Cell structure

What type of membranes surround the nuclear envelope?

Phospholipid bilayers

Why does the nuclear envelope have pores?

To control the passage of ions, molecules and RNA between the nucleoplasm and cytoplasm

What is the nucleoplasm?

A semi-solid fluid inside the nucleus where chromatin and the nucleolus are found

What is the function of the nucleus?

Controls actions of the cell, contains DNA with instructions for the synthesis of proteins

What molecules are found in the nucleolus?

Proteins, RNA + DNA

How is the purpose of the nucleolus different to that of the nucleus?

nucleolus as a site at which ribosomes are made, while nucleus is site of DNA replication and transcription

What is the function of mitochondria?

Produce ATP via aerobic respiration

What is the inner layer of membrane folds in the mitochondria called?

Cristae

What are found in the mitochondrial matrix?

Enzymes for respiration

What is a plasma membrane?

A partially-permeable barrier between cell and outside environment

What is the name of the model given to describe plasma membrane structure?

Fluid mosaic model

What does the fluid mosaic model suggest?

Membranes are made up of a variety of components that continuously move around

Why are phospholipids described as amphipathic?

They have both hydrophobic and hydrophilic regions

Which ways do the hydrophobic/philic regions of the phospholipids face?

Phobic inwards, philic outwards

What is the purpose of phospholipids being amphipathic?

Allows for bilayer to form with the hydrophobic tails turned inwards away from aqueous environment and hydrophilic heads turned outwards

What is the function of plasma membranes?

Protects cell from surroundings, partially permeable, cell signalling

What is the function of a cell wall?

Provides structural support and shape to cell

What is the cell wall in plant and fungi made of?

Plants - cellulose, fungi - chitin

What is the cytoskeleton?

A network of protein fibres

What is the function of the cytoskeleton?

Maintaining shape of cell, securing organelles in position

what are thylakoids?

stacked fluid-filled membrane sacs

Where are thylakoids found?

In the inner membranes of chloroplasts

What is each stack of thylakoids called?

Grana

What links grana in chloroplasts?

Lamellae

What is stroma?

The fluid enclosed by inner membranes in chloroplasts

what is the function of the Golgi apparatus?

Receives proteins from RER and lipids from SER, modifies them and packages them into vesicles

What is the function of the smooth endoplasmic reticulum?

Synthesising lipids

What is the function of the rough endoplasmic reticulum?

synthesis of extracellular proteins

What is the function of ribosomes?

Translation of RNA into proteins

Where can ribosomes be found in the cell?

Cytoplasm or cytoplasmic side of endoplasmic reticulum

Describe the structure of a centriole

Cylindrical, paralleled microtubules with a central cavity

In what arrangement are centrioles found in the cell?

As pairs at 90° to one another

What is the function of centrioles?

Organise spindle fibres during cell division

What is the function of flagella?

Used by organisms for locomotion

What protein are microtubules in flagella made from?

Tubulin

What is the function of cilia?

Help move substances internally in organisms

What is the cytoskeleton?

Network of protein fibres

Function of cytoskeleton

Maintains shape of cell, securing organelles in position

Magnification

Process of enlarging an object in appearance

Resolution

Ability of a microscope to distinguish 2 adjacent structures as separate

Describe how light microscopes work

Visible light passes and is bent through the lens system to enable the user to see the specimen

In what type of microscope can the specimen be alive?

Light microscopes

Describe how TEM works

Electron beam penetrates cell and provides details of internal structures

Describe how SEM works

Electrons move back and forth across a cell’s surface to show surface characteristics

What type of microscope can give 3D images?

Scanning electron microscope

Equation for magnification

M = image size/actual size

Describe the function of lysosomes

Engulf and destroy old organelles or foreign material

Where are lysosomes made?

Golgi apparatus

Describe the structure of the Golgi apparatus

Made up of fluid-filled flattened sacs surrounded by vesicles

Describe the importance of the cytoskeleton

Provides mechanical strength to cells, aid transport within cells and enables cells to move

Describe the differences in the structure of prokaryotic and eukaryotic cells

Prokaryotes - have no membrane-bound organelles, DNA consists of a single circular chromosome, have plasmids, have smaller 70s ribosomes, much smaller in size

Describe the similarities in structure of prokaryotic and eukaryotic cells

Share some of the same organelles such as cytoplasm, cell membrane and ribosomes

What organelles do prokaryotic cells have that eukaryotic cells do not?

Plasmids - small, circular rings of DNA separate from main chromosome

Pili - hair-like structures that stick out from plasma membranes, used to communicate with other cells

What genes might be found on plasmids in prokaryotic cells?

Genes that aren’t crucial for survival but might prove useful, such as antibiotic-resistance genes