cell structure & function - جامعة...

Asst. lecturer Ahmed Ghdhban Alziaydi

MSc. Biochemistry 11/15/2015 1

College of Biotechnology Medical Biotechnology department and Agricultural Biotechnology department

Second Stage

No. (1)

Cell Structure & Function

© Boardworks Ltd 2007 2 of 39

What is a cell?

Multicellular organisms consists of many cells – humans are made from an estimated 50 trillion cells!

Unicellular organisms, such as bacteria, consist of just a single cell.

A cell is the basic unit of life, from which larger structures such as tissue and organs are made.

A cell is the smallest unit that is capable of performing life functions.


Specialized cells

Most plants and animals are multicellular. The human body is made up of around 200 different types of cell, all working together.

Most cells are specialized, meaning that each type of cell has a specific structure and function.

All cells with a nucleus contain the same genes, but different cells activate different genes so they only produce the proteins they need.

However, all cells have certain common features and structures called organelles.


What do cells contain?


How do plant cells specialize?

Unlike animals, many plant cells retain the ability to differentiate and specialize throughout their life. These cells are found in tissues called meristems.

sieve cell

leaf cell root cell

meristem cell


How do animal cells specialize?

red blood cell

In animals, the first type of cells in the developing embryo are stem cells. These are unspecialized cells that go on to form all the different cell types in the adult.

muscle cell

stem cell sperm cell

nerve cell

Examples of Cells

Amoeba Proteus

Plant Stem

Red Blood Cell

Nerve Cell

Bacteria

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How do cells get their energy?

All organisms need energy to survive.

Animals obtain their energy from the food they eat, but plants can make their own food by photosynthesis.

In both cases, however, energy must first be converted into a form that can easily be used by cells. This process is called respiration.

Prokaryotic

• Do not have structures surrounded by membranes

• Few internal structures

• One-celled organisms, Bacteria

http://library.thinkquest.org/C004535/prokaryotic_cells.html 10/25/2015 AGT 9

Eukaryotic • Contain organelles surrounded by membranes • Most living organisms

Plant Animal

http://library.thinkquest.org/C004535/eukaryotic_cells.html 10/25/2015 AGT 10

“Typical” Animal Cell

http://web.jjay.cuny.edu/~acarpi/NSC/images/cell.gif 10/25/2015 AGT 11

Animal Cell

Plant Cell

http://waynesword.palomar.edu/images/plant3.gif

“Typical” Plant Cell

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Cell Parts Organelles

Surrounding the Cell

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Cell Membrane

• Outer membrane of cell that controls movement in and out of the cell

• Double layer

http://library.thinkquest.org/12413/structures.html

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• A cell membrane keeps all the parts of the cell inside.

• It controls what enters and exits the cell such as water, nutrients and waste and thereby protects and supports the cell.

• It is the outermost layer in the animal cell.

Cell

Membrane


What is a cell wall?

All plant cells have a cell wall – a rigid layer that surrounds the cell membrane.

Unlike the cell membrane, the cell wall is freely permeable to water and other molecules.

maintain the shape and structure of the cell

The plant cell wall is made from cellulose, a carbohydrate polymer. The purpose of the cell wall is to:

protect the cell’s contents from pathogens

prevent damage to the cell caused by excess water intake.

Cell Wall

• Most commonly found in plant cells & bacteria

• Supports & protects cells


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Nucleus

• Directs cell activities • Separated from cytoplasm by nuclear

membrane • Contains genetic material - DNA

Inside the Cell

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• The nucleus is located in the cytoplasm of the cell.

• It controls and regulates all cell activities. It is the "control center" of the cell and it contains the cell's DNA.

• It has a similar function to the brain of the body which is helping to control eating, movement, and reproduction.

Nucleus

Nuclear Membrane

• Surrounds nucleus • Made of two layers • Openings allow

material to enter and leave nucleus


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Chromosomes

• In nucleus • Made of DNA • Contain instructions

for traits & characteristics


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Nucleolus

• Inside nucleus • Contains RNA to build

proteins


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• Inside the cell, there is a large fluid-filled space called the cytoplasm.

• It is a jelly-like substance composed of mainly water as well as substances like dissolved nutrients.

• The cytoplasm fills up the space between the nucleus and the cell membrane.

Cytoplasm

• Gel-like mixture • Surrounded by cell membrane • Contains hereditary material

Endoplasmic Reticulum • Moves materials around

in cell • Smooth type: lacks

ribosomes • Rough type (pictured):

ribosomes embedded in surface

http://library.thinkquest.org/12413/structures.html 10/25/2015 AGT 26

Ribosomes

• Each cell contains thousands

• Make proteins • Found on ribosomes

& floating throughout the cell


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Mitochondria

• Produces energy through chemical reactions – breaking down fats & carbohydrates

• Controls level of water and other materials in cell

• Recycles and decomposes proteins, fats, and carbohydrates


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Where does respiration take place?

Mitochondria are cellular organelles in which respiration takes place.

Mitochondria use enzymes to convert the energy from glucose into ATP – the basic energy source for all cells.

Mitochondria have an inner membrane on which the enzymes are embedded.

This membrane is highly folded to increase the surface area on which respiration can take place.


What are chloroplasts?

Chloroplasts are the site of photosynthesis in plant cells.

thylakoids

A green pigment in chloroplasts called chlorophyll absorbs the energy in sunlight.

Chlorophyll is embedded in disk-like structures called thylakoids, which are arranged into stacks.

This energy is used to convert carbon dioxide and water into glucose and oxygen.

Golgi Bodies

• Protein 'packaging plant'

• Move materials within the cell

• Move materials out of the cell


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Lysosome • Digestive 'plant' for

proteins, fats, and carbohydrates

• Transports undigested material to cell membrane for removal

• Cell breaks down if lysosome explodes


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What is a vacuole?

The vacuole is a fluid–filled sac found within plant cells and some bacteria.

The vacuole has a range of functions, including:

The site of vacuoles depend on how much water the plant has absorbed.

storing waste products

regulating the turgor pressure of the cell.

maintaining the water and pH balance of the cell

Vacuoles

• Membrane-bound sacs for storage, digestion, and waste removal

• Contains water solution

• Help plants maintain shape


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Plant cells

PLANT CELL

Nucleus

Cytoplasm

Cell

Membrane

Chloroplast

Cell Wall

• A cell membrane keeps all the parts of the cell inside.

• It controls what

enters and exits the cell such as water, nutrients and waste and thereby protects and supports the cell.

• It is found just inside the cell wall in the plant cell.

Cell

Membrane

• The cell wall is found in plant cells but not in animal cells.

• This is the outermost layer in the plant cell. It is stiff and rigid and helps a plant keep its shape.

• Cell walls allow materials like water and nutrients; waste, oxygen and carbon dioxide to pass to and from the cell membrane.

Cell

Wall

• Chloroplasts are only found in plant cells. They are responsible for photosynthesis.

• Every green plant you see is working to convert the energy from the sun into sugars during the process of photosynthesis.

• Plants are the basis of all life on Earth. They make sugars, and the by-product of photosynthesis is the oxygen that we breathe.

• Chloroplasts are green because of the pigment chlorophyll.

Chloroplast

• Inside the cell, there is a large fluid-filled space called the cytoplasm.

• It is a jelly-like substance composed of mainly water as well as substances like dissolved nutrients.

• The cytoplasm is found in both plant and animal cells, filling the space between the nucleus and the cell membrane.

Cytoplasm

• The nucleus is found in both plant and animal cells.

• It is located in the cytoplasm of the cell.

• It controls and regulates all cell activities. It is the "control center" of the cell and it contains the cell's DNA.

• It has a similar function to the brain of the body which is helping to control eating, movement, and reproduction.

Nucleus

Nucleus control centre of the cell – stores information for cell functions

Chloroplasts

contain green pigment chlorophyll, needed in photosynthesis

Cytoplasm jelly-like, where cell activities take place

Cell

membrane

thin, controls the substances that enter or exit the cells

Cell wall

stiff wall which gives plant cells their shape

Plant Cell - Functions

Let’s summarise:

Animal Cell - Functions

Nucleus

control centre of the cell – stores information for cell functions

Cytoplasm jelly-like, where cell activities take place

Cell membrane thin, controls the substances that enter or exit the cells

Let’s summarise:

Differences between Plant and

Animal Cells

Plant Cell Animal Cell

•Plant cells contain chloroplasts to make food from solar energy during photosynthesis. •Underground parts of plants usually do not contain chloroplasts.

•Animal cells do not contain chloroplasts.

•Plant cells contain cell wall.

Animal cells do not have cell wall.


Glossary (1/2)

aerobic respiration – The process of releasing energy through the oxidation of glucose molecules.

anaerobic respiration – The process of releasing energy from glucose molecules in the absence of oxygen.

ATP – Adenosine triphosphate, the major form of energy used by cells.

cell – The basic structural and functional unit of life.

cell membrane – The partially-permeable barrier that regulates substances entering and leaving a cell.

cell wall – The rigid external coat that protects and supports plant cells.

chlorophyll – The green pigment found in chloroplasts.


Glossary (2/2)

chloroplast – The site of photosynthesis in plant cells.

cytoplasm – The jelly-like material in which all a cell’s

organelles are found, and in which most cellular processes and reactions occur.

mitochondria – The site of energy release by respiration.

nucleus – The location of a cell’s DNA.

photosynthesis – The chemical reaction in which light energy is used to convert carbon dioxide and water into glucose and oxygen.

ribosome – The site of protein synthesis.

vacuole – The fluid-filled cavity found in plant cells that stores water and nutrients.

cell structure & function - جامعة...

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