Biology: B1 - Cell Structure and Transport

Differences between the light and electron microscope

\-Electron microscope has higher resolution and better magnification

\-Light microscope relies on light but electron microscopes use electrons instead

Resolution

The shortest distance between two points on a specimen that can still be seen as two different points by the observer

Why does increased resolution give more information about cells?

Cells can be looked at closer and scientists can further understand their structure

Uses of the light microscope

\-Studying living cells

Uses of the electron microscope

\-Studying details within non-living cells (nucleus ext)

Magnification equation

image size/actual size

Eukaryotic cells

Cells which their genetic material is enclosed in a nucleus

Prokaryotic cells

Cells which their genetic material is not enclosed in a nucleus

Label animal cell (top to bottom)

\-Ribosome

\-Nucleus

\-Cytoplasm

\-Cell membrane

\-Mitochondria

Label plant cell (top to bottom)

\-Cell wall

\-Cell membrane

\-Ribosomes

\-Nucleus

\-Vacuole

\-Cytoplasm

\-Mitochondria

\-Chloroplast

What are the main differences between plant and animal cells?

Plant cells contain cell wall, vacuole and chloroplasts

Organelle

A specialised unit within a cell which performs a specific function

What is the function of a cytoplasm?

Place where chemical reactions happen

What is the function of a nucleus?

Holds genetic material

What is the function of a cell membrane?

Controls the movement of substances in and out of the cell

What is the function of a mitochondria?

The place where aerobic respiration occurs

What is the function of a ribosome?

Protein synthesis occurs

What is the function of a cell wall?

Provides strength and support to the plant

What is the function of a chloroplast?

Contains the enzymes needed for photosynthesis

What is the function of a vacuole?

Filled with cell sap to help keep the cell turgid

One order of magnitude is how many times bigger than the smaller object?

10

What is the rule of the order of magnitude

Each order of magnitude is 10 times bigger than the last

Specialised Cells

Cells which are adapted to help them carry out functions

Root hair cell adaptations

\-Hairs increase surface area of root so it can absorb water and minerals more effectively

\-No chloroplasts because they are underground

Xylem cell adaptations

\-Thick walls which provide support

\-End walls between cells have been broken down, making a long tube so water and minerals can flow more easily

\-No internal structures

Phloem adaptations

\-End walls of vessel cells have pores so dissolved sugars can pass through

\-No nucleus

\-Mitochondria in companion cell to provide energy

Sperm cell adaptations

\-Long tail and streamlined to they can swim to the egg

\-Only contain half the genetic information of the normal adult cell so it can bond with the egg

Muscle cell adaptations

\-Contain protein fibres which can change their length so they can contract

\-Packed with mitochondria to provide energy for contraction

Nerve cell adaptations

\-Long fibre so they can carry messages up and down the body over long distances

\-Insulated by a fat which increases the speed of the nerve impulses along the neuron

What is the link between cell structure and function?

Cells adapt their structure in order for efficiently complete their function

Diffusion

The movement of molecules from a region of higher concentration to a region of lower concentration down the concentration gradient

How do differences in concentration and temperature affect the rate of diffusion?

The greater the difference in concentration, the quicker the rate of diffusion

How do Microvilli affect the rate of diffusion?

Microvilli increase the surface area available for diffusion even more so rate of diffusion is higher.

Examples of a substances that leaves cell by diffusion

\-Carbon dioxide

\-Water

Example of a substance that enters cell by diffusion

Glucose

Osmosis

The diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane

What is active transport?

The movement of dissolved molecules from a region of lower concentration to a region of higher concentration

Differences between diffusion and active transport

simple diffusion moves molecules down concentration gradient while active transport takes them against concentration gradient

Examples of active transport in animals

Amino acids moving along the intestine

Examples of active transport in plants

Uptake of mineral ions into root hair cells

Surface area to volume ratio formula

Surface area/volume