certain ions inside and outside the cell. In order to move ions into or out of a cell, against a gradient, cells use the process of active transport. This will provide the chemical energy needed to go against the gradient .

Cell Size and Reproduction

DNA limits cell size Surface area to volume ration limits size As a cell grows, its volume increases more than its surface area.

Therefore the cell will divide before it becomes too large to function properly.

Ex. If the sides of a cell double in length, its Volume increases by 8 times and the surface area becomes 4 times as large..

Homeostasis is disrupted by a cell that is too large and therefore limits cell size

Chromosomes: Dark – staining structures that carry the genetic material.

Chromatin: Long strands of DNA wrapped around proteins. pre – chromosome.

Gene: is a segment of DNA that controls for the production of proteins.

The Cell Cycle

Cell Cycle: Sequence of growth and division of a cell.

A series of Enzymes monitors a cell’s progress from phase to phase

Two Stages:– Interphase (growth stage) (G1, S, G2)– Mitosis (nuclear division)

Interphase

Interphase: – Longest phase of the cell cycle– Busiest phase fo the cell cycle– Cell grows in size– Chromosomes are duplicated– Cell carries out metabolism– Cell produces organelles that are needed

Mitosis

Nuclear Division / occurs in 4 stages The process by which nuclear material is

divides equally between two new cells. Process by which two identical daughter cells

are formed Prophase Metaphase Anaphase Telophase

Prophase (1st stage)

Longest phase of mitosis Chromatin becomes visible chromosomes due

to the tighter coiling of the chromosomes Nuclear Envelope breaks down releasing the

chromatids Nucleolus disappears There are two distinct parts an early and a late

stage of prophase marked by the disappearance of the nuclear membrane..

Prophase cont.

Centromeres – structures that hold together sister chromatids.

Centromere – this is also the point of attachment for the chromatids to the spindle fiber

Centrioles and spindles form. Spindles – The football-shaped structure

consisting of thin fibers seen in a dividing cell. Centrioles – cylindrical rod structures that

function in anaphase

Metaphase (2nd stage)

Meta ( middle) Chromatids align along the middle or the

equator of the cell Chromosomes attach to spindle fibers This is where crossing over occurs

Anaphase ( 3rd stage)

Ana (separate) The phase in which the sister chromatids

separate from each other. The Centromeres split apart and the

chromosomes move to opposite poles pulled by the centrioles

Telophase (4th and Final stage)

Begins as the chromosomes reach opposite poles

New cells prepare for independent existence Chromosomes unwind Spindle breaks down Nucleolus reappears A new double membrane begins to form

between to the two new nuclei

Cytokinesis

Division of the cell’s cytoplasm Part of the cell cycle occurs during Telophase Differs in animals and plants Animals: Plasma membrane pinches inward

along the equator and the two new cells are separated

Plants: A Cell Plate forms (cell wall) across the equator and both plasma membranes and cell walls are formed between the two new cells.

Cell Organization

Unicellular organisms – when mitosis is complete they remain as one cells

Multicellular organisms – made of many cells that result in organization (5 levels of cell organization)

Cell – basic unit Tissue – similar cells with the same function Organ – dissimilar tissues with the same function Organ system – different organs with the same function Organism - Different systems with the same function

Control of the Cell Cycle

Normal Control is by a series of enzymes controlling the cell cycle

Loss of Control:– Cancer: uncontrolled division of cells– Caused by environmental factors or by changes

in enzyme production.– Causes are difficult to pinpoint; When people

move from one country to another, their cancer rates follow the pattern of the county where they live not their county of origin.

– 2nd leading cause of death in US

How well do you know your cells?

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quiz

membraneworksheet

organelleworksheet

a virtual cell

Anothervirtual cell